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Add support for cryptex #511

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Add support for cryptex #511

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9063d2e
WIP
murillo128 Nov 5, 2020
95b0e97
replace memmove by for loop
murillo128 Nov 5, 2020
62bf7a8
cryptex in aead
murillo128 Nov 5, 2020
4939886
fix csrcs type
murillo128 Nov 5, 2020
e16a815
cyrptex -> cryptex
murillo128 Nov 6, 2020
664da14
fix test/srtp_driver structs
murillo128 Nov 9, 2020
6fa8d3b
Merge branch 'cryptex' of https://github.com/murillo128/libsrtp into …
murillo128 Nov 9, 2020
3fe608b
clang-format
murillo128 Nov 10, 2020
696ae82
remove tabs
murillo128 Nov 11, 2020
4ab5255
[wip]
murillo128 Nov 15, 2020
ce58dd6
Fix AAD and add tests
murillo128 Nov 16, 2020
6536373
format
murillo128 Nov 16, 2020
fbf23e2
clang
murillo128 Nov 16, 2020
f09a939
Merge pull request #1 from murillo128/master
murillo128 Aug 24, 2021
3f21c3e
fix warnings
murillo128 Aug 24, 2021
5124a97
rename policy.ekt to policy.deprecated_ekt to aling with master
murillo128 Aug 24, 2021
f8a374b
fix format
murillo128 Aug 29, 2021
90d2345
fix mem leak on deallocating recv sessions
murillo128 Aug 29, 2021
85d291d
Merge branch 'main' into cryptex
murillo128 Jul 19, 2024
ed4b3e3
Update include/srtp.h
murillo128 Jul 19, 2024
e84c487
Update srtp/srtp.c
murillo128 Jul 19, 2024
b352f0c
Update include/srtp_priv.h
murillo128 Jul 19, 2024
570be3d
Update srtp/srtp.c
murillo128 Jul 19, 2024
cbb0365
Update srtp/srtp.c
murillo128 Jul 19, 2024
34d239e
Update srtp/srtp.c
murillo128 Jul 19, 2024
39bea1d
Update srtp/srtp.c
murillo128 Jul 19, 2024
2ed2ac6
Update srtp/srtp.c
murillo128 Jul 19, 2024
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2 changes: 2 additions & 0 deletions include/srtp.h
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Original file line number Diff line number Diff line change
Expand Up @@ -351,6 +351,8 @@ typedef struct srtp_policy_t {
uint8_t *enc_xtn_hdr; /**< List of header ids to encrypt. */
size_t enc_xtn_hdr_count; /**< Number of entries in list of header */
/**< ids. */
unsigned int use_cryptex; /**< Encrypt header block and CSRCS with */
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/**< cryptex. */
struct srtp_policy_t *next; /**< Pointer to next stream policy. */
} srtp_policy_t;

Expand Down
2 changes: 2 additions & 0 deletions include/srtp_priv.h
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Original file line number Diff line number Diff line change
Expand Up @@ -125,6 +125,8 @@ typedef struct srtp_stream_ctx_t_ {
uint8_t *enc_xtn_hdr;
size_t enc_xtn_hdr_count;
uint32_t pending_roc;
unsigned int use_cryptex;
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struct srtp_stream_ctx_t_ *next; /* linked list of streams */
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next was removed, I guess this slipped in while merging ?

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There have been a lot of changes in main, are you sure the merge went well ? All builds are failing.
Also the input buffer to the protect/unprotect functions is now const, not sure you should just cast that away and move the memory around.

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i think I have been too optimistic about my rebasing 😅

Wil try to get a look next week

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Yeah, I had a quick attempt a few weeks ago and understood that this was not an easy merge :( . Let me know if you want to discuss anything.

} strp_stream_ctx_t_;

/*
Expand Down
276 changes: 262 additions & 14 deletions srtp/srtp.c
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Original file line number Diff line number Diff line change
Expand Up @@ -563,6 +563,8 @@ static srtp_err_status_t srtp_stream_alloc(srtp_stream_ctx_t **str_ptr,
str->enc_xtn_hdr_count = 0;
}

str->use_cryptex = p->use_cryptex;

return srtp_err_status_ok;
}

Expand Down Expand Up @@ -673,6 +675,7 @@ static srtp_err_status_t srtp_stream_clone(
/* copy information about extensions header encryption */
str->enc_xtn_hdr = stream_template->enc_xtn_hdr;
str->enc_xtn_hdr_count = stream_template->enc_xtn_hdr_count;
str->use_cryptex = stream_template->use_cryptex;

return srtp_err_status_ok;
}
Expand Down Expand Up @@ -1856,6 +1859,12 @@ static srtp_err_status_t srtp_protect_aead(srtp_ctx_t *ctx,
size_t tag_len;
v128_t iv;
size_t aad_len;
srtp_hdr_xtnd_t *xtn_hdr = NULL;
unsigned int mki_size = 0;
uint8_t *mki_location = NULL;
int xtn_hdr_length = 0;
int xtn_profile_specific = 0;
uint32_t xtn_hdr_profile_and_value = 0;

debug_print0(mod_srtp, "function srtp_protect_aead");

Expand Down Expand Up @@ -1883,11 +1892,48 @@ static srtp_err_status_t srtp_protect_aead(srtp_ctx_t *ctx,
* find starting point for encryption and length of data to be
* encrypted - the encrypted portion starts after the rtp header
* extension, if present; otherwise, it starts after the last csrc,
* if any are present
* if any are present.
* If cryptex is used, the encryption portions also covers the
* rtp heacer extension.
*/
enc_start = srtp_get_rtp_hdr_len(hdr);

/* Cryptex can only encrypt CSRCS if header extension is present*/
if (stream->use_cryptex && hdr->cc && !hdr->x) {
return srtp_err_status_parse_err;
}

if (hdr->x == 1) {
enc_start += srtp_get_rtp_xtn_hdr_len(hdr, rtp);
xtn_hdr = (srtp_hdr_xtnd_t *)(uint32_t *)hdr + uint32s_in_rtp_header +
hdr->cc;
xtn_hdr_length = ntohs(xtn_hdr->length);
xtn_profile_specific = ntohs(xtn_hdr->profile_specific);
}

/* If no header extension is present cryptex has no effect */
if (stream->use_cryptex && hdr->x) {
/* Change profiles by cryptex values */
if (xtn_profile_specific == 0xbede) {
xtn_hdr_profile_and_value = htonl(0xc0de << 16 | xtn_hdr_length);
} else if (xtn_profile_specific == 0x1000) {
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xtn_hdr_profile_and_value = htonl(0xc2de << 16 | xtn_hdr_length);
} else {
return srtp_err_status_parse_err;
}
/* Get CSRCs block position or profile if no CSRCs */
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
/* Move CSRCS so block is contiguous with extension header block */
for (unsigned char i = hdr->cc; i > 0; --i) {
csrcs[i] = csrcs[i - 1];
}
/* Move profile and length before the CSRCs */
csrcs[0] = xtn_hdr_profile_and_value;
/* Start encrypting in the CSRCS block new position */
enc_start = csrcs + 1;
} else {
enc_start = srtp_get_rtp_hdr_len(hdr);
if (hdr->x == 1) {
enc_start += srtp_get_rtp_xtn_hdr_len(hdr, rtp);
}
}

/* note: the passed size is without the auth tag */
Expand Down Expand Up @@ -1982,6 +2028,27 @@ static srtp_err_status_t srtp_protect_aead(srtp_ctx_t *ctx,
return srtp_err_status_cipher_fail;
}

/* Restore CSRCs block before sending if using cryptex */
if (stream->use_cryptex && xtn_hdr && hdr->cc) {
/* Restore CSRCS to its original position */
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
for (unsigned char i = 0; i < hdr->cc; ++i)
csrcs[i] = csrcs[i + 1];
/* Restore extension header profile and length */
*(uint32_t *)xtn_hdr = xtn_hdr_profile_and_value;
}

/*
* If we're doing GCM, we need to get the tag
* and append that to the output
*/
status =
srtp_cipher_get_tag(session_keys->rtp_cipher,
(uint8_t *)enc_start + enc_octet_len, &tag_len);
if (status) {
return (srtp_err_status_cipher_fail);
}

if (stream->use_mki) {
srtp_inject_mki(srtp + enc_start + enc_octet_len, session_keys,
stream->mki_size);
Expand Down Expand Up @@ -2019,7 +2086,12 @@ static srtp_err_status_t srtp_unprotect_aead(srtp_ctx_t *ctx,
v128_t iv;
srtp_err_status_t status;
size_t tag_len;
size_t aad_len;
size_t int aad_len;
srtp_hdr_xtnd_t *xtn_hdr = NULL;
int xtn_hdr_length = 0;
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int xtn_profile_specific = 0;
unsigned int use_cryptex = 0;
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uint32_t xtn_hdr_profile_and_value = 0;

debug_print0(mod_srtp, "function srtp_unprotect_aead");

Expand All @@ -2045,9 +2117,40 @@ static srtp_err_status_t srtp_unprotect_aead(srtp_ctx_t *ctx,
return srtp_err_status_cipher_fail;
}

enc_start = srtp_get_rtp_hdr_len(hdr);
/*
* find starting point for decryption and length of data to be
* decrypted - the encrypted portion starts after the rtp header
* extension, if present; otherwise, it starts after the last csrc,
* if any are present.
* If cryptex is in use, the encrypted portion also covers the
* rtp header extension.
*/
if (hdr->x == 1) {
enc_start += srtp_get_rtp_xtn_hdr_len(hdr, srtp);
xtn_hdr = (srtp_hdr_xtnd_t *)(uint32_t *)hdr + uint32s_in_rtp_header +
hdr->cc;
xtn_hdr_length = ntohs(xtn_hdr->length);
xtn_profile_specific = ntohs(xtn_hdr->profile_specific);
}

/* Check if the profile is the one for cryptex */
if (xtn_profile_specific == 0xc0de || xtn_profile_specific == 0xc2de) {
/* Get the 4 bytes of defined by profile and length */
xtn_hdr_profile_and_value = *(uint32_t *)xtn_hdr;
/* Get CSRCs block position or profile if no CSRCs */
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
/* Move CSRCS so block is contiguous with extension header block */
for (unsigned char i = hdr->cc; i > 0; --i)
csrcs[i] = csrcs[i - 1];
/* Move defined by profile before the CSRCs block */
csrcs[0] = xtn_hdr_profile_and_value;
/* Start encrypting in the CSRCS block new position */
enc_start = csrcs + 1;
use_cryptex = 1;
} else {
enc_start = srtp_get_rtp_hdr_len(hdr);
if (hdr->x == 1) {
enc_start += srtp_get_rtp_xtn_hdr_len(hdr, srtp);
}
}

if (enc_start > srtp_len - tag_len - stream->mki_size) {
Expand Down Expand Up @@ -2114,6 +2217,23 @@ static srtp_err_status_t srtp_unprotect_aead(srtp_ctx_t *ctx,
return status;
}

if (use_cryptex) {
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
/* Restore CSRCS to its original position */
for (unsigned char i = 0; i < hdr->cc; ++i) {
csrcs[i] = csrcs[i + 1];
}
/* Restore extension header and change profiles by cryptex values*/
xtn_hdr->length = htons(xtn_hdr_length);
if (xtn_profile_specific == 0xc0de) {
xtn_hdr->profile_specific = htons(0xbede);
} else if (xtn_profile_specific == 0xc2de) {
xtn_hdr->profile_specific = htons(0x1000);
} else {
return srtp_err_status_parse_err;
}
}

if (hdr->x == 1 && session_keys->rtp_xtn_hdr_cipher) {
/*
* extensions header encryption RFC 6904
Expand Down Expand Up @@ -2213,6 +2333,11 @@ srtp_err_status_t srtp_protect(srtp_t ctx,
srtp_stream_ctx_t *stream;
size_t prefix_len;
srtp_session_keys_t *session_keys = NULL;
uint8_t *mki_location = NULL;
int advance_packet_index = 0;
int xtn_hdr_length = 0;
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int xtn_profile_specific = 0;
uint32_t xtn_hdr_profile_and_value = 0;

debug_print0(mod_srtp, "function srtp_protect");

Expand Down Expand Up @@ -2319,11 +2444,57 @@ srtp_err_status_t srtp_protect(srtp_t ctx,
* find starting point for encryption and length of data to be
* encrypted - the encrypted portion starts after the rtp header
* extension, if present; otherwise, it starts after the last csrc,
* if any are present
* if any are present.
* If cryptex is in use, the encrypted portion also covers the
* rtp header extension.
*/
enc_start = srtp_get_rtp_hdr_len(hdr);
if (hdr->x == 1) {
enc_start += srtp_get_rtp_xtn_hdr_len(hdr, rtp);
if (stream->rtp_services & sec_serv_conf) {
/* Cryptex can only encrypt CSRCS if header extension is present*/
if (stream->use_cryptex && hdr->cc && !hdr->x) {
return srtp_err_status_parse_err;
}
if (hdr->x == 1) {
xtn_hdr = (srtp_hdr_xtnd_t *)(uint32_t *)hdr +
uint32s_in_rtp_header + hdr->cc;
xtn_hdr_length = ntohs(xtn_hdr->length);
xtn_profile_specific = ntohs(xtn_hdr->profile_specific);
}
/* If no header extension is present cryptex has no effect */
if (stream->use_cryptex && hdr->x) {
/* Change profiles by cryptex values */
if (xtn_profile_specific == 0xbede) {
xtn_hdr_profile_and_value =
htonl(0xc0de << 16 | xtn_hdr_length);
} else if (xtn_profile_specific == 0x1000) {
xtn_hdr_profile_and_value =
htonl(0xc2de << 16 | xtn_hdr_length);
} else {
return srtp_err_status_parse_err;
}
/* Get CSRCs block position or profile if no CSRCs */
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
/* Move CSRCS so block is contiguous with extension header block */
for (unsigned char i = hdr->cc; i > 0; --i)
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@paulej paulej Aug 9, 2021 •
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Any reason to do this vs. memcpy() or memmove()? Loops are usually slower, but maybe this doesn't matter.

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just thought it would be easier to review the change and check it was spec compliant, I can change it to memcpy or memmove if needed

csrcs[i] = csrcs[i - 1];
/* Move profile and length before the CSRCs */
csrcs[0] = xtn_hdr_profile_and_value;
/* Start encrypting in the CSRCS block new position */
enc_start = csrcs + 1;
} else {
enc_start = srtp_get_rtp_hdr_len(hdr);
if (hdr->x == 1) {
enc_start += srtp_get_rtp_xtn_hdr_len(hdr, rtp);
}
}
/* note: the passed size is without the auth tag */
if (!((uint8_t *)enc_start <= (uint8_t *)hdr + *pkt_octet_len))
return srtp_err_status_parse_err;
enc_octet_len =
(int)(*pkt_octet_len - ((uint8_t *)enc_start - (uint8_t *)hdr));
if (enc_octet_len < 0)
return srtp_err_status_parse_err;
} else {
enc_start = NULL;
}

if (enc_start > rtp_len) {
Expand Down Expand Up @@ -2457,10 +2628,20 @@ srtp_err_status_t srtp_protect(srtp_t ctx,
&enc_octet_len);
if (status) {
return srtp_err_status_cipher_fail;
} else if (rtp != srtp) {
/* if no encryption and not-inplace then need to copy rest of packet */
memcpy(srtp + enc_start, rtp + enc_start, enc_octet_len);
}

/* Restore CSRCs block before sending if using cryptex */
if (stream->use_cryptex && xtn_hdr && hdr->cc) {
/* Restore CSRCS to its original position */
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
for (unsigned char i = 0; i < hdr->cc; ++i)
csrcs[i] = csrcs[i + 1];
/* Restore extension header profile and length */
*(uint32_t *)xtn_hdr = xtn_hdr_profile_and_value;
}
} else if (rtp != srtp) {
/* if no encryption and not-inplace then need to copy rest of packet */
memcpy(srtp + enc_start, rtp + enc_start, enc_octet_len);
}

/*
Expand Down Expand Up @@ -2524,6 +2705,10 @@ srtp_err_status_t srtp_unprotect(srtp_t ctx,
bool advance_packet_index = false;
uint32_t roc_to_set = 0;
uint16_t seq_to_set = 0;
int xtn_hdr_length = 0;
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int xtn_profile_specific = 0;
unsigned int use_cryptex = 0;
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uint32_t xtn_hdr_profile_and_value = 0;

debug_print0(mod_srtp, "function srtp_unprotect");

Expand Down Expand Up @@ -2730,6 +2915,51 @@ srtp_err_status_t srtp_unprotect(srtp_t ctx,
}
}

/*
* find starting point for decryption and length of data to be
* decrypted - the encrypted portion starts after the rtp header
* extension, if present; otherwise, it starts after the last csrc,
* if any are present
*
* if we're not providing confidentiality, set enc_start to NULL
*/
if (stream->rtp_services & sec_serv_conf) {
if (hdr->x == 1) {
xtn_hdr = (srtp_hdr_xtnd_t *)(uint32_t *)hdr +
uint32s_in_rtp_header + hdr->cc;
xtn_hdr_length = ntohs(xtn_hdr->length);
xtn_profile_specific = ntohs(xtn_hdr->profile_specific);
}

/* Check if the profile is the one for cryptex */
if (xtn_profile_specific == 0xc0de || xtn_profile_specific == 0xc2de) {
/* Get the 4 bytes of defined by profile and length */
xtn_hdr_profile_and_value = *(uint32_t *)xtn_hdr;
/* Get CSRCs block position or profile if no CSRCs */
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
/* Move CSRCS so block is contiguous with extension header block */
for (unsigned char i = hdr->cc; i > 0; --i)
csrcs[i] = csrcs[i - 1];
/* Move defined by profile before the CSRCs block */
csrcs[0] = xtn_hdr_profile_and_value;
/* Start encrypting in the CSRCS block new position */
enc_start = csrcs + 1;
use_cryptex = 1;
} else {
enc_start = (uint32_t *)hdr + uint32s_in_rtp_header + hdr->cc;
if (hdr->x == 1) {
enc_start += (xtn_hdr_length + 1);
}
}
if (!((uint8_t *)enc_start <=
(uint8_t *)hdr + (*pkt_octet_len - tag_len - mki_size)))
return srtp_err_status_parse_err;
enc_octet_len = (uint32_t)(*pkt_octet_len - tag_len - mki_size -
((uint8_t *)enc_start - (uint8_t *)hdr));
} else {
enc_start = NULL;
}

/*
* update the key usage limit, and check it to make sure that we
* didn't just hit either the soft limit or the hard limit, and call
Expand Down Expand Up @@ -2765,10 +2995,28 @@ srtp_err_status_t srtp_unprotect(srtp_t ctx,
if (status) {
return srtp_err_status_cipher_fail;
}
if (use_cryptex) {
uint32_t *csrcs = (uint32_t *)hdr + uint32s_in_rtp_header;
/* Restore CSRCS to its original position */
for (unsigned char i = 0; i < hdr->cc; ++i)
csrcs[i] = csrcs[i + 1];
/* Restore extension header and change profiles by cryptex values*/
xtn_hdr->length = htons(xtn_hdr_length);
if (xtn_profile_specific == 0xc0de) {
xtn_hdr->profile_specific = htons(0xbede);
} else if (xtn_profile_specific == 0xc2de) {
xtn_hdr->profile_specific = htons(0x1000);
} else {
return srtp_err_status_parse_err;
}
}
} else if (rtp != srtp) {
/* if no encryption and not-inplace then need to copy rest of packet */
memcpy(rtp + enc_start, srtp + enc_start, enc_octet_len);
}
}




/*
* verify that stream is for received traffic - this check will
Expand Down
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