[tor-commits] [tor/master] Document and test nul-terminating behavior of tor_uncompress()
nickm at torproject.org
nickm at torproject.org
Thu Apr 27 15:00:21 UTC 2017
commit 49deb1e1b810e348bfa9fb27a0f0ef54f3694cc9
Author: Nick Mathewson <nickm at torproject.org>
Date: Thu Apr 27 10:59:48 2017 -0400
Document and test nul-terminating behavior of tor_uncompress()
We added this as a safety feature, but there are a few places in the
code that actually depend on it.
---
src/common/compress.c | 6 ++++++
src/test/test_util.c | 4 ++++
2 files changed, 10 insertions(+)
diff --git a/src/common/compress.c b/src/common/compress.c
index 771f5ab..9a24025 100644
--- a/src/common/compress.c
+++ b/src/common/compress.c
@@ -221,6 +221,12 @@ tor_compress(char **out, size_t *out_len,
* *<b>out</b>, and its length in *<b>out_len</b>. Return 0 on success, -1 on
* failure.
*
+ * If any bytes are written to <b>out</b>, an extra byte NUL is always
+ * written at the end, but not counted in <b>out_len</b>. This is a
+ * safety feature to ensure that the output can be treated as a
+ * NUL-terminated string -- though of course, callers should check
+ * out_len anyway.
+ *
* If <b>complete_only</b> is true, we consider a truncated input as a
* failure; otherwise we decompress as much as we can. Warn about truncated
* or corrupt inputs at <b>protocol_warn_level</b>.
diff --git a/src/test/test_util.c b/src/test/test_util.c
index 1f37fc3..dec1d52 100644
--- a/src/test/test_util.c
+++ b/src/test/test_util.c
@@ -2262,6 +2262,7 @@ test_util_compress_impl(compress_method_t method)
tt_assert(buf3 != NULL);
tt_int_op(strlen(buf1) + 1, OP_EQ, len2);
tt_str_op(buf1, OP_EQ, buf3);
+ tt_int_op(buf3[len2], OP_EQ, 0);
/* Check whether we can uncompress concatenated, compressed strings. */
tor_free(buf3);
@@ -2273,6 +2274,7 @@ test_util_compress_impl(compress_method_t method)
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAZAAAAAAAAAAAAAAAAAAAZ\0"
"AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAZAAAAAAAAAAAAAAAAAAAZ\0",
(strlen(buf1)+1)*2);
+ tt_int_op(buf3[len2], OP_EQ, 0);
/* Check whether we can uncompress partial strings */
@@ -2296,6 +2298,8 @@ test_util_compress_impl(compress_method_t method)
tt_int_op(len2, OP_GT, 5);
tt_int_op(len2, OP_LE, len1);
tt_assert(fast_memeq(buf1, buf3, len2));
+ tt_int_op(buf3[len2], OP_EQ, 0);
+
/* when we demand a complete output, this must fail. */
tor_free(buf3);
tt_assert(tor_uncompress(&buf3, &len2, buf2, len1-16,
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