pki: Add support for comparing certificates

Signed-off-by: Jakub Jelen <jjelen@redhat.com>
Reviewed-by: Sahana Prasad <sahana@redhat.com>

include/libssh/libssh.h

@@ -295,7 +295,8 @@ enum ssh_keytypes_e{
 
 enum ssh_keycmp_e {
   SSH_KEY_CMP_PUBLIC = 0,
-  SSH_KEY_CMP_PRIVATE
+  SSH_KEY_CMP_PRIVATE = 1,
+  SSH_KEY_CMP_CERTIFICATE = 2,
 };
 
 #define SSH_ADDRSTRLEN 46

src/pki.c

@@ -685,6 +685,22 @@ int ssh_key_cmp(const ssh_key k1,
         }
     }
 
+    if (what == SSH_KEY_CMP_CERTIFICATE) {
+        if (!is_cert_type(k1->type) ||
+            !is_cert_type(k2->type)) {
+            return 1;
+        }
+        if (k1->cert == NULL || k2->cert == NULL) {
+            return 1;
+        }
+        if (ssh_buffer_get_len(k1->cert) != ssh_buffer_get_len(k2->cert)) {
+            return 1;
+        }
+        return memcmp(ssh_buffer_get(k1->cert),
+                      ssh_buffer_get(k2->cert),
+                      ssh_buffer_get_len(k1->cert));
+    }
+
     if (k1->type == SSH_KEYTYPE_ED25519 ||
         k1->type == SSH_KEYTYPE_SK_ED25519) {
         return pki_ed25519_key_cmp(k1, k2, what);

src/pki_ed25519_common.c

@@ -121,6 +121,10 @@ int pki_ed25519_key_cmp(const ssh_key k1,
         if (cmp != 0) {
             return 1;
         }
+        break;
+    case SSH_KEY_CMP_CERTIFICATE:
+        /* handled globally */
+        return 1;
     }
 
     return 0;