[PATCH 2/4] vcs-svn: cap number of bytes read from sliding view
- From
Jonathan Nieder <jrnieder@gmail.com>
- Date
- May 27, 2011, 11:11 UTC
- Message-ID
- <20110527111059.GC7972@elie>
- In-Reply-To
- <20110527110828.GA7972@elie>
Introduce a "max_off" field in struct sliding_view, roughly speaking representing a maximum number of bytes that can be read from "file". More precisely, if it is set to a nonnegative integer, a call to move_window() attempting to put the right endpoint beyond that offset will return an error instead. A value of -1 disables the check.
The idea is to use this when applying Subversion-format deltas to prevent reads past the end of the preimage (which has known length). Without such a check, corrupt deltas would cause svn-fe to block indefinitely when data in the input pipe is exhausted.
Inspired-by: Ramkumar Ramachandra <artagnon@gmail.com> Signed-off-by: Jonathan Nieder <jrnieder@gmail.com> --- test-svn-fe.c | 2 +- vcs-svn/sliding_window.c | 2 ++ vcs-svn/sliding_window.h | 3 ++- 3 files changed, 5 insertions(+), 2 deletions(-)
diff --git a/test-svn-fe.c b/test-svn-fe.c index a027626..332a5f7 100644 --- a/test-svn-fe.c +++ b/test-svn-fe.c @@ -15,7 +15,7 @@ static int apply_delta(int argc, char *argv[]) { struct line_buffer preimage = LINE_BUFFER_INIT; struct line_buffer delta = LINE_BUFFER_INIT; - struct sliding_view preimage_view = SLIDING_VIEW_INIT(&preimage); + struct sliding_view preimage_view = SLIDING_VIEW_INIT(&preimage, -1); if (argc != 5) usage(test_svnfe_usage); diff --git a/vcs-svn/sliding_window.c b/vcs-svn/sliding_window.c index 1b8d987..1bac7a4 100644 --- a/vcs-svn/sliding_window.c +++ b/vcs-svn/sliding_window.c @@ -54,6 +54,8 @@ int move_window(struct sliding_view *view, off_t off, size_t width) return -1; if (off < view->off || off + width < view->off + view->width) return error("invalid delta: window slides left"); + if (view->max_off >= 0 && view->max_off < off + width) + return error("delta preimage ends early"); file_offset = view->off + view->buf.len; if (off < file_offset) { diff --git a/vcs-svn/sliding_window.h b/vcs-svn/sliding_window.h index ed0bfdd..b43a825 100644 --- a/vcs-svn/sliding_window.h +++ b/vcs-svn/sliding_window.h @@ -7,10 +7,11 @@ struct sliding_view { struct line_buffer *file; off_t off; size_t width; + off_t max_off; /* -1 means unlimited */ struct strbuf buf; }; -#define SLIDING_VIEW_INIT(input) { (input), 0, 0, STRBUF_INIT } +#define SLIDING_VIEW_INIT(input, len) { (input), 0, 0, (len), STRBUF_INIT } extern int move_window(struct sliding_view *view, off_t off, size_t width);
-- 1.7.5.1