Implement X509_get_signature_info()

This is a slightly strange combination of OBJ_find_sigid_algs() and the
security level API necessary because OBJ_find_sigid_algs() on its own
isn't smart enough for the special needs of RSA-PSS and EdDSA.

The API extracts the hash's NID and the pubkey's NID from the certificate's
signatureAlgorithm and invokes special handlers for RSA-PSS and EdDSA
for retrieving the corresponding information. This isn't entirely free
for RSA-PSS, but for now we don't cache this information.

The security bits calculation is a bit hand-wavy, but that's something
that comes along with this sort of numerology.

ok jsing

1 files changed, 9 insertions, 1 deletions

diff --git a/src/lib/libcrypto/x509/x509.h b/src/lib/libcrypto/x509/x509.h
index 87bc6dbb33..856ad19ba4 100644
--- a/src/lib/libcrypto/x509/x509.h
+++ b/src/lib/libcrypto/x509/x509.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: x509.h,v 1.112 2024/06/12 03:55:46 tb Exp $ */
+/* $OpenBSD: x509.h,v 1.113 2024/08/28 07:15:04 tb Exp $ */
 /* Copyright (C) 1995-1998 Eric Young (eay@cryptsoft.com)
  * All rights reserved.
  *
@@ -622,6 +622,14 @@ X509 *		d2i_X509_AUX(X509 **a,const unsigned char **pp,long length);
 
 int i2d_re_X509_tbs(X509 *x, unsigned char **pp);
 
+#if defined(LIBRESSL_INTERNAL) || defined(LIBRESSL_NEXT_API)
+/* Flags returned by X509_get_signature_info(): valid and suitable for TLS. */
+#define X509_SIG_INFO_VALID     1
+#define X509_SIG_INFO_TLS       2
+int X509_get_signature_info(X509 *x, int *mdnid, int *pknid, int *secbits,
+    uint32_t *flags);
+#endif
+
 void X509_get0_signature(const ASN1_BIT_STRING **psig,
     const X509_ALGOR **palg, const X509 *x);
 int X509_get_signature_nid(const X509 *x);