[tor-commits] [tor/master] Better error handling when trying to compress/decompress into empty buffer.

[nickm at torproject.org]

commit 8d6940814a90166e468cee810820e8fc5b74e89d
Author: Alexander Færøy <ahf at torproject.org>
Date:   Thu Sep 28 16:46:10 2017 +0200

    Better error handling when trying to compress/decompress into empty buffer.
    
    This patch ensures that we return TOR_COMPRESS_BUFFER_FULL in case we
    have a input bytes left to process, but are out of output buffer or in
    case we need to finish where the compression implementation might need
    to write an epilogue.
    
    See: https://bugs.torproject.org/23551
---
 changes/bug23551      | 3 +++
 src/common/compress.c | 7 +++++++
 2 files changed, 10 insertions(+)

diff --git a/changes/bug23551 b/changes/bug23551
new file mode 100644
index 000000000..2f918bfa3
--- /dev/null
+++ b/changes/bug23551
@@ -0,0 +1,3 @@
+  o Minor bugfixes (compression):
+    - Handle a pathological case when decompressing Zstandard data when the
+      output buffer size is zero. Fixes bug 23551; bugfix on 0.3.1.1-alpha.
diff --git a/src/common/compress.c b/src/common/compress.c
index 7926faaa6..beeff5fcb 100644
--- a/src/common/compress.c
+++ b/src/common/compress.c
@@ -546,6 +546,13 @@ tor_compress_process(tor_compress_state_t *state,
   const size_t out_len_orig = *out_len;
   tor_compress_output_t rv;
 
+  if (*out_len == 0 && (*in_len > 0 || finish)) {
+    // If we still have input data, but no space for output data, we might as
+    // well return early and let the caller do the reallocation of the out
+    // variable.
+    return TOR_COMPRESS_BUFFER_FULL;
+  }
+
   switch (state->method) {
     case GZIP_METHOD:
     case ZLIB_METHOD: