Add support to retrieve the fingerprint of a public key from a cert.

Related-to: profanity-im/profanity#2069
Signed-off-by: Steffen Jaeckel <[email protected]>

Author: sjaeckel

src/common.h

@@ -29,6 +29,17 @@
 #include "parser.h"
 #include "snprintf.h"
 
+/** Define your own `STROPHE_STATIC_ASSERT` if your compiler doesn't support one
+ * of the below ones or define as noop if your compiler provides no replacement.
+ */
+#if !defined(STROPHE_STATIC_ASSERT)
+#if (__STDC_VERSION__ >= 202000L)
+#define STROPHE_STATIC_ASSERT(cond, msg) static_assert(cond, msg)
+#else
+#define STROPHE_STATIC_ASSERT(cond, msg) _Static_assert(cond, msg)
+#endif
+#endif
+
 /** handlers **/
 #if (__STDC_VERSION__ >= 202000L)
 typedef void *xmpp_void_handler;

src/tls.c

@@ -162,9 +162,13 @@ const char *xmpp_tlscert_get_description(xmpp_cert_element_t elmnt)
         "Expires On",
         "Public Key Algorithm",
         "Certificate Signature Algorithm",
-        "Fingerprint SHA-1",
-        "Fingerprint SHA-256",
+        "Certificate Fingerprint SHA-1",
+        "Certificate Fingerprint SHA-256",
+        "Public Key Fingerprint SHA-256",
     };
+    STROPHE_STATIC_ASSERT(
+        ARRAY_SIZE(descriptions) == XMPP_CERT_ELEMENT_MAX,
+        "descriptions don't match the number of enum elements");
     if (elmnt < 0 || elmnt >= XMPP_CERT_ELEMENT_MAX)
         return NULL;
     return descriptions[elmnt];

src/tls_gnutls.c

@@ -334,6 +334,12 @@ static xmpp_tlscert_t *_x509_to_tlscert(xmpp_ctx_t *ctx, gnutls_x509_crt_t cert)
     gnutls_x509_crt_get_fingerprint(cert, GNUTLS_DIG_SHA256, smallbuf, &size);
     hex_encode(buf, smallbuf, size);
     tlscert->elements[XMPP_CERT_FINGERPRINT_SHA256] = strophe_strdup(ctx, buf);
+    size = sizeof(smallbuf);
+    gnutls_x509_crt_get_key_id(cert, GNUTLS_KEYID_USE_SHA256, (void *)smallbuf,
+                               &size);
+    hex_encode(buf, smallbuf, size);
+    tlscert->elements[XMPP_CERT_PUBKEY_FINGERPRINT_SHA256] =
+        strophe_strdup(ctx, buf);
 
     strophe_snprintf(buf, sizeof(buf), "%d", gnutls_x509_crt_get_version(cert));
     tlscert->elements[XMPP_CERT_VERSION] = strophe_strdup(ctx, buf);

src/tls_openssl.c

@@ -376,18 +376,26 @@ _get_fingerprint(const xmpp_ctx_t *ctx, X509 *err_cert, xmpp_cert_element_t el)
 {
     unsigned char buf[EVP_MAX_MD_SIZE];
     unsigned int len;
+    int (*digest_fn)(const X509 *data, const EVP_MD *type, unsigned char *md,
+                     unsigned int *len);
     const EVP_MD *digest;
     switch (el) {
     case XMPP_CERT_FINGERPRINT_SHA1:
+        digest_fn = X509_digest;
         digest = EVP_sha1();
         break;
     case XMPP_CERT_FINGERPRINT_SHA256:
+        digest_fn = X509_digest;
+        digest = EVP_sha256();
+        break;
+    case XMPP_CERT_PUBKEY_FINGERPRINT_SHA256:
+        digest_fn = X509_pubkey_digest;
         digest = EVP_sha256();
         break;
     default:
         return NULL;
     }
-    if (X509_digest(err_cert, digest, buf, &len) != 0) {
+    if (digest_fn(err_cert, digest, buf, &len) != 0) {
         char fingerprint[4 * EVP_MAX_MD_SIZE];
         hex_encode(fingerprint, buf, len);
         return strophe_strdup(ctx, fingerprint);
@@ -475,6 +483,8 @@ static xmpp_tlscert_t *_x509_to_tlscert(xmpp_ctx_t *ctx, X509 *cert)
         _get_fingerprint(ctx, cert, XMPP_CERT_FINGERPRINT_SHA1);
     tlscert->elements[XMPP_CERT_FINGERPRINT_SHA256] =
         _get_fingerprint(ctx, cert, XMPP_CERT_FINGERPRINT_SHA256);
+    tlscert->elements[XMPP_CERT_PUBKEY_FINGERPRINT_SHA256] =
+        _get_fingerprint(ctx, cert, XMPP_CERT_PUBKEY_FINGERPRINT_SHA256);
 
     strophe_snprintf(buf, sizeof(buf), "%ld", X509_get_version(cert) + 1);
     tlscert->elements[XMPP_CERT_VERSION] = strophe_strdup(ctx, buf);

strophe.h

@@ -250,17 +250,18 @@ typedef enum {
  *  @ingroup TLS
  */
 typedef enum {
-    XMPP_CERT_VERSION,            /**< X.509 Version */
-    XMPP_CERT_SERIALNUMBER,       /**< SerialNumber */
-    XMPP_CERT_SUBJECT,            /**< Subject */
-    XMPP_CERT_ISSUER,             /**< Issuer */
-    XMPP_CERT_NOTBEFORE,          /**< Issued on */
-    XMPP_CERT_NOTAFTER,           /**< Expires on */
-    XMPP_CERT_KEYALG,             /**< Public Key Algorithm */
-    XMPP_CERT_SIGALG,             /**< Certificate Signature Algorithm */
-    XMPP_CERT_FINGERPRINT_SHA1,   /**< Fingerprint SHA-1 */
-    XMPP_CERT_FINGERPRINT_SHA256, /**< Fingerprint SHA-256 */
-    XMPP_CERT_ELEMENT_MAX         /**< Last element of the enum */
+    XMPP_CERT_VERSION,                   /**< X.509 Version */
+    XMPP_CERT_SERIALNUMBER,              /**< SerialNumber */
+    XMPP_CERT_SUBJECT,                   /**< Subject */
+    XMPP_CERT_ISSUER,                    /**< Issuer */
+    XMPP_CERT_NOTBEFORE,                 /**< Issued on */
+    XMPP_CERT_NOTAFTER,                  /**< Expires on */
+    XMPP_CERT_KEYALG,                    /**< Public Key Algorithm */
+    XMPP_CERT_SIGALG,                    /**< Certificate Signature Algorithm */
+    XMPP_CERT_FINGERPRINT_SHA1,          /**< Fingerprint SHA-1 */
+    XMPP_CERT_FINGERPRINT_SHA256,        /**< Fingerprint SHA-256 */
+    XMPP_CERT_PUBKEY_FINGERPRINT_SHA256, /**< SHA-256 fingerprint of pubkey */
+    XMPP_CERT_ELEMENT_MAX                /**< Last element of the enum */
 } xmpp_cert_element_t;
 
 typedef struct {