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gzip: do not store timestamp in gzip header

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Storing the original file's modification time in the output file is
harmful (precludes deterministic results) and unlike official gzip,
the busybox version provides no way to suppress this behavior; the -n
option is silently ignored. Rather than trying to make -n work, this
patch just removes the timestamp-storing functionality. It should be
considered deprecated anyway; it's not Y2038-safe and gunzip ignores
it by default.

Per RFC 1952, 0 is the correct value to store to indicate that there
is no timestamp.

Signed-off-by: Rich Felker <dalias@libc.org>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Rich Felker 2015-02-02 16:01:16 +01:00 committed by Denys Vlasenko
parent 5104645cf8
commit 7f7ade1964
1 changed files with 16 additions and 4 deletions
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20
archival/gzip.c
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@ -2007,7 +2007,7 @@ static void ct_init(void)
* IN assertions: the input and output buffers are cleared.
*/
static void zip(ulg time_stamp)
static void zip(void)
{
ush deflate_flags = 0; /* pkzip -es, -en or -ex equivalent */
@ -2018,7 +2018,7 @@ static void zip(ulg time_stamp)
/* compression method: 8 (DEFLATED) */
/* general flags: 0 */
put_32bit(0x00088b1f);
put_32bit(time_stamp);
put_32bit(0); /* Unix timestamp */
/* Write deflated file to zip file */
G1.crc = ~0;
@ -2044,8 +2044,6 @@ static void zip(ulg time_stamp)
static
IF_DESKTOP(long long) int FAST_FUNC pack_gzip(transformer_state_t *xstate UNUSED_PARAM)
{
struct stat s;
/* Clear input and output buffers */
G1.outcnt = 0;
#ifdef DEBUG
@ -2077,9 +2075,23 @@ IF_DESKTOP(long long) int FAST_FUNC pack_gzip(transformer_state_t *xstate UNUSED
G2.bl_desc.max_length = MAX_BL_BITS;
//G2.bl_desc.max_code = 0;
#if 0
/* Saving of timestamp is disabled. Why?
* - it is not Y2038-safe.
* - some people want deterministic results
* (normally they'd use -n, but our -n is a nop).
* - it's bloat.
* Per RFC 1952, gzfile.time=0 is "no timestamp".
* If users will demand this to be reinstated,
* implement -n "don't save timestamp".
*/
struct stat s;
s.st_ctime = 0;
fstat(STDIN_FILENO, &s);
zip(s.st_ctime);
#else
zip();
#endif
return 0;
}