Merge commit 'ab2ad8bd56882c0ea160b154e8b836eb71abc49d'

* commit 'ab2ad8bd56882c0ea160b154e8b836eb71abc49d':
  lavf: Add functions for SRTP decryption/encryption
  lavu: Add an API for calculating HMAC (RFC 2104)

Conflicts:
	doc/APIchanges
	libavutil/version.h

Merged-by: Michael Niedermayer <michaelni@gmx.at>

1 files changed, 293 insertions, 0 deletions

diff --git a/libavformat/srtp.c b/libavformat/srtp.c
new file mode 100644
index 0000000000..55b3b5b40c
--- /dev/null
+++ b/libavformat/srtp.c
@@ -0,0 +1,293 @@
+/*
+ * SRTP encryption/decryption
+ * Copyright (c) 2012 Martin Storsjo
+ *
+ * This file is part of FFmpeg.
+ *
+ * FFmpeg 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.
+ *
+ * FFmpeg 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 FFmpeg; 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;
+}