int GCM_add_cipher()

in src/gcm.c [250:279]

• 28 lines of code
• 9 McCabe index (conditional complexity)

int GCM_add_cipher(gcm *g,char *plain,const char *cipher,int len)
{
    /* Add ciphertext to extract plaintext, len is length of ciphertext. */
    int j=0;
    unsign32 counter;
    char oc;
    uchar B[16];
    if (g->status==GCM_ACCEPTING_HEADER) g->status=GCM_ACCEPTING_CIPHER;
    if (g->status!=GCM_ACCEPTING_CIPHER) return 0;

    while (j<len)
    {
        counter=pack((uchar *)&(g->a.f[12]));
        counter++;
        unpack(counter,(uchar *)&(g->a.f[12]));  /* increment counter */
        for (int i=0; i<16; i++) B[i]=g->a.f[i];
        AES_ecb_encrypt(&(g->a),B);        /* encrypt it  */
        for (int i=0; i<16 && j<len; i++,j++)
        {
            oc=cipher[j];
            plain[j]=(char)(cipher[j]^B[i]);
            g->stateX[i]^=oc;
            g->lenC[1]++;
            if (g->lenC[1]==0) g->lenC[0]++;
        }
        gf2mul(g);
    }
    if (len%16!=0) g->status=GCM_NOT_ACCEPTING_MORE;
    return 1;
}