[PATCH 3/4] lib-compression: istream-zstd - Guard against no-progress loop in read

If ZSTD_decompressStream() returns with neither input consumed nor
output produced, the read loop would spin indefinitely. Add a check
after each call: if input.pos is unchanged and output.pos is zero,
treat it as a corrupt stream (EIO).

Gbp-Pq: Name 0003-lib-compression-istream-zstd-Guard-against-no-progre.patch

diff --git a/src/lib-compression/istream-zstd.c b/src/lib-compression/istream-zstd.c
index 9e059bcffcee10997f6478a5730019bead8e0f31..b5505c8a09fac16e57bdcc11ce513b44b3e2c18b 100644 (file)
--- a/src/lib-compression/istream-zstd.c
+++ b/src/lib-compression/istream-zstd.c
@@ -175,12 +175,20 @@ static ssize_t i_stream_zstd_read(struct istream_private *stream)
                zstream->output.pos = 0;
                zstream->output.size = ZSTD_DStreamOutSize();
 
+               size_t old_input_pos = zstream->input.pos;
                size_t zret = ZSTD_decompressStream(zstream->dstream, &zstream->output,
                                                    &zstream->input);
                if (ZSTD_isError(zret) != 0) {
                        i_stream_zstd_read_error(zstream, zret);
                        return -1;
                }
+               if (zstream->input.pos == old_input_pos && zstream->output.pos == 0) {
+                       io_stream_set_error(&zstream->istream.iostream,
+                                           "zstd.read(%s): decompressor made no progress",
+                                           i_stream_get_name(&zstream->istream.istream));
+                       zstream->istream.istream.stream_errno = EIO;
+                       return -1;
+               }
                /* ZSTD magic number is 4 bytes, but it's only defined after v0.8 */
                if (!zstream->hdr_read && zstream->input.size > 4)
                        zstream->hdr_read = TRUE;