From 4b230808b9566322fae8d1ef0d1a5cb3e8027d3b Mon Sep 17 00:00:00 2001 From: Marvin W Date: Tue, 23 Mar 2021 20:04:28 +0100 Subject: Move SRTP implementation into crypto library for reuse --- plugins/crypto-vala/CMakeLists.txt | 27 +- plugins/crypto-vala/src/srtp.c | 836 +++++++++++++++++++++++++++++++++++++ plugins/crypto-vala/src/srtp.h | 82 ++++ plugins/crypto-vala/src/srtp.vapi | 107 +++++ plugins/rtp/CMakeLists.txt | 5 +- plugins/rtp/src/srtp.c | 836 ------------------------------------- plugins/rtp/src/srtp.h | 82 ---- plugins/rtp/src/srtp.vapi | 103 ----- plugins/rtp/src/stream.vala | 20 +- 9 files changed, 1063 insertions(+), 1035 deletions(-) create mode 100644 plugins/crypto-vala/src/srtp.c create mode 100644 plugins/crypto-vala/src/srtp.h create mode 100644 plugins/crypto-vala/src/srtp.vapi delete mode 100644 plugins/rtp/src/srtp.c delete mode 100644 plugins/rtp/src/srtp.h delete mode 100644 plugins/rtp/src/srtp.vapi (limited to 'plugins') diff --git a/plugins/crypto-vala/CMakeLists.txt b/plugins/crypto-vala/CMakeLists.txt index 036e45f6..f97b0d31 100644 --- a/plugins/crypto-vala/CMakeLists.txt +++ b/plugins/crypto-vala/CMakeLists.txt @@ -11,6 +11,7 @@ SOURCES "src/cipher_converter.vala" "src/error.vala" "src/random.vala" + "src/srtp.vapi" CUSTOM_VAPIS "${CMAKE_CURRENT_SOURCE_DIR}/vapi/gcrypt.vapi" PACKAGES @@ -21,9 +22,33 @@ GENERATE_HEADER crypto-vala ) +add_custom_command(OUTPUT "${CMAKE_BINARY_DIR}/exports/srtp.h" +COMMAND + cp "${CMAKE_CURRENT_SOURCE_DIR}/src/srtp.h" "${CMAKE_BINARY_DIR}/exports/srtp.h" +DEPENDS + "${CMAKE_CURRENT_SOURCE_DIR}/src/srtp.h" +COMMENT + Copy header file srtp.h +) + +add_custom_command(OUTPUT ${CMAKE_BINARY_DIR}/exports/crypto.vapi +COMMAND + cat "${CMAKE_BINARY_DIR}/exports/crypto-vala.vapi" "${CMAKE_CURRENT_SOURCE_DIR}/src/srtp.vapi" > "${CMAKE_BINARY_DIR}/exports/crypto.vapi" +DEPENDS + ${CMAKE_BINARY_DIR}/exports/crypto-vala.vapi + ${CMAKE_CURRENT_SOURCE_DIR}/src/srtp.vapi +) + +add_custom_target(crypto-vapi +DEPENDS + ${CMAKE_BINARY_DIR}/exports/crypto.vapi + ${CMAKE_BINARY_DIR}/exports/srtp.h +) + set(CFLAGS ${VALA_CFLAGS} -I${CMAKE_CURRENT_SOURCE_DIR}/src) add_definitions(${CFLAGS}) -add_library(crypto-vala STATIC ${CRYPTO_VALA_C}) +add_library(crypto-vala STATIC ${CRYPTO_VALA_C} src/srtp.c) +add_dependencies(crypto-vala crypto-vapi) target_link_libraries(crypto-vala ${CRYPTO_VALA_PACKAGES} gcrypt) set_property(TARGET crypto-vala PROPERTY POSITION_INDEPENDENT_CODE ON) diff --git a/plugins/crypto-vala/src/srtp.c b/plugins/crypto-vala/src/srtp.c new file mode 100644 index 00000000..708244d9 --- /dev/null +++ b/plugins/crypto-vala/src/srtp.c @@ -0,0 +1,836 @@ +/* + * Secure RTP with libgcrypt + * Copyright (C) 2007 Rémi Denis-Courmont + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public + * License as published by the Free Software Foundation; either + * version 2.1 of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU + * Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + */ + +/* TODO: + * Useless stuff (because nothing depends on it): + * - non-nul key derivation rate + * - MKI payload + */ + +#ifdef HAVE_CONFIG_H +# include +#endif + +#include +#include + +#include "srtp.h" + +#include +#include +#include +#include + +#include + +#ifdef _WIN32 +# include +#else +# include +#endif + +#define debug( ... ) (void)0 + +typedef struct srtp_proto_t +{ + gcry_cipher_hd_t cipher; + gcry_md_hd_t mac; + uint64_t window; + uint32_t salt[4]; +} srtp_proto_t; + +struct srtp_session_t +{ + srtp_proto_t rtp; + srtp_proto_t rtcp; + unsigned flags; + unsigned kdr; + uint32_t rtcp_index; + uint32_t rtp_roc; + uint16_t rtp_seq; + uint16_t rtp_rcc; + uint8_t tag_len; +}; + +enum +{ + SRTP_CRYPT, + SRTP_AUTH, + SRTP_SALT, + SRTCP_CRYPT, + SRTCP_AUTH, + SRTCP_SALT +}; + + +static inline unsigned rcc_mode (const srtp_session_t *s) +{ + return (s->flags >> 4) & 3; +} + + +static void proto_destroy (srtp_proto_t *p) +{ + gcry_md_close (p->mac); + gcry_cipher_close (p->cipher); +} + + +/** + * Releases all resources associated with a Secure RTP session. + */ +void srtp_destroy (srtp_session_t *s) +{ + assert (s != NULL); + + proto_destroy (&s->rtcp); + proto_destroy (&s->rtp); + free (s); +} + + +static int proto_create (srtp_proto_t *p, int gcipher, int gmd) +{ + if (gcry_cipher_open (&p->cipher, gcipher, GCRY_CIPHER_MODE_CTR, 0) == 0) + { + if (gcry_md_open (&p->mac, gmd, GCRY_MD_FLAG_HMAC) == 0) + return 0; + gcry_cipher_close (p->cipher); + } + return -1; +} + + +/** + * Allocates a Secure RTP one-way session. + * The same session cannot be used both ways because this would confuse + * internal cryptographic counters; it is however of course feasible to open + * multiple simultaneous sessions with the same master key. + * + * @param encr encryption algorithm number + * @param auth authentication algortihm number + * @param tag_len authentication tag byte length (NOT including RCC) + * @param flags OR'ed optional flags. + * + * @return NULL in case of error + */ +srtp_session_t * +srtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags) +{ + if ((flags & ~SRTP_FLAGS_MASK)) + return NULL; + + int cipher, md; + switch (encr) + { + case SRTP_ENCR_NULL: + cipher = GCRY_CIPHER_NONE; + break; + + case SRTP_ENCR_AES_CM: + cipher = GCRY_CIPHER_AES; + break; + + default: + return NULL; + } + + switch (auth) + { + case SRTP_AUTH_NULL: + md = GCRY_MD_NONE; + break; + + case SRTP_AUTH_HMAC_SHA1: + md = GCRY_MD_SHA1; + break; + + default: + return NULL; + } + + if (tag_len > gcry_md_get_algo_dlen (md)) + return NULL; + + if (prf != SRTP_PRF_AES_CM) + return NULL; + + srtp_session_t *s = malloc (sizeof (*s)); + if (s == NULL) + return NULL; + + memset (s, 0, sizeof (*s)); + s->flags = flags; + s->tag_len = tag_len; + s->rtp_rcc = 1; /* Default RCC rate */ + if (rcc_mode (s)) + { + if (tag_len < 4) + goto error; + } + + if (proto_create (&s->rtp, cipher, md) == 0) + { + if (proto_create (&s->rtcp, cipher, md) == 0) + return s; + proto_destroy (&s->rtp); + } + + error: + free (s); + return NULL; +} + + +/** + * Counter Mode encryption/decryption (ctr length = 16 bytes) + * with non-padded (truncated) text + */ +static int +do_ctr_crypt (gcry_cipher_hd_t hd, const void *ctr, uint8_t *data, size_t len) +{ + const size_t ctrlen = 16; + div_t d = div (len, ctrlen); + + if (gcry_cipher_setctr (hd, ctr, ctrlen) + || gcry_cipher_encrypt (hd, data, d.quot * ctrlen, NULL, 0)) + return -1; + + if (d.rem) + { + /* Truncated last block */ + uint8_t dummy[ctrlen]; + data += d.quot * ctrlen; + memcpy (dummy, data, d.rem); + memset (dummy + d.rem, 0, ctrlen - d.rem); + + if (gcry_cipher_encrypt (hd, dummy, ctrlen, data, ctrlen)) + return -1; + memcpy (data, dummy, d.rem); + } + + return 0; +} + + +/** + * AES-CM key derivation (saltlen = 14 bytes) + */ +static int +do_derive (gcry_cipher_hd_t prf, const void *salt, + const uint8_t *r, size_t rlen, uint8_t label, + void *out, size_t outlen) +{ + uint8_t iv[16]; + + memcpy (iv, salt, 14); + iv[14] = iv[15] = 0; + + assert (rlen < 14); + iv[13 - rlen] ^= label; + for (size_t i = 0; i < rlen; i++) + iv[sizeof (iv) - rlen + i] ^= r[i]; + + memset (out, 0, outlen); + return do_ctr_crypt (prf, iv, out, outlen); +} + + +/** + * Sets (or resets) the master key and master salt for a SRTP session. + * This must be done at least once before using srtp_send(), srtp_recv(), + * srtcp_send() or srtcp_recv(). Also, rekeying is required every + * 2^48 RTP packets or 2^31 RTCP packets (whichever comes first), + * otherwise the protocol security might be broken. + * + * @return 0 on success, in case of error: + * EINVAL invalid or unsupported key/salt sizes combination + */ +int +srtp_setkey (srtp_session_t *s, const void *key, size_t keylen, + const void *salt, size_t saltlen) +{ + /* SRTP/SRTCP cipher/salt/MAC keys derivation */ + gcry_cipher_hd_t prf; + uint8_t r[6], keybuf[20]; + + if (saltlen != 14) + return EINVAL; + + if (gcry_cipher_open (&prf, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR, 0) + || gcry_cipher_setkey (prf, key, keylen)) + return EINVAL; + + /* SRTP key derivation */ +#if 0 + if (s->kdr != 0) + { + uint64_t index = (((uint64_t)s->rtp_roc) << 16) | s->rtp_seq; + index /= s->kdr; + + for (int i = sizeof (r) - 1; i >= 0; i--) + { + r[i] = index & 0xff; + index = index >> 8; + } + } + else +#endif + memset (r, 0, sizeof (r)); + if (do_derive (prf, salt, r, 6, SRTP_CRYPT, keybuf, 16) + || gcry_cipher_setkey (s->rtp.cipher, keybuf, 16) + || do_derive (prf, salt, r, 6, SRTP_AUTH, keybuf, 20) + || gcry_md_setkey (s->rtp.mac, keybuf, 20) + || do_derive (prf, salt, r, 6, SRTP_SALT, s->rtp.salt, 14)) + return -1; + + /* SRTCP key derivation */ + memcpy (r, &(uint32_t){ htonl (s->rtcp_index) }, 4); + if (do_derive (prf, salt, r, 4, SRTCP_CRYPT, keybuf, 16) + || gcry_cipher_setkey (s->rtcp.cipher, keybuf, 16) + || do_derive (prf, salt, r, 4, SRTCP_AUTH, keybuf, 20) + || gcry_md_setkey (s->rtcp.mac, keybuf, 20) + || do_derive (prf, salt, r, 4, SRTCP_SALT, s->rtcp.salt, 14)) + return -1; + + (void)gcry_cipher_close (prf); + return 0; +} + +static int hexdigit (char c) +{ + if ((c >= '0') && (c <= '9')) + return c - '0'; + if ((c >= 'A') && (c <= 'F')) + return c - 'A' + 0xA; + if ((c >= 'a') && (c <= 'f')) + return c - 'a' + 0xa; + return -1; +} + +static ssize_t hexstring (const char *in, uint8_t *out, size_t outlen) +{ + size_t inlen = strlen (in); + + if ((inlen > (2 * outlen)) || (inlen & 1)) + return -1; + + for (size_t i = 0; i < inlen; i += 2) + { + int a = hexdigit (in[i]), b = hexdigit (in[i + 1]); + if ((a == -1) || (b == -1)) + return -1; + out[i / 2] = (a << 4) | b; + } + return inlen / 2; +} + +/** + * Sets (or resets) the master key and master salt for a SRTP session + * from hexadecimal strings. See also srtp_setkey(). + * + * @return 0 on success, in case of error: + * EINVAL invalid or unsupported key/salt sizes combination + */ +int +srtp_setkeystring (srtp_session_t *s, const char *key, const char *salt) +{ + uint8_t bkey[16]; /* TODO/NOTE: hard-coded for AES */ + uint8_t bsalt[14]; /* TODO/NOTE: hard-coded for the PRF-AES-CM */ + ssize_t bkeylen = hexstring (key, bkey, sizeof (bkey)); + ssize_t bsaltlen = hexstring (salt, bsalt, sizeof (bsalt)); + + if ((bkeylen == -1) || (bsaltlen == -1)) + return EINVAL; + return srtp_setkey (s, bkey, bkeylen, bsalt, bsaltlen) ? EINVAL : 0; +} + +/** + * Sets Roll-over-Counter Carry (RCC) rate for the SRTP session. If not + * specified (through this function), the default rate of ONE is assumed + * (i.e. every RTP packets will carry the RoC). RCC rate is ignored if none + * of the RCC mode has been selected. + * + * The RCC mode is selected through one of these flags for srtp_create(): + * SRTP_RCC_MODE1: integrity protection only for RoC carrying packets + * SRTP_RCC_MODE2: integrity protection for all packets + * SRTP_RCC_MODE3: no integrity protection + * + * RCC mode 3 is insecure. Compared to plain RTP, it provides confidentiality + * (through encryption) but is much more prone to DoS. It can only be used if + * anti-spoofing protection is provided by lower network layers (e.g. IPsec, + * or trusted routers and proper source address filtering). + * + * If RCC rate is 1, RCC mode 1 and 2 are functionally identical. + * + * @param rate RoC Carry rate (MUST NOT be zero) + */ +void srtp_setrcc_rate (srtp_session_t *s, uint16_t rate) +{ + assert (rate != 0); + s->rtp_rcc = rate; +} + + +/** AES-CM for RTP (salt = 14 bytes + 2 nul bytes) */ +static int +rtp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t roc, uint16_t seq, + const uint32_t *salt, uint8_t *data, size_t len) +{ + /* Determines cryptographic counter (IV) */ + uint32_t counter[4]; + counter[0] = salt[0]; + counter[1] = salt[1] ^ ssrc; + counter[2] = salt[2] ^ htonl (roc); + counter[3] = salt[3] ^ htonl (seq << 16); + + /* Encryption */ + return do_ctr_crypt (hd, counter, data, len); +} + + +/** Determines SRTP Roll-Over-Counter (in host-byte order) */ +static uint32_t +srtp_compute_roc (const srtp_session_t *s, uint16_t seq) +{ + uint32_t roc = s->rtp_roc; + + if (((seq - s->rtp_seq) & 0xffff) < 0x8000) + { + /* Sequence is ahead, good */ + if (seq < s->rtp_seq) + roc++; /* Sequence number wrap */ + } + else + { + /* Sequence is late, bad */ + if (seq > s->rtp_seq) + roc--; /* Wrap back */ + } + return roc; +} + + +/** Returns RTP sequence (in host-byte order) */ +static inline uint16_t rtp_seq (const uint8_t *buf) +{ + return (buf[2] << 8) | buf[3]; +} + + +/** Message Authentication and Integrity for RTP */ +static const uint8_t * +rtp_digest (gcry_md_hd_t md, const uint8_t *data, size_t len, + uint32_t roc) +{ + gcry_md_reset (md); + gcry_md_write (md, data, len); + gcry_md_write (md, &(uint32_t){ htonl (roc) }, 4); + return gcry_md_read (md, 0); +} + + +/** + * Encrypts/decrypts a RTP packet and updates SRTP context + * (CTR block cypher mode of operation has identical encryption and + * decryption function). + * + * @param buf RTP packet to be en-/decrypted + * @param len RTP packet length + * + * @return 0 on success, in case of error: + * EINVAL malformatted RTP packet + * EACCES replayed packet or out-of-window or sync lost + */ +static int srtp_crypt (srtp_session_t *s, uint8_t *buf, size_t len) +{ + assert (s != NULL); + assert (len >= 12u); + + if ((buf[0] >> 6) != 2) + return EINVAL; + + /* Computes encryption offset */ + uint16_t offset = 12; + offset += (buf[0] & 0xf) * 4; // skips CSRC + + if (buf[0] & 0x10) + { + uint16_t extlen; + + offset += 4; + if (len < offset) + return EINVAL; + + memcpy (&extlen, buf + offset - 2, 2); + offset += htons (extlen); // skips RTP extension header + } + + if (len < offset) + return EINVAL; + + /* Determines RTP 48-bits counter and SSRC */ + uint16_t seq = rtp_seq (buf); + uint32_t roc = srtp_compute_roc (s, seq), ssrc; + memcpy (&ssrc, buf + 8, 4); + + /* Updates ROC and sequence (it's safe now) */ + int16_t diff = seq - s->rtp_seq; + if (diff > 0) + { + /* Sequence in the future, good */ + s->rtp.window = s->rtp.window << diff; + s->rtp.window |= UINT64_C(1); + s->rtp_seq = seq, s->rtp_roc = roc; + } + else + { + /* Sequence in the past/present, bad */ + diff = -diff; + if ((diff >= 64) || ((s->rtp.window >> diff) & 1)) + return EACCES; /* Replay attack */ + s->rtp.window |= UINT64_C(1) << diff; + } + + /* Encrypt/Decrypt */ + if (s->flags & SRTP_UNENCRYPTED) + return 0; + + if (rtp_crypt (s->rtp.cipher, ssrc, roc, seq, s->rtp.salt, + buf + offset, len - offset)) + return EINVAL; + + return 0; +} + + +/** + * Turns a RTP packet into a SRTP packet: encrypt it, then computes + * the authentication tag and appends it. + * Note that you can encrypt packet in disorder. + * + * @param buf RTP packet to be encrypted/digested + * @param lenp pointer to the RTP packet length on entry, + * set to the SRTP length on exit (undefined on non-ENOSPC error) + * @param bufsize size (bytes) of the packet buffer + * + * @return 0 on success, in case of error: + * EINVAL malformatted RTP packet or internal error + * ENOSPC bufsize is too small to add authentication tag + * ( will hold the required byte size) + * EACCES packet would trigger a replay error on receiver + */ +int +srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize) +{ + size_t len = *lenp; + size_t tag_len; + size_t roc_len = 0; + + /* Compute required buffer size */ + if (len < 12u) + return EINVAL; + + if (!(s->flags & SRTP_UNAUTHENTICATED)) + { + tag_len = s->tag_len; + + if (rcc_mode (s)) + { + assert (tag_len >= 4); + assert (s->rtp_rcc != 0); + if ((rtp_seq (buf) % s->rtp_rcc) == 0) + { + roc_len = 4; + if (rcc_mode (s) == 3) + tag_len = 0; /* RCC mode 3 -> no auth*/ + else + tag_len -= 4; /* RCC mode 1 or 2 -> auth*/ + } + else + { + if (rcc_mode (s) & 1) + tag_len = 0; /* RCC mode 1 or 3 -> no auth */ + } + } + + *lenp = len + roc_len + tag_len; + } + else + tag_len = 0; + + if (bufsize < *lenp) + return ENOSPC; + + /* Encrypt payload */ + int val = srtp_crypt (s, buf, len); + if (val) + return val; + + /* Authenticate payload */ + if (!(s->flags & SRTP_UNAUTHENTICATED)) + { + uint32_t roc = srtp_compute_roc (s, rtp_seq (buf)); + const uint8_t *tag = rtp_digest (s->rtp.mac, buf, len, roc); + + if (roc_len) + { + memcpy (buf + len, &(uint32_t){ htonl (s->rtp_roc) }, 4); + len += 4; + } + memcpy (buf + len, tag, tag_len); +#if 0 + printf ("Sent : 0x"); + for (unsigned i = 0; i < tag_len; i++) + printf ("%02x", tag[i]); + puts (""); +#endif + } + + return 0; +} + + +/** + * Turns a SRTP packet into a RTP packet: authenticates the packet, + * then decrypts it. + * + * @param buf RTP packet to be digested/decrypted + * @param lenp pointer to the SRTP packet length on entry, + * set to the RTP length on exit (undefined in case of error) + * + * @return 0 on success, in case of error: + * EINVAL malformatted SRTP packet + * EACCES authentication failed (spoofed packet or out-of-sync) + */ +int +srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp) +{ + size_t len = *lenp; + if (len < 12u) + return EINVAL; + + if (!(s->flags & SRTP_UNAUTHENTICATED)) + { + size_t tag_len = s->tag_len, roc_len = 0; + if (rcc_mode (s)) + { + if ((rtp_seq (buf) % s->rtp_rcc) == 0) + { + roc_len = 4; + if (rcc_mode (s) == 3) + tag_len = 0; + else + tag_len -= 4; + } + else + { + if (rcc_mode (s) & 1) + tag_len = 0; // RCC mode 1 or 3: no auth + } + } + + if (len < (12u + roc_len + tag_len)) + return EINVAL; + len -= roc_len + tag_len; + + uint32_t roc = srtp_compute_roc (s, rtp_seq (buf)), rcc; + if (roc_len) + { + assert (roc_len == 4); + memcpy (&rcc, buf + len, 4); + rcc = ntohl (rcc); + } + else + rcc = roc; + + const uint8_t *tag = rtp_digest (s->rtp.mac, buf, len, rcc); +#if 0 + printf ("Computed: 0x"); + for (unsigned i = 0; i < tag_len; i++) + printf ("%02x", tag[i]); + printf ("\nReceived: 0x"); + for (unsigned i = 0; i < tag_len; i++) + printf ("%02x", buf[len + roc_len + i]); + puts (""); +#endif + if (memcmp (buf + len + roc_len, tag, tag_len)) + return EACCES; + + if (roc_len) + { + /* Authenticated packet carried a Roll-Over-Counter */ + s->rtp_roc += rcc - roc; + assert (srtp_compute_roc (s, rtp_seq (buf)) == rcc); + } + *lenp = len; + } + + return srtp_crypt (s, buf, len); +} + + +/** AES-CM for RTCP (salt = 14 bytes + 2 nul bytes) */ +static int +rtcp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t index, + const uint32_t *salt, uint8_t *data, size_t len) +{ + return rtp_crypt (hd, ssrc, index >> 16, index & 0xffff, salt, data, len); +} + + +/** Message Authentication and Integrity for RTCP */ +static const uint8_t * +rtcp_digest (gcry_md_hd_t md, const void *data, size_t len) +{ + gcry_md_reset (md); + gcry_md_write (md, data, len); + return gcry_md_read (md, 0); +} + + +/** + * Encrypts/decrypts a RTCP packet and updates SRTCP context + * (CTR block cypher mode of operation has identical encryption and + * decryption function). + * + * @param buf RTCP packet to be en-/decrypted + * @param len RTCP packet length + * + * @return 0 on success, in case of error: + * EINVAL malformatted RTCP packet + */ +static int srtcp_crypt (srtp_session_t *s, uint8_t *buf, size_t len) +{ + assert (s != NULL); + + /* 8-bytes unencrypted header, and 4-bytes unencrypted footer */ + if ((len < 12) || ((buf[0] >> 6) != 2)) + return EINVAL; + + uint32_t index; + memcpy (&index, buf + len, 4); + index = ntohl (index); + if (((index >> 31) != 0) != ((s->flags & SRTCP_UNENCRYPTED) == 0)) + return EINVAL; // E-bit mismatch + + index &= ~(1 << 31); // clear E-bit for counter + + /* Updates SRTCP index (safe here) */ + int32_t diff = index - s->rtcp_index; + if (diff > 0) + { + /* Packet in the future, good */ + s->rtcp.window = s->rtcp.window << diff; + s->rtcp.window |= UINT64_C(1); + s->rtcp_index = index; + } + else + { + /* Packet in the past/present, bad */ + diff = -diff; + if ((diff >= 64) || ((s->rtcp.window >> diff) & 1)) + return EACCES; // replay attack! + s->rtp.window |= UINT64_C(1) << diff; + } + + /* Crypts SRTCP */ + if (s->flags & SRTCP_UNENCRYPTED) + return 0; + + uint32_t ssrc; + memcpy (&ssrc, buf + 4, 4); + + if (rtcp_crypt (s->rtcp.cipher, ssrc, index, s->rtp.salt, + buf + 8, len - 8)) + return EINVAL; + return 0; +} + + +/** + * Turns a RTCP packet into a SRTCP packet: encrypt it, then computes + * the authentication tag and appends it. + * + * @param buf RTCP packet to be encrypted/digested + * @param lenp pointer to the RTCP packet length on entry, + * set to the SRTCP length on exit (undefined in case of error) + * @param bufsize size (bytes) of the packet buffer + * + * @return 0 on success, in case of error: + * EINVAL malformatted RTCP packet or internal error + * ENOSPC bufsize is too small (to add index and authentication tag) + */ +int +srtcp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize) +{ + size_t len = *lenp; + if (bufsize < (len + 4 + s->tag_len)) + return ENOSPC; + + uint32_t index = ++s->rtcp_index; + if (index >> 31) + s->rtcp_index = index = 0; /* 31-bit wrap */ + + if ((s->flags & SRTCP_UNENCRYPTED) == 0) + index |= 0x80000000; /* Set Encrypted bit */ + memcpy (buf + len, &(uint32_t){ htonl (index) }, 4); + + int val = srtcp_crypt (s, buf, len); + if (val) + return val; + + len += 4; /* Digests SRTCP index too */ + + const uint8_t *tag = rtcp_digest (s->rtcp.mac, buf, len); + memcpy (buf + len, tag, s->tag_len); + *lenp = len + s->tag_len; + return 0; +} + + +/** + * Turns a SRTCP packet into a RTCP packet: authenticates the packet, + * then decrypts it. + * + * @param buf RTCP packet to be digested/decrypted + * @param lenp pointer to the SRTCP packet length on entry, + * set to the RTCP length on exit (undefined in case of error) + * + * @return 0 on success, in case of error: + * EINVAL malformatted SRTCP packet + * EACCES authentication failed (spoofed packet or out-of-sync) + */ +int +srtcp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp) +{ + size_t len = *lenp; + + if (len < (4u + s->tag_len)) + return EINVAL; + len -= s->tag_len; + + const uint8_t *tag = rtcp_digest (s->rtcp.mac, buf, len); + if (memcmp (buf + len, tag, s->tag_len)) + return EACCES; + + len -= 4; /* Remove SRTCP index before decryption */ + *lenp = len; + return srtcp_crypt (s, buf, len); +} \ No newline at end of file diff --git a/plugins/crypto-vala/src/srtp.h b/plugins/crypto-vala/src/srtp.h new file mode 100644 index 00000000..abca6988 --- /dev/null +++ b/plugins/crypto-vala/src/srtp.h @@ -0,0 +1,82 @@ +/* + * Secure RTP with libgcrypt + * Copyright (C) 2007 Rémi Denis-Courmont + * + * This library is free software; you can redistribute it and/or + * modify it under the terms of the GNU Lesser General Public License + * as published by the Free Software Foundation; either version 2.1 + * of the License, or (at your option) any later version. + * + * This library is distributed in the hope that it will be useful, + * but WITHOUT ANY WARRANTY; without even the implied warranty of + * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the + * GNU Lesser General Public License for more details. + * + * You should have received a copy of the GNU Lesser General Public + * License along with this library; if not, write to the Free Software + * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA + ****************************************************************************/ + +#ifndef LIBVLC_SRTP_H +# define LIBVLC_SRTP_H 1 +#include + +typedef struct srtp_session_t srtp_session_t; + +enum +{ + SRTP_UNENCRYPTED=0x1, //< do not encrypt SRTP packets + SRTCP_UNENCRYPTED=0x2, //< do not encrypt SRTCP packets + SRTP_UNAUTHENTICATED=0x4, //< authenticate only SRTCP packets + + SRTP_RCC_MODE1=0x10, //< use Roll-over-Counter Carry mode 1 + SRTP_RCC_MODE2=0x20, //< use Roll-over-Counter Carry mode 2 + SRTP_RCC_MODE3=0x30, //< use Roll-over-Counter Carry mode 3 (insecure) + + SRTP_FLAGS_MASK=0x37 //< mask for valid flags +}; + +/** SRTP encryption algorithms (ciphers); same values as MIKEY */ +enum +{ + SRTP_ENCR_NULL=0, //< no encryption + SRTP_ENCR_AES_CM=1, //< AES counter mode + SRTP_ENCR_AES_F8=2, //< AES F8 mode (not implemented) +}; + +/** SRTP authenticaton algorithms; same values as MIKEY */ +enum +{ + SRTP_AUTH_NULL=0, //< no authentication code + SRTP_AUTH_HMAC_SHA1=1, //< HMAC-SHA1 +}; + +/** SRTP pseudo random function; same values as MIKEY */ +enum +{ + SRTP_PRF_AES_CM=0, //< AES counter mode +}; + +# ifdef __cplusplus +extern "C" { +# endif + +srtp_session_t *srtp_create (int encr, int auth, unsigned tag_len, int prf, + unsigned flags); +void srtp_destroy (srtp_session_t *s); + +int srtp_setkey (srtp_session_t *s, const void *key, size_t keylen, + const void *salt, size_t saltlen); +int srtp_setkeystring (srtp_session_t *s, const char *key, const char *salt); + +void srtp_setrcc_rate (srtp_session_t *s, uint16_t rate); + +int srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsize); +int srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp); +int srtcp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsiz); +int srtcp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp); + +# ifdef __cplusplus +} +# endif +#endif \ No newline at end of file diff --git a/plugins/crypto-vala/src/srtp.vapi b/plugins/crypto-vala/src/srtp.vapi new file mode 100644 index 00000000..0fe825c3 --- /dev/null +++ b/plugins/crypto-vala/src/srtp.vapi @@ -0,0 +1,107 @@ +[CCode (cheader_filename="srtp.h")] +namespace Crypto.Srtp { + +[Compact] +[CCode (cname = "srtp_session_t", free_function = "srtp_destroy")] +public class Session { + [CCode (cname = "srtp_create")] + public Session(Encryption encr, Authentication auth, uint tag_len, Prf prf, Flags flags); + [CCode (cname = "srtp_setkey")] + public int setkey(uint8[] key, uint8[] salt); + [CCode (cname = "srtp_setkeystring")] + public int setkeystring(string key, string salt); + [CCode (cname = "srtp_setrcc_rate")] + public void setrcc_rate(uint16 rate); + + [CCode (cname = "srtp_send")] + private int rtp_send([CCode (array_length = false)] uint8[] buf, ref size_t len, size_t maxsize); + [CCode (cname = "srtcp_send")] + private int rtcp_send([CCode (array_length = false)] uint8[] buf, ref size_t len, size_t maxsize); + [CCode (cname = "srtp_recv")] + private int rtp_recv([CCode (array_length = false)] uint8[] buf, ref size_t len); + [CCode (cname = "srtcp_recv")] + private int rtcp_recv([CCode (array_length = false)] uint8[] buf, ref size_t len); + + public uint8[] encrypt_rtp(uint8[] input, uint tag_len = 10) throws GLib.Error { + uint8[] buf = new uint8[input.length + tag_len]; + GLib.Memory.copy(buf, input, input.length); + size_t buf_use = input.length; + int res = rtp_send(buf, ref buf_use, buf.length); + if (res != 0) { + throw new GLib.Error(-1, res, "RTP encrypt failed"); + } + uint8[] ret = new uint8[buf_use]; + GLib.Memory.copy(ret, buf, buf_use); + return ret; + } + + public uint8[] encrypt_rtcp(uint8[] input, uint tag_len = 10) throws GLib.Error { + uint8[] buf = new uint8[input.length + tag_len + 4]; + GLib.Memory.copy(buf, input, input.length); + size_t buf_use = input.length; + int res = rtcp_send(buf, ref buf_use, buf.length); + if (res != 0) { + throw new GLib.Error(-1, res, "RTCP encrypt failed"); + } + uint8[] ret = new uint8[buf_use]; + GLib.Memory.copy(ret, buf, buf_use); + return ret; + } + + public uint8[] decrypt_rtp(uint8[] input) throws GLib.Error { + uint8[] buf = new uint8[input.length]; + GLib.Memory.copy(buf, input, input.length); + size_t buf_use = input.length; + int res = rtp_recv(buf, ref buf_use); + if (res != 0) { + throw new GLib.Error(-1, res, "RTP decrypt failed"); + } + uint8[] ret = new uint8[buf_use]; + GLib.Memory.copy(ret, buf, buf_use); + return ret; + } + + public uint8[] decrypt_rtcp(uint8[] input) throws GLib.Error { + uint8[] buf = new uint8[input.length]; + GLib.Memory.copy(buf, input, input.length); + size_t buf_use = input.length; + int res = rtcp_recv(buf, ref buf_use); + if (res != 0) { + throw new GLib.Error(-1, res, "RTCP decrypt failed"); + } + uint8[] ret = new uint8[buf_use]; + GLib.Memory.copy(ret, buf, buf_use); + return ret; + } +} + +[Flags] +[CCode (cname = "unsigned", cprefix = "", has_type_id = false)] +public enum Flags { + SRTP_UNENCRYPTED, + SRTCP_UNENCRYPTED, + SRTP_UNAUTHENTICATED, + SRTP_RCC_MODE1, + SRTP_RCC_MODE2, + SRTP_RCC_MODE3 +} + +[CCode (cname = "int", cprefix = "SRTP_ENCR_", has_type_id = false)] +public enum Encryption { + NULL, + AES_CM, + AES_F8 +} + +[CCode (cname = "int", cprefix = "SRTP_AUTH_", has_type_id = false)] +public enum Authentication { + NULL, + HMAC_SHA1 +} + +[CCode (cname = "int", cprefix = "SRTP_PRF_", has_type_id = false)] +public enum Prf { + AES_CM +} + +} \ No newline at end of file diff --git a/plugins/rtp/CMakeLists.txt b/plugins/rtp/CMakeLists.txt index ef2f7698..5311fac3 100644 --- a/plugins/rtp/CMakeLists.txt +++ b/plugins/rtp/CMakeLists.txt @@ -18,11 +18,10 @@ SOURCES src/video_widget.vala src/register_plugin.vala CUSTOM_VAPIS - ${CMAKE_BINARY_DIR}/exports/crypto-vala.vapi + ${CMAKE_BINARY_DIR}/exports/crypto.vapi ${CMAKE_BINARY_DIR}/exports/xmpp-vala.vapi ${CMAKE_BINARY_DIR}/exports/dino.vapi ${CMAKE_BINARY_DIR}/exports/qlite.vapi - ${CMAKE_CURRENT_SOURCE_DIR}/src/srtp.vapi PACKAGES ${RTP_PACKAGES} OPTIONS @@ -30,7 +29,7 @@ OPTIONS ) add_definitions(${VALA_CFLAGS} -DG_LOG_DOMAIN="rtp" -I${CMAKE_CURRENT_SOURCE_DIR}/src) -add_library(rtp SHARED ${RTP_VALA_C} src/srtp.c) +add_library(rtp SHARED ${RTP_VALA_C}) target_link_libraries(rtp libdino crypto-vala ${RTP_PACKAGES}) set_target_properties(rtp PROPERTIES PREFIX "") set_target_properties(rtp PROPERTIES LIBRARY_OUTPUT_DIRECTORY ${CMAKE_BINARY_DIR}/plugins/) diff --git a/plugins/rtp/src/srtp.c b/plugins/rtp/src/srtp.c deleted file mode 100644 index 708244d9..00000000 --- a/plugins/rtp/src/srtp.c +++ /dev/null @@ -1,836 +0,0 @@ -/* - * Secure RTP with libgcrypt - * Copyright (C) 2007 Rémi Denis-Courmont - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public - * License as published by the Free Software Foundation; either - * version 2.1 of the License, or (at your option) any later version. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU - * Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, write to the Free Software - * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA - */ - -/* TODO: - * Useless stuff (because nothing depends on it): - * - non-nul key derivation rate - * - MKI payload - */ - -#ifdef HAVE_CONFIG_H -# include -#endif - -#include -#include - -#include "srtp.h" - -#include -#include -#include -#include - -#include - -#ifdef _WIN32 -# include -#else -# include -#endif - -#define debug( ... ) (void)0 - -typedef struct srtp_proto_t -{ - gcry_cipher_hd_t cipher; - gcry_md_hd_t mac; - uint64_t window; - uint32_t salt[4]; -} srtp_proto_t; - -struct srtp_session_t -{ - srtp_proto_t rtp; - srtp_proto_t rtcp; - unsigned flags; - unsigned kdr; - uint32_t rtcp_index; - uint32_t rtp_roc; - uint16_t rtp_seq; - uint16_t rtp_rcc; - uint8_t tag_len; -}; - -enum -{ - SRTP_CRYPT, - SRTP_AUTH, - SRTP_SALT, - SRTCP_CRYPT, - SRTCP_AUTH, - SRTCP_SALT -}; - - -static inline unsigned rcc_mode (const srtp_session_t *s) -{ - return (s->flags >> 4) & 3; -} - - -static void proto_destroy (srtp_proto_t *p) -{ - gcry_md_close (p->mac); - gcry_cipher_close (p->cipher); -} - - -/** - * Releases all resources associated with a Secure RTP session. - */ -void srtp_destroy (srtp_session_t *s) -{ - assert (s != NULL); - - proto_destroy (&s->rtcp); - proto_destroy (&s->rtp); - free (s); -} - - -static int proto_create (srtp_proto_t *p, int gcipher, int gmd) -{ - if (gcry_cipher_open (&p->cipher, gcipher, GCRY_CIPHER_MODE_CTR, 0) == 0) - { - if (gcry_md_open (&p->mac, gmd, GCRY_MD_FLAG_HMAC) == 0) - return 0; - gcry_cipher_close (p->cipher); - } - return -1; -} - - -/** - * Allocates a Secure RTP one-way session. - * The same session cannot be used both ways because this would confuse - * internal cryptographic counters; it is however of course feasible to open - * multiple simultaneous sessions with the same master key. - * - * @param encr encryption algorithm number - * @param auth authentication algortihm number - * @param tag_len authentication tag byte length (NOT including RCC) - * @param flags OR'ed optional flags. - * - * @return NULL in case of error - */ -srtp_session_t * -srtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags) -{ - if ((flags & ~SRTP_FLAGS_MASK)) - return NULL; - - int cipher, md; - switch (encr) - { - case SRTP_ENCR_NULL: - cipher = GCRY_CIPHER_NONE; - break; - - case SRTP_ENCR_AES_CM: - cipher = GCRY_CIPHER_AES; - break; - - default: - return NULL; - } - - switch (auth) - { - case SRTP_AUTH_NULL: - md = GCRY_MD_NONE; - break; - - case SRTP_AUTH_HMAC_SHA1: - md = GCRY_MD_SHA1; - break; - - default: - return NULL; - } - - if (tag_len > gcry_md_get_algo_dlen (md)) - return NULL; - - if (prf != SRTP_PRF_AES_CM) - return NULL; - - srtp_session_t *s = malloc (sizeof (*s)); - if (s == NULL) - return NULL; - - memset (s, 0, sizeof (*s)); - s->flags = flags; - s->tag_len = tag_len; - s->rtp_rcc = 1; /* Default RCC rate */ - if (rcc_mode (s)) - { - if (tag_len < 4) - goto error; - } - - if (proto_create (&s->rtp, cipher, md) == 0) - { - if (proto_create (&s->rtcp, cipher, md) == 0) - return s; - proto_destroy (&s->rtp); - } - - error: - free (s); - return NULL; -} - - -/** - * Counter Mode encryption/decryption (ctr length = 16 bytes) - * with non-padded (truncated) text - */ -static int -do_ctr_crypt (gcry_cipher_hd_t hd, const void *ctr, uint8_t *data, size_t len) -{ - const size_t ctrlen = 16; - div_t d = div (len, ctrlen); - - if (gcry_cipher_setctr (hd, ctr, ctrlen) - || gcry_cipher_encrypt (hd, data, d.quot * ctrlen, NULL, 0)) - return -1; - - if (d.rem) - { - /* Truncated last block */ - uint8_t dummy[ctrlen]; - data += d.quot * ctrlen; - memcpy (dummy, data, d.rem); - memset (dummy + d.rem, 0, ctrlen - d.rem); - - if (gcry_cipher_encrypt (hd, dummy, ctrlen, data, ctrlen)) - return -1; - memcpy (data, dummy, d.rem); - } - - return 0; -} - - -/** - * AES-CM key derivation (saltlen = 14 bytes) - */ -static int -do_derive (gcry_cipher_hd_t prf, const void *salt, - const uint8_t *r, size_t rlen, uint8_t label, - void *out, size_t outlen) -{ - uint8_t iv[16]; - - memcpy (iv, salt, 14); - iv[14] = iv[15] = 0; - - assert (rlen < 14); - iv[13 - rlen] ^= label; - for (size_t i = 0; i < rlen; i++) - iv[sizeof (iv) - rlen + i] ^= r[i]; - - memset (out, 0, outlen); - return do_ctr_crypt (prf, iv, out, outlen); -} - - -/** - * Sets (or resets) the master key and master salt for a SRTP session. - * This must be done at least once before using srtp_send(), srtp_recv(), - * srtcp_send() or srtcp_recv(). Also, rekeying is required every - * 2^48 RTP packets or 2^31 RTCP packets (whichever comes first), - * otherwise the protocol security might be broken. - * - * @return 0 on success, in case of error: - * EINVAL invalid or unsupported key/salt sizes combination - */ -int -srtp_setkey (srtp_session_t *s, const void *key, size_t keylen, - const void *salt, size_t saltlen) -{ - /* SRTP/SRTCP cipher/salt/MAC keys derivation */ - gcry_cipher_hd_t prf; - uint8_t r[6], keybuf[20]; - - if (saltlen != 14) - return EINVAL; - - if (gcry_cipher_open (&prf, GCRY_CIPHER_AES, GCRY_CIPHER_MODE_CTR, 0) - || gcry_cipher_setkey (prf, key, keylen)) - return EINVAL; - - /* SRTP key derivation */ -#if 0 - if (s->kdr != 0) - { - uint64_t index = (((uint64_t)s->rtp_roc) << 16) | s->rtp_seq; - index /= s->kdr; - - for (int i = sizeof (r) - 1; i >= 0; i--) - { - r[i] = index & 0xff; - index = index >> 8; - } - } - else -#endif - memset (r, 0, sizeof (r)); - if (do_derive (prf, salt, r, 6, SRTP_CRYPT, keybuf, 16) - || gcry_cipher_setkey (s->rtp.cipher, keybuf, 16) - || do_derive (prf, salt, r, 6, SRTP_AUTH, keybuf, 20) - || gcry_md_setkey (s->rtp.mac, keybuf, 20) - || do_derive (prf, salt, r, 6, SRTP_SALT, s->rtp.salt, 14)) - return -1; - - /* SRTCP key derivation */ - memcpy (r, &(uint32_t){ htonl (s->rtcp_index) }, 4); - if (do_derive (prf, salt, r, 4, SRTCP_CRYPT, keybuf, 16) - || gcry_cipher_setkey (s->rtcp.cipher, keybuf, 16) - || do_derive (prf, salt, r, 4, SRTCP_AUTH, keybuf, 20) - || gcry_md_setkey (s->rtcp.mac, keybuf, 20) - || do_derive (prf, salt, r, 4, SRTCP_SALT, s->rtcp.salt, 14)) - return -1; - - (void)gcry_cipher_close (prf); - return 0; -} - -static int hexdigit (char c) -{ - if ((c >= '0') && (c <= '9')) - return c - '0'; - if ((c >= 'A') && (c <= 'F')) - return c - 'A' + 0xA; - if ((c >= 'a') && (c <= 'f')) - return c - 'a' + 0xa; - return -1; -} - -static ssize_t hexstring (const char *in, uint8_t *out, size_t outlen) -{ - size_t inlen = strlen (in); - - if ((inlen > (2 * outlen)) || (inlen & 1)) - return -1; - - for (size_t i = 0; i < inlen; i += 2) - { - int a = hexdigit (in[i]), b = hexdigit (in[i + 1]); - if ((a == -1) || (b == -1)) - return -1; - out[i / 2] = (a << 4) | b; - } - return inlen / 2; -} - -/** - * Sets (or resets) the master key and master salt for a SRTP session - * from hexadecimal strings. See also srtp_setkey(). - * - * @return 0 on success, in case of error: - * EINVAL invalid or unsupported key/salt sizes combination - */ -int -srtp_setkeystring (srtp_session_t *s, const char *key, const char *salt) -{ - uint8_t bkey[16]; /* TODO/NOTE: hard-coded for AES */ - uint8_t bsalt[14]; /* TODO/NOTE: hard-coded for the PRF-AES-CM */ - ssize_t bkeylen = hexstring (key, bkey, sizeof (bkey)); - ssize_t bsaltlen = hexstring (salt, bsalt, sizeof (bsalt)); - - if ((bkeylen == -1) || (bsaltlen == -1)) - return EINVAL; - return srtp_setkey (s, bkey, bkeylen, bsalt, bsaltlen) ? EINVAL : 0; -} - -/** - * Sets Roll-over-Counter Carry (RCC) rate for the SRTP session. If not - * specified (through this function), the default rate of ONE is assumed - * (i.e. every RTP packets will carry the RoC). RCC rate is ignored if none - * of the RCC mode has been selected. - * - * The RCC mode is selected through one of these flags for srtp_create(): - * SRTP_RCC_MODE1: integrity protection only for RoC carrying packets - * SRTP_RCC_MODE2: integrity protection for all packets - * SRTP_RCC_MODE3: no integrity protection - * - * RCC mode 3 is insecure. Compared to plain RTP, it provides confidentiality - * (through encryption) but is much more prone to DoS. It can only be used if - * anti-spoofing protection is provided by lower network layers (e.g. IPsec, - * or trusted routers and proper source address filtering). - * - * If RCC rate is 1, RCC mode 1 and 2 are functionally identical. - * - * @param rate RoC Carry rate (MUST NOT be zero) - */ -void srtp_setrcc_rate (srtp_session_t *s, uint16_t rate) -{ - assert (rate != 0); - s->rtp_rcc = rate; -} - - -/** AES-CM for RTP (salt = 14 bytes + 2 nul bytes) */ -static int -rtp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t roc, uint16_t seq, - const uint32_t *salt, uint8_t *data, size_t len) -{ - /* Determines cryptographic counter (IV) */ - uint32_t counter[4]; - counter[0] = salt[0]; - counter[1] = salt[1] ^ ssrc; - counter[2] = salt[2] ^ htonl (roc); - counter[3] = salt[3] ^ htonl (seq << 16); - - /* Encryption */ - return do_ctr_crypt (hd, counter, data, len); -} - - -/** Determines SRTP Roll-Over-Counter (in host-byte order) */ -static uint32_t -srtp_compute_roc (const srtp_session_t *s, uint16_t seq) -{ - uint32_t roc = s->rtp_roc; - - if (((seq - s->rtp_seq) & 0xffff) < 0x8000) - { - /* Sequence is ahead, good */ - if (seq < s->rtp_seq) - roc++; /* Sequence number wrap */ - } - else - { - /* Sequence is late, bad */ - if (seq > s->rtp_seq) - roc--; /* Wrap back */ - } - return roc; -} - - -/** Returns RTP sequence (in host-byte order) */ -static inline uint16_t rtp_seq (const uint8_t *buf) -{ - return (buf[2] << 8) | buf[3]; -} - - -/** Message Authentication and Integrity for RTP */ -static const uint8_t * -rtp_digest (gcry_md_hd_t md, const uint8_t *data, size_t len, - uint32_t roc) -{ - gcry_md_reset (md); - gcry_md_write (md, data, len); - gcry_md_write (md, &(uint32_t){ htonl (roc) }, 4); - return gcry_md_read (md, 0); -} - - -/** - * Encrypts/decrypts a RTP packet and updates SRTP context - * (CTR block cypher mode of operation has identical encryption and - * decryption function). - * - * @param buf RTP packet to be en-/decrypted - * @param len RTP packet length - * - * @return 0 on success, in case of error: - * EINVAL malformatted RTP packet - * EACCES replayed packet or out-of-window or sync lost - */ -static int srtp_crypt (srtp_session_t *s, uint8_t *buf, size_t len) -{ - assert (s != NULL); - assert (len >= 12u); - - if ((buf[0] >> 6) != 2) - return EINVAL; - - /* Computes encryption offset */ - uint16_t offset = 12; - offset += (buf[0] & 0xf) * 4; // skips CSRC - - if (buf[0] & 0x10) - { - uint16_t extlen; - - offset += 4; - if (len < offset) - return EINVAL; - - memcpy (&extlen, buf + offset - 2, 2); - offset += htons (extlen); // skips RTP extension header - } - - if (len < offset) - return EINVAL; - - /* Determines RTP 48-bits counter and SSRC */ - uint16_t seq = rtp_seq (buf); - uint32_t roc = srtp_compute_roc (s, seq), ssrc; - memcpy (&ssrc, buf + 8, 4); - - /* Updates ROC and sequence (it's safe now) */ - int16_t diff = seq - s->rtp_seq; - if (diff > 0) - { - /* Sequence in the future, good */ - s->rtp.window = s->rtp.window << diff; - s->rtp.window |= UINT64_C(1); - s->rtp_seq = seq, s->rtp_roc = roc; - } - else - { - /* Sequence in the past/present, bad */ - diff = -diff; - if ((diff >= 64) || ((s->rtp.window >> diff) & 1)) - return EACCES; /* Replay attack */ - s->rtp.window |= UINT64_C(1) << diff; - } - - /* Encrypt/Decrypt */ - if (s->flags & SRTP_UNENCRYPTED) - return 0; - - if (rtp_crypt (s->rtp.cipher, ssrc, roc, seq, s->rtp.salt, - buf + offset, len - offset)) - return EINVAL; - - return 0; -} - - -/** - * Turns a RTP packet into a SRTP packet: encrypt it, then computes - * the authentication tag and appends it. - * Note that you can encrypt packet in disorder. - * - * @param buf RTP packet to be encrypted/digested - * @param lenp pointer to the RTP packet length on entry, - * set to the SRTP length on exit (undefined on non-ENOSPC error) - * @param bufsize size (bytes) of the packet buffer - * - * @return 0 on success, in case of error: - * EINVAL malformatted RTP packet or internal error - * ENOSPC bufsize is too small to add authentication tag - * ( will hold the required byte size) - * EACCES packet would trigger a replay error on receiver - */ -int -srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize) -{ - size_t len = *lenp; - size_t tag_len; - size_t roc_len = 0; - - /* Compute required buffer size */ - if (len < 12u) - return EINVAL; - - if (!(s->flags & SRTP_UNAUTHENTICATED)) - { - tag_len = s->tag_len; - - if (rcc_mode (s)) - { - assert (tag_len >= 4); - assert (s->rtp_rcc != 0); - if ((rtp_seq (buf) % s->rtp_rcc) == 0) - { - roc_len = 4; - if (rcc_mode (s) == 3) - tag_len = 0; /* RCC mode 3 -> no auth*/ - else - tag_len -= 4; /* RCC mode 1 or 2 -> auth*/ - } - else - { - if (rcc_mode (s) & 1) - tag_len = 0; /* RCC mode 1 or 3 -> no auth */ - } - } - - *lenp = len + roc_len + tag_len; - } - else - tag_len = 0; - - if (bufsize < *lenp) - return ENOSPC; - - /* Encrypt payload */ - int val = srtp_crypt (s, buf, len); - if (val) - return val; - - /* Authenticate payload */ - if (!(s->flags & SRTP_UNAUTHENTICATED)) - { - uint32_t roc = srtp_compute_roc (s, rtp_seq (buf)); - const uint8_t *tag = rtp_digest (s->rtp.mac, buf, len, roc); - - if (roc_len) - { - memcpy (buf + len, &(uint32_t){ htonl (s->rtp_roc) }, 4); - len += 4; - } - memcpy (buf + len, tag, tag_len); -#if 0 - printf ("Sent : 0x"); - for (unsigned i = 0; i < tag_len; i++) - printf ("%02x", tag[i]); - puts (""); -#endif - } - - return 0; -} - - -/** - * Turns a SRTP packet into a RTP packet: authenticates the packet, - * then decrypts it. - * - * @param buf RTP packet to be digested/decrypted - * @param lenp pointer to the SRTP packet length on entry, - * set to the RTP length on exit (undefined in case of error) - * - * @return 0 on success, in case of error: - * EINVAL malformatted SRTP packet - * EACCES authentication failed (spoofed packet or out-of-sync) - */ -int -srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp) -{ - size_t len = *lenp; - if (len < 12u) - return EINVAL; - - if (!(s->flags & SRTP_UNAUTHENTICATED)) - { - size_t tag_len = s->tag_len, roc_len = 0; - if (rcc_mode (s)) - { - if ((rtp_seq (buf) % s->rtp_rcc) == 0) - { - roc_len = 4; - if (rcc_mode (s) == 3) - tag_len = 0; - else - tag_len -= 4; - } - else - { - if (rcc_mode (s) & 1) - tag_len = 0; // RCC mode 1 or 3: no auth - } - } - - if (len < (12u + roc_len + tag_len)) - return EINVAL; - len -= roc_len + tag_len; - - uint32_t roc = srtp_compute_roc (s, rtp_seq (buf)), rcc; - if (roc_len) - { - assert (roc_len == 4); - memcpy (&rcc, buf + len, 4); - rcc = ntohl (rcc); - } - else - rcc = roc; - - const uint8_t *tag = rtp_digest (s->rtp.mac, buf, len, rcc); -#if 0 - printf ("Computed: 0x"); - for (unsigned i = 0; i < tag_len; i++) - printf ("%02x", tag[i]); - printf ("\nReceived: 0x"); - for (unsigned i = 0; i < tag_len; i++) - printf ("%02x", buf[len + roc_len + i]); - puts (""); -#endif - if (memcmp (buf + len + roc_len, tag, tag_len)) - return EACCES; - - if (roc_len) - { - /* Authenticated packet carried a Roll-Over-Counter */ - s->rtp_roc += rcc - roc; - assert (srtp_compute_roc (s, rtp_seq (buf)) == rcc); - } - *lenp = len; - } - - return srtp_crypt (s, buf, len); -} - - -/** AES-CM for RTCP (salt = 14 bytes + 2 nul bytes) */ -static int -rtcp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t index, - const uint32_t *salt, uint8_t *data, size_t len) -{ - return rtp_crypt (hd, ssrc, index >> 16, index & 0xffff, salt, data, len); -} - - -/** Message Authentication and Integrity for RTCP */ -static const uint8_t * -rtcp_digest (gcry_md_hd_t md, const void *data, size_t len) -{ - gcry_md_reset (md); - gcry_md_write (md, data, len); - return gcry_md_read (md, 0); -} - - -/** - * Encrypts/decrypts a RTCP packet and updates SRTCP context - * (CTR block cypher mode of operation has identical encryption and - * decryption function). - * - * @param buf RTCP packet to be en-/decrypted - * @param len RTCP packet length - * - * @return 0 on success, in case of error: - * EINVAL malformatted RTCP packet - */ -static int srtcp_crypt (srtp_session_t *s, uint8_t *buf, size_t len) -{ - assert (s != NULL); - - /* 8-bytes unencrypted header, and 4-bytes unencrypted footer */ - if ((len < 12) || ((buf[0] >> 6) != 2)) - return EINVAL; - - uint32_t index; - memcpy (&index, buf + len, 4); - index = ntohl (index); - if (((index >> 31) != 0) != ((s->flags & SRTCP_UNENCRYPTED) == 0)) - return EINVAL; // E-bit mismatch - - index &= ~(1 << 31); // clear E-bit for counter - - /* Updates SRTCP index (safe here) */ - int32_t diff = index - s->rtcp_index; - if (diff > 0) - { - /* Packet in the future, good */ - s->rtcp.window = s->rtcp.window << diff; - s->rtcp.window |= UINT64_C(1); - s->rtcp_index = index; - } - else - { - /* Packet in the past/present, bad */ - diff = -diff; - if ((diff >= 64) || ((s->rtcp.window >> diff) & 1)) - return EACCES; // replay attack! - s->rtp.window |= UINT64_C(1) << diff; - } - - /* Crypts SRTCP */ - if (s->flags & SRTCP_UNENCRYPTED) - return 0; - - uint32_t ssrc; - memcpy (&ssrc, buf + 4, 4); - - if (rtcp_crypt (s->rtcp.cipher, ssrc, index, s->rtp.salt, - buf + 8, len - 8)) - return EINVAL; - return 0; -} - - -/** - * Turns a RTCP packet into a SRTCP packet: encrypt it, then computes - * the authentication tag and appends it. - * - * @param buf RTCP packet to be encrypted/digested - * @param lenp pointer to the RTCP packet length on entry, - * set to the SRTCP length on exit (undefined in case of error) - * @param bufsize size (bytes) of the packet buffer - * - * @return 0 on success, in case of error: - * EINVAL malformatted RTCP packet or internal error - * ENOSPC bufsize is too small (to add index and authentication tag) - */ -int -srtcp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t bufsize) -{ - size_t len = *lenp; - if (bufsize < (len + 4 + s->tag_len)) - return ENOSPC; - - uint32_t index = ++s->rtcp_index; - if (index >> 31) - s->rtcp_index = index = 0; /* 31-bit wrap */ - - if ((s->flags & SRTCP_UNENCRYPTED) == 0) - index |= 0x80000000; /* Set Encrypted bit */ - memcpy (buf + len, &(uint32_t){ htonl (index) }, 4); - - int val = srtcp_crypt (s, buf, len); - if (val) - return val; - - len += 4; /* Digests SRTCP index too */ - - const uint8_t *tag = rtcp_digest (s->rtcp.mac, buf, len); - memcpy (buf + len, tag, s->tag_len); - *lenp = len + s->tag_len; - return 0; -} - - -/** - * Turns a SRTCP packet into a RTCP packet: authenticates the packet, - * then decrypts it. - * - * @param buf RTCP packet to be digested/decrypted - * @param lenp pointer to the SRTCP packet length on entry, - * set to the RTCP length on exit (undefined in case of error) - * - * @return 0 on success, in case of error: - * EINVAL malformatted SRTCP packet - * EACCES authentication failed (spoofed packet or out-of-sync) - */ -int -srtcp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp) -{ - size_t len = *lenp; - - if (len < (4u + s->tag_len)) - return EINVAL; - len -= s->tag_len; - - const uint8_t *tag = rtcp_digest (s->rtcp.mac, buf, len); - if (memcmp (buf + len, tag, s->tag_len)) - return EACCES; - - len -= 4; /* Remove SRTCP index before decryption */ - *lenp = len; - return srtcp_crypt (s, buf, len); -} \ No newline at end of file diff --git a/plugins/rtp/src/srtp.h b/plugins/rtp/src/srtp.h deleted file mode 100644 index abca6988..00000000 --- a/plugins/rtp/src/srtp.h +++ /dev/null @@ -1,82 +0,0 @@ -/* - * Secure RTP with libgcrypt - * Copyright (C) 2007 Rémi Denis-Courmont - * - * This library is free software; you can redistribute it and/or - * modify it under the terms of the GNU Lesser General Public License - * as published by the Free Software Foundation; either version 2.1 - * of the License, or (at your option) any later version. - * - * This library is distributed in the hope that it will be useful, - * but WITHOUT ANY WARRANTY; without even the implied warranty of - * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the - * GNU Lesser General Public License for more details. - * - * You should have received a copy of the GNU Lesser General Public - * License along with this library; if not, write to the Free Software - * Foundation, Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA - ****************************************************************************/ - -#ifndef LIBVLC_SRTP_H -# define LIBVLC_SRTP_H 1 -#include - -typedef struct srtp_session_t srtp_session_t; - -enum -{ - SRTP_UNENCRYPTED=0x1, //< do not encrypt SRTP packets - SRTCP_UNENCRYPTED=0x2, //< do not encrypt SRTCP packets - SRTP_UNAUTHENTICATED=0x4, //< authenticate only SRTCP packets - - SRTP_RCC_MODE1=0x10, //< use Roll-over-Counter Carry mode 1 - SRTP_RCC_MODE2=0x20, //< use Roll-over-Counter Carry mode 2 - SRTP_RCC_MODE3=0x30, //< use Roll-over-Counter Carry mode 3 (insecure) - - SRTP_FLAGS_MASK=0x37 //< mask for valid flags -}; - -/** SRTP encryption algorithms (ciphers); same values as MIKEY */ -enum -{ - SRTP_ENCR_NULL=0, //< no encryption - SRTP_ENCR_AES_CM=1, //< AES counter mode - SRTP_ENCR_AES_F8=2, //< AES F8 mode (not implemented) -}; - -/** SRTP authenticaton algorithms; same values as MIKEY */ -enum -{ - SRTP_AUTH_NULL=0, //< no authentication code - SRTP_AUTH_HMAC_SHA1=1, //< HMAC-SHA1 -}; - -/** SRTP pseudo random function; same values as MIKEY */ -enum -{ - SRTP_PRF_AES_CM=0, //< AES counter mode -}; - -# ifdef __cplusplus -extern "C" { -# endif - -srtp_session_t *srtp_create (int encr, int auth, unsigned tag_len, int prf, - unsigned flags); -void srtp_destroy (srtp_session_t *s); - -int srtp_setkey (srtp_session_t *s, const void *key, size_t keylen, - const void *salt, size_t saltlen); -int srtp_setkeystring (srtp_session_t *s, const char *key, const char *salt); - -void srtp_setrcc_rate (srtp_session_t *s, uint16_t rate); - -int srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsize); -int srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp); -int srtcp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsiz); -int srtcp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp); - -# ifdef __cplusplus -} -# endif -#endif \ No newline at end of file diff --git a/plugins/rtp/src/srtp.vapi b/plugins/rtp/src/srtp.vapi deleted file mode 100644 index c5ce7fec..00000000 --- a/plugins/rtp/src/srtp.vapi +++ /dev/null @@ -1,103 +0,0 @@ -[Compact] -[CCode (cname = "srtp_session_t", free_function = "srtp_destroy", cheader_filename="srtp.h")] -public class Dino.Plugins.Rtp.SrtpSession { - [CCode (cname = "srtp_create")] - public SrtpSession(SrtpEncryption encr, SrtpAuthentication auth, uint tag_len, SrtpPrf prf, SrtpFlags flags); - [CCode (cname = "srtp_setkey")] - public int setkey(uint8[] key, uint8[] salt); - [CCode (cname = "srtp_setkeystring")] - public int setkeystring(string key, string salt); - [CCode (cname = "srtp_setrcc_rate")] - public void setrcc_rate(uint16 rate); - - [CCode (cname = "srtp_send")] - private int rtp_send([CCode (array_length = false)] uint8[] buf, ref size_t len, size_t maxsize); - [CCode (cname = "srtcp_send")] - private int rtcp_send([CCode (array_length = false)] uint8[] buf, ref size_t len, size_t maxsize); - [CCode (cname = "srtp_recv")] - private int rtp_recv([CCode (array_length = false)] uint8[] buf, ref size_t len); - [CCode (cname = "srtcp_recv")] - private int rtcp_recv([CCode (array_length = false)] uint8[] buf, ref size_t len); - - public uint8[] encrypt_rtp(uint8[] input, uint tag_len = 10) throws GLib.Error { - uint8[] buf = new uint8[input.length+tag_len]; - GLib.Memory.copy(buf, input, input.length); - size_t buf_use = input.length; - int res = rtp_send(buf, ref buf_use, buf.length); - if (res != 0) { - throw new GLib.Error(-1, res, "RTP encrypt failed"); - } - uint8[] ret = new uint8[buf_use]; - GLib.Memory.copy(ret, buf, buf_use); - return ret; - } - - public uint8[] encrypt_rtcp(uint8[] input, uint tag_len = 10) throws GLib.Error { - uint8[] buf = new uint8[input.length+tag_len+4]; - GLib.Memory.copy(buf, input, input.length); - size_t buf_use = input.length; - int res = rtcp_send(buf, ref buf_use, buf.length); - if (res != 0) { - throw new GLib.Error(-1, res, "RTCP encrypt failed"); - } - uint8[] ret = new uint8[buf_use]; - GLib.Memory.copy(ret, buf, buf_use); - return ret; - } - - public uint8[] decrypt_rtp(uint8[] input) throws GLib.Error { - uint8[] buf = new uint8[input.length]; - GLib.Memory.copy(buf, input, input.length); - size_t buf_use = input.length; - int res = rtp_recv(buf, ref buf_use); - if (res != 0) { - throw new GLib.Error(-1, res, "RTP decrypt failed"); - } - uint8[] ret = new uint8[buf_use]; - GLib.Memory.copy(ret, buf, buf_use); - return ret; - } - - public uint8[] decrypt_rtcp(uint8[] input) throws GLib.Error { - uint8[] buf = new uint8[input.length]; - GLib.Memory.copy(buf, input, input.length); - size_t buf_use = input.length; - int res = rtcp_recv(buf, ref buf_use); - if (res != 0) { - throw new GLib.Error(-1, res, "RTCP decrypt failed"); - } - uint8[] ret = new uint8[buf_use]; - GLib.Memory.copy(ret, buf, buf_use); - return ret; - } -} - -[Flags] -[CCode (cname = "unsigned", cprefix = "", cheader_filename="srtp.h", has_type_id = false)] -public enum Dino.Plugins.Rtp.SrtpFlags { - SRTP_UNENCRYPTED, - SRTCP_UNENCRYPTED, - SRTP_UNAUTHENTICATED, - - SRTP_RCC_MODE1, - SRTP_RCC_MODE2, - SRTP_RCC_MODE3 -} - -[CCode (cname = "int", cprefix = "SRTP_ENCR_", cheader_filename="srtp.h", has_type_id = false)] -public enum Dino.Plugins.Rtp.SrtpEncryption { - NULL, - AES_CM, - AES_F8 -} - -[CCode (cname = "int", cprefix = "SRTP_AUTH_", cheader_filename="srtp.h", has_type_id = false)] -public enum Dino.Plugins.Rtp.SrtpAuthentication { - NULL, - HMAC_SHA1 -} - -[CCode (cname = "int", cprefix = "SRTP_PRF_", cheader_filename="srtp.h", has_type_id = false)] -public enum Dino.Plugins.Rtp.SrtpPrf { - AES_CM -} \ No newline at end of file diff --git a/plugins/rtp/src/stream.vala b/plugins/rtp/src/stream.vala index 362e2d16..77080a09 100644 --- a/plugins/rtp/src/stream.vala +++ b/plugins/rtp/src/stream.vala @@ -53,8 +53,8 @@ public class Dino.Plugins.Rtp.Stream : Xmpp.Xep.JingleRtp.Stream { private Gst.Pad send_rtp_sink_pad; private Gst.Pad send_rtp_src_pad; - private SrtpSession? local_crypto_session; - private SrtpSession? remote_crypto_session; + private Crypto.Srtp.Session? local_crypto_session; + private Crypto.Srtp.Session? remote_crypto_session; public Stream(Plugin plugin, Xmpp.Xep.Jingle.Content content) { base(content); @@ -149,11 +149,11 @@ public class Dino.Plugins.Rtp.Stream : Xmpp.Xep.JingleRtp.Stream { private void prepare_local_crypto() { if (local_crypto != null && local_crypto_session == null) { - local_crypto_session = new SrtpSession( - local_crypto.crypto_suite == Xep.JingleRtp.Crypto.F8_128_HMAC_SHA1_80 ? SrtpEncryption.AES_F8 : SrtpEncryption.AES_CM, - SrtpAuthentication.HMAC_SHA1, + local_crypto_session = new Crypto.Srtp.Session( + local_crypto.crypto_suite == Xep.JingleRtp.Crypto.F8_128_HMAC_SHA1_80 ? Crypto.Srtp.Encryption.AES_F8 : Crypto.Srtp.Encryption.AES_CM, + Crypto.Srtp.Authentication.HMAC_SHA1, local_crypto.crypto_suite == Xep.JingleRtp.Crypto.AES_CM_128_HMAC_SHA1_32 ? 4 : 10, - SrtpPrf.AES_CM, + Crypto.Srtp.Prf.AES_CM, 0 ); local_crypto_session.setkey(local_crypto.key, local_crypto.salt); @@ -284,11 +284,11 @@ public class Dino.Plugins.Rtp.Stream : Xmpp.Xep.JingleRtp.Stream { private void prepare_remote_crypto() { if (remote_crypto != null && remote_crypto_session == null) { - remote_crypto_session = new SrtpSession( - remote_crypto.crypto_suite == Xep.JingleRtp.Crypto.F8_128_HMAC_SHA1_80 ? SrtpEncryption.AES_F8 : SrtpEncryption.AES_CM, - SrtpAuthentication.HMAC_SHA1, + remote_crypto_session = new Crypto.Srtp.Session( + remote_crypto.crypto_suite == Xep.JingleRtp.Crypto.F8_128_HMAC_SHA1_80 ? Crypto.Srtp.Encryption.AES_F8 : Crypto.Srtp.Encryption.AES_CM, + Crypto.Srtp.Authentication.HMAC_SHA1, remote_crypto.crypto_suite == Xep.JingleRtp.Crypto.AES_CM_128_HMAC_SHA1_32 ? 4 : 10, - SrtpPrf.AES_CM, + Crypto.Srtp.Prf.AES_CM, 0 ); remote_crypto_session.setkey(remote_crypto.key, remote_crypto.salt); -- cgit v1.2.3-54-g00ecf