834
edits
Changes
no edit summary
Line 1:
Line 1:
− + invalid=strncmp(hash1,signaturehash,HASHLENGTH);+ + if(invalid!=0) {+ pretendItsNotAWiiDisc();+
+
+
Here is a rough example implementation of roughly the same type of bug that existed until [[IOS37]]:
+Here is a pseudocode implementation of roughly the same type of bug that existed until [[IOS37]]:
− char *hash1=hash(realstuff);
+ struct rsa_cert {
− u32 key_id;
− char rsa_signature[1024];
− char metadata[32];
− char content_hash[20];
− };
+ int verify_cert (struct rsa_cert cert) {
+ char *cert_hash=SHA1(cert.metadata + cert.content_hash);
+ char *sig_hash=rsa_decrypt(cert.rsa_signature, cert.key_id);
+ if (strncmp(cert_hash, sig_hash, SHA1_LENGTH) == 0) {
+ return CERT_OK;
+ } else {
+ return CERT_BAD;
+ }
}
}
+ int is_a_valid_disc(struct rsa_cert cert, char *disc_hash) {
+ if(memcmp(disc_hash, cert.content_hash, SHA1_LENGTH) != 0) {
+ return DISC_BAD;
+ }
+
+ if(verify_cert (cert) == CERT_BAD) {
+ return DISC_BAD;
+ } else {
+ return DISC_OK;
+}
+
+The bug here is that the hash can (and very likely does) contain a NULL byte, (chr)0 that is.
The bug here is that the hash can (and very likely does) contain a NULL byte, (chr)0 that is.
To quote from the first google hit for strncmp:
To quote from the first google hit for strncmp: