}
}
+/*
+ * Verify that the public data in an RSA key matches the private
+ * data.
+ */
+int rsa_verify(struct RSAKey *key) {
+ Bignum n, ed, pm1, qm1, pm1qm1;
+ int cmp;
+
+ /* n must equal pq. */
+ n = bigmul(key->p, key->q);
+ cmp = bignum_cmp(n, key->modulus);
+ freebn(n);
+ if (cmp != 0)
+ return 0;
+
+ /* e * d must be congruent to 1, modulo (p-1)(q-1). */
+ pm1 = copybn(key->p);
+ decbn(pm1);
+ qm1 = copybn(key->q);
+ decbn(qm1);
+ pm1qm1 = bigmul(pm1, qm1);
+ freebn(pm1);
+ freebn(qm1);
+ ed = modmul(key->exponent, key->private_exponent, pm1qm1);
+ sfree(pm1qm1);
+ cmp = bignum_cmp(ed, One);
+ sfree(ed);
+ if (cmp != 0)
+ return 0;
+
+ return 1;
+}
+
void freersakey(struct RSAKey *key) {
if (key->modulus) freebn(key->modulus);
if (key->exponent) freebn(key->exponent);
len = rsastr_len(rsa);
p = smalloc(len);
- rsastr_fmt(p, rsa);
+ rsastr_fmt(p, rsa);
return p;
}
rsa->q = getmp(&pb, &priv_len);
rsa->iqmp = getmp(&pb, &priv_len);
+ if (!rsa_verify(rsa)) {
+ rsa2_freekey(rsa);
+ return NULL;
+ }
+
return rsa;
}
/*
* This is the magic ASN.1/DER prefix that goes in the decoded
* signature, between the string of FFs and the actual SHA hash
- * value. As closely as I can tell, the meaning of it is:
+ * value. The meaning of it is:
*
* 00 -- this marks the end of the FFs; not part of the ASN.1 bit itself
*
* 30 21 -- a constructed SEQUENCE of length 0x21
* 30 09 -- a constructed sub-SEQUENCE of length 9
* 06 05 -- an object identifier, length 5
- * 2B 0E 03 02 1A --
+ * 2B 0E 03 02 1A -- object id { 1 3 14 3 2 26 }
+ * (the 1,3 comes from 0x2B = 43 = 40*1+3)
* 05 00 -- NULL
* 04 14 -- a primitive OCTET STRING of length 0x14
* [0x14 bytes of hash data follows]
+ *
+ * The object id in the middle there is listed as `id-sha1' in
+ * ftp://ftp.rsasecurity.com/pub/pkcs/pkcs-1/pkcs-1v2-1d2.asn (the
+ * ASN module for PKCS #1) and its expanded form is as follows:
+ *
+ * id-sha1 OBJECT IDENTIFIER ::= {
+ * iso(1) identified-organization(3) oiw(14) secsig(3)
+ * algorithms(2) 26 }
*/
static unsigned char asn1_weird_stuff[] = {
0x00,0x30,0x21,0x30,0x09,0x06,0x05,0x2B,