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Typedefs | Enumerations | Functions
srtp.h File Reference

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Typedefs

typedef struct srtp_session_t srtp_session_t
 

Enumerations

enum  {
  SRTP_UNENCRYPTED =0x1 , SRTCP_UNENCRYPTED =0x2 , SRTP_UNAUTHENTICATED =0x4 , SRTP_RCC_MODE1 =0x10 ,
  SRTP_RCC_MODE2 =0x20 , SRTP_RCC_MODE3 =0x30 , SRTP_FLAGS_MASK =0x37
}
 
enum  { SRTP_ENCR_NULL =0 , SRTP_ENCR_AES_CM =1 , SRTP_ENCR_AES_F8 =2 }
 SRTP encryption algorithms (ciphers); same values as MIKEY. More...
 
enum  { SRTP_AUTH_NULL =0 , SRTP_AUTH_HMAC_SHA1 =1 }
 SRTP authenticaton algorithms; same values as MIKEY. More...
 
enum  { SRTP_PRF_AES_CM =0 }
 SRTP pseudo random function; same values as MIKEY. More...
 

Functions

srtp_session_tsrtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags)
 Allocates a Secure RTP one-way session. More...
 
void srtp_destroy (srtp_session_t *s)
 Releases all resources associated with a Secure RTP session. More...
 
int srtp_setkey (srtp_session_t *s, const void *key, size_t keylen, const void *salt, size_t saltlen)
 Sets (or resets) the master key and master salt for a SRTP session. More...
 
int srtp_setkeystring (srtp_session_t *s, const char *key, const char *salt)
 Sets (or resets) the master key and master salt for a SRTP session from hexadecimal strings. More...
 
void srtp_setrcc_rate (srtp_session_t *s, uint16_t rate)
 Sets Roll-over-Counter Carry (RCC) rate for the SRTP session. More...
 
int srtp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsize)
 Turns a RTP packet into a SRTP packet: encrypt it, then computes the authentication tag and appends it. More...
 
int srtp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp)
 Turns a SRTP packet into a RTP packet: authenticates the packet, then decrypts it. More...
 
int srtcp_send (srtp_session_t *s, uint8_t *buf, size_t *lenp, size_t maxsiz)
 Turns a RTCP packet into a SRTCP packet: encrypt it, then computes the authentication tag and appends it. More...
 
int srtcp_recv (srtp_session_t *s, uint8_t *buf, size_t *lenp)
 Turns a SRTCP packet into a RTCP packet: authenticates the packet, then decrypts it. More...
 

Typedef Documentation

◆ srtp_session_t

Enumeration Type Documentation

◆ anonymous enum

anonymous enum
Enumerator
SRTP_UNENCRYPTED 
SRTCP_UNENCRYPTED 
SRTP_UNAUTHENTICATED 
SRTP_RCC_MODE1 
SRTP_RCC_MODE2 
SRTP_RCC_MODE3 
SRTP_FLAGS_MASK 

◆ anonymous enum

anonymous enum

SRTP encryption algorithms (ciphers); same values as MIKEY.

Enumerator
SRTP_ENCR_NULL 
SRTP_ENCR_AES_CM 
SRTP_ENCR_AES_F8 

◆ anonymous enum

anonymous enum

SRTP authenticaton algorithms; same values as MIKEY.

Enumerator
SRTP_AUTH_NULL 
SRTP_AUTH_HMAC_SHA1 

◆ anonymous enum

anonymous enum

SRTP pseudo random function; same values as MIKEY.

Enumerator
SRTP_PRF_AES_CM 

Function Documentation

◆ srtcp_recv()

int srtcp_recv ( srtp_session_t s,
uint8_t *  buf,
size_t *  lenp 
)

Turns a SRTCP packet into a RTCP packet: authenticates the packet, then decrypts it.

Parameters
bufRTCP packet to be digested/decrypted
lenppointer to the SRTCP packet length on entry, set to the RTCP length on exit (undefined in case of error)
Returns
0 on success, in case of error: EINVAL malformatted SRTCP packet EACCES authentication failed (spoofed packet or out-of-sync)

References srtp_proto_t::mac, srtp_session_t::rtcp, rtcp_digest(), srtp_crypt(), and srtp_session_t::tag_len.

◆ srtcp_send()

int srtcp_send ( srtp_session_t s,
uint8_t *  buf,
size_t *  lenp,
size_t  bufsize 
)

Turns a RTCP packet into a SRTCP packet: encrypt it, then computes the authentication tag and appends it.

Parameters
bufRTCP packet to be encrypted/digested
lenppointer to the RTCP packet length on entry, set to the SRTCP length on exit (undefined in case of error)
bufsizesize (bytes) of the packet buffer
Returns
0 on success, in case of error: EINVAL malformatted RTCP packet or internal error ENOSPC bufsize is too small (to add index and authentication tag)

References srtp_session_t::flags, srtp_proto_t::mac, srtp_session_t::rtcp, rtcp_digest(), srtp_session_t::rtcp_index, srtcp_crypt(), SRTCP_UNENCRYPTED, and srtp_session_t::tag_len.

◆ srtp_create()

srtp_session_t* srtp_create ( int  encr,
int  auth,
unsigned  tag_len,
int  prf,
unsigned  flags 
)

Allocates a Secure RTP one-way session.

The same session cannot be used both ways because this would confuse internal cryptographic counters; it is however of course feasible to open multiple simultaneous sessions with the same master key.

Parameters
encrencryption algorithm number
authauthentication algorithm number
tag_lenauthentication tag byte length (NOT including RCC)
flagsOR'ed optional flags.
Returns
NULL in case of error

References srtp_session_t::flags, proto_create(), proto_destroy(), rcc_mode(), srtp_session_t::rtcp, srtp_session_t::rtp, srtp_session_t::rtp_rcc, SRTP_AUTH_HMAC_SHA1, SRTP_AUTH_NULL, SRTP_ENCR_AES_CM, SRTP_ENCR_NULL, SRTP_FLAGS_MASK, SRTP_PRF_AES_CM, and srtp_session_t::tag_len.

Referenced by OpenURL().

◆ srtp_destroy()

void srtp_destroy ( srtp_session_t s)

Releases all resources associated with a Secure RTP session.

References proto_destroy(), srtp_session_t::rtcp, and srtp_session_t::rtp.

Referenced by Close(), and OpenURL().

◆ srtp_recv()

int srtp_recv ( srtp_session_t s,
uint8_t *  buf,
size_t *  lenp 
)

Turns a SRTP packet into a RTP packet: authenticates the packet, then decrypts it.

Parameters
bufRTP packet to be digested/decrypted
lenppointer to the SRTP packet length on entry, set to the RTP length on exit (undefined in case of error)
Returns
0 on success, in case of error: EINVAL malformatted SRTP packet EACCES authentication failed (spoofed packet or out-of-sync)

References srtp_session_t::flags, srtp_proto_t::mac, rcc_mode(), srtp_session_t::rtp, rtp_digest(), srtp_session_t::rtp_rcc, srtp_session_t::rtp_roc, rtp_seq(), srtp_compute_roc(), srtp_crypt(), SRTP_UNAUTHENTICATED, and srtp_session_t::tag_len.

Referenced by rtp_process().

◆ srtp_send()

int srtp_send ( srtp_session_t s,
uint8_t *  buf,
size_t *  lenp,
size_t  bufsize 
)

Turns a RTP packet into a SRTP packet: encrypt it, then computes the authentication tag and appends it.

Note that you can encrypt packet in disorder.

Parameters
bufRTP packet to be encrypted/digested
lenppointer to the RTP packet length on entry, set to the SRTP length on exit (undefined on non-ENOSPC error)
bufsizesize (bytes) of the packet buffer
Returns
0 on success, in case of error: EINVAL malformatted RTP packet or internal error ENOSPC bufsize is too small to add authentication tag (<lenp> will hold the required byte size) EACCES packet would trigger a replay error on receiver

References srtp_session_t::flags, srtp_proto_t::mac, rcc_mode(), srtp_session_t::rtp, rtp_digest(), srtp_session_t::rtp_rcc, srtp_session_t::rtp_roc, rtp_seq(), srtp_compute_roc(), srtp_crypt(), SRTP_UNAUTHENTICATED, and srtp_session_t::tag_len.

◆ srtp_setkey()

int srtp_setkey ( srtp_session_t s,
const void *  key,
size_t  keylen,
const void *  salt,
size_t  saltlen 
)

Sets (or resets) the master key and master salt for a SRTP session.

This must be done at least once before using srtp_send(), srtp_recv(), srtcp_send() or srtcp_recv(). Also, rekeying is required every 2^48 RTP packets or 2^31 RTCP packets (whichever comes first), otherwise the protocol security might be broken.

Returns
0 on success, in case of error: EINVAL invalid or unsupported key/salt sizes combination

References srtp_proto_t::cipher, do_derive(), srtp_session_t::kdr, srtp_proto_t::mac, srtp_session_t::rtcp, srtp_session_t::rtcp_index, srtp_session_t::rtp, srtp_session_t::rtp_roc, srtp_session_t::rtp_seq, srtp_proto_t::salt, SRTCP_AUTH, SRTCP_CRYPT, SRTCP_SALT, SRTP_AUTH, SRTP_CRYPT, and SRTP_SALT.

Referenced by srtp_setkeystring().

◆ srtp_setkeystring()

int srtp_setkeystring ( srtp_session_t s,
const char *  key,
const char *  salt 
)

Sets (or resets) the master key and master salt for a SRTP session from hexadecimal strings.

See also srtp_setkey().

Returns
0 on success, in case of error: EINVAL invalid or unsupported key/salt sizes combination

References hexstring(), and srtp_setkey().

Referenced by OpenURL().

◆ srtp_setrcc_rate()

void srtp_setrcc_rate ( srtp_session_t s,
uint16_t  rate 
)

Sets Roll-over-Counter Carry (RCC) rate for the SRTP session.

If not specified (through this function), the default rate of ONE is assumed (i.e. every RTP packets will carry the RoC). RCC rate is ignored if none of the RCC mode has been selected.

The RCC mode is selected through one of these flags for srtp_create(): SRTP_RCC_MODE1: integrity protection only for RoC carrying packets SRTP_RCC_MODE2: integrity protection for all packets SRTP_RCC_MODE3: no integrity protection

RCC mode 3 is insecure. Compared to plain RTP, it provides confidentiality (through encryption) but is much more prone to DoS. It can only be used if anti-spoofing protection is provided by lower network layers (e.g. IPsec, or trusted routers and proper source address filtering).

If RCC rate is 1, RCC mode 1 and 2 are functionally identical.

Parameters
rateRoC Carry rate (MUST NOT be zero)

References srtp_session_t::rtp_rcc.