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

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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.
This commit is contained in:
Mark Adler 2019-01-02 18:10:40 -08:00
parent 7c0c75e990
commit 0d36ec47f3
3 changed files with 14 additions and 8 deletions
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14
inflate.c
View File

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

3
inflate.h
View File

@ -86,7 +86,8 @@ struct inflate_state {
int wrap; /* bit 0 true for zlib, bit 1 true for gzip, int wrap; /* bit 0 true for zlib, bit 1 true for gzip,
bit 2 true to validate check value */ bit 2 true to validate check value */
int havedict; /* true if dictionary provided */ 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 dmax; /* zlib header max distance (INFLATE_STRICT) */
unsigned long check; /* protected copy of check value */ unsigned long check; /* protected copy of check value */
unsigned long total; /* protected copy of output count */ unsigned long total; /* protected copy of output count */

5
test/example.c
View File

@ -440,9 +440,8 @@ void test_sync(compr, comprLen, uncompr, uncomprLen)
CHECK_ERR(err, "inflateSync"); CHECK_ERR(err, "inflateSync");
err = inflate(&d_stream, Z_FINISH); err = inflate(&d_stream, Z_FINISH);
if (err != Z_DATA_ERROR) { if (err != Z_STREAM_END) {
fprintf(stderr, "inflate should report DATA_ERROR\n"); fprintf(stderr, "inflate should report Z_STREAM_END\n");
/* Because of incorrect adler32 */
exit(1); exit(1);
} }
err = inflateEnd(&d_stream); err = inflateEnd(&d_stream);