Include dependency graph for srtp.c:

Data Structures
struct	srtp_proto_t

struct	srtp_session_t

Macros
#define	debug(...) (void)0

Typedefs
typedef struct srtp_proto_t	srtp_proto_t

Enumerations
enum	{ SRTP_CRYPT , SRTP_AUTH , SRTP_SALT , SRTCP_CRYPT , SRTCP_AUTH , SRTCP_SALT }

Functions
static unsigned	rcc_mode (const srtp_session_t *s)

static void	proto_destroy (srtp_proto_t *p)

void	srtp_destroy (srtp_session_t *s)
	Releases all resources associated with a Secure RTP session.

static int	proto_create (srtp_proto_t *p, int gcipher, int gmd)

srtp_session_t *	srtp_create (int encr, int auth, unsigned tag_len, int prf, unsigned flags)
	Allocates a Secure RTP one-way session.

static int	do_ctr_crypt (gcry_cipher_hd_t hd, const void ctr, uint8_t data, size_t len)
	Counter Mode encryption/decryption (ctr length = 16 bytes) with non-padded (truncated) text.

static int	do_derive (gcry_cipher_hd_t prf, const void salt, const uint8_t r, size_t rlen, uint8_t label, void *out, size_t outlen)
	AES-CM key derivation (saltlen = 14 bytes)

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.

static int	hexdigit (char c)

static ssize_t	hexstring (const char in, uint8_t out, size_t outlen)

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.

void	srtp_setrcc_rate (srtp_session_t *s, uint16_t rate)
	Sets Roll-over-Counter Carry (RCC) rate for the SRTP session.

static int	rtp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t roc, uint16_t seq, const uint32_t salt, uint8_t data, size_t len)
	AES-CM for RTP (salt = 14 bytes + 2 nul bytes)

static uint32_t	srtp_compute_roc (const srtp_session_t *s, uint16_t seq)
	Determines SRTP Roll-Over-Counter (in host-byte order)

static uint16_t	rtp_seq (const uint8_t *buf)
	Returns RTP sequence (in host-byte order)

static const uint8_t *	rtp_digest (gcry_md_hd_t md, const uint8_t *data, size_t len, uint32_t roc)
	Message Authentication and Integrity for RTP.

static int	srtp_crypt (srtp_session_t s, uint8_t buf, size_t len)
	Encrypts/decrypts a RTP packet and updates SRTP context (CTR block cypher mode of operation has identical encryption and decryption function).

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.

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.

static int	rtcp_crypt (gcry_cipher_hd_t hd, uint32_t ssrc, uint32_t index, const uint32_t salt, uint8_t data, size_t len)
	AES-CM for RTCP (salt = 14 bytes + 2 nul bytes)

static const uint8_t *	rtcp_digest (gcry_md_hd_t md, const void *data, size_t len)
	Message Authentication and Integrity for RTCP.

static int	srtcp_crypt (srtp_session_t s, uint8_t buf, size_t len)
	Encrypts/decrypts a RTCP packet and updates SRTCP context (CTR block cypher mode of operation has identical encryption and decryption function).

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.

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.

Macro Definition Documentation

◆ debug

#define debug ( ... ) (void)0

Typedef Documentation

◆ srtp_proto_t

typedef struct srtp_proto_t srtp_proto_t

Enumeration Type Documentation

◆ anonymous enum

anonymous enum

Enumerator
SRTP_CRYPT
SRTP_AUTH
SRTP_SALT
SRTCP_CRYPT
SRTCP_AUTH
SRTCP_SALT

Function Documentation

◆ do_ctr_crypt()

static int do_ctr_crypt	(	gcry_cipher_hd_t	hd,
		const void *	ctr,
		uint8_t *	data,
		size_t	len
	)

static

Counter Mode encryption/decryption (ctr length = 16 bytes) with non-padded (truncated) text.

Referenced by do_derive(), and rtp_crypt().

◆ do_derive()

static int do_derive	(	gcry_cipher_hd_t	prf,
		const void *	salt,
		const uint8_t *	r,
		size_t	rlen,
		uint8_t	label,
		void *	out,
		size_t	outlen
	)

static

AES-CM key derivation (saltlen = 14 bytes)

References do_ctr_crypt().

Referenced by srtp_setkey().

◆ hexdigit()

static int hexdigit ( char c )

static

Referenced by hexstring().

◆ hexstring()

static ssize_t hexstring	(	const char *	in,
		uint8_t *	out,
		size_t	outlen
	)

static

References hexdigit().

Referenced by srtp_setkeystring().

◆ proto_create()

static int proto_create	(	srtp_proto_t *	p,
		int	gcipher,
		int	gmd
	)

static

References p.

Referenced by srtp_create().

◆ proto_destroy()

static void proto_destroy ( srtp_proto_t * p )

static

References p.

Referenced by srtp_create(), and srtp_destroy().

◆ rcc_mode()

static unsigned rcc_mode ( const srtp_session_t * s )

inlinestatic

References srtp_session_t::flags.

Referenced by srtp_create(), srtp_recv(), and srtp_send().

◆ rtcp_crypt()

static int rtcp_crypt	(	gcry_cipher_hd_t	hd,
		uint32_t	ssrc,
		uint32_t	index,
		const uint32_t *	salt,
		uint8_t *	data,
		size_t	len
	)

static

AES-CM for RTCP (salt = 14 bytes + 2 nul bytes)

References rtp_crypt().

Referenced by srtcp_crypt().

◆ rtcp_digest()

static const uint8_t * rtcp_digest	(	gcry_md_hd_t	md,
		const void *	data,
		size_t	len
	)

static

Message Authentication and Integrity for RTCP.

Referenced by srtcp_recv(), and srtcp_send().

◆ rtp_crypt()

static int rtp_crypt	(	gcry_cipher_hd_t	hd,
		uint32_t	ssrc,
		uint32_t	roc,
		uint16_t	seq,
		const uint32_t *	salt,
		uint8_t *	data,
		size_t	len
	)

static

AES-CM for RTP (salt = 14 bytes + 2 nul bytes)

References do_ctr_crypt().

Referenced by rtcp_crypt(), and srtp_crypt().

◆ rtp_digest()

static const uint8_t * rtp_digest	(	gcry_md_hd_t	md,
		const uint8_t *	data,
		size_t	len,
		uint32_t	roc
	)

static

Message Authentication and Integrity for RTP.

Referenced by srtp_recv(), and srtp_send().

◆ rtp_seq()

static uint16_t rtp_seq ( const uint8_t * buf )

inlinestatic

Returns RTP sequence (in host-byte order)

Referenced by srtp_compute_roc(), srtp_crypt(), srtp_recv(), and srtp_send().

◆ srtcp_crypt()

static int srtcp_crypt	(	srtp_session_t *	s,
		uint8_t *	buf,
		size_t	len
	)

static

Encrypts/decrypts a RTCP packet and updates SRTCP context (CTR block cypher mode of operation has identical encryption and decryption function).

Parameters

s	A valid SRTP session to update
buf	RTCP packet to be en-/decrypted
len	RTCP packet length

Returns: 0 on success, in case of error: EINVAL malformatted RTCP packet

References srtp_proto_t::cipher, srtp_session_t::flags, srtp_session_t::rtcp, rtcp_crypt(), srtp_session_t::rtcp_index, srtp_session_t::rtp, srtp_proto_t::salt, SRTCP_UNENCRYPTED, and srtp_proto_t::window.

Referenced by srtcp_send().

◆ 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

s	a valid SRTP session to read from and convert the packet from
buf	RTCP packet to be digested/decrypted
lenp	pointer 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

s	a valid SRTP session to encrypt and authenticate the packet from
buf	RTCP packet to be encrypted/digested
lenp	pointer to the RTCP packet length on entry, set to the SRTCP length on exit (undefined in case of error)
bufsize	size (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_compute_roc()

static uint32_t srtp_compute_roc	(	const srtp_session_t *	s,
		uint16_t	seq
	)

static

Determines SRTP Roll-Over-Counter (in host-byte order)

References srtp_session_t::rtp_roc, srtp_session_t::rtp_seq, and rtp_seq().

Referenced by srtp_crypt(), srtp_recv(), and srtp_send().

◆ 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

encr	encryption algorithm number
auth	authentication algorithm number
tag_len	authentication tag byte length (NOT including RCC)
prf	the pseudo-random family to use for key derivation
flags	OR'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_crypt()

static int srtp_crypt	(	srtp_session_t *	s,
		uint8_t *	buf,
		size_t	len
	)

static

Encrypts/decrypts a RTP packet and updates SRTP context (CTR block cypher mode of operation has identical encryption and decryption function).

Parameters

s	a valid SRTP session to update and encrypt the packet from
buf	RTP packet to be en-/decrypted
len	RTP packet length

Returns: 0 on success, in case of error: EINVAL malformatted RTP packet EACCES replayed packet or out-of-window or sync lost

References srtp_proto_t::cipher, srtp_session_t::flags, srtp_session_t::rtp, rtp_crypt(), srtp_session_t::rtp_roc, srtp_session_t::rtp_seq, rtp_seq(), srtp_proto_t::salt, srtp_compute_roc(), SRTP_UNENCRYPTED, and srtp_proto_t::window.

Referenced by srtcp_recv(), srtp_recv(), and srtp_send().

◆ 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

s	a valid SRTP session to authenticate and decrypt the packet from
buf	RTP packet to be digested/decrypted
lenp	pointer 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

s	a valid SRTP session to convert the packet from and send to
buf	RTP packet to be encrypted/digested
lenp	pointer to the RTP packet length on entry, set to the SRTP length on exit (undefined on non-ENOSPC error)
bufsize	size (bytes) of the packet buffer

Returns: 0 on success, an error code otherwise

Return values

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.

◆ 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

s	the session to change the RCC for
rate	RoC Carry rate (MUST NOT be zero)

References srtp_session_t::rtp_rcc.

Data Structures

Macros

Typedefs

Enumerations

Functions

Macro Definition Documentation

◆ debug

Typedef Documentation

◆ srtp_proto_t

Enumeration Type Documentation

◆ anonymous enum

Function Documentation

◆ do_ctr_crypt()

◆ do_derive()

◆ hexdigit()

◆ hexstring()

◆ proto_create()

◆ proto_destroy()

◆ rcc_mode()

◆ rtcp_crypt()

◆ rtcp_digest()

◆ rtp_crypt()

◆ rtp_digest()

◆ rtp_seq()

◆ srtcp_crypt()

◆ srtcp_recv()

◆ srtcp_send()

◆ srtp_compute_roc()

◆ srtp_create()

◆ srtp_crypt()

◆ srtp_destroy()

◆ srtp_recv()

◆ srtp_send()

◆ srtp_setkey()

◆ srtp_setkeystring()

◆ srtp_setrcc_rate()