@ -26,10 +26,11 @@
* /
package net.java.sip.communicator.impl.media.transform.srtp ;
import java.security.* ;
import org.bouncycastle.crypto.digests.SHA1Digest ;
import org.bouncycastle.crypto.macs.HMac ;
import org.bouncycastle.crypto.params.KeyParameter ;
import javax.crypto.* ;
import javax.crypto.spec.* ;
import org.bouncycastle.crypto.engines.AESFastEngine ;
import net.java.sip.communicator.impl.media.transform.* ;
@ -135,29 +136,27 @@ public class SRTPCryptoContext
private final SRTPPolicy policy ;
/ * *
* The SRTPDigest object we used to do packet authentication
* The HMAC object we used to do packet authentication
* /
private SRTPDigest digest ;
private HMac hmacSha1 ; // used for various HMAC computations
/ * *
* The cryptographic services provider
* /
private Provider cryptoProvider ;
// The symmetric cipher engines we need here
private AESFastEngine AEScipher = null ;
private AESFastEngine AEScipherF8 = null ; // used inside F8 mode only
/ * *
* Used for various HMAC computations
* /
private Mac hmacSha1 ;
// implements the counter cipher mode for RTP according to RFC 3711
private final SRTPCipherCTR cipherCtr = new SRTPCipherCTR ( ) ;
// Here some fields that a allocated here or in constructor. The methods
// use these fields to avoid too many new operations
/ * *
* The AES cipher for counter mode
* /
private Cipher AEScipher = null ;
private final byte [ ] tagStore ;
private final byte [ ] ivStore = new byte [ 16 ] ;
private final byte [ ] rbStore = new byte [ 4 ] ;
/ * *
* The AES cipher for F8 mode
* /
private Cipher AEScipherF8 = null ;
// this is some working store, used by some methods to avoid new operations
// the methods must use this only to store some reults for immediate processing
private final byte [ ] tempStore = new byte [ 100 ] ;
/ * *
* Construct an empty SRTPCryptoContext using ssrc .
@ -165,129 +164,122 @@ public class SRTPCryptoContext
*
* @param ssrc SSRC of this SRTPCryptoContext
* /
public SRTPCryptoContext ( long ssrc )
public SRTPCryptoContext ( long ssrc In )
{
this . ssrc = ssrc ;
this . = null ;
this . = 0 ;
this . = 0 ;
this . = 0 ;
this . = 0 ;
this . = null ;
this . = null ;
this . = null ;
this . = null ;
this . = null ;
this . = false ;
this . = null ;
this . cryptoProvider = null ;
ssrc = ssrcIn ;
= null ;
= 0 ;
= 0 ;
= 0 ;
= 0 ;
= null ;
= null ;
= null ;
= null ;
= null ;
= false ;
= null ;
tagStore = null ;
}
/ * *
* Construct a normal SRTPCryptoContext based on the given parameters .
*
* @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 keyDerivationRate the key derivation rate defines when to recompute
* the SRTP session keys . Refer to chapter 4.3 .1 in the RFC .
* @param masterKey byte array holding the master key for this SRTP
* cryptographic context . Refer to chapter 3.2 .1 of the RFC about the
* role of the master key .
* @param masterSalt byte array holding the master salt for this SRTP
* cryptographic context . It is used to computer the initialization vector
* that in turn is input to compute the session key , session
* authentication key and the session salt .
* @param policy SRTP policy for this SRTP cryptographic context , defined
* the encryption algorithm , the authentication algorithm , etc
* @param cryptoProvider cryptographic services provider
* /
public SRTPCryptoContext ( long ssrc ,
int roc ,
long keyDerivationRate ,
byte [ ] masterKey ,
byte [ ] masterSalt ,
SRTPPolicy policy ,
Provider cryptoProvider )
throws GeneralSecurityException
*
* @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 keyDerivationRate
* the key derivation rate defines when to recompute the SRTP
* session keys . Refer to chapter 4.3 .1 in the RFC .
* @param masterKey
* byte array holding the master key for this SRTP cryptographic
* context . Refer to chapter 3.2 .1 of the RFC about the role of
* the master key .
* @param masterSalt
* byte array holding the master salt for this SRTP cryptographic
* context . It is used to computer the initialization vector that
* in turn is input to compute the session key , session
* authentication key and the session salt .
* @param policy
* SRTP policy for this SRTP cryptographic context , defined the
* encryption algorithm , the authentication algorithm , etc
* /
public SRTPCryptoContext ( long ssrcIn , int rocIn , long kdr ,
byte [ ] masterK , byte [ ] masterS , SRTPPolicy policyIn )
{
this . ssrc = ssrc ;
this . mki = null ;
this . roc = roc ;
this . guessedROC = 0 ;
this . seqNum = 0 ;
this . keyDerivationRate = keyDerivationRate ;
this . seqNumSet = false ;
this . cryptoProvider = cryptoProvider ;
this . policy = policy ;
this . masterKey = new byte [ this . policy . getEncKeyLength ( ) ] ;
System . arraycopy ( masterKey , 0 , this . masterKey , 0 , this . policy . getEncKeyLength ( ) ) ;
this . masterSalt = new byte [ this . policy . getSaltKeyLength ( ) ] ;
System . arraycopy ( masterSalt , 0 , this . masterSalt , 0 , this . policy . getSaltKeyLength ( ) ) ;
switch ( policy . getEncType ( ) )
{
case SRTPPolicy . NULL_ENCRYPTION :
this . encKey = null ;
this . saltKey = null ;
break ;
case SRTPPolicy . AESCM_ENCRYPTION :
hmacSha1 = Mac . getInstance ( "HMACSHA1" , cryptoProvider ) ;
AEScipher = Cipher . getInstance ( "AES/ECB/NOPADDING" , cryptoProvider ) ;
this . encKey = new byte [ this . policy . getEncKeyLength ( ) ] ;
this . saltKey = new byte [ this . policy . getSaltKeyLength ( ) ] ;
break ;
case SRTPPolicy . AESF8_ENCRYPTION :
hmacSha1 = Mac . getInstance ( "HMACSHA1" , cryptoProvider ) ;
AEScipher = Cipher . getInstance ( "AES/ECB/NOPADDING" , cryptoProvider ) ;
AEScipherF8 = Cipher . getInstance ( "AES/ECB/NOPADDING" , cryptoProvider ) ;
this . encKey = new byte [ this . policy . getEncKeyLength ( ) ] ;
this . saltKey = new byte [ this . policy . getSaltKeyLength ( ) ] ;
break ;
}
switch ( policy . getAuthType ( ) )
{
case SRTPPolicy . NULL_AUTHENTICATION :
this . authKey = null ;
break ;
case SRTPPolicy . HMACSHA1_AUTHENTICATION :
this . authKey = new byte [ policy . getAuthKeyLength ( ) ] ;
break ;
ssrc = ssrcIn ;
mki = null ;
roc = rocIn ;
guessedROC = 0 ;
seqNum = 0 ;
keyDerivationRate = kdr ;
seqNumSet = false ;
policy = policyIn ;
masterKey = new byte [ policy . getEncKeyLength ( ) ] ;
System . arraycopy ( masterK , 0 , masterKey , 0 , policy
. getEncKeyLength ( ) ) ;
masterSalt = new byte [ policy . getSaltKeyLength ( ) ] ;
System . arraycopy ( masterS , 0 , masterSalt , 0 , policy
. getSaltKeyLength ( ) ) ;
hmacSha1 = new HMac ( new SHA1Digest ( ) ) ;
AEScipher = new AESFastEngine ( ) ;
switch ( policy . getEncType ( ) ) {
case SRTPPolicy . NULL_ENCRYPTION :
encKey = null ;
saltKey = null ;
break ;
case SRTPPolicy . AESF8_ENCRYPTION :
AEScipherF8 = new AESFastEngine ( ) ;
case SRTPPolicy . AESCM_ENCRYPTION :
encKey = new byte [ policy . getEncKeyLength ( ) ] ;
saltKey = new byte [ policy . getSaltKeyLength ( ) ] ;
break ;
}
switch ( policy . getAuthType ( ) ) {
case SRTPPolicy . NULL_AUTHENTICATION :
authKey = null ;
tagStore = null ;
break ;
case SRTPPolicy . HMACSHA1_AUTHENTICATION :
authKey = new byte [ policy . getAuthKeyLength ( ) ] ;
tagStore = new byte [ hmacSha1 . getMacSize ( ) ] ;
break ;
default :
tagStore = null ;
}
}
/ * *
* Get the authentication tag length of this SRTP cryptographic context
*
*
* @return the authentication tag length of this SRTP cryptographic context
* /
public int getAuthTagLength ( )
{
return this . policy . getAuthTagLength ( ) ;
public int getAuthTagLength ( ) {
return policy . getAuthTagLength ( ) ;
}
/ * *
* Get the MKI length of this SRTP cryptographic context
*
*
* @return the MKI length of this SRTP cryptographic context
* /
public int getMKILength ( )
{
if ( this . mki ! = null )
{
return this . mki . length ;
}
else
{
public int getMKILength ( ) {
if ( mki ! = null ) {
return mki . length ;
} else {
return 0 ;
}
}
@ -297,19 +289,17 @@ public int getMKILength()
*
* @return the SSRC of this SRTP cryptographic context
* /
public long getSSRC ( )
{
return this . ssrc ;
public long getSSRC ( ) {
return ssrc ;
}
/ * *
* Get the Roll - Over - Counter of this SRTP cryptographic context
*
* @return the Roll - Over - Counter of this SRTP cryptographic context
* /
public int getROC ( )
{
return this . roc ;
public int getROC ( ) {
return roc ;
}
/ * *
@ -317,9 +307,8 @@ public int getROC()
*
* @param roc the Roll - Over - Counter of this SRTP cryptographic context
* /
public void setROC ( int roc )
{
this . roc = roc ;
public void setROC ( int rocIn ) {
roc = rocIn ;
}
/ * *
@ -339,32 +328,27 @@ public void setROC(int roc)
*
* @param pkt the RTP packet that is going to be sent out
* /
public void transformPacket ( RawPacket pkt )
{
public void transformPacket ( RawPacket pkt ) {
/* Encrypt the packet using Counter Mode encryption */
if ( this . policy . getEncType ( ) = = SRTPPolicy . AESCM_ENCRYPTION )
{
if ( policy . getEncType ( ) = = SRTPPolicy . AESCM_ENCRYPTION ) {
processPacketAESCM ( pkt ) ;
}
/* Encrypt the packet using F8 Mode encryption */
else if ( this . policy . getEncType ( ) = = SRTPPolicy . AESF8_ENCRYPTION )
{
else if ( policy . getEncType ( ) = = SRTPPolicy . AESF8_ENCRYPTION ) {
processPacketAESF8 ( pkt ) ;
}
/* Authenticate the packet */
if ( this . policy . getAuthType ( ) = = SRTPPolicy . HMACSHA1_AUTHENTICATION )
{
byte [ ] tag = authenticatePacketHMCSHA1 ( pkt , this . roc ) ;
pkt . append ( tag , policy . getAuthTagLength ( ) ) ;
if ( policy . getAuthType ( ) = = SRTPPolicy . HMACSHA1_AUTHENTICATION ) {
authenticatePacketHMCSHA1 ( pkt , roc ) ;
pkt . append ( tagStore , policy . getAuthTagLength ( ) ) ;
}
/* Update the ROC if necessary */
int seqNum = PacketManipulator . GetRTPSequenceNumber ( pkt ) ;
if ( seqNum = = 0xFFFF )
{
this . roc + + ;
int seqNo = PacketManipulator . GetRTPSequenceNumber ( pkt ) ;
if ( seqNo = = 0xFFFF ) {
roc + + ;
}
}
@ -386,51 +370,53 @@ else if (this.policy.getEncType() == SRTPPolicy.AESF8_ENCRYPTION)
* @return true if the packet can be accepted
* false if the packet failed authentication or failed replay check
* /
public boolean reverseTransformPacket ( RawPacket pkt )
{
int seqNum = PacketManipulator . GetRTPSequenceNumber ( pkt ) ;
public boolean reverseTransformPacket ( RawPacket pkt ) {
int seqNo = PacketManipulator . GetRTPSequenceNumber ( pkt ) ;
if ( ! seqNumSet ) {
seqNumSet = true ;
seqNum = seqNo ;
}
// Guess the SRTP index (48 bit), see rFC 3711, 3.3.1
// Stores the guessed roc in this.guessedROC
long guessedIndex = guessIndex ( seqNo ) ;
/* Replay control */
if ( ! checkReplay ( seqNum ) ) {
if ( ! checkReplay ( seqN o, guessedIndex ) ) {
return false ;
}
/* Authenticate the packet */
if ( this . policy . getAuthType ( ) = = SRTPPolicy . HMACSHA1_AUTHENTICATION )
{
int tagLength = this . policy . getAuthTagLength ( ) ;
if ( policy . getAuthType ( ) = = SRTPPolicy . HMACSHA1_AUTHENTICATION ) {
int tagLength = policy . getAuthTagLength ( ) ;
// get original authentication and store in tempStore
pkt . readRegionToBuff ( pkt . getLength ( ) - tagLength ,
tagLength , tempStore ) ;
byte [ ] originalTag =
pkt . readRegion ( pkt . getLength ( ) - tagLength , tagLength ) ;
pkt . shrink ( tagLength ) ;
/* Guess the SRTP index (48 bit) */
long guessedIndex = guessIndex ( seqNum ) ;
int guessedRoc = ( int ) ( guessedIndex > > 16 ) ; // extract the roc (32 bit)
byte [ ] calculatedTag = authenticatePacketHMCSHA1 ( pkt , guessedRoc ) ;
// save computed authentication in tagStore
authenticatePacketHMCSHA1 ( pkt , guessedROC ) ;
for ( int i = 0 ; i < tagLength ; i + + ) {
if ( ( originalTag[ i ] & 0xff ) = = ( calculatedTag [ i ] & 0xff ) )
if ( ( tempStore[ i ] & 0xff ) = = ( tagStore [ i ] & 0xff ) )
continue ;
else
return false ;
}
}
/* Decrypt the packet using Counter Mode encryption*/
if ( this . policy . getEncType ( ) = = SRTPPolicy . AESCM_ENCRYPTION )
{
if ( policy . getEncType ( ) = = SRTPPolicy . AESCM_ENCRYPTION ) {
processPacketAESCM ( pkt ) ;
}
/* Decrypt the packet using F8 Mode encryption*/
else if ( this . policy . getEncType ( ) = = SRTPPolicy . AESF8_ENCRYPTION )
{
else if ( policy . getEncType ( ) = = SRTPPolicy . AESF8_ENCRYPTION ) {
processPacketAESF8 ( pkt ) ;
}
update ( seqN um ) ;
update ( seqN o, guessedIndex ) ;
return true ;
}
@ -439,82 +425,59 @@ else if (this.policy.getEncType() == SRTPPolicy.AESF8_ENCRYPTION)
* Perform Counter Mode AES encryption / decryption
* @param pkt the RTP packet to be encrypted / decrypted
* /
public void processPacketAESCM ( RawPacket pkt )
{
long ssrc = PacketManipulator . GetRTPSSRC ( pkt ) ;
int seqNum = PacketManipulator . GetRTPSequenceNumber ( pkt ) ;
long index = ( ( long ) this . roc < < 16 ) | ( long ) seqNum ;
public void processPacketAESCM ( RawPacket pkt ) {
long ssrc = PacketManipulator . GetRTPSSRC ( pkt ) ;
int seqNum = PacketManipulator . GetRTPSequenceNumber ( pkt ) ;
long index = ( ( long ) this . roc < < 16 ) | ( long ) seqNum ;
byte [ ] iv = new byte [ 16 ] ;
System . arraycopy ( this . saltKey , 0 , iv , 0 , 4 ) ;
// byte[] iv = new byte[16];
ivStore [ 0 ] = saltKey [ 0 ] ;
ivStore [ 1 ] = saltKey [ 1 ] ;
ivStore [ 2 ] = saltKey [ 2 ] ;
ivStore [ 3 ] = saltKey [ 3 ] ;
int i ;
for ( i = 4 ; i < 8 ; i + + )
{
iv [ i ] = ( byte ) ( ( 0xFF & ( ssrc > > ( ( 7 - i ) * 8 ) ) ) ^ this . saltKey [ i ] ) ;
for ( i = 4 ; i < 8 ; i + + ) {
ivStore [ i ] = ( byte ) ( ( 0xFF & ( ssrc > > ( ( 7 - i ) * 8 ) ) ) ^ this . saltKey [ i ] ) ;
}
for ( i = 8 ; i < 14 ; i + + )
{
iv [ i ] =
( byte ) ( ( 0xFF & ( byte ) ( index > > ( ( 13 - i ) * 8 ) ) ) ^ this . saltKey [ i ] ) ;
for ( i = 8 ; i < 14 ; i + + ) {
ivStore [ i ] = ( byte ) ( ( 0xFF & ( byte ) ( index > > ( ( 13 - i ) * 8 ) ) ) ^ this . saltKey [ i ] ) ;
}
iv [ 14 ] = iv [ 15 ] = 0 ;
iv Store [ 14 ] = iv Store [ 15 ] = 0 ;
final int payloadOffset = PacketManipulator . GetRTPHeaderLength ( pkt ) ;
final int payloadLength = PacketManipulator . GetRTPPayloadLength ( pkt ) ;
SRTPCipherCTR . process ( AEScipher , pkt . getBuffer ( ) , pkt . getOffset ( ) + payloadOffset ,
payloadLength , iv ) ;
cipherCtr . process ( AEScipher , pkt . getBuffer ( ) , pkt . getOffset ( ) + payloadOffset ,
payloadLength , iv Store ) ;
}
/ * *
* Perform F8 Mode AES encryption / decryption
*
* @param pkt the RTP packet to be encrypted / decrypted
* /
public void processPacketAESF8 ( RawPacket pkt )
{
//long ssrc = PacketManipulator.GetRTPSSRC(pkt);
//boolean isMarked = PacketManipulator.IsPacketMarked(pkt);
//int seqNum = PacketManipulator.GetRTPSequenceNumber(pkt);
//byte payload = PacketManipulator.GetRTPPayloadType(pkt);
public void processPacketAESF8 ( RawPacket pkt ) {
// byte[] iv = new byte[16];
byte [ ] iv = new byte [ 16 ] ;
//iv[0] = 0;
//iv[1] = (byte) (isMarked ? 0x80 : 0x00);
//iv[1] |= payload & 0x7f;
//iv[2] = (byte) (seqNum >> 8);
//iv[3] = (byte) seqNum;
// set the TimeStamp in network order into IV
//byte[] timeStamp = PacketManipulator.ReadTimeStampIntoByteArray(pkt);
//System.arraycopy(timeStamp, 0, iv, 4, 4);
// set the SSRC in network order into IV
//iv[8] = (byte) (ssrc >> 24);
//iv[9] = (byte) (ssrc >> 16);
//iv[10] = (byte) (ssrc >> 8);
//iv[11] = (byte) ssrc;
// set the ROC in network order into IV
// 11 bytes of the RTP header are the 11 bytes of the iv
// the first byte of the RTP header is not used.
System . arraycopy ( pkt . getBuffer ( ) , pkt . getOffset ( ) , iv , 0 , 12 ) ;
iv [ 0 ] = 0 ;
iv [ 12 ] = ( byte ) ( this . roc > > 24 ) ;
iv [ 13 ] = ( byte ) ( this . roc > > 16 ) ;
iv [ 14 ] = ( byte ) ( this . roc > > 8 ) ;
iv [ 15 ] = ( byte ) this . roc ;
System . arraycopy ( pkt . getBuffer ( ) , pkt . getOffset ( ) , ivStore , 0 , 12 ) ;
ivStore [ 0 ] = 0 ;
// set the ROC in network order into IV
ivStore [ 12 ] = ( byte ) ( this . roc > > 24 ) ;
ivStore [ 13 ] = ( byte ) ( this . roc > > 16 ) ;
ivStore [ 14 ] = ( byte ) ( this . roc > > 8 ) ;
ivStore [ 15 ] = ( byte ) this . roc ;
final int payloadOffset = PacketManipulator . GetRTPHeaderLength ( pkt ) ;
final int payloadLength = PacketManipulator . GetRTPPayloadLength ( pkt ) ;
SRTPCipherF8 . process ( AEScipher , pkt . getBuffer ( ) , pkt . getOffset ( ) + payloadOffset ,
payloadLength , iv , encKey , saltKey , AEScipherF8 ) ;
payloadLength , ivStore , encKey , saltKey , AEScipherF8 ) ;
}
/ * *
@ -524,19 +487,18 @@ public void processPacketAESF8(RawPacket pkt)
* @param pkt the RTP packet to be authenticated
* @return authentication tag of pkt
* /
private byte[ ] authenticatePacketHMCSHA1 ( RawPacket pkt , int rocIn )
{
private void authenticatePacketHMCSHA1 ( RawPacket pkt , int rocIn ) {
hmacSha1 . update ( pkt . getBuffer ( ) , 0 , pkt . getLength ( ) ) ;
byte [ ] rb = new byte [ 4 ] ;
rb [ 0 ] = ( byte ) ( rocIn > > 24 ) ;
rb [ 1 ] = ( byte ) ( rocIn > > 16 ) ;
rb [ 2 ] = ( byte ) ( rocIn > > 8 ) ;
rb [ 3 ] = ( byte ) rocIn ;
hmacSha1 . update ( rb ) ;
return hmacSha1 . doFinal ( ) ;
// byte[] rb = new byte[4];
rbStore [ 0 ] = ( byte ) ( rocIn > > 24 ) ;
rbStore [ 1 ] = ( byte ) ( rocIn > > 16 ) ;
rbStore [ 2 ] = ( byte ) ( rocIn > > 8 ) ;
rbStore [ 3 ] = ( byte ) rocIn ;
hmacSha1 . update ( rbStore , 0 , rbStore . length ) ;
hmacSha1 . doFinal ( tagStore , 0 ) ;
}
/ * *
* Checks if a packet is a replayed on based on its sequence number .
*
@ -550,43 +512,24 @@ private byte[] authenticatePacketHMCSHA1(RawPacket pkt, int rocIn)
* @return true if this sequence number indicates the packet is not a
* replayed one , false if not
* /
boolean checkReplay ( int seqNum )
{
/ *
* Initialize the sequences number on first call that uses the
* sequence number . Either guessIndex ( ) or checkReplay ( ) .
* /
if ( ! this . seqNumSet )
{
this . seqNumSet = true ;
this . seqNum = seqNum ;
}
long guessedIndex = guessIndex ( seqNum ) ;
long localIndex = ( ( long ) this . roc ) < < 16 | this . seqNum ;
boolean checkReplay ( int seqNo , long guessedIndex ) {
// compute the index of previously received packet and its
// delta to the new received packet
long localIndex = ( ( ( long ) this . roc ) < < 16 ) | this . seqNum ;
long delta = guessedIndex - localIndex ;
if ( delta > 0 )
{
if ( delta > 0 ) {
/* Packet not yet received */
return true ;
}
else
{
if ( - delta > REPLAY_WINDOW_SIZE )
{
} else {
if ( - delta > REPLAY_WINDOW_SIZE ) {
/* Packet too old */
return false ;
}
else
{
if ( ( ( this . replayWindow > > ( - delta ) ) & 0x1 ) ! = 0 )
{
} else {
if ( ( ( this . replayWindow > > ( - delta ) ) & 0x1 ) ! = 0 ) {
/* Packet already received ! */
return false ;
}
else
{
} else {
/* Packet not yet received */
return true ;
}
@ -594,7 +537,6 @@ boolean checkReplay(int seqNum)
}
}
/ * *
* Compute the initialization vector , used later by encryption algorithms ,
* based on the lable , the packet index , key derivation rate and master
@ -606,141 +548,83 @@ boolean checkReplay(int seqNum)
* @param kdv key derivation rate of this SRTPCryptoContext
* @param masterSalt master salt key
* /
private static void computeIv ( byte [ ] iv , long label , long index ,
long kdv , byte [ ] masterSalt )
{
private void computeIv ( long label , long index ) {
long key_id ;
if ( kdv = = 0 )
{
if ( keyDerivationRate = = 0 ) {
key_id = label < < 48 ;
} else {
key_id = ( ( label < < 48 ) | ( index / keyDerivationRate ) ) ;
}
else
{
key_id = ( ( label < < 48 ) | ( index / kdv ) ) ;
for ( int i = 0 ; i < 7 ; i + + ) {
ivStore [ i ] = masterSalt [ i ] ;
}
for ( int i = 0 ; i < 7 ; i + + )
{
iv [ i ] = masterSalt [ i ] ;
}
for ( int i = 7 ; i < 14 ; i + + )
{
iv [ i ] = ( byte )
( ( byte ) ( 0xFF & ( key_id > > ( 8 * ( 13 - i ) ) ) ) ^ masterSalt [ i ] ) ;
for ( int i = 7 ; i < 14 ; i + + ) {
ivStore [ i ] = ( byte ) ( ( byte ) ( 0xFF & ( key_id > > ( 8 * ( 13 - i ) ) ) ) ^ masterSalt [ i ] ) ;
}
iv [ 14 ] = iv [ 15 ] = 0 ;
ivStore [ 14 ] = ivStore [ 15 ] = 0 ;
}
/ * *
* Derives the srtp session keys from the master key
* @param index the 48 bit SRTP packet index
*
* @param index
* the 48 bit SRTP packet index
* /
public void deriveSrtpKeys ( long index )
{
byte [ ] iv = new byte [ 16 ] ;
public void deriveSrtpKeys ( long index ) {
// compute the session encryption key
long label = 0 ;
computeIv ( iv , label , index , this . keyDerivationRate , this . masterSalt ) ;
SecretKey encryptionKey = new SecretKeySpec ( masterKey , 0 , policy . getEncKeyLength ( ) , "AES" ) ;
try
{
AEScipher . init ( Cipher . ENCRYPT_MODE , encryptionKey ) ;
}
catch ( InvalidKeyException e1 )
{
// TODO Auto-generated catch block
e1 . printStackTrace ( ) ;
}
SRTPCipherCTR . getCipherStream ( AEScipher , encKey , policy . getEncKeyLength ( ) , iv ) ;
computeIv ( label , index ) ;
KeyParameter encryptionKey = new KeyParameter ( masterKey ) ;
AEScipher . init ( true , encryptionKey ) ;
cipherCtr . getCipherStream ( AEScipher , encKey , policy . getEncKeyLength ( ) , ivStore ) ;
// compute the session authentication key
if ( this . authKey ! = null )
{
if ( authKey ! = null ) {
label = 0x01 ;
computeIv ( iv , label , index , this . keyDerivationRate , this . masterSalt ) ;
SRTPCipherCTR . getCipherStream ( AEScipher , authKey , policy . getAuthKeyLength ( ) , iv ) ;
SecretKey key = new SecretKeySpec ( authKey , "HMAC" ) ;
try
{
hmacSha1 . init ( key ) ;
}
catch ( InvalidKeyException e )
{
// TODO Auto-generated catch block
e . printStackTrace ( ) ;
}
computeIv ( label , index ) ;
cipherCtr . getCipherStream ( AEScipher , authKey , policy . getAuthKeyLength ( ) , ivStore ) ;
KeyParameter key = new KeyParameter ( authKey ) ;
hmacSha1 . init ( key ) ;
}
// compute the session salt
label = 0x02 ;
computeIv ( iv , label , index , this . keyDerivationRate , this . masterSalt ) ;
SRTPCipherCTR . getCipherStream ( AEScipher , saltKey , policy . getSaltKeyLength ( ) , iv ) ;
computeIv ( label , index ) ;
cipherCtr . getCipherStream ( AEScipher , saltKey , policy . getSaltKeyLength ( ) , ivStore ) ;
// As last step: initialize AES cipher with derived encryption key.
encryptionKey = new SecretKeySpec ( encKey , 0 , policy . getEncKeyLength ( ) , "AES" ) ;
try
{
AEScipher . init ( Cipher . ENCRYPT_MODE , encryptionKey ) ;
}
catch ( InvalidKeyException e )
{
// TODO Auto-generated catch block
e . printStackTrace ( ) ;
}
encryptionKey = new KeyParameter ( encKey ) ;
AEScipher . init ( true , encryptionKey ) ;
}
/ * *
* Compute ( guess ) the new SRTP index based on the sequence number of
* a received RTP packet .
* Compute ( guess ) the new SRTP index based on the sequence number of a
* received RTP packet .
*
* @param seqNum sequence number of the received RTP packet
* @param seqNum
* sequence number of the received RTP packet
* @return the new SRTP packet index
* /
private long guessIndex ( int seqNum )
{
if ( ! this . seqNumSet )
{
this . seqNumSet = true ;
this . seqNum = seqNum ;
}
private long guessIndex ( int seqNo ) {
if ( this . seqNum < 32768 )
{
if ( seqNum - this . seqNum > 32768 )
this . guessedROC = this . roc - 1 ;
if ( this . seqNum < 32768 ) {
if ( seqNo - this . seqNum > 32768 ) {
guessedROC = roc - 1 ;
} else {
guessedROC = roc ;
}
else
{
this . guessedROC = this . roc ;
}
}
else
{
if ( this . seqNum - 32768 > seqNum )
{
this . guessedROC = this . roc + 1 ;
}
else
{
this . guessedROC = this . roc ;
} else {
if ( seqNum - 32768 > seqNo ) {
guessedROC = roc + 1 ;
} else {
guessedROC = roc ;
}
}
return ( ( long ) this . guessedROC ) < < 16 | seqNum ;
return ( ( long ) guessedROC ) < < 16 | seqNo ;
}
/ * *
@ -751,9 +635,8 @@ private long guessIndex(int seqNum)
*
* @param seqNum sequence number of the accepted packet
* /
private void update ( int seqNum )
{
long delta = guessIndex ( seqNum ) - ( ( ( long ) this . roc ) < < 16 | this . seqNum ) ;
private void update ( int seqNo , long guessedIndex ) {
long delta = guessedIndex - ( ( ( long ) this . roc ) < < 16 | this . seqNum ) ;
/* update the replay bit mask */
if ( delta > 0 ) {
@ -764,49 +647,39 @@ private void update(int seqNum)
replayWindow | = ( 1 < < delta ) ;
}
if ( seqNum > this . seqNum )
{
this . seqNum = seqNum & 0xffff ; // make short
if ( seqNo > seqNum ) {
seqNum = seqNo & 0xffff ;
}
if ( this . guessedROC > this . roc )
{
this . roc = this . guessedROC ;
this . seqNum = seqNum & 0xffff ; // make short
if ( this . guessedROC > this . roc ) {
roc = guessedROC ;
seqNum = seqNo & 0xffff ;
}
}
/ * *
* Derive a new SRTPCryptoContext for use with a new SSRC
*
* This method returns a new SRTPCryptoContext initialized with the data
* of this SRTPCryptoContext . Replacing the SSRC , Roll - over - Counter , and
* the key derivation rate the application cab use this SRTPCryptoContext
* to encrypt / decrypt a new stream ( Synchronization source ) inside
* one RTP session.
*
*
* This method returns a new SRTPCryptoContext initialized with the data of
* this SRTPCryptoContext . Replacing the SSRC , Roll - over - Counter , and the
* derivation rate the application cab use this SRTPCryptoContext to
* / decrypt a new stream ( Synchronization source ) inside one RTP
* .
*
* Before the application can use this SRTPCryptoContext it must call the
* deriveSrtpKeys method .
*
* @param ssrc The SSRC for this context
* @param roc The Roll - Over - Counter for this context
* @param deriveRate The key derivation rate for this context
*
* @param ssrc
* The SSRC for this context
* @param roc
* The Roll - Over - Counter for this context
* @param deriveRate
* The key derivation rate for this context
* @return a new SRTPCryptoContext with all relevant data set .
* /
public SRTPCryptoContext deriveContext ( long ssrc , int roc , long deriveRate )
{
public SRTPCryptoContext deriveContext ( long ssrc , int roc , long deriveRate ) {
SRTPCryptoContext pcc = null ;
try
{
pcc = new SRTPCryptoContext ( ssrc , roc , deriveRate ,
this . masterKey , this . masterSalt , this . policy ,
this . cryptoProvider ) ;
}
catch ( GeneralSecurityException e )
{
// TODO Auto-generated catch block
e . printStackTrace ( ) ;
}
pcc = new SRTPCryptoContext ( ssrc , roc , deriveRate , masterKey ,
masterSalt , policy ) ;
return pcc ;
}
}
Werner Dittmann
17 years ago