Rust wrapper: require fixed length index buffers for SRTP/SRTCP

Author: holtrop-wolfssl

wolfcrypt/src/kdf.c

@@ -984,7 +984,7 @@ static int wc_srtp_kdf_derive_key(byte* block, int idxSz, byte label,
  * @param [in]  saltSz   Size of random in bytes.
  * @param [in]  kdrIdx   Key derivation rate. kdr = 0 when -1, otherwise
  *                       kdr = 2^kdrIdx.
- * @param [in]  index    Index value to XOR in.
+ * @param [in]  idx      Index value to XOR in.
  * @param [out] key1     First key. Label value of 0x00.
  * @param [in]  key1Sz   Size of first key in bytes.
  * @param [out] key2     Second key. Label value of 0x01.
@@ -1069,7 +1069,7 @@ int wc_SRTP_KDF(const byte* key, word32 keySz, const byte* salt, word32 saltSz,
  * @param [in]  saltSz   Size of random in bytes.
  * @param [in]  kdrIdx   Key derivation rate index. kdr = 0 when -1, otherwise
  *                       kdr = 2^kdrIdx. See wc_SRTP_KDF_kdr_to_idx()
- * @param [in]  index    Index value to XOR in.
+ * @param [in]  idx      Index value to XOR in.
  * @param [out] key1     First key. Label value of 0x03.
  * @param [in]  key1Sz   Size of first key in bytes.
  * @param [out] key2     Second key. Label value of 0x04.
@@ -1171,7 +1171,7 @@ int wc_SRTCP_KDF(const byte* key, word32 keySz, const byte* salt, word32 saltSz,
  * @param [in]  saltSz    Size of random in bytes.
  * @param [in]  kdrIdx    Key derivation rate index. kdr = 0 when -1, otherwise
  *                        kdr = 2^kdrIdx. See wc_SRTP_KDF_kdr_to_idx()
- * @param [in]  index     Index value to XOR in.
+ * @param [in]  idx       Index value to XOR in.
  * @param [in]  label     Label to use when deriving key.
  * @param [out] outKey    Derived key.
  * @param [in]  outKeySz  Size of derived key in bytes.
@@ -1244,7 +1244,7 @@ int wc_SRTP_KDF_label(const byte* key, word32 keySz, const byte* salt,
  * @param [in]  saltSz    Size of random in bytes.
  * @param [in]  kdrIdx    Key derivation rate index. kdr = 0 when -1, otherwise
  *                        kdr = 2^kdrIdx. See wc_SRTP_KDF_kdr_to_idx()
- * @param [in]  index     Index value to XOR in.
+ * @param [in]  idx       Index value to XOR in.
  * @param [in]  label     Label to use when deriving key.
  * @param [out] outKey    Derived key.
  * @param [in]  outKeySz  Size of derived key in bytes.

wrapper/rust/wolfssl-wolfcrypt/src/kdf.rs

@@ -43,6 +43,10 @@ pub const SRTCP_LABEL_SALT: u8 = sys::WC_SRTCP_LABEL_SALT as u8;
 pub const SRTP_LABEL_HDR_ENCRYPTION: u8 = sys::WC_SRTP_LABEL_HDR_ENCRYPTION as u8;
 #[cfg(kdf_srtp)]
 pub const SRTP_LABEL_HDR_SALT: u8 = sys::WC_SRTP_LABEL_HDR_SALT as u8;
+#[cfg(kdf_srtp)]
+pub const SRTP_INDEX_LEN: usize = sys::WC_SRTP_INDEX_LEN as usize;
+#[cfg(kdf_srtp)]
+pub const SRTCP_INDEX_LEN: usize = sys::WC_SRTCP_INDEX_LEN as usize;
 
 /// Implement Password Based Key Derivation Function 2 (PBKDF2) converting an
 /// input password with a concatenated salt into a more secure key which is
@@ -582,13 +586,8 @@ pub fn ssh_kdf(typ: i32, key_id: u8, k: &[u8], h: &[u8], session_id: &[u8], key:
 /// }
 /// ```
 #[cfg(kdf_srtp)]
-pub fn srtp_kdf(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
+pub fn srtp_kdf(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8; SRTP_INDEX_LEN],
         key1: &mut [u8], key2: &mut [u8], key3: &mut [u8]) -> Result<(), i32> {
-    if !(kdr_index == -1 || (0 <= kdr_index && (kdr_index as usize) <= idx.len() * 8)) {
-        // The kdr_index value must be either -1 or the number of bits that
-        // will be read from the idx slice.
-        return Err(sys::wolfCrypt_ErrorCodes_BAD_FUNC_ARG);
-    }
     let key_size = crate::buffer_len_to_u32(key.len())?;
     let salt_size = crate::buffer_len_to_u32(salt.len())?;
     let key1_size = crate::buffer_len_to_u32(key1.len())?;
@@ -637,7 +636,7 @@ pub fn srtp_kdf(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
 /// }
 /// ```
 #[cfg(kdf_srtp)]
-pub fn srtp_kdf_label(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
+pub fn srtp_kdf_label(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8; SRTP_INDEX_LEN],
         label: u8, keyout: &mut [u8]) -> Result<(), i32> {
     let key_size = crate::buffer_len_to_u32(key.len())?;
     let salt_size = crate::buffer_len_to_u32(salt.len())?;
@@ -679,21 +678,16 @@ pub fn srtp_kdf_label(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
 ///     0x8e, 0x26, 0xad, 0xb5, 0x32, 0x12, 0x98, 0x90];
 /// let salt = [0x0eu8, 0x23, 0x00, 0x6c, 0x6c, 0x04, 0x4f, 0x56,
 ///     0x62, 0x40, 0x0e, 0x9d, 0x1b, 0xd6];
-/// let index = [0x48u8, 0x71, 0x65, 0x64, 0x9c, 0xca];
+/// let index = [0x48u8, 0x71, 0x65, 0x64];
 /// let mut key_e = [0u8; 16];
 /// let mut key_a = [0u8; 20];
 /// let mut key_s = [0u8; 14];
 /// srtcp_kdf(&key, &salt, -1, &index, &mut key_e, &mut key_a, &mut key_s).expect("Error with srtcp_kdf()");
 /// }
 /// ```
 #[cfg(kdf_srtp)]
-pub fn srtcp_kdf(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
+pub fn srtcp_kdf(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8; SRTCP_INDEX_LEN],
         key1: &mut [u8], key2: &mut [u8], key3: &mut [u8]) -> Result<(), i32> {
-    if !(kdr_index == -1 || (0 <= kdr_index && (kdr_index as usize) <= idx.len() * 8)) {
-        // The kdr_index value must be either -1 or the number of bits that
-        // will be read from the idx slice.
-        return Err(sys::wolfCrypt_ErrorCodes_BAD_FUNC_ARG);
-    }
     let key_size = crate::buffer_len_to_u32(key.len())?;
     let salt_size = crate::buffer_len_to_u32(salt.len())?;
     let key1_size = crate::buffer_len_to_u32(key1.len())?;
@@ -736,13 +730,13 @@ pub fn srtcp_kdf(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
 ///     0x8e, 0x26, 0xad, 0xb5, 0x32, 0x12, 0x98, 0x90];
 /// let salt = [0x0eu8, 0x23, 0x00, 0x6c, 0x6c, 0x04, 0x4f, 0x56,
 ///     0x62, 0x40, 0x0e, 0x9d, 0x1b, 0xd6];
-/// let index = [0x48u8, 0x71, 0x65, 0x64, 0x9c, 0xca];
+/// let index = [0x48u8, 0x71, 0x65, 0x64];
 /// let mut key_a = [0u8; 20];
 /// srtcp_kdf_label(&key, &salt, -1, &index, SRTCP_LABEL_MSG_AUTH, &mut key_a).expect("Error with srtcp_kdf_label()");
 /// }
 /// ```
 #[cfg(kdf_srtp)]
-pub fn srtcp_kdf_label(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8],
+pub fn srtcp_kdf_label(key: &[u8], salt: &[u8], kdr_index: i32, idx: &[u8; SRTCP_INDEX_LEN],
         label: u8, keyout: &mut [u8]) -> Result<(), i32> {
     let key_size = crate::buffer_len_to_u32(key.len())?;
     let salt_size = crate::buffer_len_to_u32(salt.len())?;