| /* |
| * rtp_decoder.c |
| * |
| * decoder structures and functions for SRTP pcap decoder |
| * |
| * Example: |
| * $ wget --no-check-certificate https://raw.githubusercontent.com/gteissier/srtp-decrypt/master/marseillaise-srtp.pcap |
| * $ ./test/rtp_decoder -a -t 0 -e 128 -b aSBrbm93IGFsbCB5b3VyIGxpdHRsZSBzZWNyZXRz \ |
| * < ~/marseillaise-srtp.pcap | text2pcap -t "%M:%S." -u 10000,10000 - - > ./marseillaise-rtp.pcap |
| * |
| * Bernardo Torres <bernardo@torresautomacao.com.br> |
| * |
| * Some structure and code from https://github.com/gteissier/srtp-decrypt |
| */ |
| /* |
| * |
| * Copyright (c) 2001-2006 Cisco Systems, Inc. |
| * All rights reserved. |
| * |
| * Redistribution and use in source and binary forms, with or without |
| * modification, are permitted provided that the following conditions |
| * are met: |
| * |
| * Redistributions of source code must retain the above copyright |
| * notice, this list of conditions and the following disclaimer. |
| * |
| * Redistributions in binary form must reproduce the above |
| * copyright notice, this list of conditions and the following |
| * disclaimer in the documentation and/or other materials provided |
| * with the distribution. |
| * |
| * Neither the name of the Cisco Systems, Inc. nor the names of its |
| * contributors may be used to endorse or promote products derived |
| * from this software without specific prior written permission. |
| * |
| * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS |
| * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT |
| * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS |
| * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE |
| * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, |
| * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES |
| * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR |
| * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) |
| * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, |
| * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) |
| * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED |
| * OF THE POSSIBILITY OF SUCH DAMAGE. |
| * |
| */ |
| #include "getopt_s.h" /* for local getopt() */ |
| #include <assert.h> /* for assert() */ |
| |
| #include <pcap.h> |
| #include "rtp_decoder.h" |
| #include "util.h" |
| |
| #define MAX_KEY_LEN 96 |
| #define MAX_FILTER 256 |
| |
| int |
| main (int argc, char *argv[]) { |
| char errbuf[PCAP_ERRBUF_SIZE]; |
| bpf_u_int32 pcap_net = 0; |
| pcap_t *pcap_handle; |
| #if BEW |
| struct sockaddr_in local; |
| #endif |
| srtp_sec_serv_t sec_servs = sec_serv_none; |
| int c; |
| int key_size = 128; |
| int tag_size = 8; |
| int gcm_on = 0; |
| char *input_key = NULL; |
| int b64_input = 0; |
| char key[MAX_KEY_LEN]; |
| struct bpf_program fp; |
| char filter_exp[MAX_FILTER] = ""; |
| rtp_decoder_t dec; |
| srtp_policy_t policy; |
| srtp_err_status_t status; |
| int len; |
| int expected_len; |
| int do_list_mods = 0; |
| |
| fprintf(stderr, "Using %s [0x%x]\n", srtp_get_version_string(), srtp_get_version()); |
| |
| /* initialize srtp library */ |
| status = srtp_init(); |
| if (status) { |
| fprintf(stderr, "error: srtp initialization failed with error code %d\n", status); |
| exit(1); |
| } |
| |
| /* check args */ |
| while (1) { |
| c = getopt_s(argc, argv, "b:k:gt:ae:ld:f:"); |
| if (c == -1) { |
| break; |
| } |
| switch (c) { |
| case 'b': |
| b64_input = 1; |
| /* fall thru */ |
| case 'k': |
| input_key = optarg_s; |
| break; |
| case 'e': |
| key_size = atoi(optarg_s); |
| if (key_size != 128 && key_size != 256) { |
| fprintf(stderr, "error: encryption key size must be 128 or 256 (%d)\n", key_size); |
| exit(1); |
| } |
| input_key = malloc(key_size); |
| sec_servs |= sec_serv_conf; |
| break; |
| case 't': |
| tag_size = atoi(optarg_s); |
| if (tag_size != 8 && tag_size != 16) { |
| fprintf(stderr, "error: GCM tag size must be 8 or 16 (%d)\n", tag_size); |
| //exit(1); |
| } |
| break; |
| case 'a': |
| sec_servs |= sec_serv_auth; |
| break; |
| case 'g': |
| gcm_on = 1; |
| sec_servs |= sec_serv_auth; |
| break; |
| case 'd': |
| status = srtp_crypto_kernel_set_debug_module(optarg_s, 1); |
| if (status) { |
| fprintf(stderr, "error: set debug module (%s) failed\n", optarg_s); |
| exit(1); |
| } |
| break; |
| case 'f': |
| if(strlen(optarg_s) > MAX_FILTER){ |
| fprintf(stderr, "error: filter bigger than %d characters\n", MAX_FILTER); |
| exit(1); |
| } |
| fprintf(stderr, "Setting filter as %s\n", optarg_s); |
| strcpy(filter_exp, optarg_s); |
| break; |
| case 'l': |
| do_list_mods = 1; |
| break; |
| default: |
| usage(argv[0]); |
| } |
| } |
| |
| if (do_list_mods) { |
| status = srtp_crypto_kernel_list_debug_modules(); |
| if (status) { |
| fprintf(stderr, "error: list of debug modules failed\n"); |
| exit(1); |
| } |
| return 0; |
| } |
| |
| if ((sec_servs && !input_key) || (!sec_servs && input_key)) { |
| /* |
| * a key must be provided if and only if security services have |
| * been requested |
| */ |
| if(input_key == NULL){ |
| fprintf(stderr, "key not provided\n"); |
| } |
| if(!sec_servs){ |
| fprintf(stderr, "no secservs\n"); |
| } |
| fprintf(stderr, "provided\n"); |
| usage(argv[0]); |
| } |
| |
| |
| |
| /* report security services selected on the command line */ |
| fprintf(stderr, "security services: "); |
| if (sec_servs & sec_serv_conf) |
| fprintf(stderr, "confidentiality "); |
| if (sec_servs & sec_serv_auth) |
| fprintf(stderr, "message authentication"); |
| if (sec_servs == sec_serv_none) |
| fprintf(stderr, "none"); |
| fprintf(stderr, "\n"); |
| |
| /* set up the srtp policy and master key */ |
| if (sec_servs) { |
| /* |
| * create policy structure, using the default mechanisms but |
| * with only the security services requested on the command line, |
| * using the right SSRC value |
| */ |
| switch (sec_servs) { |
| case sec_serv_conf_and_auth: |
| if (gcm_on) { |
| #ifdef OPENSSL |
| switch (key_size) { |
| case 128: |
| srtp_crypto_policy_set_aes_gcm_128_8_auth(&policy.rtp); |
| srtp_crypto_policy_set_aes_gcm_128_8_auth(&policy.rtcp); |
| break; |
| case 256: |
| srtp_crypto_policy_set_aes_gcm_256_8_auth(&policy.rtp); |
| srtp_crypto_policy_set_aes_gcm_256_8_auth(&policy.rtcp); |
| break; |
| } |
| #else |
| fprintf(stderr, "error: GCM mode only supported when using the OpenSSL crypto engine.\n"); |
| return 0; |
| #endif |
| } else { |
| switch (key_size) { |
| case 128: |
| srtp_crypto_policy_set_rtp_default(&policy.rtp); |
| srtp_crypto_policy_set_rtcp_default(&policy.rtcp); |
| break; |
| case 256: |
| srtp_crypto_policy_set_aes_cm_256_hmac_sha1_80(&policy.rtp); |
| srtp_crypto_policy_set_rtcp_default(&policy.rtcp); |
| break; |
| } |
| } |
| break; |
| case sec_serv_conf: |
| if (gcm_on) { |
| fprintf(stderr, "error: GCM mode must always be used with auth enabled\n"); |
| return -1; |
| } else { |
| switch (key_size) { |
| case 128: |
| srtp_crypto_policy_set_aes_cm_128_null_auth(&policy.rtp); |
| srtp_crypto_policy_set_rtcp_default(&policy.rtcp); |
| break; |
| case 256: |
| srtp_crypto_policy_set_aes_cm_256_null_auth(&policy.rtp); |
| srtp_crypto_policy_set_rtcp_default(&policy.rtcp); |
| break; |
| } |
| } |
| break; |
| case sec_serv_auth: |
| if (gcm_on) { |
| #ifdef OPENSSL |
| switch (key_size) { |
| case 128: |
| srtp_crypto_policy_set_aes_gcm_128_8_only_auth(&policy.rtp); |
| srtp_crypto_policy_set_aes_gcm_128_8_only_auth(&policy.rtcp); |
| break; |
| case 256: |
| srtp_crypto_policy_set_aes_gcm_256_8_only_auth(&policy.rtp); |
| srtp_crypto_policy_set_aes_gcm_256_8_only_auth(&policy.rtcp); |
| break; |
| } |
| #else |
| printf("error: GCM mode only supported when using the OpenSSL crypto engine.\n"); |
| return 0; |
| #endif |
| } else { |
| srtp_crypto_policy_set_null_cipher_hmac_sha1_80(&policy.rtp); |
| srtp_crypto_policy_set_rtcp_default(&policy.rtcp); |
| } |
| break; |
| default: |
| fprintf(stderr, "error: unknown security service requested\n"); |
| return -1; |
| } |
| |
| policy.key = (uint8_t *) key; |
| policy.ekt = NULL; |
| policy.next = NULL; |
| policy.window_size = 128; |
| policy.allow_repeat_tx = 0; |
| policy.rtp.sec_serv = sec_servs; |
| policy.rtcp.sec_serv = sec_servs; //sec_serv_none; /* we don't do RTCP anyway */ |
| fprintf(stderr, "setting tag len %d\n", tag_size); |
| policy.rtp.auth_tag_len = tag_size; |
| |
| if (gcm_on && tag_size != 8) { |
| fprintf(stderr, "setted tag len %d\n", tag_size); |
| policy.rtp.auth_tag_len = tag_size; |
| } |
| |
| /* |
| * read key from hexadecimal or base64 on command line into an octet string |
| */ |
| if (b64_input) { |
| int pad; |
| expected_len = policy.rtp.cipher_key_len*4/3; |
| len = base64_string_to_octet_string(key, &pad, input_key, expected_len); |
| if (pad != 0) { |
| fprintf(stderr, "error: padding in base64 unexpected\n"); |
| exit(1); |
| } |
| } else { |
| expected_len = policy.rtp.cipher_key_len*2; |
| len = hex_string_to_octet_string(key, input_key, expected_len); |
| } |
| /* check that hex string is the right length */ |
| if (len < expected_len) { |
| fprintf(stderr, |
| "error: too few digits in key/salt " |
| "(should be %d digits, found %d)\n", |
| expected_len, len); |
| exit(1); |
| } |
| if (strlen(input_key) > policy.rtp.cipher_key_len*2) { |
| fprintf(stderr, |
| "error: too many digits in key/salt " |
| "(should be %d hexadecimal digits, found %u)\n", |
| policy.rtp.cipher_key_len*2, (unsigned)strlen(input_key)); |
| exit(1); |
| } |
| |
| fprintf(stderr, "set master key/salt to %s/", octet_string_hex_string(key, 16)); |
| fprintf(stderr, "%s\n", octet_string_hex_string(key+16, 14)); |
| |
| } else { |
| fprintf(stderr, "error: neither encryption or authentication were selected"); |
| exit(1); |
| } |
| |
| pcap_handle = pcap_open_offline("-", errbuf); |
| |
| if (!pcap_handle) { |
| fprintf(stderr, "libpcap failed to open file '%s'\n", errbuf); |
| exit(1); |
| } |
| assert(pcap_handle != NULL); |
| if ((pcap_compile(pcap_handle, &fp, filter_exp, 1, pcap_net)) == -1){ |
| fprintf(stderr, "Couldn't parse filter %s: %s\n", filter_exp, |
| pcap_geterr(pcap_handle)); |
| return (2); |
| } |
| if (pcap_setfilter(pcap_handle, &fp) == -1){ |
| fprintf(stderr, "couldn't install filter %s: %s\n", filter_exp, |
| pcap_geterr(pcap_handle)); |
| return (2); |
| } |
| dec = rtp_decoder_alloc(); |
| if (dec == NULL) { |
| fprintf(stderr, "error: malloc() failed\n"); |
| exit(1); |
| } |
| fprintf(stderr, "Starting decoder\n"); |
| rtp_decoder_init(dec, policy); |
| |
| pcap_loop(pcap_handle, 0, rtp_decoder_handle_pkt, (u_char *)dec); |
| |
| rtp_decoder_deinit_srtp(dec); |
| rtp_decoder_dealloc(dec); |
| |
| status = srtp_shutdown(); |
| if (status) { |
| fprintf(stderr, "error: srtp shutdown failed with error code %d\n", status); |
| exit(1); |
| } |
| |
| return 0; |
| } |
| |
| |
| void |
| usage(char *string) { |
| |
| fprintf(stderr, "usage: %s [-d <debug>]* [[-k][-b] <key> [-a][-e]]\n" |
| "or %s -l\n" |
| "where -a use message authentication\n" |
| " -e <key size> use encryption (use 128 or 256 for key size)\n" |
| " -g Use AES-GCM mode (must be used with -e)\n" |
| " -t <tag size> Tag size to use in GCM mode (use 8 or 16)\n" |
| " -k <key> sets the srtp master key given in hexadecimal\n" |
| " -b <key> sets the srtp master key given in base64\n" |
| " -l list debug modules\n" |
| " -f \"<pcap filter>\" to filter only the desired SRTP packets\n" |
| " -d <debug> turn on debugging for module <debug>\n", |
| string, string); |
| exit(1); |
| |
| } |
| |
| rtp_decoder_t |
| rtp_decoder_alloc(void) { |
| return (rtp_decoder_t)malloc(sizeof(rtp_decoder_ctx_t)); |
| } |
| |
| void |
| rtp_decoder_dealloc(rtp_decoder_t rtp_ctx) { |
| free(rtp_ctx); |
| } |
| |
| srtp_err_status_t |
| rtp_decoder_init_srtp(rtp_decoder_t decoder, unsigned int ssrc) { |
| decoder->policy.ssrc.value = htonl(ssrc); |
| return srtp_create(&decoder->srtp_ctx, &decoder->policy); |
| } |
| |
| int |
| rtp_decoder_deinit_srtp(rtp_decoder_t decoder) { |
| return srtp_dealloc(decoder->srtp_ctx); |
| } |
| |
| int |
| rtp_decoder_init(rtp_decoder_t dcdr, srtp_policy_t policy){ |
| dcdr->rtp_offset = DEFAULT_RTP_OFFSET; |
| dcdr->srtp_ctx = NULL; |
| dcdr->start_tv.tv_usec = 0; |
| dcdr->start_tv.tv_sec = 0; |
| dcdr->frame_nr = -1; |
| dcdr->policy = policy; |
| dcdr->policy.ssrc.type = ssrc_specific; |
| return 0; |
| } |
| |
| /* |
| * decodes key as base64 |
| */ |
| |
| void hexdump(const void *ptr, size_t size) { |
| int i, j; |
| const unsigned char *cptr = ptr; |
| |
| for (i = 0; i < size; i += 16) { |
| fprintf(stdout, "%04x ", i); |
| for (j = 0; j < 16 && i+j < size; j++) { |
| fprintf(stdout, "%02x ", cptr[i+j]); |
| } |
| fprintf(stdout, "\n"); |
| } |
| } |
| |
| void |
| rtp_decoder_handle_pkt(u_char *arg, const struct pcap_pkthdr *hdr, |
| const u_char *bytes){ |
| rtp_decoder_t dcdr = (rtp_decoder_t)arg; |
| int pktsize; |
| struct timeval delta; |
| int octets_recvd; |
| srtp_err_status_t status; |
| dcdr->frame_nr++; |
| |
| if (dcdr->start_tv.tv_sec == 0 && dcdr->start_tv.tv_sec == 0) { |
| dcdr->start_tv = hdr->ts; |
| } |
| |
| if (hdr->caplen < dcdr->rtp_offset) { |
| return; |
| } |
| const void *rtp_packet = bytes + dcdr->rtp_offset; |
| |
| memcpy((void *)&dcdr->message, rtp_packet, hdr->caplen - dcdr->rtp_offset); |
| pktsize = hdr->caplen - dcdr->rtp_offset; |
| octets_recvd = pktsize; |
| |
| if (octets_recvd == -1) { |
| return; |
| } |
| |
| /* verify rtp header */ |
| if (dcdr->message.header.version != 2) { |
| return; //return -1; |
| } |
| if(dcdr->srtp_ctx == NULL){ |
| status = rtp_decoder_init_srtp(dcdr, dcdr->message.header.ssrc); |
| if (status) { |
| exit(1); |
| } |
| } |
| if(dcdr->srtp_ctx != NULL){ |
| } |
| status = srtp_unprotect(dcdr->srtp_ctx, &dcdr->message, &octets_recvd); |
| if (status){ |
| return; |
| } |
| timersub(&hdr->ts, &dcdr->start_tv, &delta); |
| fprintf(stdout, "%02ld:%02ld.%06lu\n", delta.tv_sec/60, delta.tv_sec%60, delta.tv_usec); |
| hexdump(&dcdr->message, pktsize); |
| } |
| |
| void rtp_print_error(srtp_err_status_t status, char *message){ |
| fprintf(stderr, |
| "error: %s %d%s\n", message, status, |
| status == srtp_err_status_replay_fail ? " (replay check failed)" : |
| status == srtp_err_status_bad_param ? " (bad param)" : |
| status == srtp_err_status_no_ctx ? " (no context)" : |
| status == srtp_err_status_cipher_fail ? " (cipher failed)" : |
| status == srtp_err_status_key_expired ? " (key expired)" : |
| status == srtp_err_status_auth_fail ? " (auth check failed)" : ""); |
| } |