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SRTP-KDF: use two bytes of index #9733

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SRTP-KDF: use two bytes of index #9733

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5 changes: 3 additions & 2 deletions wolfcrypt/src/kdf.c
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Original file line number Diff line number Diff line change
Expand Up @@ -896,8 +896,7 @@ static void wc_srtp_kdf_first_block(const byte* salt, word32 saltSz, int kdrIdx,
block[i] = 0;
}
XMEMCPY(block + WC_SRTP_MAX_SALT - saltSz, salt, saltSz);
block[WC_SRTP_MAX_SALT] = 0;
/* block[15] is counter. */
/* block[14-15] are counter. */

/* When kdrIdx is -1, don't XOR in index. */
if (kdrIdx >= 0) {
Expand Down Expand Up @@ -947,6 +946,7 @@ static int wc_srtp_kdf_derive_key(byte* block, int idxSz, byte label,
block[WC_SRTP_MAX_SALT - idxSz - 1] ^= label;
for (i = 0; (ret == 0) && (i < blocks); i++) {
/* Set counter. */
block[14] = (byte)(i >> 8);
block[15] = (byte)i;
/* Encrypt block into key buffer. */
ret = wc_AesEcbEncrypt(aes, key, block, WC_AES_BLOCK_SIZE);
Expand All @@ -959,6 +959,7 @@ static int wc_srtp_kdf_derive_key(byte* block, int idxSz, byte label,
if ((ret == 0) && (keySz > 0)) {
byte enc[WC_AES_BLOCK_SIZE];
/* Set counter. */
block[14] = (byte)(i >> 8);
block[15] = (byte)i;
/* Encrypt block into temporary. */
ret = wc_AesEcbEncrypt(aes, enc, block, WC_AES_BLOCK_SIZE);
Expand Down
38 changes: 38 additions & 0 deletions wolfcrypt/test/test.c
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Original file line number Diff line number Diff line change
Expand Up @@ -31783,6 +31783,8 @@ typedef struct Srtp_Kdf_Tv {
word32 ksSz;
} Srtp_Kdf_Tv;

#define SRTP_KDF_LONG_KEY 5000

WOLFSSL_TEST_SUBROUTINE wc_test_ret_t srtpkdf_test(void)
{
wc_test_ret_t ret = 0;
Expand Down Expand Up @@ -32034,6 +32036,18 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t srtpkdf_test(void)
unsigned char keyE[32];
unsigned char keyA[20];
unsigned char keyS[14];
#ifndef BENCH_EMBEDDED
WC_DECLARE_VAR(keyELong, byte, SRTP_KDF_LONG_KEY, HEAP_HINT);
WC_DECLARE_VAR(keyALong, byte, SRTP_KDF_LONG_KEY, HEAP_HINT);
WC_DECLARE_VAR(keySLong, byte, SRTP_KDF_LONG_KEY, HEAP_HINT);
#endif

#ifndef BENCH_EMBEDDED
WC_ALLOC_VAR(keyELong, byte, SRTP_KDF_LONG_KEY, HEAP_HINT);
WC_ALLOC_VAR(keyALong, byte, SRTP_KDF_LONG_KEY, HEAP_HINT);
WC_ALLOC_VAR(keySLong, byte, SRTP_KDF_LONG_KEY, HEAP_HINT);
#endif

WOLFSSL_ENTER("srtpkdf_test");

for (i = 0; (ret == 0) && (i < SRTP_TV_CNT); i++) {
Expand Down Expand Up @@ -32284,6 +32298,30 @@ WOLFSSL_TEST_SUBROUTINE wc_test_ret_t srtpkdf_test(void)
return WC_TEST_RET_ENC_NC;
}

#ifndef BENCH_EMBEDDED
/* Check that long messages can be created. */
ret = wc_SRTP_KDF(tv[0].key, tv[0].keySz, tv[0].salt, tv[0].saltSz,
tv[0].kdfIdx, tv[0].index_c, keyELong, SRTP_KDF_LONG_KEY, keyALong,
SRTP_KDF_LONG_KEY, keySLong, SRTP_KDF_LONG_KEY);
if (ret != 0)
return WC_TEST_RET_ENC_EC(ret);

/* Check that two bytes of counter are being used. */
if (XMEMCMP(keyELong, keyELong + 4096, SRTP_KDF_LONG_KEY - 4096) == 0) {
return WC_TEST_RET_ENC_NC;
}
if (XMEMCMP(keyELong, keyALong + 4096, SRTP_KDF_LONG_KEY - 4096) == 0) {
return WC_TEST_RET_ENC_NC;
}
if (XMEMCMP(keyELong, keySLong + 4096, SRTP_KDF_LONG_KEY - 4096) == 0) {
return WC_TEST_RET_ENC_NC;
}

WC_FREE_VAR(keyELong, HEAP_HINT);
WC_FREE_VAR(keyALong, HEAP_HINT);
WC_FREE_VAR(keySLong, HEAP_HINT);
#endif

return 0;
}
#endif
Expand Down