/* * The RSA public-key cryptosystem * * Copyright The Mbed TLS Contributors * SPDX-License-Identifier: Apache-2.0 * * Licensed under the Apache License, Version 2.0 (the "License"); you may * not use this file except in compliance with the License. * You may obtain a copy of the License at * * http://www.apache.org/licenses/LICENSE-2.0 * * Unless required by applicable law or agreed to in writing, software * distributed under the License is distributed on an "AS IS" BASIS, WITHOUT * WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied. * See the License for the specific language governing permissions and * limitations under the License. */ /* * The following sources were referenced in the design of this implementation * of the RSA algorithm: * * [1] A method for obtaining digital signatures and public-key cryptosystems * R Rivest, A Shamir, and L Adleman * http://people.csail.mit.edu/rivest/pubs.html#RSA78 * * [2] Handbook of Applied Cryptography - 1997, Chapter 8 * Menezes, van Oorschot and Vanstone * * [3] Malware Guard Extension: Using SGX to Conceal Cache Attacks * Michael Schwarz, Samuel Weiser, Daniel Gruss, Clémentine Maurice and * Stefan Mangard * https://arxiv.org/abs/1702.08719v2 * */ #include "common.h" #if defined(MBEDTLS_RSA_C) #include "mbedtls/rsa.h" #include "mbedtls/rsa_internal.h" #include "mbedtls/oid.h" #include "mbedtls/platform_util.h" #include "mbedtls/error.h" #include #if defined(MBEDTLS_PKCS1_V21) #include "mbedtls/md.h" #endif #if defined(MBEDTLS_PKCS1_V15) && !defined(__OpenBSD__) && !defined(__NetBSD__) #include #endif #if defined(MBEDTLS_PLATFORM_C) #include "mbedtls/platform.h" #else #include #define mbedtls_printf printf #define mbedtls_calloc calloc #define mbedtls_free free #endif #if !defined(MBEDTLS_RSA_ALT) /* Parameter validation macros */ #define RSA_VALIDATE_RET( cond ) \ MBEDTLS_INTERNAL_VALIDATE_RET( cond, MBEDTLS_ERR_RSA_BAD_INPUT_DATA ) #define RSA_VALIDATE( cond ) \ MBEDTLS_INTERNAL_VALIDATE( cond ) #if defined(MBEDTLS_PKCS1_V15) /* constant-time buffer comparison */ static inline int mbedtls_safer_memcmp(const void *a, const void *b, size_t n) { size_t i; const unsigned char *A = (const unsigned char *) a; const unsigned char *B = (const unsigned char *) b; unsigned char diff = 0; for (i = 0; i < n; i++) diff |= A[i] ^ B[i]; return (diff); } #endif /* MBEDTLS_PKCS1_V15 */ int mbedtls_rsa_import(mbedtls_rsa_context *ctx, const mbedtls_mpi *N, const mbedtls_mpi *P, const mbedtls_mpi *Q, const mbedtls_mpi *D, const mbedtls_mpi *E) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; RSA_VALIDATE_RET(ctx != NULL); if ((N != NULL && (ret = mbedtls_mpi_copy(&ctx->N, N)) != 0) || (P != NULL && (ret = mbedtls_mpi_copy(&ctx->P, P)) != 0) || (Q != NULL && (ret = mbedtls_mpi_copy(&ctx->Q, Q)) != 0) || (D != NULL && (ret = mbedtls_mpi_copy(&ctx->D, D)) != 0) || (E != NULL && (ret = mbedtls_mpi_copy(&ctx->E, E)) != 0)) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } if (N != NULL) ctx->len = mbedtls_mpi_size(&ctx->N); return (0); } int mbedtls_rsa_import_raw(mbedtls_rsa_context *ctx, unsigned char const *N, size_t N_len, unsigned char const *P, size_t P_len, unsigned char const *Q, size_t Q_len, unsigned char const *D, size_t D_len, unsigned char const *E, size_t E_len) { int ret = 0; RSA_VALIDATE_RET(ctx != NULL); if (N != NULL) { MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&ctx->N, N, N_len)); ctx->len = mbedtls_mpi_size(&ctx->N); } if (P != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&ctx->P, P, P_len)); if (Q != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&ctx->Q, Q, Q_len)); if (D != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&ctx->D, D, D_len)); if (E != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&ctx->E, E, E_len)); cleanup: if (ret != 0) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); return (0); } /* * Checks whether the context fields are set in such a way * that the RSA primitives will be able to execute without error. * It does *not* make guarantees for consistency of the parameters. */ static int rsa_check_context(mbedtls_rsa_context const *ctx, int is_priv, int blinding_needed) { #if !defined(MBEDTLS_RSA_NO_CRT) /* blinding_needed is only used for NO_CRT to decide whether * P,Q need to be present or not. */ ((void) blinding_needed); #endif if (ctx->len != mbedtls_mpi_size(&ctx->N) || ctx->len > MBEDTLS_MPI_MAX_SIZE) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } /* * 1. Modular exponentiation needs positive, odd moduli. */ /* Modular exponentiation wrt. N is always used for * RSA public key operations. */ if (mbedtls_mpi_cmp_int(&ctx->N, 0) <= 0 || mbedtls_mpi_get_bit(&ctx->N, 0) == 0) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } #if !defined(MBEDTLS_RSA_NO_CRT) /* Modular exponentiation for P and Q is only * used for private key operations and if CRT * is used. */ if (is_priv && (mbedtls_mpi_cmp_int(&ctx->P, 0) <= 0 || mbedtls_mpi_get_bit(&ctx->P, 0) == 0 || mbedtls_mpi_cmp_int(&ctx->Q, 0) <= 0 || mbedtls_mpi_get_bit(&ctx->Q, 0) == 0)) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } #endif /* !MBEDTLS_RSA_NO_CRT */ /* * 2. Exponents must be positive */ /* Always need E for public key operations */ if (mbedtls_mpi_cmp_int(&ctx->E, 0) <= 0) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); #if defined(MBEDTLS_RSA_NO_CRT) /* For private key operations, use D or DP & DQ * as (unblinded) exponents. */ if (is_priv && mbedtls_mpi_cmp_int(&ctx->D, 0) <= 0) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); #else if (is_priv && (mbedtls_mpi_cmp_int(&ctx->DP, 0) <= 0 || mbedtls_mpi_cmp_int(&ctx->DQ, 0) <= 0)) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } #endif /* MBEDTLS_RSA_NO_CRT */ /* Blinding shouldn't make exponents negative either, * so check that P, Q >= 1 if that hasn't yet been * done as part of 1. */ #if defined(MBEDTLS_RSA_NO_CRT) if (is_priv && blinding_needed && (mbedtls_mpi_cmp_int(&ctx->P, 0) <= 0 || mbedtls_mpi_cmp_int(&ctx->Q, 0) <= 0)) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } #endif /* It wouldn't lead to an error if it wasn't satisfied, * but check for QP >= 1 nonetheless. */ #if !defined(MBEDTLS_RSA_NO_CRT) if (is_priv && mbedtls_mpi_cmp_int(&ctx->QP, 0) <= 0) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } #endif return (0); } int mbedtls_rsa_complete(mbedtls_rsa_context *ctx) { int ret = 0; int have_N, have_P, have_Q, have_D, have_E; #if !defined(MBEDTLS_RSA_NO_CRT) int have_DP, have_DQ, have_QP; #endif int n_missing, pq_missing, d_missing, is_pub, is_priv; RSA_VALIDATE_RET(ctx != NULL); have_N = (mbedtls_mpi_cmp_int(&ctx->N, 0) != 0); have_P = (mbedtls_mpi_cmp_int(&ctx->P, 0) != 0); have_Q = (mbedtls_mpi_cmp_int(&ctx->Q, 0) != 0); have_D = (mbedtls_mpi_cmp_int(&ctx->D, 0) != 0); have_E = (mbedtls_mpi_cmp_int(&ctx->E, 0) != 0); #if !defined(MBEDTLS_RSA_NO_CRT) have_DP = (mbedtls_mpi_cmp_int(&ctx->DP, 0) != 0); have_DQ = (mbedtls_mpi_cmp_int(&ctx->DQ, 0) != 0); have_QP = (mbedtls_mpi_cmp_int(&ctx->QP, 0) != 0); #endif /* * Check whether provided parameters are enough * to deduce all others. The following incomplete * parameter sets for private keys are supported: * * (1) P, Q missing. * (2) D and potentially N missing. * */ n_missing = have_P && have_Q && have_D && have_E; pq_missing = have_N && !have_P && !have_Q && have_D && have_E; d_missing = have_P && have_Q && !have_D && have_E; is_pub = have_N && !have_P && !have_Q && !have_D && have_E; /* These three alternatives are mutually exclusive */ is_priv = n_missing || pq_missing || d_missing; if (!is_priv && !is_pub) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); /* * Step 1: Deduce N if P, Q are provided. */ if (!have_N && have_P && have_Q) { if ((ret = mbedtls_mpi_mul_mpi(&ctx->N, &ctx->P, &ctx->Q)) != 0) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } ctx->len = mbedtls_mpi_size(&ctx->N); } /* * Step 2: Deduce and verify all remaining core parameters. */ if (pq_missing) { ret = mbedtls_rsa_deduce_primes(&ctx->N, &ctx->E, &ctx->D, &ctx->P, &ctx->Q); if (ret != 0) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } else if (d_missing) { if ((ret = mbedtls_rsa_deduce_private_exponent(&ctx->P, &ctx->Q, &ctx->E, &ctx->D)) != 0) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } } /* * Step 3: Deduce all additional parameters specific * to our current RSA implementation. */ #if !defined(MBEDTLS_RSA_NO_CRT) if (is_priv && !(have_DP && have_DQ && have_QP)) { ret = mbedtls_rsa_deduce_crt(&ctx->P, &ctx->Q, &ctx->D, &ctx->DP, &ctx->DQ, &ctx->QP); if (ret != 0) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } #endif /* MBEDTLS_RSA_NO_CRT */ /* * Step 3: Basic sanity checks */ return (rsa_check_context(ctx, is_priv, 1)); } int mbedtls_rsa_export_raw(const mbedtls_rsa_context *ctx, unsigned char *N, size_t N_len, unsigned char *P, size_t P_len, unsigned char *Q, size_t Q_len, unsigned char *D, size_t D_len, unsigned char *E, size_t E_len) { int ret = 0; int is_priv; RSA_VALIDATE_RET(ctx != NULL); /* Check if key is private or public */ is_priv = mbedtls_mpi_cmp_int(&ctx->N, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->P, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->Q, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->D, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->E, 0) != 0; if (!is_priv) { /* If we're trying to export private parameters for a public key, * something must be wrong. */ if (P != NULL || Q != NULL || D != NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } if (N != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&ctx->N, N, N_len)); if (P != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&ctx->P, P, P_len)); if (Q != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&ctx->Q, Q, Q_len)); if (D != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&ctx->D, D, D_len)); if (E != NULL) MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&ctx->E, E, E_len)); cleanup: return (ret); } int mbedtls_rsa_export(const mbedtls_rsa_context *ctx, mbedtls_mpi *N, mbedtls_mpi *P, mbedtls_mpi *Q, mbedtls_mpi *D, mbedtls_mpi *E) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; int is_priv; RSA_VALIDATE_RET(ctx != NULL); /* Check if key is private or public */ is_priv = mbedtls_mpi_cmp_int(&ctx->N, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->P, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->Q, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->D, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->E, 0) != 0; if (!is_priv) { /* If we're trying to export private parameters for a public key, * something must be wrong. */ if (P != NULL || Q != NULL || D != NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } /* Export all requested core parameters. */ if ((N != NULL && (ret = mbedtls_mpi_copy(N, &ctx->N)) != 0) || (P != NULL && (ret = mbedtls_mpi_copy(P, &ctx->P)) != 0) || (Q != NULL && (ret = mbedtls_mpi_copy(Q, &ctx->Q)) != 0) || (D != NULL && (ret = mbedtls_mpi_copy(D, &ctx->D)) != 0) || (E != NULL && (ret = mbedtls_mpi_copy(E, &ctx->E)) != 0)) { return (ret); } return (0); } /* * Export CRT parameters * This must also be implemented if CRT is not used, for being able to * write DER encoded RSA keys. The helper function mbedtls_rsa_deduce_crt * can be used in this case. */ int mbedtls_rsa_export_crt(const mbedtls_rsa_context *ctx, mbedtls_mpi *DP, mbedtls_mpi *DQ, mbedtls_mpi *QP) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; int is_priv; RSA_VALIDATE_RET(ctx != NULL); /* Check if key is private or public */ is_priv = mbedtls_mpi_cmp_int(&ctx->N, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->P, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->Q, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->D, 0) != 0 && mbedtls_mpi_cmp_int(&ctx->E, 0) != 0; if (!is_priv) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); #if !defined(MBEDTLS_RSA_NO_CRT) /* Export all requested blinding parameters. */ if ((DP != NULL && (ret = mbedtls_mpi_copy(DP, &ctx->DP)) != 0) || (DQ != NULL && (ret = mbedtls_mpi_copy(DQ, &ctx->DQ)) != 0) || (QP != NULL && (ret = mbedtls_mpi_copy(QP, &ctx->QP)) != 0)) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } #else if ((ret = mbedtls_rsa_deduce_crt(&ctx->P, &ctx->Q, &ctx->D, DP, DQ, QP)) != 0) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA + ret); } #endif return (0); } /* * Initialize an RSA context */ void mbedtls_rsa_init(mbedtls_rsa_context *ctx, int padding, int hash_id) { RSA_VALIDATE(ctx != NULL); RSA_VALIDATE(padding == MBEDTLS_RSA_PKCS_V15 || padding == MBEDTLS_RSA_PKCS_V21); memset(ctx, 0, sizeof(mbedtls_rsa_context)); mbedtls_rsa_set_padding(ctx, padding, hash_id); #if defined(MBEDTLS_THREADING_C) /* Set ctx->ver to nonzero to indicate that the mutex has been * initialized and will need to be freed. */ ctx->ver = 1; mbedtls_mutex_init(&ctx->mutex); #endif } /* * Set padding for an existing RSA context */ void mbedtls_rsa_set_padding(mbedtls_rsa_context *ctx, int padding, int hash_id) { RSA_VALIDATE(ctx != NULL); RSA_VALIDATE(padding == MBEDTLS_RSA_PKCS_V15 || padding == MBEDTLS_RSA_PKCS_V21); ctx->padding = padding; ctx->hash_id = hash_id; } /* * Get length in bytes of RSA modulus */ size_t mbedtls_rsa_get_len(const mbedtls_rsa_context *ctx) { return (ctx->len); } #if defined(MBEDTLS_GENPRIME) /* * Generate an RSA keypair * * This generation method follows the RSA key pair generation procedure of * FIPS 186-4 if 2^16 < exponent < 2^256 and nbits = 2048 or nbits = 3072. */ int mbedtls_rsa_gen_key(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, unsigned int nbits, int exponent) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; mbedtls_mpi H, G, L; int prime_quality = 0; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(f_rng != NULL); /* * If the modulus is 1024 bit long or shorter, then the security strength of * the RSA algorithm is less than or equal to 80 bits and therefore an error * rate of 2^-80 is sufficient. */ if (nbits > 1024) prime_quality = MBEDTLS_MPI_GEN_PRIME_FLAG_LOW_ERR; mbedtls_mpi_init(&H); mbedtls_mpi_init(&G); mbedtls_mpi_init(&L); if (nbits < 128 || exponent < 3 || nbits % 2 != 0) { ret = MBEDTLS_ERR_RSA_BAD_INPUT_DATA; goto cleanup; } /* * find primes P and Q with Q < P so that: * 1. |P-Q| > 2^( nbits / 2 - 100 ) * 2. GCD( E, (P-1)*(Q-1) ) == 1 * 3. E^-1 mod LCM(P-1, Q-1) > 2^( nbits / 2 ) */ MBEDTLS_MPI_CHK(mbedtls_mpi_lset(&ctx->E, exponent)); do { MBEDTLS_MPI_CHK(mbedtls_mpi_gen_prime(&ctx->P, nbits >> 1, prime_quality, f_rng, p_rng)); MBEDTLS_MPI_CHK(mbedtls_mpi_gen_prime(&ctx->Q, nbits >> 1, prime_quality, f_rng, p_rng)); /* make sure the difference between p and q is not too small (FIPS 186-4 §B.3.3 step 5.4) */ MBEDTLS_MPI_CHK(mbedtls_mpi_sub_mpi(&H, &ctx->P, &ctx->Q)); if (mbedtls_mpi_bitlen(&H) <= ((nbits >= 200) ? ((nbits >> 1) - 99) : 0)) continue; /* not required by any standards, but some users rely on the fact that P > Q */ if (H.s < 0) mbedtls_mpi_swap(&ctx->P, &ctx->Q); /* Temporarily replace P,Q by P-1, Q-1 */ MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&ctx->P, &ctx->P, 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&ctx->Q, &ctx->Q, 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&H, &ctx->P, &ctx->Q)); /* check GCD( E, (P-1)*(Q-1) ) == 1 (FIPS 186-4 §B.3.1 criterion 2(a)) */ MBEDTLS_MPI_CHK(mbedtls_mpi_gcd(&G, &ctx->E, &H)); if (mbedtls_mpi_cmp_int(&G, 1) != 0) continue; /* compute smallest possible D = E^-1 mod LCM(P-1, Q-1) (FIPS 186-4 §B.3.1 criterion 3(b)) */ MBEDTLS_MPI_CHK(mbedtls_mpi_gcd(&G, &ctx->P, &ctx->Q)); MBEDTLS_MPI_CHK(mbedtls_mpi_div_mpi(&L, NULL, &H, &G)); MBEDTLS_MPI_CHK(mbedtls_mpi_inv_mod(&ctx->D, &ctx->E, &L)); if (mbedtls_mpi_bitlen(&ctx->D) <= ((nbits + 1) / 2)) // (FIPS 186-4 §B.3.1 criterion 3(a)) continue; break; } while (1); /* Restore P,Q */ MBEDTLS_MPI_CHK(mbedtls_mpi_add_int(&ctx->P, &ctx->P, 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_add_int(&ctx->Q, &ctx->Q, 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&ctx->N, &ctx->P, &ctx->Q)); ctx->len = mbedtls_mpi_size(&ctx->N); #if !defined(MBEDTLS_RSA_NO_CRT) /* * DP = D mod (P - 1) * DQ = D mod (Q - 1) * QP = Q^-1 mod P */ MBEDTLS_MPI_CHK(mbedtls_rsa_deduce_crt(&ctx->P, &ctx->Q, &ctx->D, &ctx->DP, &ctx->DQ, &ctx->QP)); #endif /* MBEDTLS_RSA_NO_CRT */ /* Double-check */ MBEDTLS_MPI_CHK(mbedtls_rsa_check_privkey(ctx)); cleanup: mbedtls_mpi_free(&H); mbedtls_mpi_free(&G); mbedtls_mpi_free(&L); if (ret != 0) { mbedtls_rsa_free(ctx); if ((-ret & ~0x7f) == 0) ret = MBEDTLS_ERR_RSA_KEY_GEN_FAILED + ret; return (ret); } return (0); } #endif /* MBEDTLS_GENPRIME */ /* * Check a public RSA key */ int mbedtls_rsa_check_pubkey(const mbedtls_rsa_context *ctx) { RSA_VALIDATE_RET(ctx != NULL); if (rsa_check_context(ctx, 0 /* public */, 0 /* no blinding */) != 0) return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); if (mbedtls_mpi_bitlen(&ctx->N) < 128) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } if (mbedtls_mpi_get_bit(&ctx->E, 0) == 0 || mbedtls_mpi_bitlen(&ctx->E) < 2 || mbedtls_mpi_cmp_mpi(&ctx->E, &ctx->N) >= 0) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } return (0); } /* * Check for the consistency of all fields in an RSA private key context */ int mbedtls_rsa_check_privkey(const mbedtls_rsa_context *ctx) { RSA_VALIDATE_RET(ctx != NULL); if (mbedtls_rsa_check_pubkey(ctx) != 0 || rsa_check_context(ctx, 1 /* private */, 1 /* blinding */) != 0) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } if (mbedtls_rsa_validate_params(&ctx->N, &ctx->P, &ctx->Q, &ctx->D, &ctx->E, NULL, NULL) != 0) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } #if !defined(MBEDTLS_RSA_NO_CRT) else if (mbedtls_rsa_validate_crt(&ctx->P, &ctx->Q, &ctx->D, &ctx->DP, &ctx->DQ, &ctx->QP) != 0) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } #endif return (0); } /* * Check if contexts holding a public and private key match */ int mbedtls_rsa_check_pub_priv(const mbedtls_rsa_context *pub, const mbedtls_rsa_context *prv) { RSA_VALIDATE_RET(pub != NULL); RSA_VALIDATE_RET(prv != NULL); if (mbedtls_rsa_check_pubkey(pub) != 0 || mbedtls_rsa_check_privkey(prv) != 0) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } if (mbedtls_mpi_cmp_mpi(&pub->N, &prv->N) != 0 || mbedtls_mpi_cmp_mpi(&pub->E, &prv->E) != 0) { return (MBEDTLS_ERR_RSA_KEY_CHECK_FAILED); } return (0); } /* * Do an RSA public key operation */ int mbedtls_rsa_public(mbedtls_rsa_context *ctx, const unsigned char *input, unsigned char *output) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t olen; mbedtls_mpi T; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(input != NULL); RSA_VALIDATE_RET(output != NULL); if (rsa_check_context(ctx, 0 /* public */, 0 /* no blinding */)) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); mbedtls_mpi_init(&T); #if defined(MBEDTLS_THREADING_C) if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) return (ret); #endif MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&T, input, ctx->len)); if (mbedtls_mpi_cmp_mpi(&T, &ctx->N) >= 0) { ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA; goto cleanup; } olen = ctx->len; MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&T, &T, &ctx->E, &ctx->N, &ctx->RN)); MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&T, output, olen)); cleanup: #if defined(MBEDTLS_THREADING_C) if (mbedtls_mutex_unlock(&ctx->mutex) != 0) return (MBEDTLS_ERR_THREADING_MUTEX_ERROR); #endif mbedtls_mpi_free(&T); if (ret != 0) return (MBEDTLS_ERR_RSA_PUBLIC_FAILED + ret); return (0); } /* * Generate or update blinding values, see section 10 of: * KOCHER, Paul C. Timing attacks on implementations of Diffie-Hellman, RSA, * DSS, and other systems. In : Advances in Cryptology-CRYPTO'96. Springer * Berlin Heidelberg, 1996. p. 104-113. */ static int rsa_prepare_blinding(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng) { int ret, count = 0; mbedtls_mpi R; mbedtls_mpi_init(&R); if (ctx->Vf.p != NULL) { /* We already have blinding values, just update them by squaring */ MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&ctx->Vi, &ctx->Vi, &ctx->Vi)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&ctx->Vi, &ctx->Vi, &ctx->N)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&ctx->Vf, &ctx->Vf, &ctx->Vf)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&ctx->Vf, &ctx->Vf, &ctx->N)); goto cleanup; } /* Unblinding value: Vf = random number, invertible mod N */ do { if (count++ > 10) { ret = MBEDTLS_ERR_RSA_RNG_FAILED; goto cleanup; } MBEDTLS_MPI_CHK(mbedtls_mpi_fill_random(&ctx->Vf, ctx->len - 1, f_rng, p_rng)); /* Compute Vf^-1 as R * (R Vf)^-1 to avoid leaks from inv_mod. */ MBEDTLS_MPI_CHK(mbedtls_mpi_fill_random(&R, ctx->len - 1, f_rng, p_rng)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&ctx->Vi, &ctx->Vf, &R)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&ctx->Vi, &ctx->Vi, &ctx->N)); /* At this point, Vi is invertible mod N if and only if both Vf and R * are invertible mod N. If one of them isn't, we don't need to know * which one, we just loop and choose new values for both of them. * (Each iteration succeeds with overwhelming probability.) */ ret = mbedtls_mpi_inv_mod(&ctx->Vi, &ctx->Vi, &ctx->N); if (ret != 0 && ret != MBEDTLS_ERR_MPI_NOT_ACCEPTABLE) goto cleanup; } while (ret == MBEDTLS_ERR_MPI_NOT_ACCEPTABLE); /* Finish the computation of Vf^-1 = R * (R Vf)^-1 */ MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&ctx->Vi, &ctx->Vi, &R)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&ctx->Vi, &ctx->Vi, &ctx->N)); /* Blinding value: Vi = Vf^(-e) mod N * (Vi already contains Vf^-1 at this point) */ MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&ctx->Vi, &ctx->Vi, &ctx->E, &ctx->N, &ctx->RN)); cleanup: mbedtls_mpi_free(&R); return (ret); } /* * Exponent blinding supposed to prevent side-channel attacks using multiple * traces of measurements to recover the RSA key. The more collisions are there, * the more bits of the key can be recovered. See [3]. * * Collecting n collisions with m bit long blinding value requires 2^(m-m/n) * observations on avarage. * * For example with 28 byte blinding to achieve 2 collisions the adversary has * to make 2^112 observations on avarage. * * (With the currently (as of 2017 April) known best algorithms breaking 2048 * bit RSA requires approximately as much time as trying out 2^112 random keys. * Thus in this sense with 28 byte blinding the security is not reduced by * side-channel attacks like the one in [3]) * * This countermeasure does not help if the key recovery is possible with a * single trace. */ #define RSA_EXPONENT_BLINDING 28 /* * Do an RSA private key operation */ int mbedtls_rsa_private(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, const unsigned char *input, unsigned char *output) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t olen; /* Temporary holding the result */ mbedtls_mpi T; /* Temporaries holding P-1, Q-1 and the * exponent blinding factor, respectively. */ mbedtls_mpi P1, Q1, R; #if !defined(MBEDTLS_RSA_NO_CRT) /* Temporaries holding the results mod p resp. mod q. */ mbedtls_mpi TP, TQ; /* Temporaries holding the blinded exponents for * the mod p resp. mod q computation (if used). */ mbedtls_mpi DP_blind, DQ_blind; /* Pointers to actual exponents to be used - either the unblinded * or the blinded ones, depending on the presence of a PRNG. */ mbedtls_mpi *DP = &ctx->DP; mbedtls_mpi *DQ = &ctx->DQ; #else /* Temporary holding the blinded exponent (if used). */ mbedtls_mpi D_blind; /* Pointer to actual exponent to be used - either the unblinded * or the blinded one, depending on the presence of a PRNG. */ mbedtls_mpi *D = &ctx->D; #endif /* MBEDTLS_RSA_NO_CRT */ /* Temporaries holding the initial input and the double * checked result; should be the same in the end. */ mbedtls_mpi I, C; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(input != NULL); RSA_VALIDATE_RET(output != NULL); if (rsa_check_context(ctx, 1 /* private key checks */, f_rng != NULL /* blinding y/n */) != 0) { return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } #if defined(MBEDTLS_THREADING_C) if ((ret = mbedtls_mutex_lock(&ctx->mutex)) != 0) return (ret); #endif /* MPI Initialization */ mbedtls_mpi_init(&T); mbedtls_mpi_init(&P1); mbedtls_mpi_init(&Q1); mbedtls_mpi_init(&R); if (f_rng != NULL) { #if defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_init(&D_blind); #else mbedtls_mpi_init(&DP_blind); mbedtls_mpi_init(&DQ_blind); #endif } #if !defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_init(&TP); mbedtls_mpi_init(&TQ); #endif mbedtls_mpi_init(&I); mbedtls_mpi_init(&C); /* End of MPI initialization */ MBEDTLS_MPI_CHK(mbedtls_mpi_read_binary(&T, input, ctx->len)); if (mbedtls_mpi_cmp_mpi(&T, &ctx->N) >= 0) { ret = MBEDTLS_ERR_MPI_BAD_INPUT_DATA; goto cleanup; } MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&I, &T)); if (f_rng != NULL) { /* * Blinding * T = T * Vi mod N */ MBEDTLS_MPI_CHK(rsa_prepare_blinding(ctx, f_rng, p_rng)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&T, &T, &ctx->Vi)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&T, &T, &ctx->N)); /* * Exponent blinding */ MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&P1, &ctx->P, 1)); MBEDTLS_MPI_CHK(mbedtls_mpi_sub_int(&Q1, &ctx->Q, 1)); #if defined(MBEDTLS_RSA_NO_CRT) /* * D_blind = ( P - 1 ) * ( Q - 1 ) * R + D */ MBEDTLS_MPI_CHK(mbedtls_mpi_fill_random(&R, RSA_EXPONENT_BLINDING, f_rng, p_rng)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&D_blind, &P1, &Q1)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&D_blind, &D_blind, &R)); MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&D_blind, &D_blind, &ctx->D)); D = &D_blind; #else /* * DP_blind = ( P - 1 ) * R + DP */ MBEDTLS_MPI_CHK(mbedtls_mpi_fill_random(&R, RSA_EXPONENT_BLINDING, f_rng, p_rng)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&DP_blind, &P1, &R)); MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&DP_blind, &DP_blind, &ctx->DP)); DP = &DP_blind; /* * DQ_blind = ( Q - 1 ) * R + DQ */ MBEDTLS_MPI_CHK(mbedtls_mpi_fill_random(&R, RSA_EXPONENT_BLINDING, f_rng, p_rng)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&DQ_blind, &Q1, &R)); MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&DQ_blind, &DQ_blind, &ctx->DQ)); DQ = &DQ_blind; #endif /* MBEDTLS_RSA_NO_CRT */ } #if defined(MBEDTLS_RSA_NO_CRT) MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&T, &T, D, &ctx->N, &ctx->RN)); #else /* * Faster decryption using the CRT * * TP = input ^ dP mod P * TQ = input ^ dQ mod Q */ MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&TP, &T, DP, &ctx->P, &ctx->RP)); MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&TQ, &T, DQ, &ctx->Q, &ctx->RQ)); /* * T = (TP - TQ) * (Q^-1 mod P) mod P */ MBEDTLS_MPI_CHK(mbedtls_mpi_sub_mpi(&T, &TP, &TQ)); MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&TP, &T, &ctx->QP)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&T, &TP, &ctx->P)); /* * T = TQ + T * Q */ MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&TP, &T, &ctx->Q)); MBEDTLS_MPI_CHK(mbedtls_mpi_add_mpi(&T, &TQ, &TP)); #endif /* MBEDTLS_RSA_NO_CRT */ if (f_rng != NULL) { /* * Unblind * T = T * Vf mod N */ MBEDTLS_MPI_CHK(mbedtls_mpi_mul_mpi(&T, &T, &ctx->Vf)); MBEDTLS_MPI_CHK(mbedtls_mpi_mod_mpi(&T, &T, &ctx->N)); } /* Verify the result to prevent glitching attacks. */ MBEDTLS_MPI_CHK(mbedtls_mpi_exp_mod(&C, &T, &ctx->E, &ctx->N, &ctx->RN)); if (mbedtls_mpi_cmp_mpi(&C, &I) != 0) { ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; goto cleanup; } olen = ctx->len; MBEDTLS_MPI_CHK(mbedtls_mpi_write_binary(&T, output, olen)); cleanup: #if defined(MBEDTLS_THREADING_C) if (mbedtls_mutex_unlock(&ctx->mutex) != 0) return (MBEDTLS_ERR_THREADING_MUTEX_ERROR); #endif mbedtls_mpi_free(&P1); mbedtls_mpi_free(&Q1); mbedtls_mpi_free(&R); if (f_rng != NULL) { #if defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_free(&D_blind); #else mbedtls_mpi_free(&DP_blind); mbedtls_mpi_free(&DQ_blind); #endif } mbedtls_mpi_free(&T); #if !defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_free(&TP); mbedtls_mpi_free(&TQ); #endif mbedtls_mpi_free(&C); mbedtls_mpi_free(&I); if (ret != 0 && ret >= -0x007f) return (MBEDTLS_ERR_RSA_PRIVATE_FAILED + ret); return (ret); } #if defined(MBEDTLS_PKCS1_V21) /** * Generate and apply the MGF1 operation (from PKCS#1 v2.1) to a buffer. * * \param dst buffer to mask * \param dlen length of destination buffer * \param src source of the mask generation * \param slen length of the source buffer * \param md_ctx message digest context to use */ static int mgf_mask(unsigned char *dst, size_t dlen, unsigned char *src, size_t slen, mbedtls_md_context_t *md_ctx) { unsigned char mask[MBEDTLS_MD_MAX_SIZE]; unsigned char counter[4]; unsigned char *p; unsigned int hlen; size_t i, use_len; int ret = 0; memset(mask, 0, MBEDTLS_MD_MAX_SIZE); memset(counter, 0, 4); hlen = mbedtls_md_get_size(md_ctx->md_info); /* Generate and apply dbMask */ p = dst; while (dlen > 0) { use_len = hlen; if (dlen < hlen) use_len = dlen; if ((ret = mbedtls_md_starts(md_ctx)) != 0) goto exit; if ((ret = mbedtls_md_update(md_ctx, src, slen)) != 0) goto exit; if ((ret = mbedtls_md_update(md_ctx, counter, 4)) != 0) goto exit; if ((ret = mbedtls_md_finish(md_ctx, mask)) != 0) goto exit; for (i = 0; i < use_len; ++i) *p++ ^= mask[i]; counter[3]++; dlen -= use_len; } exit: mbedtls_platform_zeroize(mask, sizeof(mask)); return (ret); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSAES-OAEP-ENCRYPT function */ int mbedtls_rsa_rsaes_oaep_encrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, const unsigned char *label, size_t label_len, size_t ilen, const unsigned char *input, unsigned char *output) { size_t olen; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = output; unsigned int hlen; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(output != NULL); RSA_VALIDATE_RET(ilen == 0 || input != NULL); RSA_VALIDATE_RET(label_len == 0 || label != NULL); if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V21) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); if (f_rng == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); md_info = mbedtls_md_info_from_type((mbedtls_md_type_t) ctx->hash_id); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); olen = ctx->len; hlen = mbedtls_md_get_size(md_info); /* first comparison checks for overflow */ if (ilen + 2 * hlen + 2 < ilen || olen < ilen + 2 * hlen + 2) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); memset(output, 0, olen); *p++ = 0; /* Generate a random octet string seed */ if ((ret = f_rng(p_rng, p, hlen)) != 0) return (MBEDTLS_ERR_RSA_RNG_FAILED + ret); p += hlen; /* Construct DB */ if ((ret = mbedtls_md(md_info, label, label_len, p)) != 0) return (ret); p += hlen; p += olen - 2 * hlen - 2 - ilen; *p++ = 1; if (ilen != 0) memcpy(p, input, ilen); mbedtls_md_init(&md_ctx); if ((ret = mbedtls_md_setup(&md_ctx, md_info, 0)) != 0) goto exit; /* maskedDB: Apply dbMask to DB */ if ((ret = mgf_mask(output + hlen + 1, olen - hlen - 1, output + 1, hlen, &md_ctx)) != 0) goto exit; /* maskedSeed: Apply seedMask to seed */ if ((ret = mgf_mask(output + 1, hlen, output + hlen + 1, olen - hlen - 1, &md_ctx)) != 0) goto exit; exit: mbedtls_md_free(&md_ctx); if (ret != 0) return (ret); return ((mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, output, output) : mbedtls_rsa_private(ctx, f_rng, p_rng, output, output)); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /* * Implementation of the PKCS#1 v2.1 RSAES-PKCS1-V1_5-ENCRYPT function */ int mbedtls_rsa_rsaes_pkcs1_v15_encrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, size_t ilen, const unsigned char *input, unsigned char *output) { size_t nb_pad, olen; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *p = output; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(output != NULL); RSA_VALIDATE_RET(ilen == 0 || input != NULL); if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V15) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); olen = ctx->len; /* first comparison checks for overflow */ if (ilen + 11 < ilen || olen < ilen + 11) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); nb_pad = olen - 3 - ilen; *p++ = 0; if (mode == MBEDTLS_RSA_PUBLIC) { if (f_rng == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); *p++ = MBEDTLS_RSA_CRYPT; while (nb_pad-- > 0) { int rng_dl = 100; do { ret = f_rng(p_rng, p, 1); } while (*p == 0 && --rng_dl && ret == 0); /* Check if RNG failed to generate data */ if (rng_dl == 0 || ret != 0) return (MBEDTLS_ERR_RSA_RNG_FAILED + ret); p++; } } else { *p++ = MBEDTLS_RSA_SIGN; while (nb_pad-- > 0) *p++ = 0xFF; } *p++ = 0; if (ilen != 0) memcpy(p, input, ilen); return ((mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, output, output) : mbedtls_rsa_private(ctx, f_rng, p_rng, output, output)); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Add the message padding, then do an RSA operation */ int mbedtls_rsa_pkcs1_encrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, size_t ilen, const unsigned char *input, unsigned char *output) { RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(output != NULL); RSA_VALIDATE_RET(ilen == 0 || input != NULL); switch (ctx->padding) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsaes_pkcs1_v15_encrypt(ctx, f_rng, p_rng, mode, ilen, input, output); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsaes_oaep_encrypt(ctx, f_rng, p_rng, mode, NULL, 0, ilen, input, output); #endif default: return (MBEDTLS_ERR_RSA_INVALID_PADDING); } } #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSAES-OAEP-DECRYPT function */ int mbedtls_rsa_rsaes_oaep_decrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, const unsigned char *label, size_t label_len, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t ilen, i, pad_len; unsigned char *p, bad, pad_done; unsigned char buf[MBEDTLS_MPI_MAX_SIZE]; unsigned char lhash[MBEDTLS_MD_MAX_SIZE]; unsigned int hlen; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(output_max_len == 0 || output != NULL); RSA_VALIDATE_RET(label_len == 0 || label != NULL); RSA_VALIDATE_RET(input != NULL); RSA_VALIDATE_RET(olen != NULL); /* * Parameters sanity checks */ if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V21) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); ilen = ctx->len; if (ilen < 16 || ilen > sizeof(buf)) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); md_info = mbedtls_md_info_from_type((mbedtls_md_type_t) ctx->hash_id); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hlen = mbedtls_md_get_size(md_info); // checking for integer underflow if (2 * hlen + 2 > ilen) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); /* * RSA operation */ ret = (mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, input, buf) : mbedtls_rsa_private(ctx, f_rng, p_rng, input, buf); if (ret != 0) goto cleanup; /* * Unmask data and generate lHash */ mbedtls_md_init(&md_ctx); if ((ret = mbedtls_md_setup(&md_ctx, md_info, 0)) != 0) { mbedtls_md_free(&md_ctx); goto cleanup; } /* seed: Apply seedMask to maskedSeed */ if ((ret = mgf_mask(buf + 1, hlen, buf + hlen + 1, ilen - hlen - 1, &md_ctx)) != 0 || /* DB: Apply dbMask to maskedDB */ (ret = mgf_mask(buf + hlen + 1, ilen - hlen - 1, buf + 1, hlen, &md_ctx)) != 0) { mbedtls_md_free(&md_ctx); goto cleanup; } mbedtls_md_free(&md_ctx); /* Generate lHash */ if ((ret = mbedtls_md(md_info, label, label_len, lhash)) != 0) goto cleanup; /* * Check contents, in "constant-time" */ p = buf; bad = 0; bad |= *p++; /* First byte must be 0 */ p += hlen; /* Skip seed */ /* Check lHash */ for (i = 0; i < hlen; i++) bad |= lhash[i] ^ *p++; /* Get zero-padding len, but always read till end of buffer * (minus one, for the 01 byte) */ pad_len = 0; pad_done = 0; for (i = 0; i < ilen - 2 * hlen - 2; i++) { pad_done |= p[i]; pad_len += ((pad_done | (unsigned char) - pad_done) >> 7) ^ 1; } p += pad_len; bad |= *p++ ^ 0x01; /* * The only information "leaked" is whether the padding was correct or not * (eg, no data is copied if it was not correct). This meets the * recommendations in PKCS#1 v2.2: an opponent cannot distinguish between * the different error conditions. */ if (bad != 0) { ret = MBEDTLS_ERR_RSA_INVALID_PADDING; goto cleanup; } if (ilen - (p - buf) > output_max_len) { ret = MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE; goto cleanup; } *olen = ilen - (p - buf); if (*olen != 0) memcpy(output, p, *olen); ret = 0; cleanup: mbedtls_platform_zeroize(buf, sizeof(buf)); mbedtls_platform_zeroize(lhash, sizeof(lhash)); return (ret); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /** Turn zero-or-nonzero into zero-or-all-bits-one, without branches. * * \param value The value to analyze. * \return Zero if \p value is zero, otherwise all-bits-one. */ static unsigned all_or_nothing_int(unsigned value) { /* MSVC has a warning about unary minus on unsigned, but this is * well-defined and precisely what we want to do here */ #if defined(_MSC_VER) #pragma warning( push ) #pragma warning( disable : 4146 ) #endif return (- ((value | - value) >> (sizeof(value) * 8 - 1))); #if defined(_MSC_VER) #pragma warning( pop ) #endif } /** Check whether a size is out of bounds, without branches. * * This is equivalent to `size > max`, but is likely to be compiled to * to code using bitwise operation rather than a branch. * * \param size Size to check. * \param max Maximum desired value for \p size. * \return \c 0 if `size <= max`. * \return \c 1 if `size > max`. */ static unsigned size_greater_than(size_t size, size_t max) { /* Return the sign bit (1 for negative) of (max - size). */ return ((max - size) >> (sizeof(size_t) * 8 - 1)); } /** Choose between two integer values, without branches. * * This is equivalent to `cond ? if1 : if0`, but is likely to be compiled * to code using bitwise operation rather than a branch. * * \param cond Condition to test. * \param if1 Value to use if \p cond is nonzero. * \param if0 Value to use if \p cond is zero. * \return \c if1 if \p cond is nonzero, otherwise \c if0. */ static unsigned if_int(unsigned cond, unsigned if1, unsigned if0) { unsigned mask = all_or_nothing_int(cond); return ((mask & if1) | (~mask & if0)); } /** Shift some data towards the left inside a buffer without leaking * the length of the data through side channels. * * `mem_move_to_left(start, total, offset)` is functionally equivalent to * ``` * memmove(start, start + offset, total - offset); * memset(start + offset, 0, total - offset); * ``` * but it strives to use a memory access pattern (and thus total timing) * that does not depend on \p offset. This timing independence comes at * the expense of performance. * * \param start Pointer to the start of the buffer. * \param total Total size of the buffer. * \param offset Offset from which to copy \p total - \p offset bytes. */ static void mem_move_to_left(void *start, size_t total, size_t offset) { volatile unsigned char *buf = start; size_t i, n; if (total == 0) return; for (i = 0; i < total; i++) { unsigned no_op = size_greater_than(total - offset, i); /* The first `total - offset` passes are a no-op. The last * `offset` passes shift the data one byte to the left and * zero out the last byte. */ for (n = 0; n < total - 1; n++) { unsigned char current = buf[n]; unsigned char next = buf[n + 1]; buf[n] = if_int(no_op, current, next); } buf[total - 1] = if_int(no_op, buf[total - 1], 0); } } /* * Implementation of the PKCS#1 v2.1 RSAES-PKCS1-V1_5-DECRYPT function */ int mbedtls_rsa_rsaes_pkcs1_v15_decrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t ilen, i, plaintext_max_size; unsigned char buf[MBEDTLS_MPI_MAX_SIZE]; /* The following variables take sensitive values: their value must * not leak into the observable behavior of the function other than * the designated outputs (output, olen, return value). Otherwise * this would open the execution of the function to * side-channel-based variants of the Bleichenbacher padding oracle * attack. Potential side channels include overall timing, memory * access patterns (especially visible to an adversary who has access * to a shared memory cache), and branches (especially visible to * an adversary who has access to a shared code cache or to a shared * branch predictor). */ size_t pad_count = 0; unsigned bad = 0; unsigned char pad_done = 0; size_t plaintext_size = 0; unsigned output_too_large; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(output_max_len == 0 || output != NULL); RSA_VALIDATE_RET(input != NULL); RSA_VALIDATE_RET(olen != NULL); ilen = ctx->len; plaintext_max_size = (output_max_len > ilen - 11 ? ilen - 11 : output_max_len); if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V15) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); if (ilen < 16 || ilen > sizeof(buf)) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); ret = (mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, input, buf) : mbedtls_rsa_private(ctx, f_rng, p_rng, input, buf); if (ret != 0) goto cleanup; /* Check and get padding length in constant time and constant * memory trace. The first byte must be 0. */ bad |= buf[0]; if (mode == MBEDTLS_RSA_PRIVATE) { /* Decode EME-PKCS1-v1_5 padding: 0x00 || 0x02 || PS || 0x00 * where PS must be at least 8 nonzero bytes. */ bad |= buf[1] ^ MBEDTLS_RSA_CRYPT; /* Read the whole buffer. Set pad_done to nonzero if we find * the 0x00 byte and remember the padding length in pad_count. */ for (i = 2; i < ilen; i++) { pad_done |= ((buf[i] | (unsigned char) - buf[i]) >> 7) ^ 1; pad_count += ((pad_done | (unsigned char) - pad_done) >> 7) ^ 1; } } else { /* Decode EMSA-PKCS1-v1_5 padding: 0x00 || 0x01 || PS || 0x00 * where PS must be at least 8 bytes with the value 0xFF. */ bad |= buf[1] ^ MBEDTLS_RSA_SIGN; /* Read the whole buffer. Set pad_done to nonzero if we find * the 0x00 byte and remember the padding length in pad_count. * If there's a non-0xff byte in the padding, the padding is bad. */ for (i = 2; i < ilen; i++) { pad_done |= if_int(buf[i], 0, 1); pad_count += if_int(pad_done, 0, 1); bad |= if_int(pad_done, 0, buf[i] ^ 0xFF); } } /* If pad_done is still zero, there's no data, only unfinished padding. */ bad |= if_int(pad_done, 0, 1); /* There must be at least 8 bytes of padding. */ bad |= size_greater_than(8, pad_count); /* If the padding is valid, set plaintext_size to the number of * remaining bytes after stripping the padding. If the padding * is invalid, avoid leaking this fact through the size of the * output: use the maximum message size that fits in the output * buffer. Do it without branches to avoid leaking the padding * validity through timing. RSA keys are small enough that all the * size_t values involved fit in unsigned int. */ plaintext_size = if_int(bad, (unsigned) plaintext_max_size, (unsigned)(ilen - pad_count - 3)); /* Set output_too_large to 0 if the plaintext fits in the output * buffer and to 1 otherwise. */ output_too_large = size_greater_than(plaintext_size, plaintext_max_size); /* Set ret without branches to avoid timing attacks. Return: * - INVALID_PADDING if the padding is bad (bad != 0). * - OUTPUT_TOO_LARGE if the padding is good but the decrypted * plaintext does not fit in the output buffer. * - 0 if the padding is correct. */ ret = - (int) if_int(bad, - MBEDTLS_ERR_RSA_INVALID_PADDING, if_int(output_too_large, - MBEDTLS_ERR_RSA_OUTPUT_TOO_LARGE, 0)); /* If the padding is bad or the plaintext is too large, zero the * data that we're about to copy to the output buffer. * We need to copy the same amount of data * from the same buffer whether the padding is good or not to * avoid leaking the padding validity through overall timing or * through memory or cache access patterns. */ bad = all_or_nothing_int(bad | output_too_large); for (i = 11; i < ilen; i++) buf[i] &= ~bad; /* If the plaintext is too large, truncate it to the buffer size. * Copy anyway to avoid revealing the length through timing, because * revealing the length is as bad as revealing the padding validity * for a Bleichenbacher attack. */ plaintext_size = if_int(output_too_large, (unsigned) plaintext_max_size, (unsigned) plaintext_size); /* Move the plaintext to the leftmost position where it can start in * the working buffer, i.e. make it start plaintext_max_size from * the end of the buffer. Do this with a memory access trace that * does not depend on the plaintext size. After this move, the * starting location of the plaintext is no longer sensitive * information. */ mem_move_to_left(buf + ilen - plaintext_max_size, plaintext_max_size, plaintext_max_size - plaintext_size); /* Finally copy the decrypted plaintext plus trailing zeros into the output * buffer. If output_max_len is 0, then output may be an invalid pointer * and the result of memcpy() would be undefined; prevent undefined * behavior making sure to depend only on output_max_len (the size of the * user-provided output buffer), which is independent from plaintext * length, validity of padding, success of the decryption, and other * secrets. */ if (output_max_len != 0) memcpy(output, buf + ilen - plaintext_max_size, plaintext_max_size); /* Report the amount of data we copied to the output buffer. In case * of errors (bad padding or output too large), the value of *olen * when this function returns is not specified. Making it equivalent * to the good case limits the risks of leaking the padding validity. */ *olen = plaintext_size; cleanup: mbedtls_platform_zeroize(buf, sizeof(buf)); return (ret); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Do an RSA operation, then remove the message padding */ int mbedtls_rsa_pkcs1_decrypt(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, size_t *olen, const unsigned char *input, unsigned char *output, size_t output_max_len) { RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(output_max_len == 0 || output != NULL); RSA_VALIDATE_RET(input != NULL); RSA_VALIDATE_RET(olen != NULL); switch (ctx->padding) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsaes_pkcs1_v15_decrypt(ctx, f_rng, p_rng, mode, olen, input, output, output_max_len); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsaes_oaep_decrypt(ctx, f_rng, p_rng, mode, NULL, 0, olen, input, output, output_max_len); #endif default: return (MBEDTLS_ERR_RSA_INVALID_PADDING); } } #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSASSA-PSS-SIGN function */ int mbedtls_rsa_rsassa_pss_sign(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig) { size_t olen; unsigned char *p = sig; unsigned char salt[MBEDTLS_MD_MAX_SIZE]; size_t slen, min_slen, hlen, offset = 0; int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t msb; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); RSA_VALIDATE_RET(sig != NULL); if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V21) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); if (f_rng == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); olen = ctx->len; if (md_alg != MBEDTLS_MD_NONE) { /* Gather length of hash to sign */ md_info = mbedtls_md_info_from_type(md_alg); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hashlen = mbedtls_md_get_size(md_info); } md_info = mbedtls_md_info_from_type((mbedtls_md_type_t) ctx->hash_id); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hlen = mbedtls_md_get_size(md_info); /* Calculate the largest possible salt length. Normally this is the hash * length, which is the maximum length the salt can have. If there is not * enough room, use the maximum salt length that fits. The constraint is * that the hash length plus the salt length plus 2 bytes must be at most * the key length. This complies with FIPS 186-4 §5.5 (e) and RFC 8017 * (PKCS#1 v2.2) §9.1.1 step 3. */ min_slen = hlen - 2; if (olen < hlen + min_slen + 2) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); else if (olen >= hlen + hlen + 2) slen = hlen; else slen = olen - hlen - 2; memset(sig, 0, olen); /* Generate salt of length slen */ if ((ret = f_rng(p_rng, salt, slen)) != 0) return (MBEDTLS_ERR_RSA_RNG_FAILED + ret); /* Note: EMSA-PSS encoding is over the length of N - 1 bits */ msb = mbedtls_mpi_bitlen(&ctx->N) - 1; p += olen - hlen - slen - 2; *p++ = 0x01; memcpy(p, salt, slen); p += slen; mbedtls_md_init(&md_ctx); if ((ret = mbedtls_md_setup(&md_ctx, md_info, 0)) != 0) goto exit; /* Generate H = Hash( M' ) */ if ((ret = mbedtls_md_starts(&md_ctx)) != 0) goto exit; if ((ret = mbedtls_md_update(&md_ctx, p, 8)) != 0) goto exit; if ((ret = mbedtls_md_update(&md_ctx, hash, hashlen)) != 0) goto exit; if ((ret = mbedtls_md_update(&md_ctx, salt, slen)) != 0) goto exit; if ((ret = mbedtls_md_finish(&md_ctx, p)) != 0) goto exit; /* Compensate for boundary condition when applying mask */ if (msb % 8 == 0) offset = 1; /* maskedDB: Apply dbMask to DB */ if ((ret = mgf_mask(sig + offset, olen - hlen - 1 - offset, p, hlen, &md_ctx)) != 0) goto exit; msb = mbedtls_mpi_bitlen(&ctx->N) - 1; sig[0] &= 0xFF >> (olen * 8 - msb); p += hlen; *p++ = 0xBC; mbedtls_platform_zeroize(salt, sizeof(salt)); exit: mbedtls_md_free(&md_ctx); if (ret != 0) return (ret); return ((mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, sig, sig) : mbedtls_rsa_private(ctx, f_rng, p_rng, sig, sig)); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /* * Implementation of the PKCS#1 v2.1 RSASSA-PKCS1-V1_5-SIGN function */ /* Construct a PKCS v1.5 encoding of a hashed message * * This is used both for signature generation and verification. * * Parameters: * - md_alg: Identifies the hash algorithm used to generate the given hash; * MBEDTLS_MD_NONE if raw data is signed. * - hashlen: Length of hash in case hashlen is MBEDTLS_MD_NONE. * - hash: Buffer containing the hashed message or the raw data. * - dst_len: Length of the encoded message. * - dst: Buffer to hold the encoded message. * * Assumptions: * - hash has size hashlen if md_alg == MBEDTLS_MD_NONE. * - hash has size corresponding to md_alg if md_alg != MBEDTLS_MD_NONE. * - dst points to a buffer of size at least dst_len. * */ static int rsa_rsassa_pkcs1_v15_encode(mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, size_t dst_len, unsigned char *dst) { size_t oid_size = 0; size_t nb_pad = dst_len; unsigned char *p = dst; const char *oid = NULL; /* Are we signing hashed or raw data? */ if (md_alg != MBEDTLS_MD_NONE) { const mbedtls_md_info_t *md_info = mbedtls_md_info_from_type(md_alg); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); if (mbedtls_oid_get_oid_by_md(md_alg, &oid, &oid_size) != 0) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hashlen = mbedtls_md_get_size(md_info); /* Double-check that 8 + hashlen + oid_size can be used as a * 1-byte ASN.1 length encoding and that there's no overflow. */ if (8 + hashlen + oid_size >= 0x80 || 10 + hashlen < hashlen || 10 + hashlen + oid_size < 10 + hashlen) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); /* * Static bounds check: * - Need 10 bytes for five tag-length pairs. * (Insist on 1-byte length encodings to protect against variants of * Bleichenbacher's forgery attack against lax PKCS#1v1.5 verification) * - Need hashlen bytes for hash * - Need oid_size bytes for hash alg OID. */ if (nb_pad < 10 + hashlen + oid_size) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); nb_pad -= 10 + hashlen + oid_size; } else { if (nb_pad < hashlen) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); nb_pad -= hashlen; } /* Need space for signature header and padding delimiter (3 bytes), * and 8 bytes for the minimal padding */ if (nb_pad < 3 + 8) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); nb_pad -= 3; /* Now nb_pad is the amount of memory to be filled * with padding, and at least 8 bytes long. */ /* Write signature header and padding */ *p++ = 0; *p++ = MBEDTLS_RSA_SIGN; memset(p, 0xFF, nb_pad); p += nb_pad; *p++ = 0; /* Are we signing raw data? */ if (md_alg == MBEDTLS_MD_NONE) { memcpy(p, hash, hashlen); return (0); } /* Signing hashed data, add corresponding ASN.1 structure * * DigestInfo ::= SEQUENCE { * digestAlgorithm DigestAlgorithmIdentifier, * digest Digest } * DigestAlgorithmIdentifier ::= AlgorithmIdentifier * Digest ::= OCTET STRING * * Schematic: * TAG-SEQ + LEN [ TAG-SEQ + LEN [ TAG-OID + LEN [ OID ] * TAG-NULL + LEN [ NULL ] ] * TAG-OCTET + LEN [ HASH ] ] */ *p++ = MBEDTLS_ASN1_SEQUENCE | MBEDTLS_ASN1_CONSTRUCTED; *p++ = (unsigned char)(0x08 + oid_size + hashlen); *p++ = MBEDTLS_ASN1_SEQUENCE | MBEDTLS_ASN1_CONSTRUCTED; *p++ = (unsigned char)(0x04 + oid_size); *p++ = MBEDTLS_ASN1_OID; *p++ = (unsigned char) oid_size; memcpy(p, oid, oid_size); p += oid_size; *p++ = MBEDTLS_ASN1_NULL; *p++ = 0x00; *p++ = MBEDTLS_ASN1_OCTET_STRING; *p++ = (unsigned char) hashlen; memcpy(p, hash, hashlen); p += hashlen; /* Just a sanity-check, should be automatic * after the initial bounds check. */ if (p != dst + dst_len) { mbedtls_platform_zeroize(dst, dst_len); return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); } return (0); } /* * Do an RSA operation to sign the message digest */ int mbedtls_rsa_rsassa_pkcs1_v15_sign(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; unsigned char *sig_try = NULL, *verif = NULL; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); RSA_VALIDATE_RET(sig != NULL); if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V15) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); /* * Prepare PKCS1-v1.5 encoding (padding and hash identifier) */ if ((ret = rsa_rsassa_pkcs1_v15_encode(md_alg, hashlen, hash, ctx->len, sig)) != 0) return (ret); /* * Call respective RSA primitive */ if (mode == MBEDTLS_RSA_PUBLIC) { /* Skip verification on a public key operation */ return (mbedtls_rsa_public(ctx, sig, sig)); } /* Private key operation * * In order to prevent Lenstra's attack, make the signature in a * temporary buffer and check it before returning it. */ sig_try = mbedtls_calloc(1, ctx->len); if (sig_try == NULL) return (MBEDTLS_ERR_MPI_ALLOC_FAILED); verif = mbedtls_calloc(1, ctx->len); if (verif == NULL) { mbedtls_free(sig_try); return (MBEDTLS_ERR_MPI_ALLOC_FAILED); } MBEDTLS_MPI_CHK(mbedtls_rsa_private(ctx, f_rng, p_rng, sig, sig_try)); MBEDTLS_MPI_CHK(mbedtls_rsa_public(ctx, sig_try, verif)); if (mbedtls_safer_memcmp(verif, sig, ctx->len) != 0) { ret = MBEDTLS_ERR_RSA_PRIVATE_FAILED; goto cleanup; } memcpy(sig, sig_try, ctx->len); cleanup: mbedtls_free(sig_try); mbedtls_free(verif); return (ret); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Do an RSA operation to sign the message digest */ int mbedtls_rsa_pkcs1_sign(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, unsigned char *sig) { RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); RSA_VALIDATE_RET(sig != NULL); switch (ctx->padding) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsassa_pkcs1_v15_sign(ctx, f_rng, p_rng, mode, md_alg, hashlen, hash, sig); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsassa_pss_sign(ctx, f_rng, p_rng, mode, md_alg, hashlen, hash, sig); #endif default: return (MBEDTLS_ERR_RSA_INVALID_PADDING); } } #if defined(MBEDTLS_PKCS1_V21) /* * Implementation of the PKCS#1 v2.1 RSASSA-PSS-VERIFY function */ int mbedtls_rsa_rsassa_pss_verify_ext(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, mbedtls_md_type_t mgf1_hash_id, int expected_salt_len, const unsigned char *sig) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; size_t siglen; unsigned char *p; unsigned char *hash_start; unsigned char result[MBEDTLS_MD_MAX_SIZE]; unsigned char zeros[8]; unsigned int hlen; size_t observed_salt_len, msb; const mbedtls_md_info_t *md_info; mbedtls_md_context_t md_ctx; unsigned char buf[MBEDTLS_MPI_MAX_SIZE]; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(sig != NULL); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V21) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); siglen = ctx->len; if (siglen < 16 || siglen > sizeof(buf)) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); ret = (mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, sig, buf) : mbedtls_rsa_private(ctx, f_rng, p_rng, sig, buf); if (ret != 0) return (ret); p = buf; if (buf[siglen - 1] != 0xBC) return (MBEDTLS_ERR_RSA_INVALID_PADDING); if (md_alg != MBEDTLS_MD_NONE) { /* Gather length of hash to sign */ md_info = mbedtls_md_info_from_type(md_alg); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hashlen = mbedtls_md_get_size(md_info); } md_info = mbedtls_md_info_from_type(mgf1_hash_id); if (md_info == NULL) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hlen = mbedtls_md_get_size(md_info); memset(zeros, 0, 8); /* * Note: EMSA-PSS verification is over the length of N - 1 bits */ msb = mbedtls_mpi_bitlen(&ctx->N) - 1; if (buf[0] >> (8 - siglen * 8 + msb)) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); /* Compensate for boundary condition when applying mask */ if (msb % 8 == 0) { p++; siglen -= 1; } if (siglen < hlen + 2) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); hash_start = p + siglen - hlen - 1; mbedtls_md_init(&md_ctx); if ((ret = mbedtls_md_setup(&md_ctx, md_info, 0)) != 0) goto exit; ret = mgf_mask(p, siglen - hlen - 1, hash_start, hlen, &md_ctx); if (ret != 0) goto exit; buf[0] &= 0xFF >> (siglen * 8 - msb); while (p < hash_start - 1 && *p == 0) p++; if (*p++ != 0x01) { ret = MBEDTLS_ERR_RSA_INVALID_PADDING; goto exit; } observed_salt_len = hash_start - p; if (expected_salt_len != MBEDTLS_RSA_SALT_LEN_ANY && observed_salt_len != (size_t) expected_salt_len) { ret = MBEDTLS_ERR_RSA_INVALID_PADDING; goto exit; } /* * Generate H = Hash( M' ) */ ret = mbedtls_md_starts(&md_ctx); if (ret != 0) goto exit; ret = mbedtls_md_update(&md_ctx, zeros, 8); if (ret != 0) goto exit; ret = mbedtls_md_update(&md_ctx, hash, hashlen); if (ret != 0) goto exit; ret = mbedtls_md_update(&md_ctx, p, observed_salt_len); if (ret != 0) goto exit; ret = mbedtls_md_finish(&md_ctx, result); if (ret != 0) goto exit; if (memcmp(hash_start, result, hlen) != 0) { ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; goto exit; } exit: mbedtls_md_free(&md_ctx); return (ret); } /* * Simplified PKCS#1 v2.1 RSASSA-PSS-VERIFY function */ int mbedtls_rsa_rsassa_pss_verify(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig) { mbedtls_md_type_t mgf1_hash_id; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(sig != NULL); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); mgf1_hash_id = (ctx->hash_id != MBEDTLS_MD_NONE) ? (mbedtls_md_type_t) ctx->hash_id : md_alg; return (mbedtls_rsa_rsassa_pss_verify_ext(ctx, f_rng, p_rng, mode, md_alg, hashlen, hash, mgf1_hash_id, MBEDTLS_RSA_SALT_LEN_ANY, sig)); } #endif /* MBEDTLS_PKCS1_V21 */ #if defined(MBEDTLS_PKCS1_V15) /* * Implementation of the PKCS#1 v2.1 RSASSA-PKCS1-v1_5-VERIFY function */ int mbedtls_rsa_rsassa_pkcs1_v15_verify(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig) { int ret = 0; size_t sig_len; unsigned char *encoded = NULL, *encoded_expected = NULL; RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(sig != NULL); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); sig_len = ctx->len; if (mode == MBEDTLS_RSA_PRIVATE && ctx->padding != MBEDTLS_RSA_PKCS_V15) return (MBEDTLS_ERR_RSA_BAD_INPUT_DATA); /* * Prepare expected PKCS1 v1.5 encoding of hash. */ if ((encoded = mbedtls_calloc(1, sig_len)) == NULL || (encoded_expected = mbedtls_calloc(1, sig_len)) == NULL) { ret = MBEDTLS_ERR_MPI_ALLOC_FAILED; goto cleanup; } if ((ret = rsa_rsassa_pkcs1_v15_encode(md_alg, hashlen, hash, sig_len, encoded_expected)) != 0) goto cleanup; /* * Apply RSA primitive to get what should be PKCS1 encoded hash. */ ret = (mode == MBEDTLS_RSA_PUBLIC) ? mbedtls_rsa_public(ctx, sig, encoded) : mbedtls_rsa_private(ctx, f_rng, p_rng, sig, encoded); if (ret != 0) goto cleanup; /* * Compare */ if ((ret = mbedtls_safer_memcmp(encoded, encoded_expected, sig_len)) != 0) { ret = MBEDTLS_ERR_RSA_VERIFY_FAILED; goto cleanup; } cleanup: if (encoded != NULL) { mbedtls_platform_zeroize(encoded, sig_len); mbedtls_free(encoded); } if (encoded_expected != NULL) { mbedtls_platform_zeroize(encoded_expected, sig_len); mbedtls_free(encoded_expected); } return (ret); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Do an RSA operation and check the message digest */ int mbedtls_rsa_pkcs1_verify(mbedtls_rsa_context *ctx, int (*f_rng)(void *, unsigned char *, size_t), void *p_rng, int mode, mbedtls_md_type_t md_alg, unsigned int hashlen, const unsigned char *hash, const unsigned char *sig) { RSA_VALIDATE_RET(ctx != NULL); RSA_VALIDATE_RET(mode == MBEDTLS_RSA_PRIVATE || mode == MBEDTLS_RSA_PUBLIC); RSA_VALIDATE_RET(sig != NULL); RSA_VALIDATE_RET((md_alg == MBEDTLS_MD_NONE && hashlen == 0) || hash != NULL); switch (ctx->padding) { #if defined(MBEDTLS_PKCS1_V15) case MBEDTLS_RSA_PKCS_V15: return mbedtls_rsa_rsassa_pkcs1_v15_verify(ctx, f_rng, p_rng, mode, md_alg, hashlen, hash, sig); #endif #if defined(MBEDTLS_PKCS1_V21) case MBEDTLS_RSA_PKCS_V21: return mbedtls_rsa_rsassa_pss_verify(ctx, f_rng, p_rng, mode, md_alg, hashlen, hash, sig); #endif default: return (MBEDTLS_ERR_RSA_INVALID_PADDING); } } /* * Copy the components of an RSA key */ int mbedtls_rsa_copy(mbedtls_rsa_context *dst, const mbedtls_rsa_context *src) { int ret = MBEDTLS_ERR_ERROR_CORRUPTION_DETECTED; RSA_VALIDATE_RET(dst != NULL); RSA_VALIDATE_RET(src != NULL); dst->len = src->len; MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->N, &src->N)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->E, &src->E)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->D, &src->D)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->P, &src->P)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->Q, &src->Q)); #if !defined(MBEDTLS_RSA_NO_CRT) MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->DP, &src->DP)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->DQ, &src->DQ)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->QP, &src->QP)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->RP, &src->RP)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->RQ, &src->RQ)); #endif MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->RN, &src->RN)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->Vi, &src->Vi)); MBEDTLS_MPI_CHK(mbedtls_mpi_copy(&dst->Vf, &src->Vf)); dst->padding = src->padding; dst->hash_id = src->hash_id; cleanup: if (ret != 0) mbedtls_rsa_free(dst); return (ret); } /* * Free the components of an RSA key */ void mbedtls_rsa_free(mbedtls_rsa_context *ctx) { if (ctx == NULL) return; mbedtls_mpi_free(&ctx->Vi); mbedtls_mpi_free(&ctx->Vf); mbedtls_mpi_free(&ctx->RN); mbedtls_mpi_free(&ctx->D); mbedtls_mpi_free(&ctx->Q); mbedtls_mpi_free(&ctx->P); mbedtls_mpi_free(&ctx->E); mbedtls_mpi_free(&ctx->N); #if !defined(MBEDTLS_RSA_NO_CRT) mbedtls_mpi_free(&ctx->RQ); mbedtls_mpi_free(&ctx->RP); mbedtls_mpi_free(&ctx->QP); mbedtls_mpi_free(&ctx->DQ); mbedtls_mpi_free(&ctx->DP); #endif /* MBEDTLS_RSA_NO_CRT */ #if defined(MBEDTLS_THREADING_C) /* Free the mutex, but only if it hasn't been freed already. */ if (ctx->ver != 0) { mbedtls_mutex_free(&ctx->mutex); ctx->ver = 0; } #endif } #endif /* !MBEDTLS_RSA_ALT */ #if defined(MBEDTLS_SELF_TEST) #include "mbedtls/sha1.h" /* * Example RSA-1024 keypair, for test purposes */ #define KEY_LEN 128 #define RSA_N "9292758453063D803DD603D5E777D788" \ "8ED1D5BF35786190FA2F23EBC0848AEA" \ "DDA92CA6C3D80B32C4D109BE0F36D6AE" \ "7130B9CED7ACDF54CFC7555AC14EEBAB" \ "93A89813FBF3C4F8066D2D800F7C38A8" \ "1AE31942917403FF4946B0A83D3D3E05" \ "EE57C6F5F5606FB5D4BC6CD34EE0801A" \ "5E94BB77B07507233A0BC7BAC8F90F79" #define RSA_E "10001" #define RSA_D "24BF6185468786FDD303083D25E64EFC" \ "66CA472BC44D253102F8B4A9D3BFA750" \ "91386C0077937FE33FA3252D28855837" \ "AE1B484A8A9A45F7EE8C0C634F99E8CD" \ "DF79C5CE07EE72C7F123142198164234" \ "CABB724CF78B8173B9F880FC86322407" \ "AF1FEDFDDE2BEB674CA15F3E81A1521E" \ "071513A1E85B5DFA031F21ECAE91A34D" #define RSA_P "C36D0EB7FCD285223CFB5AABA5BDA3D8" \ "2C01CAD19EA484A87EA4377637E75500" \ "FCB2005C5C7DD6EC4AC023CDA285D796" \ "C3D9E75E1EFC42488BB4F1D13AC30A57" #define RSA_Q "C000DF51A7C77AE8D7C7370C1FF55B69" \ "E211C2B9E5DB1ED0BF61D0D9899620F4" \ "910E4168387E3C30AA1E00C339A79508" \ "8452DD96A9A5EA5D9DCA68DA636032AF" #define PT_LEN 24 #define RSA_PT "\xAA\xBB\xCC\x03\x02\x01\x00\xFF\xFF\xFF\xFF\xFF" \ "\x11\x22\x33\x0A\x0B\x0C\xCC\xDD\xDD\xDD\xDD\xDD" #if defined(MBEDTLS_PKCS1_V15) static int myrand(void *rng_state, unsigned char *output, size_t len) { #if !defined(__OpenBSD__) && !defined(__NetBSD__) size_t i; if (rng_state != NULL) rng_state = NULL; for (i = 0; i < len; ++i) output[i] = rand(); #else if (rng_state != NULL) rng_state = NULL; arc4random_buf(output, len); #endif /* !OpenBSD && !NetBSD */ return (0); } #endif /* MBEDTLS_PKCS1_V15 */ /* * Checkup routine */ int mbedtls_rsa_self_test(int verbose) { int ret = 0; #if defined(MBEDTLS_PKCS1_V15) size_t len; mbedtls_rsa_context rsa; unsigned char rsa_plaintext[PT_LEN]; unsigned char rsa_decrypted[PT_LEN]; unsigned char rsa_ciphertext[KEY_LEN]; #if defined(MBEDTLS_SHA1_C) unsigned char sha1sum[20]; #endif mbedtls_mpi K; mbedtls_mpi_init(&K); mbedtls_rsa_init(&rsa, MBEDTLS_RSA_PKCS_V15, 0); MBEDTLS_MPI_CHK(mbedtls_mpi_read_string(&K, 16, RSA_N)); MBEDTLS_MPI_CHK(mbedtls_rsa_import(&rsa, &K, NULL, NULL, NULL, NULL)); MBEDTLS_MPI_CHK(mbedtls_mpi_read_string(&K, 16, RSA_P)); MBEDTLS_MPI_CHK(mbedtls_rsa_import(&rsa, NULL, &K, NULL, NULL, NULL)); MBEDTLS_MPI_CHK(mbedtls_mpi_read_string(&K, 16, RSA_Q)); MBEDTLS_MPI_CHK(mbedtls_rsa_import(&rsa, NULL, NULL, &K, NULL, NULL)); MBEDTLS_MPI_CHK(mbedtls_mpi_read_string(&K, 16, RSA_D)); MBEDTLS_MPI_CHK(mbedtls_rsa_import(&rsa, NULL, NULL, NULL, &K, NULL)); MBEDTLS_MPI_CHK(mbedtls_mpi_read_string(&K, 16, RSA_E)); MBEDTLS_MPI_CHK(mbedtls_rsa_import(&rsa, NULL, NULL, NULL, NULL, &K)); MBEDTLS_MPI_CHK(mbedtls_rsa_complete(&rsa)); if (verbose != 0) mbedtls_printf(" RSA key validation: "); if (mbedtls_rsa_check_pubkey(&rsa) != 0 || mbedtls_rsa_check_privkey(&rsa) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); ret = 1; goto cleanup; } if (verbose != 0) mbedtls_printf("passed\n PKCS#1 encryption : "); memcpy(rsa_plaintext, RSA_PT, PT_LEN); if (mbedtls_rsa_pkcs1_encrypt(&rsa, myrand, NULL, MBEDTLS_RSA_PUBLIC, PT_LEN, rsa_plaintext, rsa_ciphertext) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); ret = 1; goto cleanup; } if (verbose != 0) mbedtls_printf("passed\n PKCS#1 decryption : "); if (mbedtls_rsa_pkcs1_decrypt(&rsa, myrand, NULL, MBEDTLS_RSA_PRIVATE, &len, rsa_ciphertext, rsa_decrypted, sizeof(rsa_decrypted)) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); ret = 1; goto cleanup; } if (memcmp(rsa_decrypted, rsa_plaintext, len) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); ret = 1; goto cleanup; } if (verbose != 0) mbedtls_printf("passed\n"); #if defined(MBEDTLS_SHA1_C) if (verbose != 0) mbedtls_printf(" PKCS#1 data sign : "); if (mbedtls_sha1_ret(rsa_plaintext, PT_LEN, sha1sum) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); return (1); } if (mbedtls_rsa_pkcs1_sign(&rsa, myrand, NULL, MBEDTLS_RSA_PRIVATE, MBEDTLS_MD_SHA1, 0, sha1sum, rsa_ciphertext) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); ret = 1; goto cleanup; } if (verbose != 0) mbedtls_printf("passed\n PKCS#1 sig. verify: "); if (mbedtls_rsa_pkcs1_verify(&rsa, NULL, NULL, MBEDTLS_RSA_PUBLIC, MBEDTLS_MD_SHA1, 0, sha1sum, rsa_ciphertext) != 0) { if (verbose != 0) mbedtls_printf("failed\n"); ret = 1; goto cleanup; } if (verbose != 0) mbedtls_printf("passed\n"); #endif /* MBEDTLS_SHA1_C */ if (verbose != 0) mbedtls_printf("\n"); cleanup: mbedtls_mpi_free(&K); mbedtls_rsa_free(&rsa); #else /* MBEDTLS_PKCS1_V15 */ ((void) verbose); #endif /* MBEDTLS_PKCS1_V15 */ return (ret); } #endif /* MBEDTLS_SELF_TEST */ #endif /* MBEDTLS_RSA_C */