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, 21 insertions, 1 deletions

diff --git a/src/lib/libcrypto/ec/ecx_methods.c b/src/lib/libcrypto/ec/ecx_methods.c
index 70475e8dc1..6b5759d4fa 100644
--- a/src/lib/libcrypto/ec/ecx_methods.c
+++ b/src/lib/libcrypto/ec/ecx_methods.c
@@ -1,4 +1,4 @@
-/*      $OpenBSD: ecx_methods.c,v 1.13 2024/04/02 04:04:07 tb Exp $ */
+/*      $OpenBSD: ecx_methods.c,v 1.14 2024/08/28 07:15:04 tb Exp $ */
 /*
  * Copyright (c) 2022 Joel Sing <jsing@openbsd.org>
  *
@@ -510,6 +510,24 @@ ecx_security_bits(const EVP_PKEY *pkey)
 }
 
 static int
+ecx_signature_info(const X509_ALGOR *algor, int *md_nid, int *pkey_nid,
+    int *security_bits, uint32_t *flags)
+{
+        const ASN1_OBJECT *aobj;
+
+        X509_ALGOR_get0(&aobj, NULL, NULL, algor);
+        if (OBJ_obj2nid(aobj) != EVP_PKEY_ED25519)
+                return 0;
+
+        *md_nid = NID_undef;
+        *pkey_nid = NID_ED25519;
+        *security_bits = ED25519_SECURITY_BITS;
+        *flags = X509_SIG_INFO_TLS | X509_SIG_INFO_VALID;
+
+        return 1;
+}
+
+static int
 ecx_param_cmp(const EVP_PKEY *pkey1, const EVP_PKEY *pkey2)
 {
         /* No parameters, so always equivalent. */
@@ -929,6 +947,8 @@ const EVP_PKEY_ASN1_METHOD ed25519_asn1_meth = {
         .pkey_bits = ecx_bits,
         .pkey_security_bits = ecx_security_bits,
 
+        .signature_info = ecx_signature_info,
+
         .param_cmp = ecx_param_cmp,
 
         .pkey_free = ecx_free,