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ar: read_num(): fix reading fields using the entire width

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ar fields are fixed length text strings (padded with spaces). Ensure
bb_strtou doesn't read past the field in case the full width is used.

The fields are only read once, so the simplest/smallest solution to me
seems to be to just pass the length to read_num() and then zero terminate
the string before passing it to bb_strtou. This does mean that the fields
MUST be read in reverse order, so some minor reshuffling was needed.

Bloat-o-meter:
function                                             old     new   delta
get_header_ar                                        394     414     +20
read_num                                              29      36      +7
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/0 up/down: 27/0)               Total: 27 bytes

Signed-off-by: Peter Korsgaard <jacmet@sunsite.dk>
Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>
This commit is contained in:
Peter Korsgaard 2013-09-10 11:52:35 +02:00 committed by Denys Vlasenko
parent dc57294485
commit 2a053a2430
1 changed files with 20 additions and 12 deletions
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32
archival/libarchive/get_header_ar.c
View File

@ -8,11 +8,19 @@
#include "bb_archive.h"
#include "ar.h"
static unsigned read_num(const char *str, int base)
/* WARNING: Clobbers str[len], so fields must be read in reverse order! */
static unsigned read_num(char *str, int base, int len)
{
int err;
/* ar fields are fixed length text strings (padded with spaces).
* Ensure bb_strtou doesn't read past the field in case the full
* width is used. */
str[len] = 0;
/* This code works because
* on misformatted numbers bb_strtou returns all-ones */
int err = bb_strtou(str, NULL, base);
err = bb_strtou(str, NULL, base);
if (err == -1)
bb_error_msg_and_die("invalid ar header");
return err;
@ -51,11 +59,8 @@ char FAST_FUNC get_header_ar(archive_handle_t *archive_handle)
if (ar.formatted.magic[0] != '`' || ar.formatted.magic[1] != '\n')
bb_error_msg_and_die("invalid ar header");
/* FIXME: more thorough routine would be in order here
* (we have something like that in tar)
* but for now we are lax. */
ar.formatted.magic[0] = '\0'; /* else 4G-2 file will have size="4294967294`\n..." */
typed->size = size = read_num(ar.formatted.size, 10);
typed->size = size = read_num(ar.formatted.size, 10,
sizeof(ar.formatted.size));
/* special filenames have '/' as the first character */
if (ar.formatted.name[0] == '/') {
@ -86,11 +91,13 @@ char FAST_FUNC get_header_ar(archive_handle_t *archive_handle)
/* Only size is always present, the rest may be missing in
* long filename pseudo file. Thus we decode the rest
* after dealing with long filename pseudo file.
* Note that the fields MUST be read in reverse order as
* read_num() clobbers the next byte after the field!
*/
typed->mode = read_num(ar.formatted.mode, 8);
typed->mtime = read_num(ar.formatted.date, 10);
typed->uid = read_num(ar.formatted.uid, 10);
typed->gid = read_num(ar.formatted.gid, 10);
typed->mode = read_num(ar.formatted.mode, 8, sizeof(ar.formatted.mode));
typed->gid = read_num(ar.formatted.gid, 10, sizeof(ar.formatted.gid));
typed->uid = read_num(ar.formatted.uid, 10, sizeof(ar.formatted.uid));
typed->mtime = read_num(ar.formatted.date, 10, sizeof(ar.formatted.date));
#if ENABLE_FEATURE_AR_LONG_FILENAMES
if (ar.formatted.name[0] == '/') {
@ -98,7 +105,8 @@ char FAST_FUNC get_header_ar(archive_handle_t *archive_handle)
/* The number after the '/' indicates the offset in the ar data section
* (saved in ar_long_names) that conatains the real filename */
long_offset = read_num(&ar.formatted.name[1], 10);
long_offset = read_num(&ar.formatted.name[1], 10,
sizeof(ar.formatted.name) - 1);
if (long_offset >= ar_long_name_size) {
bb_error_msg_and_die("can't resolve long filename");
}