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Implement ccm_auth_decrypt()

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This commit is contained in:
Manuel Pégourié-Gonnard
2014-05-06 18:06:52 +02:00
parent 002323340a
commit ce77d55023
3 changed files with 498 additions and 15 deletions
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66
library/ccm.c
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@ -146,9 +146,6 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
if( add_len > 0xFF00 )
return( POLARSSL_ERR_CCM_BAD_INPUT );
if( mode != CCM_ENCRYPT )
return( POLARSSL_ERR_CCM_BAD_INPUT ); /* Not implemented yet */
/*
* First block B_0:
* 0 .. 0 flags
@ -238,18 +235,34 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
dst = output;
/*
* Authenticate and encrypt message
* Authenticate and crypt message
* The only difference between encryption and decryption is
* the respective order of authentication and {en,de}cryption
*/
while( len_left > 16 )
{
memcpy( b, src, 16 );
UPDATE_CBC_MAC( b );
if( mode == CCM_ENCRYPT )
{
memcpy( b, src, 16 );
UPDATE_CBC_MAC( b );
}
CTR_CRYPT_BLOCK( dst, src );
if( mode == CCM_DECRYPT )
{
memcpy( b, dst, 16 );
UPDATE_CBC_MAC( b );
}
dst += 16;
src += 16;
len_left -= 16;
/*
* Increment counter.
* No need to check for overflow thanks to the length check above.
*/
for( i = 0; i < q; i++ )
if( ++ctr[15-i] != 0 )
break;
@ -260,10 +273,12 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
unsigned char mask[16];
size_t olen;
memset( b, 0, 16 );
memcpy( b, src, len_left );
UPDATE_CBC_MAC( b );
if( mode == CCM_ENCRYPT )
{
memset( b, 0, 16 );
memcpy( b, src, len_left );
UPDATE_CBC_MAC( b );
}
if( ( ret = cipher_update( &ctx->cipher_ctx, ctr, 16,
mask, &olen ) ) != 0 )
@ -273,10 +288,17 @@ static int ccm_auth_crypt( ccm_context *ctx, int mode, size_t length,
for( i = 0; i < len_left; i++ )
dst[i] = src[i] ^ mask[i];
if( mode == CCM_DECRYPT )
{
memset( b, 0, 16 );
memcpy( b, dst, len_left );
UPDATE_CBC_MAC( b );
}
}
/*
* Authentication: reset counter and encrypt internal tag
* Authentication: reset counter and {en,de}crypt internal tag
*/
for( i = 0; i < q; i++ )
ctr[15-i] = 0;
@ -410,10 +432,10 @@ int ccm_self_test( int verbose )
if( verbose != 0 )
polarssl_printf( " CCM-AES #%u: ", (unsigned int) i + 1 );
ret = ccm_encrypt_and_tag( &ctx, msg_len[i],
iv, iv_len[i], ad, add_len[i],
msg, out,
out + msg_len[i], tag_len[i] );
ret = ccm_encrypt_and_tag( &ctx, msg_len[i],
iv, iv_len[i], ad, add_len[i],
msg, out,
out + msg_len[i], tag_len[i] );
if( ret != 0 ||
memcmp( out, res[i], msg_len[i] + tag_len[i] ) != 0 )
@ -424,6 +446,20 @@ int ccm_self_test( int verbose )
return( 1 );
}
ret = ccm_auth_decrypt( &ctx, msg_len[i],
iv, iv_len[i], ad, add_len[i],
res[i], out,
res[i] + msg_len[i], tag_len[i] );
if( ret != 0 ||
memcmp( out, msg, msg_len[i] ) != 0 )
{
if( verbose != 0 )
polarssl_printf( "failed\n" );
return( 1 );
}
if( verbose != 0 )
polarssl_printf( "passed\n" );
}