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-rw-r--r--libavformat/srtp.c293
-rw-r--r--libavformat/srtp.h52
2 files changed, 345 insertions, 0 deletions
diff --git a/libavformat/srtp.c b/libavformat/srtp.c
new file mode 100644
index 0000000000..6c589b0354
--- /dev/null
+++ b/libavformat/srtp.c
@@ -0,0 +1,293 @@
+/*
+ * SRTP encryption/decryption
+ * Copyright (c) 2012 Martin Storsjo
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#include "libavutil/base64.h"
+#include "libavutil/aes.h"
+#include "libavutil/hmac.h"
+#include "libavutil/intreadwrite.h"
+#include "libavutil/log.h"
+#include "rtp.h"
+#include "srtp.h"
+
+void ff_srtp_free(struct SRTPContext *s)
+{
+ if (!s)
+ return;
+ av_freep(&s->aes);
+ if (s->hmac)
+ av_hmac_free(s->hmac);
+ s->hmac = NULL;
+}
+
+static void encrypt_counter(struct AVAES *aes, uint8_t *iv, uint8_t *outbuf,
+ int outlen)
+{
+ int i, j, outpos;
+ for (i = 0, outpos = 0; outpos < outlen; i++) {
+ uint8_t keystream[16];
+ AV_WB16(&iv[14], i);
+ av_aes_crypt(aes, keystream, iv, 1, NULL, 0);
+ for (j = 0; j < 16 && outpos < outlen; j++, outpos++)
+ outbuf[outpos] ^= keystream[j];
+ }
+}
+
+static void derive_key(struct AVAES *aes, const uint8_t *salt, int label,
+ uint8_t *out, int outlen)
+{
+ uint8_t input[16] = { 0 };
+ memcpy(input, salt, 14);
+ // Key derivation rate assumed to be zero
+ input[14 - 7] ^= label;
+ memset(out, 0, outlen);
+ encrypt_counter(aes, input, out, outlen);
+}
+
+int ff_srtp_set_crypto(struct SRTPContext *s, const char *suite,
+ const char *params)
+{
+ uint8_t buf[30];
+
+ ff_srtp_free(s);
+
+ // RFC 4568
+ if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_80")) {
+ s->hmac_size = 10;
+ } else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
+ s->hmac_size = 4;
+ } else {
+ av_log(NULL, AV_LOG_WARNING, "SRTP Crypto suite %s not supported\n",
+ suite);
+ return AVERROR(EINVAL);
+ }
+ if (av_base64_decode(buf, params, sizeof(buf)) != sizeof(buf)) {
+ av_log(NULL, AV_LOG_WARNING, "Incorrect amount of SRTP params\n");
+ return AVERROR(EINVAL);
+ }
+ // MKI and lifetime not handled yet
+ s->aes = av_aes_alloc();
+ s->hmac = av_hmac_alloc(AV_HMAC_SHA1);
+ if (!s->aes || !s->hmac)
+ return AVERROR(ENOMEM);
+ memcpy(s->master_key, buf, 16);
+ memcpy(s->master_salt, buf + 16, 14);
+
+ // RFC 3711
+ av_aes_init(s->aes, s->master_key, 128, 0);
+
+ derive_key(s->aes, s->master_salt, 0x00, s->rtp_key, sizeof(s->rtp_key));
+ derive_key(s->aes, s->master_salt, 0x02, s->rtp_salt, sizeof(s->rtp_salt));
+ derive_key(s->aes, s->master_salt, 0x01, s->rtp_auth, sizeof(s->rtp_auth));
+
+ derive_key(s->aes, s->master_salt, 0x03, s->rtcp_key, sizeof(s->rtcp_key));
+ derive_key(s->aes, s->master_salt, 0x05, s->rtcp_salt, sizeof(s->rtcp_salt));
+ derive_key(s->aes, s->master_salt, 0x04, s->rtcp_auth, sizeof(s->rtcp_auth));
+ return 0;
+}
+
+static void create_iv(uint8_t *iv, const uint8_t *salt, uint64_t index,
+ uint32_t ssrc)
+{
+ uint8_t indexbuf[8];
+ int i;
+ memset(iv, 0, 16);
+ AV_WB32(&iv[4], ssrc);
+ AV_WB64(indexbuf, index);
+ for (i = 0; i < 8; i++) // index << 16
+ iv[6 + i] ^= indexbuf[i];
+ for (i = 0; i < 14; i++)
+ iv[i] ^= salt[i];
+}
+
+int ff_srtp_decrypt(struct SRTPContext *s, uint8_t *buf, int *lenptr)
+{
+ uint8_t iv[16] = { 0 }, hmac[20];
+ int len = *lenptr;
+ int ext, seq_largest;
+ uint32_t ssrc, roc;
+ uint64_t index;
+ int rtcp;
+
+ // TODO: Missing replay protection
+
+ if (len < s->hmac_size)
+ return AVERROR_INVALIDDATA;
+
+ rtcp = RTP_PT_IS_RTCP(buf[1]);
+
+ // Authentication HMAC
+ av_hmac_init(s->hmac, rtcp ? s->rtcp_auth : s->rtp_auth, sizeof(s->rtp_auth));
+ // If MKI is used, this should exclude the MKI as well
+ av_hmac_update(s->hmac, buf, len - s->hmac_size);
+
+ if (!rtcp) {
+ int seq = AV_RB16(buf + 2);
+ uint32_t v;
+ uint8_t rocbuf[4];
+
+ // RFC 3711 section 3.3.1, appendix A
+ seq_largest = s->seq_initialized ? s->seq_largest : seq;
+ v = roc = s->roc;
+ if (seq_largest < 32768) {
+ if (seq - seq_largest > 32768)
+ v = roc - 1;
+ } else {
+ if (seq_largest - 32768 > seq)
+ v = roc + 1;
+ }
+ if (v == roc) {
+ seq_largest = FFMAX(seq_largest, seq);
+ } else if (v == roc + 1) {
+ seq_largest = seq;
+ roc = v;
+ }
+ index = seq + (((uint64_t)v) << 16);
+
+ AV_WB32(rocbuf, roc);
+ av_hmac_update(s->hmac, rocbuf, 4);
+ }
+
+ av_hmac_final(s->hmac, hmac, sizeof(hmac));
+ if (memcmp(hmac, buf + len - s->hmac_size, s->hmac_size)) {
+ av_log(NULL, AV_LOG_WARNING, "HMAC mismatch\n");
+ return AVERROR_INVALIDDATA;
+ }
+
+ len -= s->hmac_size;
+ *lenptr = len;
+
+ if (len < 12)
+ return AVERROR_INVALIDDATA;
+
+ if (rtcp) {
+ uint32_t srtcp_index = AV_RB32(buf + len - 4);
+ len -= 4;
+ *lenptr = len;
+
+ ssrc = AV_RB32(buf + 4);
+ index = srtcp_index & 0x7fffffff;
+
+ buf += 8;
+ len -= 8;
+ if (!(srtcp_index & 0x80000000))
+ return 0;
+ } else {
+ s->seq_initialized = 1;
+ s->seq_largest = seq_largest;
+ s->roc = roc;
+
+ ext = buf[0] & 0x10;
+ ssrc = AV_RB32(buf + 8);
+
+ buf += 12;
+ len -= 12;
+
+ if (ext) {
+ if (len < 4)
+ return AVERROR_INVALIDDATA;
+ ext = (AV_RB16(buf + 2) + 1) * 4;
+ if (len < ext)
+ return AVERROR_INVALIDDATA;
+ len -= ext;
+ buf += ext;
+ }
+ }
+
+ create_iv(iv, rtcp ? s->rtcp_salt : s->rtp_salt, index, ssrc);
+ av_aes_init(s->aes, rtcp ? s->rtcp_key : s->rtp_key, 128, 0);
+ encrypt_counter(s->aes, iv, buf, len);
+
+ return 0;
+}
+
+int ff_srtp_encrypt(struct SRTPContext *s, const uint8_t *in, int len,
+ uint8_t *out, int outlen)
+{
+ uint8_t iv[16] = { 0 }, hmac[20];
+ uint64_t index;
+ uint32_t ssrc;
+ int rtcp;
+ uint8_t *buf;
+
+ if (len + 14 > outlen)
+ return 0;
+ if (len < 12)
+ return 0;
+
+ memcpy(out, in, len);
+ buf = out;
+
+ rtcp = RTP_PT_IS_RTCP(buf[1]);
+
+ if (rtcp) {
+ ssrc = AV_RB32(buf + 4);
+ index = s->rtcp_index++;
+
+ buf += 8;
+ len -= 8;
+ } else {
+ int ext;
+ int seq = AV_RB16(buf + 2);
+ ssrc = AV_RB32(buf + 8);
+
+ if (seq < s->seq_largest)
+ s->roc++;
+ s->seq_largest = seq;
+ index = seq + (((uint64_t)s->roc) << 16);
+
+ ext = buf[0] & 0x10;
+
+ buf += 12;
+ len -= 12;
+
+ if (ext) {
+ if (len < 4)
+ return AVERROR_INVALIDDATA;
+ ext = (AV_RB16(buf + 2) + 1) * 4;
+ if (len < ext)
+ return AVERROR_INVALIDDATA;
+ len -= ext;
+ buf += ext;
+ }
+ }
+
+ create_iv(iv, rtcp ? s->rtcp_salt : s->rtp_salt, index, ssrc);
+ av_aes_init(s->aes, rtcp ? s->rtcp_key : s->rtp_key, 128, 0);
+ encrypt_counter(s->aes, iv, buf, len);
+
+ if (rtcp) {
+ AV_WB32(buf + len, 0x80000000 | index);
+ len += 4;
+ }
+
+ av_hmac_init(s->hmac, rtcp ? s->rtcp_auth : s->rtp_auth, sizeof(s->rtp_auth));
+ av_hmac_update(s->hmac, out, buf + len - out);
+ if (!rtcp) {
+ uint8_t rocbuf[4];
+ AV_WB32(rocbuf, s->roc);
+ av_hmac_update(s->hmac, rocbuf, 4);
+ }
+ av_hmac_final(s->hmac, hmac, sizeof(hmac));
+
+ memcpy(buf + len, hmac, s->hmac_size);
+ len += s->hmac_size;
+ return buf + len - out;
+}
diff --git a/libavformat/srtp.h b/libavformat/srtp.h
new file mode 100644
index 0000000000..a1cb92d2ba
--- /dev/null
+++ b/libavformat/srtp.h
@@ -0,0 +1,52 @@
+/*
+ * SRTP encryption/decryption
+ * Copyright (c) 2012 Martin Storsjo
+ *
+ * This file is part of Libav.
+ *
+ * Libav 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.
+ *
+ * Libav 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 Libav; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+ */
+
+#ifndef AVFORMAT_SRTP_H
+#define AVFORMAT_SRTP_H
+
+#include <stdint.h>
+
+struct AVAES;
+struct AVHMAC;
+
+struct SRTPContext {
+ struct AVAES *aes;
+ struct AVHMAC *hmac;
+ int hmac_size;
+ uint8_t master_key[16];
+ uint8_t master_salt[14];
+ uint8_t rtp_key[16], rtcp_key[16];
+ uint8_t rtp_salt[14], rtcp_salt[14];
+ uint8_t rtp_auth[20], rtcp_auth[20];
+ int seq_largest, seq_initialized;
+ uint32_t roc;
+
+ uint32_t rtcp_index;
+};
+
+int ff_srtp_set_crypto(struct SRTPContext *s, const char *suite,
+ const char *params);
+void ff_srtp_free(struct SRTPContext *s);
+int ff_srtp_decrypt(struct SRTPContext *s, uint8_t *buf, int *lenptr);
+int ff_srtp_encrypt(struct SRTPContext *s, const uint8_t *in, int len,
+ uint8_t *out, int outlen);
+
+#endif /* AVFORMAT_SRTP_H */
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