cli: mime node: abstract decryption and signature verification

The code filled with #ifdef GMIME_ATLEAST_26 is difficult to
read. Abstract the decryption and signature verification into
functions, with separate implementations for GMime 2.4 and 2.6, to
clarify the code.

There should be no functional changes.

mime-node.c

@@ -130,26 +130,163 @@ DONE:
 }
 
 #ifdef GMIME_ATLEAST_26
+
+/* Signature list destructor (GMime 2.6) */
 static int
 _signature_list_free (GMimeSignatureList **proxy)
 {
     g_object_unref (*proxy);
     return 0;
 }
-#else
+
+/* Set up signature list destructor (GMime 2.6) */
+static void
+set_signature_list_destructor (mime_node_t *node)
+{
+    GMimeSignatureList **proxy = talloc (node, GMimeSignatureList *);
+    if (proxy) {
+	*proxy = node->sig_list;
+	talloc_set_destructor (proxy, _signature_list_free);
+    }
+}
+
+/* Verify a signed mime node (GMime 2.6) */
+static void
+node_verify (mime_node_t *node, GMimeObject *part,
+	     notmuch_crypto_context_t *cryptoctx)
+{
+    GError *err = NULL;
+
+    node->verify_attempted = TRUE;
+    node->sig_list = g_mime_multipart_signed_verify
+	(GMIME_MULTIPART_SIGNED (part), cryptoctx, &err);
+
+    if (node->sig_list)
+	set_signature_list_destructor (node);
+    else
+	fprintf (stderr, "Failed to verify signed part: %s\n",
+		 err ? err->message : "no error explanation given");
+
+    if (err)
+	g_error_free (err);
+}
+
+/* Decrypt and optionally verify an encrypted mime node (GMime 2.6) */
+static void
+node_decrypt_and_verify (mime_node_t *node, GMimeObject *part,
+			 notmuch_crypto_context_t *cryptoctx)
+{
+    GError *err = NULL;
+    GMimeDecryptResult *decrypt_result = NULL;
+    GMimeMultipartEncrypted *encrypteddata = GMIME_MULTIPART_ENCRYPTED (part);
+
+    node->decrypt_attempted = TRUE;
+    node->decrypted_child = g_mime_multipart_encrypted_decrypt
+	(encrypteddata, cryptoctx, &decrypt_result, &err);
+    if (! node->decrypted_child) {
+	fprintf (stderr, "Failed to decrypt part: %s\n",
+		 err ? err->message : "no error explanation given");
+	goto DONE;
+    }
+
+    node->decrypt_success = TRUE;
+    node->verify_attempted = TRUE;
+
+    /* This may be NULL if the part is not signed. */
+    node->sig_list = g_mime_decrypt_result_get_signatures (decrypt_result);
+    if (node->sig_list) {
+	g_object_ref (node->sig_list);
+	set_signature_list_destructor (node);
+    }
+    g_object_unref (decrypt_result);
+
+ DONE:
+    if (err)
+	g_error_free (err);
+}
+
+#else /* GMIME_ATLEAST_26 */
+
+/* Signature validity destructor (GMime 2.4) */
 static int
 _signature_validity_free (GMimeSignatureValidity **proxy)
 {
     g_mime_signature_validity_free (*proxy);
     return 0;
 }
-#endif
+
+/* Set up signature validity destructor (GMime 2.4) */
+static void
+set_signature_validity_destructor (mime_node_t *node)
+{
+    GMimeSignatureValidity **proxy = talloc (node, GMimeSignatureValidity *);
+    if (proxy) {
+	*proxy = node->sig_validity;
+	talloc_set_destructor (proxy, _signature_validity_free);
+    }
+}
+
+/* Verify a signed mime node (GMime 2.4) */
+static void
+node_verify (mime_node_t *node, GMimeObject *part,
+	     notmuch_crypto_context_t *cryptoctx)
+{
+    GError *err = NULL;
+
+    node->verify_attempted = TRUE;
+    node->sig_validity = g_mime_multipart_signed_verify
+	(GMIME_MULTIPART_SIGNED (part), cryptoctx, &err);
+    if (node->sig_validity) {
+	set_signature_validity_destructor (node);
+    } else {
+	fprintf (stderr, "Failed to verify signed part: %s\n",
+		 err ? err->message : "no error explanation given");
+    }
+
+    if (err)
+	g_error_free (err);
+}
+
+/* Decrypt and optionally verify an encrypted mime node (GMime 2.4) */
+static void
+node_decrypt_and_verify (mime_node_t *node, GMimeObject *part,
+			 notmuch_crypto_context_t *cryptoctx)
+{
+    GError *err = NULL;
+    GMimeMultipartEncrypted *encrypteddata = GMIME_MULTIPART_ENCRYPTED (part);
+
+    node->decrypt_attempted = TRUE;
+    node->decrypted_child = g_mime_multipart_encrypted_decrypt
+	(encrypteddata, cryptoctx, &err);
+    if (! node->decrypted_child) {
+	fprintf (stderr, "Failed to decrypt part: %s\n",
+		 err ? err->message : "no error explanation given");
+	goto DONE;
+    }
+
+    node->decrypt_success = TRUE;
+    node->verify_attempted = TRUE;
+
+    /* The GMimeSignatureValidity returned here is a const, unlike the
+     * one returned by g_mime_multipart_signed_verify() in
+     * node_verify() above, so the destructor is not needed.
+     */
+    node->sig_validity = g_mime_multipart_encrypted_get_signature_validity (encrypteddata);
+    if (! node->sig_validity)
+	fprintf (stderr, "Failed to verify encrypted signed part: %s\n",
+		 err ? err->message : "no error explanation given");
+
+ DONE:
+    if (err)
+	g_error_free (err);
+}
+
+#endif  /* GMIME_ATLEAST_26 */
 
 static mime_node_t *
 _mime_node_create (mime_node_t *parent, GMimeObject *part)
 {
     mime_node_t *node = talloc_zero (parent, mime_node_t);
-    GError *err = NULL;
     notmuch_crypto_context_t *cryptoctx = NULL;
 
     /* Set basic node properties */
@@ -198,32 +335,7 @@ _mime_node_create (mime_node_t *parent, GMimeObject *part)
 		     "message (must be exactly 2)\n",
 		     node->nchildren);
 	} else {
-	    GMimeMultipartEncrypted *encrypteddata =
+	    node_decrypt_and_verify (node, part, cryptoctx);
-		GMIME_MULTIPART_ENCRYPTED (part);
-	    node->decrypt_attempted = TRUE;
-#ifdef GMIME_ATLEAST_26
-	    GMimeDecryptResult *decrypt_result = NULL;
-	    node->decrypted_child = g_mime_multipart_encrypted_decrypt
-		(encrypteddata, cryptoctx, &decrypt_result, &err);
-#else
-	    node->decrypted_child = g_mime_multipart_encrypted_decrypt
-		(encrypteddata, cryptoctx, &err);
-#endif
-	    if (node->decrypted_child) {
-		node->decrypt_success = node->verify_attempted = TRUE;
-#ifdef GMIME_ATLEAST_26
-		/* This may be NULL if the part is not signed. */
-		node->sig_list = g_mime_decrypt_result_get_signatures (decrypt_result);
-		if (node->sig_list)
-		    g_object_ref (node->sig_list);
-		g_object_unref (decrypt_result);
-#else
-		node->sig_validity = g_mime_multipart_encrypted_get_signature_validity (encrypteddata);
-#endif
-	    } else {
-		fprintf (stderr, "Failed to decrypt part: %s\n",
-			 (err ? err->message : "no error explanation given"));
-	    }
 	}
     } else if (GMIME_IS_MULTIPART_SIGNED (part) && node->ctx->crypto->verify && cryptoctx) {
 	if (node->nchildren != 2) {
@@ -232,56 +344,10 @@ _mime_node_create (mime_node_t *parent, GMimeObject *part)
 		     "(must be exactly 2)\n",
 		     node->nchildren);
 	} else {
-#ifdef GMIME_ATLEAST_26
+	    node_verify (node, part, cryptoctx);
-	    node->sig_list = g_mime_multipart_signed_verify
-		(GMIME_MULTIPART_SIGNED (part), cryptoctx, &err);
-	    node->verify_attempted = TRUE;
-
-	    if (!node->sig_list)
-		fprintf (stderr, "Failed to verify signed part: %s\n",
-			 (err ? err->message : "no error explanation given"));
-#else
-	    /* For some reason the GMimeSignatureValidity returned
-	     * here is not a const (inconsistent with that
-	     * returned by
-	     * g_mime_multipart_encrypted_get_signature_validity,
-	     * and therefore needs to be properly disposed of.
-	     *
-	     * In GMime 2.6, they're both non-const, so we'll be able
-	     * to clean up this asymmetry. */
-	    GMimeSignatureValidity *sig_validity = g_mime_multipart_signed_verify
-		(GMIME_MULTIPART_SIGNED (part), cryptoctx, &err);
-	    node->verify_attempted = TRUE;
-	    node->sig_validity = sig_validity;
-	    if (sig_validity) {
-		GMimeSignatureValidity **proxy =
-		    talloc (node, GMimeSignatureValidity *);
-		*proxy = sig_validity;
-		talloc_set_destructor (proxy, _signature_validity_free);
-	    }
-#endif
 	}
     }
 
-#ifdef GMIME_ATLEAST_26
-    /* sig_list may be created in both above cases, so we need to
-     * cleanly handle it here. */
-    if (node->sig_list) {
-	GMimeSignatureList **proxy = talloc (node, GMimeSignatureList *);
-	*proxy = node->sig_list;
-	talloc_set_destructor (proxy, _signature_list_free);
-    }
-#endif
-
-#ifndef GMIME_ATLEAST_26
-    if (node->verify_attempted && !node->sig_validity)
-	fprintf (stderr, "Failed to verify signed part: %s\n",
-		 (err ? err->message : "no error explanation given"));
-#endif
-
-    if (err)
-	g_error_free (err);
-
     return node;
 }