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PKCS#1 v1.5 decoding: fix empty payload case

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This commit is contained in:
Gilles Peskine 2018-10-05 18:11:27 +02:00
parent c5ccd7a1e7
commit ec2a5fdee1
1 changed files with 7 additions and 6 deletions
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13
library/rsa.c
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@ -1522,9 +1522,9 @@ int mbedtls_rsa_rsaes_pkcs1_v15_decrypt( mbedtls_rsa_context *ctx,
* where PS must be at least 8 nonzero bytes. */ * where PS must be at least 8 nonzero bytes. */
bad |= buf[1] ^ MBEDTLS_RSA_CRYPT; bad |= buf[1] ^ MBEDTLS_RSA_CRYPT;
/* Get padding len, but always read till end of buffer /* Read the whole buffer. Set pad_done to nonzero if we find
* (minus one, for the 00 byte) */ * the 0x00 byte and remember the padding length in pad_count. */
for( i = 2; i < ilen - 1; i++ ) for( i = 2; i < ilen; i++ )
{ {
pad_done |= ((buf[i] | (unsigned char)-buf[i]) >> 7) ^ 1; pad_done |= ((buf[i] | (unsigned char)-buf[i]) >> 7) ^ 1;
pad_count += ((pad_done | (unsigned char)-pad_done) >> 7) ^ 1; pad_count += ((pad_done | (unsigned char)-pad_done) >> 7) ^ 1;
@ -1536,9 +1536,10 @@ int mbedtls_rsa_rsaes_pkcs1_v15_decrypt( mbedtls_rsa_context *ctx,
* where PS must be at least 8 bytes with the value 0xFF. */ * where PS must be at least 8 bytes with the value 0xFF. */
bad |= buf[1] ^ MBEDTLS_RSA_SIGN; bad |= buf[1] ^ MBEDTLS_RSA_SIGN;
/* Get padding len, but always read till end of buffer /* Read the whole buffer. Set pad_done to nonzero if we find
* (minus one, for the 00 byte) */ * the 0x00 byte and remember the padding length in pad_count.
for( i = 2; i < ilen - 1; i++ ) * If there's a non-0xff byte in the padding, the padding is bad. */
for( i = 2; i < ilen; i++ )
{ {
pad_done |= if_int( buf[i], 0, 1 ); pad_done |= if_int( buf[i], 0, 1 );
pad_count += if_int( pad_done, 0, 1 ); pad_count += if_int( pad_done, 0, 1 );