8000 Properly support null crypto and null auth scenario by pabuhler · Pull Request #760 · cisco/libsrtp · GitHub
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Properly support null crypto and null auth scenario #760

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Properly support null crypto and null auth scenario #760

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33 changes: 27 additions & 6 deletions srtp/srtp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -847,6 +847,7 @@ static inline int full_key_length(const srtp_cipher_type_t *cipher)
{
switch (cipher->id) {
case SRTP_NULL_CIPHER:
return 0;
case SRTP_AES_ICM_128:
return SRTP_AES_ICM_128_KEY_LEN_WSALT;
case SRTP_AES_ICM_192:
Expand All @@ -862,6 +863,19 @@ static inline int full_key_length(const srtp_cipher_type_t *cipher)
}
}

/* Get the key length that the application should supply for the given auth */
static inline int full_auth_key_length(const srtp_auth_type_t *auth)
{
switch (auth->id) {
case SRTP_NULL_AUTH:
return 0;
case SRTP_HMAC_SHA1:
return SRTP_AES_ICM_128_KEY_LEN_WSALT;
default:
return 0;
}
}

static unsigned int srtp_validate_policy_master_keys(
const srtp_policy_t *policy)
{
Expand Down Expand Up @@ -957,7 +971,7 @@ srtp_err_status_t srtp_stream_init_keys(srtp_stream_ctx_t *srtp,
srtp_err_status_t stat;
srtp_kdf_t kdf;
uint8_t tmp_key[MAX_SRTP_KEY_LEN];
int input_keylen, input_keylen_rtcp;
int input_keylen, full_keylen;
int kdf_keylen = 30, rtp_keylen, rtcp_keylen;
int rtp_base_key_len, rtp_salt_len;
int rtcp_base_key_len, rtcp_salt_len;
Expand Down Expand Up @@ -995,9 +1009,17 @@ srtp_err_status_t srtp_stream_init_keys(srtp_stream_ctx_t *srtp,
session_keys->mki_size = master_key->mki_size;

input_keylen = full_key_length(session_keys->rtp_cipher->type);
input_keylen_rtcp = full_key_length(session_keys->rtcp_cipher->type);
if (input_keylen_rtcp > input_keylen) {
input_keylen = input_keylen_rtcp;
full_keylen = full_auth_key_length(session_keys->rtp_auth->type);
if (full_keylen > input_keylen) {
input_keylen = full_keylen;
}
full_keylen = full_key_length(session_keys->rtcp_cipher->type);
if (full_keylen > input_keylen) {
input_keylen = full_keylen;
}
full_keylen = full_auth_key_length(session_keys->rtcp_auth->type);
if (full_keylen > input_keylen) {
input_keylen = full_keylen;
}

rtp_keylen = srtp_cipher_get_key_length(session_keys->rtp_cipher);
Expand Down Expand Up @@ -3410,8 +3432,7 @@ void srtp_crypto_policy_set_null_cipher_hmac_null(srtp_crypto_policy_t *p)
*/

p->cipher_type = SRTP_NULL_CIPHER;
p->cipher_key_len =
SRTP_AES_ICM_128_KEY_LEN_WSALT; /* 128 bit key, 112 bit salt */
p->cipher_key_len = 0;
p->auth_type = SRTP_NULL_AUTH;
p->auth_key_len = 0;
p->auth_tag_len = 0;
Expand Down
195 changes: 188 additions & 7 deletions test/srtp_driver.c
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Original file line number Diff line number Diff line change
Expand Up @@ -62,7 +62,9 @@

srtp_err_status_t srtp_validate(void);

srtp_err_status_t srtp_validate_null(void);
srtp_err_status_t srtp_validate_null_sha1_80(void);

srtp_err_status_t srtp_validate_null_null(void);

#ifdef GCM
srtp_err_status_t srtp_validate_gcm(void);
Expand Down Expand Up @@ -458,8 +460,17 @@ int main(int argc, char *argv[])
}

printf("testing srtp_protect and srtp_unprotect against "
"reference packet using null cipher and HMAC\n");
if (srtp_validate_null() == srtp_err_status_ok) {
"reference packet using null cipher and SHA1-80 HMAC\n");
if (srtp_validate_null_sha1_80() == srtp_err_status_ok) {
printf("passed\n\n");
} else {
printf("failed\n");
exit(1);
}

printf("testing srtp_protect and srtp_unprotect against "
"reference packet using null cipher and null HMAC\n");
if (srtp_validate_null_null() == srtp_err_status_ok) {
printf("passed\n\n");
} else {
printf("failed\n");
Expand Down Expand Up @@ -1901,13 +1912,13 @@ srtp_err_status_t srtp_validate(void)
}

/*
* srtp_validate_null() verifies the correctness of libsrtp by comparing
* srtp_validate_null_sha1_80() verifies the correctness of libsrtp by comparing
* some computed packets against some pre-computed reference values.
* These packets were made with a policy that applies null encryption
* and HMAC authentication.
*/

srtp_err_status_t srtp_validate_null(void)
srtp_err_status_t srtp_validate_null_sha1_80(void)
{
// clang-format off
uint8_t srtp_plaintext_ref[28] = {
Expand Down Expand Up @@ -1957,8 +1968,8 @@ srtp_err_status_t srtp_validate_null(void)
srtp_policy_t policy;

/*
* create a session with a single stream using the default srtp
* policy and with the SSRC value 0xcafebabe
* create a session with a single stream using the null cipher
* and sha1_80 policy and with the SSRC value 0xcafebabe
*/
memset(&policy, 0, sizeof(policy));
srtp_crypto_policy_set_null_cipher_hmac_sha1_80(&policy.rtp);
Expand Down Expand Up @@ -2060,6 +2071,176 @@ srtp_err_status_t srtp_validate_null(void)
return srtp_err_status_ok;
}

/*
* srtp_validate_null_null() verifies the correctness of libsrtp by comparing
* some computed packets against some pre-computed reference values.
* These packets were made with a policy that applies null encryption
* and null authentication.
*/

srtp_err_status_t srtp_validate_null_null(void)
{
// clang-format off
uint8_t srtp_plaintext_ref[28] = {
0x80, 0x0f, 0x12, 0x34, 0xde, 0xca, 0xfb, 0xad,
0xca, 0xfe, 0xba, 0xbe, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab
};
uint8_t srtp_plaintext[28] = {
0x80, 0x0f, 0x12, 0x34, 0xde, 0xca, 0xfb, 0xad,
0xca, 0xfe, 0xba, 0xbe, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab,
};
uint8_t srtp_ciphertext[28] = {
0x80, 0x0f, 0x12, 0x34, 0xde, 0xca, 0xfb, 0xad,
0xca, 0xfe, 0xba, 0xbe, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab,
};
uint8_t rtcp_plaintext_ref[24] = {
0x81, 0xc8, 0x00, 0x0b, 0xca, 0xfe, 0xba, 0xbe,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
};
uint8_t rtcp_plaintext[28] = {
0x81, 0xc8, 0x00, 0x0b, 0xca, 0xfe, 0xba, 0xbe,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0x00, 0x00, 0x00, 0x00,
};
uint8_t srtcp_ciphertext[28] = {
0x81, 0xc8, 0x00, 0x0b, 0xca, 0xfe, 0xba, 0xbe,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab, 0xab,
0x00, 0x00, 0x00, 0x01,
};
// clang-format on

srtp_t srtp_snd, srtp_recv;
srtp_err_status_t status;
int len;
srtp_policy_t policy;

/*
* create a session with a single stream using the null cipher
* and null hmac policy and with the SSRC value 0xcafebabe
*/
memset(&policy, 0, sizeof(policy));
srtp_crypto_policy_set_null_cipher_hmac_null(&policy.rtp);
srtp_crypto_policy_set_null_cipher_hmac_null(&policy.rtcp);
policy.ssrc.type = ssrc_specific;
policy.ssrc.value = 0xcafebabe;
/*
* We need some non-zero value set here
*/
policy.key = (void *)(uintptr_t)-1;
policy.window_size = 128;
policy.allow_repeat_tx = 0;
policy.next = NULL;

status = srtp_create(&srtp_snd, &policy);
if (status) {
return status;
}

/*
* protect plaintext, then compare with ciphertext
*/
len = 28;
status = srtp_protect(srtp_snd, srtp_plaintext, &len);
if (status || (len != 28)) {
return srtp_err_status_fail;
}
if (status) {
return status;
}

debug_print(mod_driver, "ciphertext:\n %s",
octet_string_hex_string(srtp_plaintext, len));
debug_print(mod_driver, "ciphertext reference:\n %s",
octet_string_hex_string(srtp_ciphertext, len));

if (srtp_octet_string_is_eq(srtp_plaintext, srtp_ciphertext, len)) {
return srtp_err_status_fail;
}

/*
* protect plaintext rtcp, then compare with srtcp ciphertext
*/
len = 24;
status = srtp_protect_rtcp(srtp_snd, rtcp_plaintext, &len);
if (!status && (len != 28)) {
status = srtp_err_status_fail;
}
if (status) {
return status;
}

debug_print(mod_driver, "srtcp ciphertext:\n %s",
octet_string_hex_string(rtcp_plaintext, len));
debug_print(mod_driver, "srtcp ciphertext reference:\n %s",
octet_string_hex_string(srtcp_ciphertext, len));

if (srtp_octet_string_is_eq(rtcp_plaintext, srtcp_ciphertext, len)) {
return srtp_err_status_fail;
}

/*
* create a receiver session context comparable to the one created
* above - we need to do this so that the replay checking doesn't
* complain
*/
status = srtp_create(&srtp_recv, &policy);
if (status) {
return status;
}

/*
* unprotect ciphertext, then compare with plaintext
*/
status = srtp_unprotect(srtp_recv, srtp_ciphertext, &len);
if (!status && (len != 28)) {
status = srtp_err_status_fail;
}
if (status) {
return status;
}

if (srtp_octet_string_is_eq(srtp_ciphertext, srtp_plaintext_ref, len)) {
return srtp_err_status_fail;
}

/*
* unprotect srtcp ciphertext, then compare with rtcp plaintext
*/
len = 28;
status = srtp_unprotect_rtcp(srtp_recv, srtcp_ciphertext, &len);
if (!status && (len != 24)) {
status = srtp_err_status_fail;
}
if (status) {
return status;
}

if (srtp_octet_string_is_eq(srtcp_ciphertext, rtcp_plaintext_ref, len)) {
return srtp_err_status_fail;
}

status = srtp_dealloc(srtp_snd);
if (status) {
return status;
}

status = srtp_dealloc(srtp_recv);
if (status) {
return status;
}

return srtp_err_status_ok;
}

#ifdef GCM
/*
* srtp_validate_gcm() verifies the correctness of libsrtp by comparing
Expand Down
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