libavformat/srtp.c - play-games/ffmpeg - Git at Google


            
            /*

            
             * 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 "rtpdec.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") ||

            
                    !strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_80")) {

            
                    s->rtp_hmac_size = s->rtcp_hmac_size = 10;

            
                } else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {

            
                    s->rtp_hmac_size = s->rtcp_hmac_size = 4;

            
                } else if (!strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_32")) {

            
                    // RFC 5764 section 4.1.2

            
                    s->rtp_hmac_size  = 4;

            
                    s->rtcp_hmac_size = 10;

            
                } 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 av_uninit(seq_largest);

            
                uint32_t ssrc, av_uninit(roc);

            
                uint64_t index;

            
                int rtcp, hmac_size;


                // TODO: Missing replay protection


                if (len < 2)

            
                    return AVERROR_INVALIDDATA;


                rtcp = RTP_PT_IS_RTCP(buf[1]);

            
                hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;


                if (len < hmac_size)

            
                    return AVERROR_INVALIDDATA;


                // 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 - 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 - hmac_size, hmac_size)) {

            
                    av_log(NULL, AV_LOG_WARNING, "HMAC mismatch\n");

            
                    return AVERROR_INVALIDDATA;

            
                }


                len -= 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 {

            
                    int ext, csrc;

            
                    s->seq_initialized = 1;

            
                    s->seq_largest     = seq_largest;

            
                    s->roc             = roc;


                    csrc = buf[0] & 0x0f;

            
                    ext  = buf[0] & 0x10;

            
                    ssrc = AV_RB32(buf + 8);


                    buf += 12;

            
                    len -= 12;


                    buf += 4 * csrc;

            
                    len -= 4 * csrc;

            
                    if (len < 0)

            
                        return AVERROR_INVALIDDATA;


                    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, hmac_size, padding;

            
                uint8_t *buf;


                if (len < 8)

            
                    return AVERROR_INVALIDDATA;


                rtcp = RTP_PT_IS_RTCP(in[1]);

            
                hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;

            
                padding = hmac_size;

            
                if (rtcp)

            
                    padding += 4; // For the RTCP index


                if (len + padding > outlen)

            
                    return 0;


                memcpy(out, in, len);

            
                buf = out;


                if (rtcp) {

            
                    ssrc = AV_RB32(buf + 4);

            
                    index = s->rtcp_index++;


                    buf += 8;

            
                    len -= 8;

            
                } else {

            
                    int ext, csrc;

            
                    int seq = AV_RB16(buf + 2);


                    if (len < 12)

            
                        return AVERROR_INVALIDDATA;


                    ssrc = AV_RB32(buf + 8);


                    if (seq < s->seq_largest)

            
                        s->roc++;

            
                    s->seq_largest = seq;

            
                    index = seq + (((uint64_t)s->roc) << 16);


                    csrc = buf[0] & 0x0f;

            
                    ext = buf[0] & 0x10;


                    buf += 12;

            
                    len -= 12;


                    buf += 4 * csrc;

            
                    len -= 4 * csrc;

            
                    if (len < 0)

            
                        return AVERROR_INVALIDDATA;


                    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, hmac_size);

            
                len += hmac_size;

            
                return buf + len - out;

            
            }
	/*
	* 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 "rtpdec.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") \|\|
	!strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_80")) {
	s->rtp_hmac_size = s->rtcp_hmac_size = 10;
	} else if (!strcmp(suite, "AES_CM_128_HMAC_SHA1_32")) {
	s->rtp_hmac_size = s->rtcp_hmac_size = 4;
	} else if (!strcmp(suite, "SRTP_AES128_CM_HMAC_SHA1_32")) {
	// RFC 5764 section 4.1.2
	s->rtp_hmac_size = 4;
	s->rtcp_hmac_size = 10;
	} 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 av_uninit(seq_largest);
	uint32_t ssrc, av_uninit(roc);
	uint64_t index;
	int rtcp, hmac_size;

	// TODO: Missing replay protection

	if (len < 2)
	return AVERROR_INVALIDDATA;

	rtcp = RTP_PT_IS_RTCP(buf[1]);
	hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;

	if (len < hmac_size)
	return AVERROR_INVALIDDATA;

	// 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 - 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 - hmac_size, hmac_size)) {
	av_log(NULL, AV_LOG_WARNING, "HMAC mismatch\n");
	return AVERROR_INVALIDDATA;
	}

	len -= 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 {
	int ext, csrc;
	s->seq_initialized = 1;
	s->seq_largest = seq_largest;
	s->roc = roc;

	csrc = buf[0] & 0x0f;
	ext = buf[0] & 0x10;
	ssrc = AV_RB32(buf + 8);

	buf += 12;
	len -= 12;

	buf += 4 * csrc;
	len -= 4 * csrc;
	if (len < 0)
	return AVERROR_INVALIDDATA;

	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, hmac_size, padding;
	uint8_t *buf;

	if (len < 8)
	return AVERROR_INVALIDDATA;

	rtcp = RTP_PT_IS_RTCP(in[1]);
	hmac_size = rtcp ? s->rtcp_hmac_size : s->rtp_hmac_size;
	padding = hmac_size;
	if (rtcp)
	padding += 4; // For the RTCP index

	if (len + padding > outlen)
	return 0;

	memcpy(out, in, len);
	buf = out;

	if (rtcp) {
	ssrc = AV_RB32(buf + 4);
	index = s->rtcp_index++;

	buf += 8;
	len -= 8;
	} else {
	int ext, csrc;
	int seq = AV_RB16(buf + 2);

	if (len < 12)
	return AVERROR_INVALIDDATA;

	ssrc = AV_RB32(buf + 8);

	if (seq < s->seq_largest)
	s->roc++;
	s->seq_largest = seq;
	index = seq + (((uint64_t)s->roc) << 16);

	csrc = buf[0] & 0x0f;
	ext = buf[0] & 0x10;

	buf += 12;
	len -= 12;

	buf += 4 * csrc;
	len -= 4 * csrc;
	if (len < 0)
	return AVERROR_INVALIDDATA;

	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, hmac_size);
	len += hmac_size;
	return buf + len - out;
	}