Fix XML CDATA injection (credits to @andreymal for the report)

crates/common/src/manager/boot.rs

@@ -5,7 +5,6 @@
  */
 
 use std::{
-    collections::BTreeMap,
     net::{IpAddr, Ipv4Addr},
     path::PathBuf,
     sync::Arc,

crates/dav-proto/src/responses/mod.rs

@@ -25,6 +25,10 @@ trait XmlEscape {
     fn write_escaped_to(&self, out: &mut impl Write) -> std::fmt::Result;
 }
 
+trait XmlCdataEscape {
+    fn write_cdata_escaped_to(&self, out: &mut impl Write) -> std::fmt::Result;
+}
+
 impl<T: AsRef<str>> XmlEscape for T {
     fn write_escaped_to(&self, out: &mut impl Write) -> std::fmt::Result {
         let str = self.as_ref();
@@ -44,6 +48,30 @@ impl<T: AsRef<str>> XmlEscape for T {
     }
 }
 
+impl<T: AsRef<str>> XmlCdataEscape for T {
+    fn write_cdata_escaped_to(&self, out: &mut impl Write) -> std::fmt::Result {
+        let str = self.as_ref();
+        let mut last_ch = '\0';
+        let mut last_ch2 = '\0';
+
+        out.write_str("<![CDATA[")?;
+
+        for ch in str.chars() {
+            match ch {
+                '>' if last_ch == ']' && last_ch2 == ']' => {
+                    out.write_str("]]><![CDATA[>")?;
+                }
+                _ => out.write_char(ch)?,
+            }
+
+            last_ch2 = last_ch;
+            last_ch = ch;
+        }
+
+        out.write_str("]]>")
+    }
+}
+
 impl Display for Namespaces {
     fn fmt(&self, f: &mut std::fmt::Formatter<'_>) -> std::fmt::Result {
         f.write_str("xmlns:D=\"DAV:\"")?;
@@ -176,6 +204,7 @@ mod tests {
 
     use crate::{
         parser::{tokenizer::Tokenizer, Token},
+        responses::XmlCdataEscape,
         schema::{
             property::{
                 ActiveLock, CalDavProperty, CardDavProperty, DavValue, LockScope, Privilege,
@@ -199,6 +228,18 @@ mod tests {
         }
     }
 
+    impl From<ICalendar> for DavValue {
+        fn from(v: ICalendar) -> Self {
+            DavValue::ICalendar(v)
+        }
+    }
+
+    impl From<VCard> for DavValue {
+        fn from(v: VCard) -> Self {
+            DavValue::VCard(v)
+        }
+    }
+
     #[test]
     fn parse_responses() {
         for (num, test) in [
@@ -634,4 +675,30 @@ END:VCARD
             }
         }
     }
+
+    #[test]
+    fn escape_cdata() {
+        for (test, expected) in [
+            ("", "<![CDATA[]]>"),
+            ("hello", "<![CDATA[hello]]>"),
+            ("hello world", "<![CDATA[hello world]]>"),
+            ("<hello>", "<![CDATA[<hello>]]>"),
+            ("&hello;", "<![CDATA[&hello;]]>"),
+            ("'hello'", "<![CDATA['hello']]>"),
+            ("\"hello\"", "<![CDATA[\"hello\"]]>"),
+            ("<>&'\"", "<![CDATA[<>&'\"]]>"),
+            (">", "<![CDATA[>]]>"),
+            ("]]>]", "<![CDATA[]]]]><![CDATA[>]]]>"),
+            ("]]>", "<![CDATA[]]]]><![CDATA[>]]>"),
+            ("hello]]>world", "<![CDATA[hello]]]]><![CDATA[>world]]>"),
+            (
+                "hello]]><nasty-xml>pure-evil</nasty-xml>",
+                "<![CDATA[hello]]]]><![CDATA[><nasty-xml>pure-evil</nasty-xml>]]>",
+            ),
+        ] {
+            let mut output = String::new();
+            test.write_cdata_escaped_to(&mut output).unwrap();
+            assert_eq!(output, expected, "failed for input: {test:?}");
+        }
+    }
 }

crates/dav-proto/src/responses/property.rs

@@ -4,7 +4,7 @@
  * SPDX-License-Identifier: AGPL-3.0-only OR LicenseRef-SEL
  */
 
-use super::XmlEscape;
+use super::{XmlCdataEscape, XmlEscape};
 use crate::schema::{
     property::{
         ActiveLock, CalDavProperty, CardDavProperty, Comp, DavProperty, DavValue, LockDiscovery,
@@ -15,7 +15,6 @@ use crate::schema::{
     response::{Ace, AclRestrictions, Href, List, PropResponse, SupportedPrivilege},
     Namespace, Namespaces,
 };
-use calcard::{icalendar::ICalendar, vcard::VCard};
 use mail_parser::{
     parsers::fields::date::{DOW, MONTH},
     DateTime,
@@ -88,15 +87,7 @@ impl Display for DavValue {
             DavValue::ActiveLocks(v) => v.fmt(f),
             DavValue::LockEntries(v) => v.fmt(f),
             DavValue::ReportSets(v) => v.fmt(f),
-            DavValue::VCard(v) => {
-                write!(f, "<![CDATA[{v}]]>")
-            }
-            DavValue::ICalendar(v) => {
-                write!(f, "<![CDATA[{v}]]>")
-            }
-            DavValue::CData(v) => {
-                write!(f, "<![CDATA[{v}]]>")
-            }
+            DavValue::CData(v) => v.write_cdata_escaped_to(f),
             DavValue::Components(v) => v.fmt(f),
             DavValue::Collations(v) => v.fmt(f),
             DavValue::Href(v) => v.fmt(f),
@@ -145,7 +136,7 @@ impl Display for DavValue {
                 )
             }
             DavValue::Response(v) => v.fmt(f),
-            DavValue::Null => Ok(()),
+            DavValue::VCard(_) | DavValue::ICalendar(_) | DavValue::Null => Ok(()),
         }
     }
 }
@@ -353,18 +344,6 @@ impl From<Vec<SupportedCollation>> for DavValue {
     }
 }
 
-impl From<ICalendar> for DavValue {
-    fn from(v: ICalendar) -> Self {
-        DavValue::ICalendar(v)
-    }
-}
-
-impl From<VCard> for DavValue {
-    fn from(v: VCard) -> Self {
-        DavValue::VCard(v)
-    }
-}
-
 impl From<SupportedLock> for DavValue {
     fn from(v: SupportedLock) -> Self {
         DavValue::LockEntries(v.0)