RSA-PSS – Provably secure RSA Signatures and their ...

static SECStatusemsa_pss_verify ( const unsigned char * mHash ,const unsigned char *em , unsigned int emLen ,unsigned int emBits , HASH_HashType hashAlg ,HASH_HashType maskHashAlg , unsigned int sLen ){const SECHashObject * hash ;void * hashContext ;unsigned char *db;unsigned char *H_; /* H’ from the RFC */unsigned int i, dbMaskLen , zeroBits ;SECStatus rv;hash = HASH_GetRawHashObject ( hashAlg );dbMaskLen = emLen - hash -> length - 1;/* Step 3 + 4 */if (( emLen < (hash -> length + sLen + 2)) ||(em[ emLen - 1] != 0 xbc )) {PORT_SetError ( SEC_ERROR_BAD_SIGNATURE );return SECFailure ;}/* Step 6 */zeroBits = emLen *8 - emBits ;if (( em [0] >> (8 - zeroBits )) != 0) {PORT_SetError ( SEC_ERROR_BAD_SIGNATURE );return SECFailure ;}/* Step 7 */db = ( unsigned char *) PORT_Alloc ( dbMaskLen );if (db == NULL ) {PORT_SetError ( SEC_ERROR_NO_MEMORY );return SECFailure ;}/* &em[ dbMaskLen ] points to H, used as mgfSeed */MGF1 ( maskHashAlg , db , dbMaskLen , &em[ dbMaskLen ], hash -> length );/* Step 8 */for (i = 0; i < dbMaskLen ; i ++) {db[i] ^= em[i];}Listing 3: Beginning of emsa pss verify from rsawrapr.c33