Don't bother computing check value after successful inflateSync().

inflateSync() is used to skip invalid deflate data, which means
that the check value that was being computed is no longer useful.
This commit turns off the check value computation, and furthermore
allows a successful return if the compressed data terminated in a
graceful manner. This commit also fixes a bug in the case that
inflateSync() is used before a header is ever processed. In that
case, there is no knowledge of a trailer, so the remainder is
treated as raw.

diff --git a/inflate.c b/inflate.c
index 575fcdf82ad1060679ab144dc66b33a89d9001ef..2c1b17f16a0fbf3463ae2b8973952aee35e03d77 100644 (file)
--- a/inflate.c
+++ b/inflate.c
@@ -130,6 +130,7 @@ z_streamp strm;
     state->mode = HEAD;
     state->last = 0;
     state->havedict = 0;
+    state->flags = -1;
     state->dmax = 32768U;
     state->head = Z_NULL;
     state->hold = 0;
@@ -670,7 +671,6 @@ int flush;
                 state->mode = FLAGS;
                 break;
             }
-            state->flags = 0;           /* expect zlib header */
             if (state->head != Z_NULL)
                 state->head->done = -1;
             if (!(state->wrap & 1) ||   /* check if zlib header allowed */
@@ -697,6 +697,7 @@ int flush;
                 break;
             }
             state->dmax = 1U << len;
+            state->flags = 0;               /* indicate zlib header */
             Tracev((stderr, "inflate:   zlib header ok\n"));
             strm->adler = state->check = adler32(0L, Z_NULL, 0);
             state->mode = hold & 0x200 ? DICTID : TYPE;
@@ -1221,7 +1222,7 @@ int flush;
         case LENGTH:
             if (state->wrap && state->flags) {
                 NEEDBITS(32);
-                if (hold != (state->total & 0xffffffffUL)) {
+                if ((state->wrap & 4) && hold != (state->total & 0xffffffff)) {
                     strm->msg = (char *)"incorrect length check";
                     state->mode = BAD;
                     break;
@@ -1401,6 +1402,7 @@ int ZEXPORT inflateSync(strm)
 z_streamp strm;
 {
     unsigned len;               /* number of bytes to look at or looked at */
+    int flags;                  /* temporary to save header status */
     unsigned long in, out;      /* temporary to save total_in and total_out */
     unsigned char buf[4];       /* to restore bit buffer to byte string */
     struct inflate_state FAR *state;
@@ -1433,11 +1435,15 @@ z_streamp strm;
 
     /* return no joy or set up to restart inflate() on a new block */
     if (state->have != 4) return Z_DATA_ERROR;
-    if (state->mode == HEAD)
-        state->wrap = 0;    /* never processed header, so assume raw */
+    if (state->flags == -1)
+        state->wrap = 0;    /* if no header yet, treat as raw */
+    else
+        state->wrap &= ~4;  /* no point in computing a check value now */
+    flags = state->flags;
     in = strm->total_in;  out = strm->total_out;
     inflateReset(strm);
     strm->total_in = in;  strm->total_out = out;
+    state->flags = flags;
     state->mode = TYPE;
     return Z_OK;
 }

diff --git a/inflate.h b/inflate.h
index a46cce6b6d05ef994d2a386257cf09068f0aa298..98679fa9bc245e3366a7fd5799c179ebd33f3837 100644 (file)
--- a/inflate.h
+++ b/inflate.h
@@ -86,7 +86,8 @@ struct inflate_state {
     int wrap;                   /* bit 0 true for zlib, bit 1 true for gzip,
                                    bit 2 true to validate check value */
     int havedict;               /* true if dictionary provided */
-    int flags;                  /* gzip header method and flags (0 if zlib) */
+    int flags;                  /* gzip header method and flags, 0 if zlib, or
+                                   -1 if raw or no header yet */
     unsigned dmax;              /* zlib header max distance (INFLATE_STRICT) */
     unsigned long check;        /* protected copy of check value */
     unsigned long total;        /* protected copy of output count */

diff --git a/test/example.c b/test/example.c
index eee17ce7c1591f35bef47ca27c9d6bb1961712dc..949f4f6256f11fd1ff538cacf2acc9adb0d2bf0e 100644 (file)
--- a/test/example.c
+++ b/test/example.c
@@ -440,9 +440,8 @@ void test_sync(compr, comprLen, uncompr, uncomprLen)
     CHECK_ERR(err, "inflateSync");
 
     err = inflate(&d_stream, Z_FINISH);
-    if (err != Z_DATA_ERROR) {
-        fprintf(stderr, "inflate should report DATA_ERROR\n");
-        /* Because of incorrect adler32 */
+    if (err != Z_STREAM_END) {
+        fprintf(stderr, "inflate should report Z_STREAM_END\n");
         exit(1);
     }
     err = inflateEnd(&d_stream);