[gcab/wip/hughsie/future: 17/18] Return detailed errors from gcab_cabinet_get_signature()

[Richard Hughes <rhughes src gnome org>]

commit bce9d7e18069a73177738e4dab6654d32b8c52cd
Author: Richard Hughes <richard hughsie com>
Date:   Wed Dec 13 22:07:17 2017 +0000

    Return detailed errors from gcab_cabinet_get_signature()
    
    This commit ensures there is a GError set if NULL is returned. Although
    technically a behaviour change, nothing seems to use this except the gcab
    command line tool.

 gcab.c                 |   13 +++++++------
 libgcab/gcab-cabinet.c |   38 ++++++++++++++++++++++++++++++--------
 2 files changed, 37 insertions(+), 14 deletions(-)
---
diff --git a/gcab.c b/gcab.c
index e94fa97..29db578 100644
--- a/gcab.c
+++ b/gcab.c
@@ -231,13 +231,14 @@ individual files from the archive.\
             }
 
             reserved = (GByteArray *)gcab_cabinet_get_signature (cabinet, cancellable, &error);
-            if (reserved == NULL)
+            if (reserved == NULL) {
                 g_printerr ("%s: %s\n", _("Error while reading signature"), error->message);
-            if (reserved != NULL)
-                if (!save_array_to_file (reserved, args[0], "signature", &error)) {
-                    g_printerr ("%s\n", error->message);
-                    return EXIT_FAILURE;
-                }
+                return EXIT_FAILURE;
+            }
+            if (!save_array_to_file (reserved, args[0], "signature", &error)) {
+                g_printerr ("%s\n", error->message);
+                return EXIT_FAILURE;
+            }
         }
         return EXIT_SUCCESS;
     }
diff --git a/libgcab/gcab-cabinet.c b/libgcab/gcab-cabinet.c
index 975d747..d877399 100644
--- a/libgcab/gcab-cabinet.c
+++ b/libgcab/gcab-cabinet.c
@@ -567,8 +567,8 @@ gcab_cabinet_extract_simple (GCabCabinet *cabinet,
  * Lookup the cabinet authenticode signature if any.
  *
  * Since: 0.5
- * Returns: the array containing the PKCS#7 signed data or %NULL if
- * none found or error.
+ *
+ * Returns: the array containing the PKCS#7 signed data or %NULL on error.
  **/
 const GByteArray *
 gcab_cabinet_get_signature (GCabCabinet *self,
@@ -576,6 +576,7 @@ gcab_cabinet_get_signature (GCabCabinet *self,
                             GError **error)
 {
     const guint8 magic[] = { 0x00, 0x00, 0x10, 0x00 };
+    gssize sz;
     guint8 *reserved;
     guint32 offset;
     guint32 size;
@@ -587,15 +588,24 @@ gcab_cabinet_get_signature (GCabCabinet *self,
     if (self->signature)
         return self->signature;
 
-    if (!G_IS_SEEKABLE (self->stream))
+    if (!G_IS_SEEKABLE (self->stream)) {
+        g_set_error (error, GCAB_ERROR, GCAB_ERROR_FAILED,
+                     "Cabinet stream is not seekable");
         return NULL;
+    }
 
-    if (!self->reserved || self->reserved->len != 20)
+    if (!self->reserved || self->reserved->len != 20) {
+        g_set_error (error, GCAB_ERROR, GCAB_ERROR_FAILED,
+                     "Cabinet has no reserved area");
         return NULL;
+    }
 
     reserved = self->reserved->data;
-    if (memcmp (reserved, magic, sizeof (magic)) != 0)
+    if (memcmp (reserved, magic, sizeof (magic)) != 0) {
+        g_set_error (error, GCAB_ERROR, GCAB_ERROR_FORMAT,
+                     "Cabinet reserved magic was not correct");
         return NULL;
+    }
 
     offset = GCAB_READ_UINT32_LE (reserved + 4);
     size = GCAB_READ_UINT32_LE (reserved + 8);
@@ -605,12 +615,24 @@ gcab_cabinet_get_signature (GCabCabinet *self,
     self->signature = g_byte_array_sized_new (size);
     g_byte_array_set_size (self->signature, size);
 
-    if (!g_seekable_seek (G_SEEKABLE (self->stream), offset, G_SEEK_SET, cancellable, error))
+    if (!g_seekable_seek (G_SEEKABLE (self->stream), offset, G_SEEK_SET, cancellable, error)) {
+        g_set_error (error, GCAB_ERROR, GCAB_ERROR_FAILED,
+                     "Cannot seek to reserved area");
         return NULL;
+    }
 
-    if (g_input_stream_read (self->stream, self->signature->data, self->signature->len,
-                             cancellable, error) != self->signature->len)
+    sz = g_input_stream_read (self->stream,
+                              self->signature->data, self->signature->len,
+                              cancellable, error);
+    if (sz < 0) {
+        g_prefix_error (error, "Failed to read signature from stream: ");
+        return NULL;
+    }
+    if (sz != self->signature->len) {
+        g_set_error (error, GCAB_ERROR, GCAB_ERROR_FAILED,
+                     "Failed to read correct size signature from stream: ");
         return NULL;
+    }
 
     return self->signature;
 }