/usr/include/ccrtp/CryptoContext.h is in libccrtp-dev 2.0.9-2.2+b2.
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Copyright (C) 2004-2006 the Minisip Team
This library 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.
This library 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 this library; if not, write to the Free Software
Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#ifndef CRYPTOCONTEXT_H
#define CRYPTOCONTEXT_H
#include <commoncpp/config.h>
#include <ccrtp/rtppkt.h>
#define REPLAY_WINDOW_SIZE 64
const int SrtpAuthenticationNull = 0;
const int SrtpAuthenticationSha1Hmac = 1;
const int SrtpAuthenticationSkeinHmac = 2;
const int SrtpEncryptionNull = 0;
const int SrtpEncryptionAESCM = 1;
const int SrtpEncryptionAESF8 = 2;
const int SrtpEncryptionTWOCM = 3;
const int SrtpEncryptionTWOF8 = 4;
#ifndef CRYPTOCONTEXTCTRL_H
#include <stdint.h>
#ifdef SRTP_SUPPORT
#include <ccrtp/crypto/SrtpSymCrypto.h>
#endif
class SrtpSymCrypto;
NAMESPACE_COMMONCPP
class RTPPacket;
/**
* The implementation for a SRTP cryptographic context.
*
* This class holds data and provides functions that implement a
* cryptographic context for SRTP, Refer to RFC 3711, chapter 3.2 for some
* more detailed information about the SRTP cryptographic context.
*
* Each SRTP cryptographic context maintains a RTP source identified by
* its SSRC. Thus you can independently protect each source inside a RTP
* session.
*
* Key management mechanisms negotiate the parameters for the SRTP
* cryptographic context, such as master key, key length, authentication
* length and so on. The key management mechanisms are not part of
* SRTP. Refer to MIKEY (RFC 3880) or to Phil Zimmermann's ZRTP protocol
* (draft-zimmermann-avt-zrtp-01). After key management negotiated the
* data the application can setup the SRTP cryptographic context and
* enable SRTP processing.
*
* Currently this implementation supports RTP only, not RTCP.
*
* @author Israel Abad <i_abad@terra.es>
* @author Erik Eliasson <eliasson@it.kth.se>
* @author Johan Bilien <jobi@via.ecp.fr>
* @author Joachim Orrblad <joachim@orrblad.com>
* @author Werner Dittmann <Werner.Dittmann@t-online.de>
*/
class __EXPORT CryptoContext {
public:
/**
* Constructor for empty SRTP cryptographic context.
*
* This constructor creates an empty SRTP cryptographic context were
* all algorithms are set to the null algorithm, that is no SRTP processing
* is performed.
*
* @param ssrc The RTP SSRC that this SRTP cryptographic context protects.
*/
CryptoContext( uint32 ssrc );
/**
* Constructor for an active SRTP cryptographic context.
*
* This constructor creates an active SRTP cryptographic context were
* algorithms are enabled, keys are computed and so on. This SRTP
* cryptographic context can protect a RTP SSRC stream.
*
* @param ssrc
* The RTP SSRC that this SRTP cryptographic context protects.
*
* @param roc
* The initial Roll-Over-Counter according to RFC 3711. These are the
* upper 32 bit of the overall 48 bit SRTP packet index. Refer to
* chapter 3.2.1 of the RFC.
*
* @param keyDerivRate
* The key derivation rate defines when to recompute the SRTP session
* keys. Refer to chapter 4.3.1 in the RFC.
*
* @param ealg
* The encryption algorithm to use. Possible values are <code>
* SrtpEncryptionNull, SrtpEncryptionAESCM, SrtpEncryptionAESF8
* </code>. See chapter 4.1.1 for AESCM (Counter mode) and 4.1.2
* for AES F8 mode.
*
* @param aalg
* The authentication algorithm to use. Possible values are <code>
* SrtpEncryptionNull, SrtpAuthenticationSha1Hmac</code>. The only
* active algorithm here is SHA1 HMAC, a SHA1 based hashed message
* authentication code as defined in RFC 2104.
*
* @param masterKey
* Pointer to the master key for this SRTP cryptographic context.
* Must point to <code>masterKeyLength</code> bytes. Refer to chapter
* 3.2.1 of the RFC about the role of the master key.
*
* @param masterKeyLength
* The length in bytes of the master key in bytes. The length must
* match the selected encryption algorithm. Because SRTP uses AES
* based encryption only, then master key length may be 16 or 32
* bytes (128 or 256 bit master key)
*
* @param masterSalt
* SRTP uses the master salt to computer the initialization vector
* that in turn is input to compute the session key, session
* authentication key and the session salt.
*
* @param masterSaltLength
* The length in bytes of the master salt data in bytes. SRTP uses
* AES as encryption algorithm. AES encrypts 16 byte blocks
* (independent of the key length). According to RFC3711 the standard
* value for the master salt length should be 112 bit (14 bytes).
*
* @param ekeyl
* The length in bytes of the session encryption key that SRTP shall
* compute and use. Usually the same length as for the master key
* length. But you may use a different length as well. Be carefull
* that the key management mechanisms supports different key lengths.
*
* @param akeyl
* The length in bytes of the session authentication key. SRTP
* computes this key and uses it as input to the authentication
* algorithm.
* The standard value is 160 bits (20 bytes).
*
* @param skeyl
* The length in bytes of the session salt. SRTP computes this salt
* key and uses it as input during encryption. The length usually
* is the same as the master salt length.
*
* @param tagLength
* The length is bytes of the authentication tag that SRTP appends
* to the RTP packet. Refer to chapter 4.2. in the RFC 3711.
*/
CryptoContext( uint32 ssrc, int32 roc,
int64 keyDerivRate,
const int32 ealg,
const int32 aalg,
uint8* masterKey,
int32 masterKeyLength,
uint8* masterSalt,
int32 masterSaltLength,
int32 ekeyl,
int32 akeyl,
int32 skeyl,
int32 tagLength );
/**
* Destructor.
*
* Cleans the SRTP cryptographic context.
*/
~CryptoContext();
/**
* Set the Roll-Over-Counter.
*
* Ths method sets the upper 32 bit of the 48 bit SRTP packet index
* (the roll-over-part)
*
* @param r
* The roll-over-counter
*/
inline void
setRoc(uint32 r)
{roc = r;}
/**
* Get the Roll-Over-Counter.
*
* Ths method get the upper 32 bit of the 48 bit SRTP packet index
* (the roll-over-part)
*
* @return The roll-over-counter
*/
inline uint32
getRoc() const
{return roc;}
/**
* Perform SRTP encryption.
*
* This method encrypts <em>and</em> decrypts SRTP payload data. Plain
* data gets encrypted, encrypted data get decrypted.
*
* @param rtp
* The RTP packet that contains the data to encrypt.
*
* @param index
* The 48 bit SRTP packet index. See the <code>guessIndex</code>
* method.
*
* @param ssrc
* The RTP SSRC data in <em>host</em> order.
*/
void srtpEncrypt( RTPPacket* rtp, uint64 index, uint32 ssrc );
/**
* Compute the authentication tag.
*
* Compute the authentication tag according the the parameters in the
* SRTP Cryptograhic context.
*
* @param rtp
* The RTP packet that contains the data to authenticate.
*
* @param roc
* The 32 bit SRTP roll-over-counter.
*
* @param tag
* Points to a buffer that hold the computed tag. This buffer must
* be able to hold <code>tagLength</code> bytes.
*/
void srtpAuthenticate(RTPPacket* rtp, uint32 roc, uint8* tag );
/**
* Perform key derivation according to SRTP specification
*
* This method computes the session key, session authentication key and the
* session salt key. This method must be called at least once after the
* SRTP Cryptograhic context was set up.
*
* @param index
* The 48 bit SRTP packet index. See the <code>guessIndex</code>
* method.
*/
void deriveSrtpKeys(uint64 index);
/**
* Compute (guess) the new SRTP index based on the sequence number of
* a received RTP packet.
*
* The method uses the algorithm show in RFC3711, Appendix A, to compute
* the new index.
*
* @param newSeqNumber
* The sequence number of the received RTP packet in host order.
*
* @return The new SRTP packet index
*/
uint64 guessIndex(uint16 newSeqNumber);
/**
* Check for packet replay.
*
* The method check if a received packet is either to old or was already
* received.
*
* The method supports a 64 packet history relative the the given
* sequence number.
*
* @param newSeqNumber
* The sequence number of the received RTP packet in host order.
*
* @return <code>true</code> if no replay, <code>false</code> if packet
* is too old ar was already received.
*/
bool checkReplay(uint16 newSeqNumber);
/**
* Update the SRTP packet index.
*
* Call this method after all checks were successful. See chapter
* 3.3.1 in the RFC when to update the ROC and ROC processing.
*
* @param newSeqNumber
* The sequence number of the received RTP packet in host order.
*/
void update( uint16 newSeqNumber );
/**
* Get the length of the SRTP authentication tag in bytes.
*
* @return the length of the authentication tag.
*/
inline int32
getTagLength() const
{return tagLength;}
/**
* Get the length of the MKI in bytes.
*
* @return the length of the MKI.
*/
inline int32
getMkiLength() const
{return mkiLength;}
/**
* Get the SSRC of this SRTP Cryptograhic context.
*
* @return the SSRC.
*/
inline uint32
getSsrc() const
{return ssrcCtx;}
/**
* Derive a new Crypto Context for use with a new SSRC
*
* This method returns a new Crypto Context initialized with the data
* of this crypto context. Replacing the SSRC, Roll-over-Counter, and
* the key derivation rate the application cab use this Crypto Context
* to encrypt / decrypt a new stream (Synchronization source) inside
* one RTP session.
*
* Before the application can use this crypto context it must call
* the <code>deriveSrtpKeys</code> method.
*
* @param ssrc
* The SSRC for this context
* @param roc
* The Roll-Over-Counter for this context
* @param keyDerivRate
* The key derivation rate for this context
* @return
* a new CryptoContext with all relevant data set.
*/
CryptoContext* newCryptoContextForSSRC(uint32 ssrc, int roc, int64 keyDerivRate);
private:
uint32 ssrcCtx;
bool using_mki;
uint32 mkiLength;
uint8* mki;
uint32 roc;
uint32 guessed_roc;
uint16 s_l;
int64 key_deriv_rate;
/* bitmask for replay check */
uint64 replay_window;
uint8* master_key;
uint32 master_key_length;
uint32 master_key_srtp_use_nb;
uint32 master_key_srtcp_use_nb;
uint8* master_salt;
uint32 master_salt_length;
/* Session Encryption, Authentication keys, Salt */
int32 n_e;
uint8* k_e;
int32 n_a;
uint8* k_a;
int32 n_s;
uint8* k_s;
int32 ealg;
int32 aalg;
int32 ekeyl;
int32 akeyl;
int32 skeyl;
int32 tagLength;
bool seqNumSet;
void* macCtx;
#ifdef SRTP_SUPPORT
SrtpSymCrypto* cipher;
SrtpSymCrypto* f8Cipher;
#else
void* cipher;
void* f8Cipher;
#endif
};
END_NAMESPACE
#endif
#endif
/** EMACS **
* Local variables:
* mode: c++
* c-default-style: ellemtel
* c-basic-offset: 4
* End:
*/
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