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131 lines
5.0 KiB
131 lines
5.0 KiB
From: Bastien Nocera
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Date: Thu, 6 Jul 2017 20:02:00 +0200
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Subject: comics: Remove support for tar and tar-like commands
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When handling tar files, or using a command with tar-compatible syntax,
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to open comic-book archives, both the archive name (the name of the
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comics file) and the filename (the name of a page within the archive)
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are quoted to not be interpreted by the shell.
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But the filename is completely with the attacker's control and can start
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with "--" which leads to tar interpreting it as a command line flag.
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This can be exploited by creating a CBT file (a tar archive with the
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.cbt suffix) with an embedded file named something like this:
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"--checkpoint-action=exec=bash -c 'touch ~/hacked;'.jpg"
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CBT files are infinitely rare (CBZ is usually used for DRM-free
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commercial releases, CBR for those from more dubious provenance), so
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removing support is the easiest way to avoid the bug triggering. All
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this code was rewritten in the development release for GNOME 3.26 to not
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shell out to any command, closing off this particular attack vector.
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This also removes the ability to use libarchive's bsdtar-compatible
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binary for CBZ (ZIP), CB7 (7zip), and CBR (RAR) formats. The first two
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are already supported by unzip and 7zip respectively. libarchive's RAR
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support is limited, so unrar is a requirement anyway.
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Discovered by Felix Wilhelm from the Google Security Team.
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https://bugzilla.gnome.org/show_bug.cgi?id=784630
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---
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backend/comics/comics-document.c | 40 +---------------------------------------
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configure.ac | 2 +-
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2 files changed, 2 insertions(+), 40 deletions(-)
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diff --git a/backend/comics/comics-document.c b/backend/comics/comics-document.c
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index 96ed26e..3af119a 100644
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--- a/backend/comics/comics-document.c
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+++ b/backend/comics/comics-document.c
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@@ -56,8 +56,7 @@ typedef enum
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RARLABS,
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GNAUNRAR,
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UNZIP,
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- P7ZIP,
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- TAR
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+ P7ZIP
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} ComicBookDecompressType;
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typedef struct _ComicsDocumentClass ComicsDocumentClass;
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@@ -117,9 +116,6 @@ static const ComicBookDecompressCommand command_usage_def[] = {
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/* 7zip */
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{NULL , "%s l -- %s" , "%s x -y %s -o%s", FALSE, OFFSET_7Z},
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-
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- /* tar */
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- {"%s -xOf" , "%s -tf %s" , NULL , FALSE, NO_OFFSET}
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};
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static GSList* get_supported_image_extensions (void);
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@@ -364,13 +360,6 @@ comics_check_decompress_command (gchar *mime_type,
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comics_document->command_usage = GNAUNRAR;
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return TRUE;
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}
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- comics_document->selected_command =
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- g_find_program_in_path ("bsdtar");
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- if (comics_document->selected_command) {
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- comics_document->command_usage = TAR;
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- return TRUE;
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- }
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-
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} else if (g_content_type_is_a (mime_type, "application/x-cbz") ||
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g_content_type_is_a (mime_type, "application/zip")) {
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/* InfoZIP's unzip program */
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@@ -396,12 +385,6 @@ comics_check_decompress_command (gchar *mime_type,
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comics_document->command_usage = P7ZIP;
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return TRUE;
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}
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- comics_document->selected_command =
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- g_find_program_in_path ("bsdtar");
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- if (comics_document->selected_command) {
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- comics_document->command_usage = TAR;
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- return TRUE;
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- }
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} else if (g_content_type_is_a (mime_type, "application/x-cb7") ||
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g_content_type_is_a (mime_type, "application/x-7z-compressed")) {
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@@ -425,27 +408,6 @@ comics_check_decompress_command (gchar *mime_type,
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comics_document->command_usage = P7ZIP;
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return TRUE;
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}
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- comics_document->selected_command =
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- g_find_program_in_path ("bsdtar");
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- if (comics_document->selected_command) {
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- comics_document->command_usage = TAR;
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- return TRUE;
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- }
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- } else if (g_content_type_is_a (mime_type, "application/x-cbt") ||
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- g_content_type_is_a (mime_type, "application/x-tar")) {
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- /* tar utility (Tape ARchive) */
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- comics_document->selected_command =
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- g_find_program_in_path ("tar");
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- if (comics_document->selected_command) {
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- comics_document->command_usage = TAR;
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- return TRUE;
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- }
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- comics_document->selected_command =
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- g_find_program_in_path ("bsdtar");
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- if (comics_document->selected_command) {
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- comics_document->command_usage = TAR;
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- return TRUE;
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- }
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} else {
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g_set_error (error,
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EV_DOCUMENT_ERROR,
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diff --git a/configure.ac b/configure.ac
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index 36e866a..26a1a7d 100644
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--- a/configure.ac
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+++ b/configure.ac
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@@ -795,7 +795,7 @@ AC_SUBST(TIFF_MIME_TYPES)
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AC_SUBST(APPDATA_TIFF_MIME_TYPES)
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AM_SUBST_NOTMAKE(APPDATA_TIFF_MIME_TYPES)
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if test "x$enable_comics" = "xyes"; then
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- COMICS_MIME_TYPES="application/x-cbr;application/x-cbz;application/x-cb7;application/x-cbt;application/x-ext-cbr;application/x-ext-cbz;application/vnd.comicbook+zip;application/x-ext-cb7;application/x-ext-cbt"
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+ COMICS_MIME_TYPES="application/x-cbr;application/x-cbz;application/x-cb7;application/x-ext-cbr;application/x-ext-cbz;application/vnd.comicbook+zip;application/x-ext-cb7;"
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APPDATA_COMICS_MIME_TYPES=$(echo "<mimetype>$COMICS_MIME_TYPES</mimetype>" | sed -e 's/;/<\/mimetype>\n <mimetype>/g')
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if test -z "$EVINCE_MIME_TYPES"; then
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EVINCE_MIME_TYPES="${COMICS_MIME_TYPES}"
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--
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cgit v0.12
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