[PATCH 3/9] index encrypted parts when the message is flagged appropriately

[Daniel Kahn Gillmor <dkg@fifthhorseman.net>]

We add a new message flag that indicates desire for indexing the
cleartext of a given message.

If that flag is set while indexing, we'll try to descend into it.

If we can decrypt, we tag the message with index-decrypted.

If we can't decrypt (or recognize the encrypted type of mail), we tag
with decryption-failed.

Note that a single message may be tagged with "encrypted" and
"index-decrypted" and "decryption-failed".  For example, consider a
message that includes multiple layers of encryption.  It is
automatically tagged with "encrypted".  If we decrypt the outer layer
("index-decrypted"), but fail on the inner layer
("decryption-failed").
---
 lib/index.cc  | 52 +++++++++++++++++++++++++++++++++++++++++++++++++++-
 lib/notmuch.h |  5 +++++
 2 files changed, 56 insertions(+), 1 deletion(-)

diff --git a/lib/index.cc b/lib/index.cc
index 2fa6616..bd028cb 100644
--- a/lib/index.cc
+++ b/lib/index.cc
@@ -300,6 +300,10 @@ _index_address_list (notmuch_message_t *message,
     }
 }
 
+static void
+_index_encrypted_mime_part (notmuch_message_t *message, GMimeContentType *content_type,
+			    GMimeMultipartEncrypted *part);
+
 /* Callback to generate terms for each mime part of a message. */
 static void
 _index_mime_part (notmuch_message_t *message,
@@ -346,7 +350,10 @@ _index_mime_part (notmuch_message_t *message,
 		_notmuch_database_log (_notmuch_message_database (message),
 				       "Warning: Unexpected extra parts of multipart/signed. Indexing anyway.\n");
 	} else if (GMIME_IS_MULTIPART_ENCRYPTED (multipart)) {
-	    /* Don't index encrypted parts */
+	    _notmuch_message_add_term (message, "tag", "encrypted");
+	    if (notmuch_message_get_flag (message, NOTMUCH_MESSAGE_FLAG_INDEX_DECRYPTED)) {
+		_index_encrypted_mime_part(message, content_type, GMIME_MULTIPART_ENCRYPTED (part));
+	    }
 	} else {
 	    for (i = 0; i < g_mime_multipart_get_count (multipart); i++) {
 		_index_mime_part (message,
@@ -431,6 +438,49 @@ _index_mime_part (notmuch_message_t *message,
     }
 }
 
+/* descend (if possible) into the cleartext part of an encrypted MIME
+ * part while indexing. */
+static void
+_index_encrypted_mime_part (notmuch_message_t *message,
+			    GMimeContentType *content_type,
+			    GMimeMultipartEncrypted *encrypted_data)
+{
+    notmuch_private_status_t status;
+    GMimeCryptoContext* crypto_ctx = NULL;
+    const char *protocol = g_mime_content_type_get_parameter (content_type, "protocol");
+    GError *err = NULL;
+    notmuch_database_t * notmuch = _notmuch_message_database (message);
+    GMimeObject *clear = NULL;
+    
+    status = _notmuch_database_get_crypto_for_protocol (notmuch, protocol,
+							&crypto_ctx);
+    if (status) {
+	_notmuch_database_log (notmuch, "Warning: setup failed for decrypting "
+			       "during indexing. (%d)\n", status);
+	_notmuch_message_add_term (message, "tag", "index-decryption-failed");
+	return;
+    }
+
+    /* we don't need the GMimeDecryptResult, because we're not looking
+     * at validating signatures, and we don't care about indexing who
+     * the message was ostensibly encrypted to.
+     */
+    clear = g_mime_multipart_encrypted_decrypt(encrypted_data, crypto_ctx,
+					       NULL, &err);
+    if (err) {
+	_notmuch_database_log (notmuch, "Failed to decrypt during indexing. (%d:%d) [%s]\n",
+			       err->domain, err->code, err->message);
+	g_error_free(err);
+	/* Indicate that we failed to decrypt during indexing */
+	_notmuch_message_add_term (message, "tag", "index-decryption-failed");
+	return;
+    }
+    _index_mime_part (message, clear);
+    g_object_unref (clear);
+    
+    _notmuch_message_add_term (message, "tag", "index-decrypted");
+}
+
 notmuch_status_t
 _notmuch_message_index_file (notmuch_message_t *message,
 			     notmuch_message_file_t *message_file)
diff --git a/lib/notmuch.h b/lib/notmuch.h
index 310a8b8..e7085b7 100644
--- a/lib/notmuch.h
+++ b/lib/notmuch.h
@@ -1357,6 +1357,11 @@ typedef enum _notmuch_message_flag {
      * thread ID.
      */
     NOTMUCH_MESSAGE_FLAG_GHOST,
+    
+    /* Some part(s) of this message is encrypted, but the message is
+     * indexed in the clear.
+     */
+    NOTMUCH_MESSAGE_FLAG_INDEX_DECRYPTED
 } notmuch_message_flag_t;
 
 /**
-- 
2.6.2