AES_CBC_IV0_DECRYPT: function()

in src/ecdh.js [436:505]
58 lines of code
17 McCabe index (conditional complexity)

        AES_CBC_IV0_DECRYPT: function(K, C) { /* padding is removed */
            var a = new ctx.AES(),
                buff = [],
                MM = [],
                ipt = 0,
                opt = 0,
                M, ch, fin, bad, padlen, i;

            a.init(ctx.AES.CBC, K.length, K, null);

            if (C.length === 0) {
                return [];
            }
            ch = C[ipt++];

            fin = false;

            for (;;) {
                for (i = 0; i < 16; i++) {
                    buff[i] = ch;
                    if (ipt >= C.length) {
                        fin = true;
                        break;
                    } else {
                        ch = C[ipt++];
                    }
                }
                a.decrypt(buff);
                if (fin) {
                    break;
                }

                for (i = 0; i < 16; i++) {
                    MM[opt++] = buff[i];
                }
            }

            a.end();
            bad = false;
            padlen = buff[15];

            if (i != 15 || padlen < 1 || padlen > 16) {
                bad = true;
            }

            if (padlen >= 2 && padlen <= 16) {
                for (i = 16 - padlen; i < 16; i++) {
                    if (buff[i] != padlen) {
                        bad = true;
                    }
                }
            }

            if (!bad) {
                for (i = 0; i < 16 - padlen; i++) {
                    MM[opt++] = buff[i];
                }
            }

            M = [];
            if (bad) {
                return M;
            }

            for (i = 0; i < opt; i++) {
                M[i] = MM[i];
            }

            return M;
        },