Remove support for zlib <= 1.1

zlib 1.2 came out in 2003; earlier versions should be dead by now.

Our workaround code was only preventing us from using the gzip
encoding (if we decide to do so), and having some dead code linger
around in torgzip.c

changes/zlib_12

@@ -0,0 +1,4 @@
+  o New system requirements:
+    - We now require zlib version 1.2 or later. (Back when we started,
+      zlib 1.1 and zlib 1.0 were still found in the wild. 1.2 was released in
+      2003. We recommend the latest version.)

src/common/torgzip.c

@@ -46,34 +46,16 @@
 
 #include <zlib.h>
 
+#if defined ZLIB_VERNUM && ZLIB_VERNUM < 0x1200
+#error "We require zlib version 1.2 or later."
+#endif
+
 static size_t tor_zlib_state_size_precalc(int inflate,
                                           int windowbits, int memlevel);
 
 /** Total number of bytes allocated for zlib state */
 static size_t total_zlib_allocation = 0;
 
-/** Set to 1 if zlib is a version that supports gzip; set to 0 if it doesn't;
- * set to -1 if we haven't checked yet. */
-static int gzip_is_supported = -1;
-
-/** Return true iff we support gzip-based compression.  Otherwise, we need to
- * use zlib. */
-int
-is_gzip_supported(void)
-{
-  if (gzip_is_supported >= 0)
-    return gzip_is_supported;
-
-  if (!strcmpstart(ZLIB_VERSION, "0.") ||
-      !strcmpstart(ZLIB_VERSION, "1.0") ||
-      !strcmpstart(ZLIB_VERSION, "1.1"))
-    gzip_is_supported = 0;
-  else
-    gzip_is_supported = 1;
-
-  return gzip_is_supported;
-}
-
 /** Return a string representation of the version of the currently running
  * version of zlib. */
 const char *
@@ -165,12 +147,6 @@ tor_gzip_compress(char **out, size_t *out_len,
 
   *out = NULL;
 
-  if (method == GZIP_METHOD && !is_gzip_supported()) {
-    /* Old zlib version don't support gzip in deflateInit2 */
-    log_warn(LD_BUG, "Gzip not supported with zlib %s", ZLIB_VERSION);
-    goto err;
-  }
-
   stream = tor_malloc_zero(sizeof(struct z_stream_s));
   stream->zalloc = Z_NULL;
   stream->zfree = Z_NULL;
@@ -291,12 +267,6 @@ tor_gzip_uncompress(char **out, size_t *out_len,
   tor_assert(in);
   tor_assert(in_len < UINT_MAX);
 
-  if (method == GZIP_METHOD && !is_gzip_supported()) {
-    /* Old zlib version don't support gzip in inflateInit2 */
-    log_warn(LD_BUG, "Gzip not supported with zlib %s", ZLIB_VERSION);
-    return -1;
-  }
-
   *out = NULL;
 
   stream = tor_malloc_zero(sizeof(struct z_stream_s));
@@ -451,12 +421,6 @@ tor_zlib_new(int compress, compress_method_t method,
   tor_zlib_state_t *out;
   int bits, memlevel;
 
-  if (method == GZIP_METHOD && !is_gzip_supported()) {
-    /* Old zlib version don't support gzip in inflateInit2 */
-    log_warn(LD_BUG, "Gzip not supported with zlib %s", ZLIB_VERSION);
-    return NULL;
- }
-
  if (! compress) {
    /* use this setting for decompression, since we might have the
     * max number of window bits */

src/test/test_util.c

@@ -1737,7 +1737,8 @@ test_util_gzip(void *arg)
   (void)arg;
   buf1 = tor_strdup("AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAZAAAAAAAAAAAAAAAAAAAZ");
   tt_assert(detect_compression_method(buf1, strlen(buf1)) == UNKNOWN_METHOD);
-  if (is_gzip_supported()) {
+
+  if (1) {
     tt_assert(!tor_gzip_compress(&buf2, &len1, buf1, strlen(buf1)+1,
                                    GZIP_METHOD));
     tt_assert(buf2);