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https://github.com/yuzu-emu/mbedtls.git
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Merged more constant-time checking in RSA
This commit is contained in:
Paul Bakker
commit
4040d7e95c
@ -6,6 +6,7 @@ Changes
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* Speedup of ECP multiplication operation
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* Relaxed some SHA2 ciphersuite's version requirements
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* Dropped use of readdir_r() instead of readdir() with threading support
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* More constant-time checks in the RSA module
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Bugfix
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* Fixed X.509 hostname comparison (with non-regular characters)
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152
library/rsa.c
152
library/rsa.c
@ -646,14 +646,17 @@ int rsa_rsaes_oaep_decrypt( rsa_context *ctx,
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size_t output_max_len )
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{
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int ret;
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size_t ilen;
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unsigned char *p;
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size_t ilen, i, pad_len;
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unsigned char *p, bad, pad_done;
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unsigned char buf[POLARSSL_MPI_MAX_SIZE];
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unsigned char lhash[POLARSSL_MD_MAX_SIZE];
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unsigned int hlen;
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const md_info_t *md_info;
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md_context_t md_ctx;
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/*
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* Parameters sanity checks
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*/
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if( ctx->padding != RSA_PKCS_V21 )
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return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
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@ -662,6 +665,13 @@ int rsa_rsaes_oaep_decrypt( rsa_context *ctx,
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if( ilen < 16 || ilen > sizeof( buf ) )
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return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
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md_info = md_info_from_type( ctx->hash_id );
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if( md_info == NULL )
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return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
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/*
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* RSA operation
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*/
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ret = ( mode == RSA_PUBLIC )
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? rsa_public( ctx, input, buf )
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: rsa_private( ctx, f_rng, p_rng, input, buf );
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@ -669,50 +679,60 @@ int rsa_rsaes_oaep_decrypt( rsa_context *ctx,
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if( ret != 0 )
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return( ret );
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p = buf;
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if( *p++ != 0 )
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return( POLARSSL_ERR_RSA_INVALID_PADDING );
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md_info = md_info_from_type( ctx->hash_id );
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if( md_info == NULL )
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return( POLARSSL_ERR_RSA_BAD_INPUT_DATA );
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/*
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* Unmask data and generate lHash
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*/
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hlen = md_get_size( md_info );
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md_init_ctx( &md_ctx, md_info );
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// Generate lHash
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//
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/* Generate lHash */
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md( md_info, label, label_len, lhash );
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// seed: Apply seedMask to maskedSeed
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//
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/* seed: Apply seedMask to maskedSeed */
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mgf_mask( buf + 1, hlen, buf + hlen + 1, ilen - hlen - 1,
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&md_ctx );
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// DB: Apply dbMask to maskedDB
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//
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/* DB: Apply dbMask to maskedDB */
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mgf_mask( buf + hlen + 1, ilen - hlen - 1, buf + 1, hlen,
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&md_ctx );
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p += hlen;
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md_free_ctx( &md_ctx );
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// Check validity
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//
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if( memcmp( lhash, p, hlen ) != 0 )
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return( POLARSSL_ERR_RSA_INVALID_PADDING );
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/*
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* Check contents, in "constant-time"
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*/
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p = buf;
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bad = 0;
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p += hlen;
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bad |= *p++; /* First byte must be 0 */
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while( *p == 0 && p < buf + ilen )
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p++;
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p += hlen; /* Skip seed */
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if( p == buf + ilen )
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return( POLARSSL_ERR_RSA_INVALID_PADDING );
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/* Check lHash */
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for( i = 0; i < hlen; i++ )
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bad |= lhash[i] ^ *p++;
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if( *p++ != 0x01 )
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/* Get zero-padding len, but always read till end of buffer
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* (minus one, for the 01 byte) */
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pad_len = 0;
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pad_done = 0;
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for( i = 0; i < ilen - 2 * hlen - 2; i++ )
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{
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pad_done |= p[i];
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pad_len += ( pad_done == 0 );
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}
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p += pad_len;
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bad |= *p++ ^ 0x01;
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/*
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* The only information "leaked" is whether the padding was correct or not
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* (eg, no data is copied if it was not correct). This meets the
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* recommendations in PKCS#1 v2.2: an opponent cannot distinguish between
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* the different error conditions.
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*/
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if( bad != 0 )
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return( POLARSSL_ERR_RSA_INVALID_PADDING );
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if (ilen - (p - buf) > output_max_len)
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@ -737,10 +757,9 @@ int rsa_rsaes_pkcs1_v15_decrypt( rsa_context *ctx,
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unsigned char *output,
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size_t output_max_len)
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{
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int ret, correct = 1;
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size_t ilen, pad_count = 0;
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unsigned char *p, *q;
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unsigned char bt;
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int ret;
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size_t ilen, pad_count = 0, i;
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unsigned char *p, bad, pad_done = 0;
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unsigned char buf[POLARSSL_MPI_MAX_SIZE];
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if( ctx->padding != RSA_PKCS_V15 )
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@ -759,57 +778,46 @@ int rsa_rsaes_pkcs1_v15_decrypt( rsa_context *ctx,
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return( ret );
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p = buf;
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bad = 0;
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if( *p++ != 0 )
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correct = 0;
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/*
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* Check and get padding len in "constant-time"
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*/
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bad |= *p++; /* First byte must be 0 */
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bt = *p++;
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if( ( bt != RSA_CRYPT && mode == RSA_PRIVATE ) ||
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( bt != RSA_SIGN && mode == RSA_PUBLIC ) )
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/* This test does not depend on secret data */
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if( mode == RSA_PRIVATE )
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{
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correct = 0;
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bad |= *p++ ^ RSA_CRYPT;
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/* Get padding len, but always read till end of buffer
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* (minus one, for the 00 byte) */
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for( i = 0; i < ilen - 3; i++ )
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{
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pad_done |= ( p[i] == 0 );
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pad_count += ( pad_done == 0 );
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}
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if( bt == RSA_CRYPT )
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{
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while( *p != 0 && p < buf + ilen - 1 )
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pad_count += ( *p++ != 0 );
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correct &= ( *p == 0 && p < buf + ilen - 1 );
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q = p;
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// Also pass over all other bytes to reduce timing differences
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//
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while ( q < buf + ilen - 1 )
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pad_count += ( *q++ != 0 );
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// Prevent compiler optimization of pad_count
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//
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correct |= pad_count & 0x100000; /* Always 0 unless 1M bit keys */
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p++;
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p += pad_count;
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bad |= *p++; /* Must be zero */
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}
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else
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{
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while( *p == 0xFF && p < buf + ilen - 1 )
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pad_count += ( *p++ == 0xFF );
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bad |= *p++ ^ RSA_SIGN;
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correct &= ( *p == 0 && p < buf + ilen - 1 );
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q = p;
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// Also pass over all other bytes to reduce timing differences
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//
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while ( q < buf + ilen - 1 )
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pad_count += ( *q++ != 0 );
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// Prevent compiler optimization of pad_count
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//
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correct |= pad_count & 0x100000; /* Always 0 unless 1M bit keys */
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p++;
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/* Get padding len, but always read till end of buffer
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* (minus one, for the 00 byte) */
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for( i = 0; i < ilen - 3; i++ )
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{
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pad_done |= ( p[i] == 0xFF );
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pad_count += ( pad_done == 0 );
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}
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if( correct == 0 )
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p += pad_count;
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bad |= *p++; /* Must be zero */
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}
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if( bad )
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return( POLARSSL_ERR_RSA_INVALID_PADDING );
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if (ilen - (p - buf) > output_max_len)
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