[PATCH] Fix GLib "critical" warning

[Albrecht Dreß <albrecht dress arcor de>]

Hi all,

I noticed that Balsa emits a critical warning on the console, e.g. when I select an encrypted message, but 
cancel the decryption:

GLib-GIO-CRITICAL **: g_content_type_guess: assertion 'data_size != (gsize) -1' failed

Looking into the details, this message originates from balsa-mime-widget.c, function 
balsa_mime_widget_new_unknown(), line 260 ff.

Apparently, in the case above, reading data from the stream fails (g_mime_stream_read() returns -1), but 
libbalsa_vfs_content_type_of_buffer() is called with the broken data.

However, I wonder why this code does *not* crash:
(1) the buffer is allocated with a size of 1k,
(2) g_mime_stream_read() tries to fill it completely, so it is *not* NUL-terminated, but
(3) if libbalsa_vfs_content_type_of_buffer() guesses a text/* type, libbalsa_text_attr_string() is called 
which assumes a NUL-terminated string.

The attached patch fixes both issues by
- checking if g_mime_stream_read() failed, and assuming application/octet-stream in this case and
- assuring that the buffer is always NUL-terminated.

Cheers,
Albrecht.

diff --git a/src/balsa-mime-widget.c b/src/balsa-mime-widget.c
index 3375c24..fdd11a9 100644
--- a/src/balsa-mime-widget.c
+++ b/src/balsa-mime-widget.c
@@ -249,7 +249,6 @@ balsa_mime_widget_new_unknown(BalsaMessage * bm,
         g_ascii_strcasecmp(content_type, "application/octet-stream") == 0)
        && LIBBALSA_IS_MAILBOX_LOCAL(mime_body->message->mailbox)) {
         GError *err = NULL;
-       gpointer buffer;
        GMimeStream *stream = 
             libbalsa_message_body_get_stream(mime_body, &err);
         if(!stream) {
@@ -259,20 +258,25 @@ balsa_mime_widget_new_unknown(BalsaMessage * bm,
             g_clear_error(&err);
             use_content_type = g_strdup(content_type);
         } else {
+               gpointer buffer;
             ssize_t length = 1024 /* g_mime_stream_length(stream) */ ;
             ssize_t size;
 
-            buffer = g_malloc(length);
+            buffer = g_malloc0(length + 1);
             libbalsa_mime_stream_shared_lock(stream);
             size = g_mime_stream_read(stream, buffer, length);
             libbalsa_mime_stream_shared_unlock(stream);
             g_object_unref(stream);
-            use_content_type = libbalsa_vfs_content_type_of_buffer(buffer, size);
-            if (g_ascii_strncasecmp(use_content_type, "text", 4) == 0
-                && (libbalsa_text_attr_string(buffer) & LIBBALSA_TEXT_HI_BIT)) {
-                /* Hmmm...better stick with application/octet-stream. */
-                g_free(use_content_type);
-                use_content_type = g_strdup("application/octet-stream");
+            if (size != -1) {
+               use_content_type = libbalsa_vfs_content_type_of_buffer(buffer, size);
+                if (g_ascii_strncasecmp(use_content_type, "text", 4) == 0
+                    && (libbalsa_text_attr_string(buffer) & LIBBALSA_TEXT_HI_BIT)) {
+                    /* Hmmm...better stick with application/octet-stream. */
+                    g_free(use_content_type);
+                    use_content_type = g_strdup("application/octet-stream");
+                }
+            } else {
+               use_content_type = g_strdup("application/octet-stream");
             }
             g_free(buffer);
         }

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