svn commit: r424117 - in head/security/mbedtls: . files
Tijl Coosemans
tijl at FreeBSD.org
Mon Oct 17 14:03:20 UTC 2016
Author: tijl
Date: Mon Oct 17 14:03:18 2016
New Revision: 424117
URL: https://svnweb.freebsd.org/changeset/ports/424117
Log:
Add DTLS-SRTP (RFC 5764) support for use within Linphone.
Obtained from: git://git.linphone.org/linphone-desktop.git
Added:
head/security/mbedtls/files/patch-dtls-srtp (contents, props changed)
Modified:
head/security/mbedtls/Makefile
Modified: head/security/mbedtls/Makefile
==============================================================================
--- head/security/mbedtls/Makefile Mon Oct 17 13:41:22 2016 (r424116)
+++ head/security/mbedtls/Makefile Mon Oct 17 14:03:18 2016 (r424117)
@@ -3,7 +3,7 @@
PORTNAME= mbedtls
PORTVERSION= 2.3.0
DISTVERSIONSUFFIX= -apache
-PORTREVISION= 1
+PORTREVISION= 2
CATEGORIES= security devel
MASTER_SITES= https://tls.mbed.org/download/
Added: head/security/mbedtls/files/patch-dtls-srtp
==============================================================================
--- /dev/null 00:00:00 1970 (empty, because file is newly added)
+++ head/security/mbedtls/files/patch-dtls-srtp Mon Oct 17 14:03:18 2016 (r424117)
@@ -0,0 +1,659 @@
+Add DTLS-SRTP (RFC 5764) support.
+
+Obtained from: git://git.linphone.org/linphone-desktop.git
+
+diff --git a/include/mbedtls/config.h b/include/mbedtls/config.h
+index d1db0d8..72e2d04 100644
+--- include/mbedtls/config.h
++++ include/mbedtls/config.h
+@@ -1154,6 +1154,17 @@
+ #define MBEDTLS_SSL_DTLS_HELLO_VERIFY
+
+ /**
++ * \def MBEDTLS_SSL_DTLS_SRTP
++ *
++ * Enable support for DTLS-SRTP, RFC5764
++ *
++ * Requires: MBEDTLS_SSL_PROTO_DTLS
++ *
++ * Comment this to disable support for DTLS-SRTP.
++ */
++#define MBEDTLS_SSL_DTLS_SRTP
++
++/**
+ * \def MBEDTLS_SSL_DTLS_CLIENT_PORT_REUSE
+ *
+ * Enable server-side support for clients that reconnect from the same port.
+diff --git a/include/mbedtls/ssl.h b/include/mbedtls/ssl.h
+index 00e1c6c..729e95f 100644
+--- include/mbedtls/ssl.h
++++ include/mbedtls/ssl.h
+@@ -326,6 +326,8 @@
+
+ #define MBEDTLS_TLS_EXT_SIG_ALG 13
+
++#define MBEDTLS_TLS_EXT_USE_SRTP 14
++
+ #define MBEDTLS_TLS_EXT_ALPN 16
+
+ #define MBEDTLS_TLS_EXT_ENCRYPT_THEN_MAC 22 /* 0x16 */
+@@ -338,6 +340,14 @@
+ #define MBEDTLS_TLS_EXT_RENEGOTIATION_INFO 0xFF01
+
+ /*
++ * use_srtp extension protection profiles values as defined in http://www.iana.org/assignments/srtp-protection/srtp-protection.xhtml
++ */
++#define MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE 0x0001
++#define MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE 0x0002
++#define MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE 0x0005
++#define MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE 0x0006
++
++/*
+ * Size defines
+ */
+ #if !defined(MBEDTLS_PSK_MAX_LEN)
+@@ -426,6 +436,19 @@ typedef struct mbedtls_ssl_key_cert mbedtls_ssl_key_cert;
+ typedef struct mbedtls_ssl_flight_item mbedtls_ssl_flight_item;
+ #endif
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++/*
++ * List of SRTP profiles for DTLS-SRTP
++ */
++enum mbedtls_DTLS_SRTP_protection_profiles {
++ MBEDTLS_SRTP_UNSET_PROFILE,
++ MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80,
++ MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32,
++ MBEDTLS_SRTP_NULL_HMAC_SHA1_80,
++ MBEDTLS_SRTP_NULL_HMAC_SHA1_32,
++};
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * This structure is used for storing current session data.
+ */
+@@ -566,6 +589,14 @@ struct mbedtls_ssl_config
+ const char **alpn_list; /*!< ordered list of protocols */
+ #endif
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ /*
++ * use_srtp extension
++ */
++ enum mbedtls_DTLS_SRTP_protection_profiles *dtls_srtp_profiles_list; /*!< ordered list of supported srtp profile */
++ size_t dtls_srtp_profiles_list_len; /*!< number of supported profiles */
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * Numerical settings (int then char)
+ */
+@@ -765,6 +796,15 @@ struct mbedtls_ssl_context
+ const char *alpn_chosen; /*!< negotiated protocol */
+ #endif
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ /*
++ * use_srtp extension
++ */
++ enum mbedtls_DTLS_SRTP_protection_profiles chosen_dtls_srtp_profile; /*!< negotiated SRTP profile */
++ unsigned char *dtls_srtp_keys; /*<! master keys and master salt for SRTP generated during handshake */
++ size_t dtls_srtp_keys_len; /*<! length in bytes of master keys and master salt for SRTP generated during handshake */
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * Information for DTLS hello verify
+ */
+@@ -1781,6 +1821,45 @@ int mbedtls_ssl_conf_alpn_protocols( mbedtls_ssl_config *conf, const char **prot
+ const char *mbedtls_ssl_get_alpn_protocol( const mbedtls_ssl_context *ssl );
+ #endif /* MBEDTLS_SSL_ALPN */
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++/**
++ * \brief Set the supported DTLS-SRTP protection profiles.
++ *
++ * \param ssl SSL configuration
++ * \param protos List of supported protection profiles,
++ * in decreasing preference order.
++ * \param profiles_number Number of supported profiles.
++ *
++ * \return 0 on success, or MBEDTLS_ERR_SSL_BAD_INPUT_DATA.
++ */
++int mbedtls_ssl_conf_dtls_srtp_protection_profiles( mbedtls_ssl_config *conf, const enum mbedtls_DTLS_SRTP_protection_profiles *profiles, size_t profiles_number);
++
++/**
++ * \brief Get the negotiated DTLS-SRTP Protection Profile.
++ * This function should be called after the handshake is
++ * completed.
++ *
++ * \param ssl SSL context
++ *
++ * \return Protection Profile enum member, MBEDTLS_SRTP_UNSET_PROFILE if no protocol was negotiated.
++ */
++enum mbedtls_DTLS_SRTP_protection_profiles mbedtls_ssl_get_dtls_srtp_protection_profile( const mbedtls_ssl_context *ssl);
++
++/**
++ * \brief Get the generated DTLS-SRTP key material.
++ * This function should be called after the handshake is
++ * completed. It shall returns 80 bytes of key material generated according to RFC5764
++ *
++ * \param ssl SSL context
++ * \param key Buffer to hold the generated key material
++ * \param key_buffer_len Length in bytes of the key buffer
++ * \param key_len Actual length of data written in the key buffer
++ *
++ * \return 0 on succes, MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL if the key buffer is too small to hold the generated key
++ */
++int mbedtls_ssl_get_dtls_srtp_key_material( const mbedtls_ssl_context *ssl, unsigned char *key, const size_t key_buffer_len, size_t *key_len );
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /**
+ * \brief Set the maximum supported version sent from the client side
+ * and/or accepted at the server side
+diff --git a/library/ssl_cli.c b/library/ssl_cli.c
+index 4452169..91569ed 100644
+--- library/ssl_cli.c
++++ library/ssl_cli.c
+@@ -656,6 +656,79 @@ static void ssl_write_alpn_ext( mbedtls_ssl_context *ssl,
+ }
+ #endif /* MBEDTLS_SSL_ALPN */
+
++#if defined (MBEDTLS_SSL_DTLS_SRTP)
++static void ssl_write_use_srtp_ext( mbedtls_ssl_context *ssl,
++ unsigned char *buf, size_t *olen )
++{
++ unsigned char *p = buf;
++ size_t protection_profiles_index = 0;
++
++ *olen = 0;
++
++ if( (ssl->conf->dtls_srtp_profiles_list == NULL) || (ssl->conf->dtls_srtp_profiles_list_len == 0) )
++ {
++ return;
++ }
++
++ MBEDTLS_SSL_DEBUG_MSG( 3, ( "client hello, adding use_srtp extension" ) );
++
++ *p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_USE_SRTP >> 8 ) & 0xFF );
++ *p++ = (unsigned char)( ( MBEDTLS_TLS_EXT_USE_SRTP ) & 0xFF );
++
++ /* RFC5764 section 4.1.1
++ * uint8 SRTPProtectionProfile[2];
++ *
++ * struct {
++ * SRTPProtectionProfiles SRTPProtectionProfiles;
++ * opaque srtp_mki<0..255>;
++ * } UseSRTPData;
++
++ * SRTPProtectionProfile SRTPProtectionProfiles<2..2^16-1>;
++ *
++ * Note: srtp_mki is not supported
++ */
++
++ /* Extension length = 2bytes for profiles lenght, ssl->conf->dtls_srtp_profiles_list_len*2 (each profile is 2 bytes length ) + 1 byte for the non implemented srtp_mki vector length (always 0) */
++ *p++ = (unsigned char)( ( ( 2 + 2*(ssl->conf->dtls_srtp_profiles_list_len) + 1 ) >> 8 ) & 0xFF );
++ *p++ = (unsigned char)( ( ( 2 + 2*(ssl->conf->dtls_srtp_profiles_list_len) + 1 ) ) & 0xFF );
++
++
++ /* protection profile length: 2*(ssl->conf->dtls_srtp_profiles_list_len) */
++ *p++ = (unsigned char)( ( ( 2*(ssl->conf->dtls_srtp_profiles_list_len) ) >> 8 ) & 0xFF );
++ *p++ = (unsigned char)( ( 2*(ssl->conf->dtls_srtp_profiles_list_len) ) & 0xFF );
++
++ for( protection_profiles_index=0; protection_profiles_index < ssl->conf->dtls_srtp_profiles_list_len; protection_profiles_index++ )
++ {
++ switch (ssl->conf->dtls_srtp_profiles_list[protection_profiles_index]) {
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80:
++ *p++ = ( ( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE ) >> 8 ) & 0xFF);
++ *p++ = ( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE ) & 0xFF);
++ break;
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32:
++ *p++ = ( ( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE ) >> 8 ) & 0xFF);
++ *p++ = ( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE ) & 0xFF);
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_80:
++ *p++ = ( ( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE ) >> 8 ) & 0xFF);
++ *p++ = ( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE ) & 0xFF);
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_32:
++ *p++ = ( ( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE ) >> 8 ) & 0xFF);
++ *p++ = ( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE ) & 0xFF);
++ break;
++ default:
++ /* Note: we shall never arrive here as protection profiles is checked by ssl_set_dtls_srtp_protection_profiles function */
++ MBEDTLS_SSL_DEBUG_MSG( 1, ( "client hello, ignore illegal DTLS-SRTP protection profile %d", ssl->conf->dtls_srtp_profiles_list[protection_profiles_index]) );
++ break;
++ }
++ }
++
++ *p++ = 0x00; /* non implemented srtp_mki vector length is always 0 */
++ /* total extension length: extension type (2 bytes) + extension length (2 bytes) + protection profile length (2 bytes) + 2*nb protection profiles + srtp_mki vector length(1 byte)*/
++ *olen = 2 + 2 + 2 + 2*(ssl->conf->dtls_srtp_profiles_list_len) + 1;
++}
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * Generate random bytes for ClientHello
+ */
+@@ -1006,6 +1079,11 @@ static int ssl_write_client_hello( mbedtls_ssl_context *ssl )
+ ext_len += olen;
+ #endif
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ ssl_write_use_srtp_ext( ssl, p + 2 + ext_len, &olen );
++ ext_len += olen;
++#endif
++
+ #if defined(MBEDTLS_SSL_SESSION_TICKETS)
+ ssl_write_session_ticket_ext( ssl, p + 2 + ext_len, &olen );
+ ext_len += olen;
+@@ -1308,6 +1386,81 @@ static int ssl_parse_alpn_ext( mbedtls_ssl_context *ssl,
+ }
+ #endif /* MBEDTLS_SSL_ALPN */
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
++ const unsigned char *buf, size_t len )
++{
++ enum mbedtls_DTLS_SRTP_protection_profiles server_protection = MBEDTLS_SRTP_UNSET_PROFILE;
++ size_t i;
++ uint16_t server_protection_profile_value = 0;
++
++ /* If use_srtp is not configured, just ignore the extension */
++ if( ( ssl->conf->dtls_srtp_profiles_list == NULL ) || ( ssl->conf->dtls_srtp_profiles_list_len == 0 ) )
++ return( 0 );
++
++ /* RFC5764 section 4.1.1
++ * uint8 SRTPProtectionProfile[2];
++ *
++ * struct {
++ * SRTPProtectionProfiles SRTPProtectionProfiles;
++ * opaque srtp_mki<0..255>;
++ * } UseSRTPData;
++
++ * SRTPProtectionProfile SRTPProtectionProfiles<2..2^16-1>;
++ *
++ * Note: srtp_mki is not supported
++ */
++
++ /* Length is 5 : one protection profile(2 bytes) + length(2 bytes) and potential srtp_mki which won't be parsed */
++ if( len < 5 )
++ return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
++
++ /*
++ * get the server protection profile
++ */
++ if (((uint16_t)(buf[0]<<8 | buf[1])) != 0x0002) { /* protection profile length must be 0x0002 as we must have only one protection profile in server Hello */
++ return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
++ } else {
++ server_protection_profile_value = buf[2]<<8 | buf[3];
++ }
++
++ /*
++ * Check we have the server profile in our list
++ */
++ for( i=0; i < ssl->conf->dtls_srtp_profiles_list_len; i++)
++ {
++ switch ( server_protection_profile_value ) {
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE:
++ server_protection = MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80;
++ break;
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE:
++ server_protection = MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32;
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE:
++ server_protection = MBEDTLS_SRTP_NULL_HMAC_SHA1_80;
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE:
++ server_protection = MBEDTLS_SRTP_NULL_HMAC_SHA1_32;
++ break;
++ default:
++ server_protection = MBEDTLS_SRTP_UNSET_PROFILE;
++ break;
++ }
++
++ if (server_protection == ssl->conf->dtls_srtp_profiles_list[i]) {
++ ssl->chosen_dtls_srtp_profile = ssl->conf->dtls_srtp_profiles_list[i];
++ return 0;
++ }
++ }
++
++ /* If we get there, no match was found : server problem, it shall never answer with incompatible profile */
++ ssl->chosen_dtls_srtp_profile = MBEDTLS_SRTP_UNSET_PROFILE;
++ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
++ MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE );
++ return( MBEDTLS_ERR_SSL_BAD_HS_SERVER_HELLO );
++}
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * Parse HelloVerifyRequest. Only called after verifying the HS type.
+ */
+@@ -1786,6 +1939,16 @@ static int ssl_parse_server_hello( mbedtls_ssl_context *ssl )
+ break;
+ #endif /* MBEDTLS_SSL_ALPN */
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ case MBEDTLS_TLS_EXT_USE_SRTP:
++ MBEDTLS_SSL_DEBUG_MSG( 3, ( "found use_srtp extension" ) );
++
++ if( ( ret = ssl_parse_use_srtp_ext( ssl, ext + 4, ext_size ) ) != 0 )
++ return( ret );
++
++ break;
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ default:
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "unknown extension found: %d (ignoring)",
+ ext_id ) );
+diff --git a/library/ssl_srv.c b/library/ssl_srv.c
+index 6b5b461..72b50ab 100644
+--- library/ssl_srv.c
++++ library/ssl_srv.c
+@@ -573,6 +573,78 @@ static int ssl_parse_alpn_ext( mbedtls_ssl_context *ssl,
+ }
+ #endif /* MBEDTLS_SSL_ALPN */
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++static int ssl_parse_use_srtp_ext( mbedtls_ssl_context *ssl,
++ const unsigned char *buf, size_t len )
++{
++ enum mbedtls_DTLS_SRTP_protection_profiles client_protection = MBEDTLS_SRTP_UNSET_PROFILE;
++ size_t i,j;
++ uint16_t profile_length;
++
++ /* If use_srtp is not configured, just ignore the extension */
++ if( ( ssl->conf->dtls_srtp_profiles_list == NULL ) || ( ssl->conf->dtls_srtp_profiles_list_len == 0 ) )
++ return( 0 );
++
++ /* RFC5764 section 4.1.1
++ * uint8 SRTPProtectionProfile[2];
++ *
++ * struct {
++ * SRTPProtectionProfiles SRTPProtectionProfiles;
++ * opaque srtp_mki<0..255>;
++ * } UseSRTPData;
++
++ * SRTPProtectionProfile SRTPProtectionProfiles<2..2^16-1>;
++ *
++ * Note: srtp_mki is not supported
++ */
++
++ /* Min length is 5 : at least one protection profile(2 bytes) and length(2 bytes) + srtp_mki length(1 byte) */
++ if( len < 5 )
++ return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
++
++ /*
++ * Use our order of preference
++ */
++ profile_length = buf[0]<<8|buf[1]; /* first 2 bytes are protection profile length(in bytes) */
++ for( i=0; i < ssl->conf->dtls_srtp_profiles_list_len; i++)
++ {
++ /* parse the extension list values are defined in http://www.iana.org/assignments/srtp-protection/srtp-protection.xhtml */
++ for (j=0; j<profile_length; j+=2) { /* parse only the protection profile, srtp_mki is not supported and ignored */
++ uint16_t protection_profile_value = buf[j+2]<<8 | buf[j+3]; /* +2 to skip the length field */
++
++ switch ( protection_profile_value ) {
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE:
++ client_protection = MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80;
++ break;
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE:
++ client_protection = MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32;
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE:
++ client_protection = MBEDTLS_SRTP_NULL_HMAC_SHA1_80;
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE:
++ client_protection = MBEDTLS_SRTP_NULL_HMAC_SHA1_32;
++ break;
++ default:
++ client_protection = MBEDTLS_SRTP_UNSET_PROFILE;
++ break;
++ }
++
++ if (client_protection == ssl->conf->dtls_srtp_profiles_list[i]) {
++ ssl->chosen_dtls_srtp_profile = ssl->conf->dtls_srtp_profiles_list[i];
++ return 0;
++ }
++ }
++ }
++
++ /* If we get there, no match was found */
++ ssl->chosen_dtls_srtp_profile = MBEDTLS_SRTP_UNSET_PROFILE;
++ mbedtls_ssl_send_alert_message( ssl, MBEDTLS_SSL_ALERT_LEVEL_FATAL,
++ MBEDTLS_SSL_ALERT_MSG_HANDSHAKE_FAILURE );
++ return( MBEDTLS_ERR_SSL_BAD_HS_CLIENT_HELLO );
++}
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * Auxiliary functions for ServerHello parsing and related actions
+ */
+@@ -1675,7 +1747,16 @@ read_record_header:
+ if( ret != 0 )
+ return( ret );
+ break;
+-#endif /* MBEDTLS_SSL_SESSION_TICKETS */
++#endif /* MBEDTLS_SSL_ALPN */
++
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ case MBEDTLS_TLS_EXT_USE_SRTP:
++ MBEDTLS_SSL_DEBUG_MSG( 3, ( "found use_srtp extension" ) );
++ ret = ssl_parse_use_srtp_ext( ssl, ext + 4, ext_size );
++ if ( ret != 0)
++ return( ret );
++ break;
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
+
+ default:
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "unknown extension found: %d (ignoring)",
+@@ -2144,6 +2225,57 @@ static void ssl_write_alpn_ext( mbedtls_ssl_context *ssl,
+ }
+ #endif /* MBEDTLS_ECDH_C || MBEDTLS_ECDSA_C */
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP )
++static void ssl_write_use_srtp_ext( mbedtls_ssl_context *ssl,
++ unsigned char *buf, size_t *olen )
++{
++ if( ssl->chosen_dtls_srtp_profile == MBEDTLS_SRTP_UNSET_PROFILE )
++ {
++ *olen = 0;
++ return;
++ }
++
++ MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, adding use_srtp extension" ) );
++
++ /* extension */
++ buf[0] = (unsigned char)( ( MBEDTLS_TLS_EXT_USE_SRTP >> 8 ) & 0xFF );
++ buf[1] = (unsigned char)( ( MBEDTLS_TLS_EXT_USE_SRTP ) & 0xFF );
++ /* total length (5: only one profile(2 bytes) and length(2bytes) and srtp_mki not supported so zero length(1byte) ) */
++ buf[2] = 0x00;
++ buf[3] = 0x05;
++
++ /* protection profile length: 2 */
++ buf[4] = 0x00;
++ buf[5] = 0x02;
++ switch (ssl->chosen_dtls_srtp_profile) {
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80:
++ buf[6] = (unsigned char)( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE >> 8) & 0xFF );
++ buf[7] = (unsigned char)( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80_IANA_VALUE ) & 0xFF );
++ break;
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32:
++ buf[6] = (unsigned char)( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE >> 8) & 0xFF );
++ buf[7] = (unsigned char)( ( MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32_IANA_VALUE ) & 0xFF );
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_80:
++ buf[6] = (unsigned char)( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE >> 8) & 0xFF );
++ buf[7] = (unsigned char)( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_80_IANA_VALUE ) & 0xFF );
++ break;
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_32:
++ buf[6] = (unsigned char)( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE >> 8) & 0xFF );
++ buf[7] = (unsigned char)( ( MBEDTLS_SRTP_NULL_HMAC_SHA1_32_IANA_VALUE ) & 0xFF );
++ break;
++ default:
++ *olen = 0;
++ return;
++ break;
++ }
++
++ buf[8] = 0x00; /* unsupported srtp_mki variable length vector set to 0 */
++
++ *olen = 9;
++}
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ #if defined(MBEDTLS_SSL_DTLS_HELLO_VERIFY)
+ static int ssl_write_hello_verify_request( mbedtls_ssl_context *ssl )
+ {
+@@ -2408,6 +2540,11 @@ static int ssl_write_server_hello( mbedtls_ssl_context *ssl )
+ ext_len += olen;
+ #endif
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ ssl_write_use_srtp_ext( ssl, p + 2 + ext_len, &olen);
++ ext_len += olen;
++#endif
++
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "server hello, total extension length: %d", ext_len ) );
+
+ if( ext_len > 0 )
+diff --git a/library/ssl_tls.c b/library/ssl_tls.c
+index 4424f56..940f8aa 100644
+--- library/ssl_tls.c
++++ library/ssl_tls.c
+@@ -373,7 +373,7 @@ static int tls_prf_generic( mbedtls_md_type_t md_type,
+ {
+ size_t nb;
+ size_t i, j, k, md_len;
+- unsigned char tmp[128];
++ unsigned char tmp[144];
+ unsigned char h_i[MBEDTLS_MD_MAX_SIZE];
+ const mbedtls_md_info_t *md_info;
+ mbedtls_md_context_t md_ctx;
+@@ -636,6 +636,30 @@ int mbedtls_ssl_derive_keys( mbedtls_ssl_context *ssl )
+ else
+ MBEDTLS_SSL_DEBUG_MSG( 3, ( "no premaster (session resumed)" ) );
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ /* check if we have a chosen srtp protection profile */
++ if (ssl->chosen_dtls_srtp_profile != MBEDTLS_SRTP_UNSET_PROFILE) {
++ /* derive key material for srtp session RFC5764 section 4.2 */
++ /* master key and master salt are respectively 128 bits and 112 bits for all currently available modes :
++ * SRTP_AES128_CM_HMAC_SHA1_80, SRTP_AES128_CM_HMAC_SHA1_32
++ * SRTP_NULL_HMAC_SHA1_80, SRTP_NULL_HMAC_SHA1_32
++ * So we must export 2*(128 + 112) = 480 bits
++ */
++ ssl->dtls_srtp_keys_len = 60;
++
++ ssl->dtls_srtp_keys = (unsigned char *)mbedtls_calloc(1, ssl->dtls_srtp_keys_len);
++
++ ret = handshake->tls_prf( session->master, 48, "EXTRACTOR-dtls_srtp",
++ handshake->randbytes, 64, ssl->dtls_srtp_keys, ssl->dtls_srtp_keys_len );
++
++ if( ret != 0 )
++ {
++ MBEDTLS_SSL_DEBUG_RET( 1, "dtls srtp prf", ret );
++ return( ret );
++ }
++ }
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ /*
+ * Swap the client and server random values.
+ */
+@@ -5408,6 +5432,12 @@ int mbedtls_ssl_setup( mbedtls_ssl_context *ssl,
+ ssl->in_msg = ssl->in_buf + 13;
+ }
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++ ssl->chosen_dtls_srtp_profile = MBEDTLS_SRTP_UNSET_PROFILE;
++ ssl->dtls_srtp_keys = NULL;
++ ssl->dtls_srtp_keys_len = 0;
++#endif
++
+ if( ( ret = ssl_handshake_init( ssl ) ) != 0 )
+ return( ret );
+
+@@ -5997,6 +6027,61 @@ const char *mbedtls_ssl_get_alpn_protocol( const mbedtls_ssl_context *ssl )
+ }
+ #endif /* MBEDTLS_SSL_ALPN */
+
++#if defined(MBEDTLS_SSL_DTLS_SRTP)
++int mbedtls_ssl_conf_dtls_srtp_protection_profiles( mbedtls_ssl_config *conf, const enum mbedtls_DTLS_SRTP_protection_profiles *profiles, size_t profiles_number)
++{
++ size_t i;
++ /* check in put validity : must be a list of profiles from enumeration */
++ /* maximum length is 4 as only 4 protection profiles are defined */
++ if (profiles_number>4) {
++ return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
++ }
++
++ mbedtls_free(conf->dtls_srtp_profiles_list);
++ conf->dtls_srtp_profiles_list = (enum mbedtls_DTLS_SRTP_protection_profiles *)mbedtls_calloc(1, profiles_number*sizeof(enum mbedtls_DTLS_SRTP_protection_profiles));
++
++ for (i=0; i<profiles_number; i++) {
++ switch (profiles[i]) {
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_80:
++ case MBEDTLS_SRTP_AES128_CM_HMAC_SHA1_32:
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_80:
++ case MBEDTLS_SRTP_NULL_HMAC_SHA1_32:
++ conf->dtls_srtp_profiles_list[i] = profiles[i];
++ break;
++ default:
++ mbedtls_free(conf->dtls_srtp_profiles_list);
++ conf->dtls_srtp_profiles_list = NULL;
++ conf->dtls_srtp_profiles_list_len = 0;
++ return MBEDTLS_ERR_SSL_BAD_INPUT_DATA;
++ }
++ }
++
++ /* assign array length */
++ conf->dtls_srtp_profiles_list_len = profiles_number;
++
++ return( 0 );
++}
++
++enum mbedtls_DTLS_SRTP_protection_profiles mbedtls_ssl_get_dtls_srtp_protection_profile( const mbedtls_ssl_context *ssl)
++{
++ return( ssl->chosen_dtls_srtp_profile);
++}
++
++int mbedtls_ssl_get_dtls_srtp_key_material( const mbedtls_ssl_context *ssl, unsigned char *key, const size_t key_buffer_len, size_t *key_len ) {
++ *key_len = 0;
++
++ /* check output buffer size */
++ if ( key_buffer_len < ssl->dtls_srtp_keys_len) {
++ return MBEDTLS_ERR_SSL_BUFFER_TOO_SMALL;
++ }
++
++ memcpy( key, ssl->dtls_srtp_keys, ssl->dtls_srtp_keys_len);
++ *key_len = ssl->dtls_srtp_keys_len;
++
++ return 0;
++}
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ void mbedtls_ssl_conf_max_version( mbedtls_ssl_config *conf, int major, int minor )
+ {
+ conf->max_major_ver = major;
+@@ -7083,6 +7169,11 @@ void mbedtls_ssl_free( mbedtls_ssl_context *ssl )
+ mbedtls_free( ssl->cli_id );
+ #endif
+
++#if defined (MBEDTLS_SSL_DTLS_SRTP)
++ mbedtls_zeroize( ssl->dtls_srtp_keys, ssl->dtls_srtp_keys_len );
++ mbedtls_free( ssl->dtls_srtp_keys );
++#endif /* MBEDTLS_SSL_DTLS_SRTP */
++
+ MBEDTLS_SSL_DEBUG_MSG( 2, ( "<= free" ) );
+
+ /* Actually clear after last debug message */
+@@ -7311,6 +7402,10 @@ void mbedtls_ssl_config_free( mbedtls_ssl_config *conf )
+ ssl_key_cert_free( conf->key_cert );
+ #endif
+
++#if defined (MBEDTLS_SSL_DTLS_SRTP)
++ mbedtls_free( conf->dtls_srtp_profiles_list );
++#endif
++
+ mbedtls_zeroize( conf, sizeof( mbedtls_ssl_config ) );
+ }
+
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