mirror of
https://github.com/RfidResearchGroup/proxmark3.git
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78 lines
2.3 KiB
C
78 lines
2.3 KiB
C
/*
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* (c) 2015-2017 Marcos Del Sol Vives
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* (c) 2016 javiMaD
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*
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* SPDX-License-Identifier: MIT
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*/
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#include "drbg.h"
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#include <assert.h>
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#include <string.h>
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#include <mbedtls/md.h>
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void nfc3d_drbg_init(nfc3d_drbg_ctx *ctx, const uint8_t *hmacKey, size_t hmacKeySize, const uint8_t *seed, size_t seedSize) {
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assert(ctx != NULL);
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assert(hmacKey != NULL);
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assert(seed != NULL);
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assert(seedSize <= NFC3D_DRBG_MAX_SEED_SIZE);
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// Initialize primitives
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ctx->used = false;
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ctx->iteration = 0;
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ctx->bufferSize = sizeof(ctx->iteration) + seedSize;
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// The 16-bit counter is prepended to the seed when hashing, so we'll leave 2 bytes at the start
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memcpy(ctx->buffer + sizeof(uint16_t), seed, seedSize);
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// Initialize underlying HMAC context
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mbedtls_md_init(&ctx->hmacCtx);
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mbedtls_md_setup(&ctx->hmacCtx, mbedtls_md_info_from_type(MBEDTLS_MD_SHA256), 1);
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mbedtls_md_hmac_starts(&ctx->hmacCtx, hmacKey, hmacKeySize);
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}
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void nfc3d_drbg_step(nfc3d_drbg_ctx *ctx, uint8_t *output) {
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assert(ctx != NULL);
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assert(output != NULL);
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if (ctx->used) {
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// If used at least once, reinitialize the HMAC
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mbedtls_md_hmac_reset(&ctx->hmacCtx);
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} else {
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ctx->used = true;
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}
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// Store counter in big endian, and increment it
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ctx->buffer[0] = ctx->iteration >> 8;
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ctx->buffer[1] = ctx->iteration >> 0;
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ctx->iteration++;
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// Do HMAC magic
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mbedtls_md_hmac_update(&ctx->hmacCtx, ctx->buffer, ctx->bufferSize);
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mbedtls_md_hmac_finish(&ctx->hmacCtx, output);
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}
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void nfc3d_drbg_cleanup(nfc3d_drbg_ctx *ctx) {
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assert(ctx != NULL);
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mbedtls_md_free(&ctx->hmacCtx);
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}
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void nfc3d_drbg_generate_bytes(const uint8_t *hmacKey, size_t hmacKeySize, const uint8_t *seed, size_t seedSize, uint8_t *output, size_t outputSize) {
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uint8_t temp[NFC3D_DRBG_OUTPUT_SIZE];
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nfc3d_drbg_ctx rngCtx;
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nfc3d_drbg_init(&rngCtx, hmacKey, hmacKeySize, seed, seedSize);
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while (outputSize > 0) {
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if (outputSize < NFC3D_DRBG_OUTPUT_SIZE) {
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nfc3d_drbg_step(&rngCtx, temp);
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memcpy(output, temp, outputSize);
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break;
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}
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nfc3d_drbg_step(&rngCtx, output);
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output += NFC3D_DRBG_OUTPUT_SIZE;
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outputSize -= NFC3D_DRBG_OUTPUT_SIZE;
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}
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nfc3d_drbg_cleanup(&rngCtx);
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}
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