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/*
* debsig-verify - Debian package signature verification tool
*
* Copyright © 2000 Ben Collins <bcollins@debian.org>
*
* This is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program. If not, see <https://www.gnu.org/licenses/>.
*/
/*
* processes ar style archives (the format of a .deb package)
*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <assert.h>
#include <errno.h>
#include <ar.h>
#include <dpkg/ar.h>
#include "debsig.h"
/* This function takes a member name as an argument. It then goes through
* the archive trying to find it. If it does, it returns the size of the
* member's data, and leaves the deb_fs file pointer at the start of that
* data. Yes, we may have a zero length member in here somewhere, but
* nothing important is going to be zero length anyway, so we treat it as
* "non-existant". */
off_t
findMember(const char *name)
{
char magic[SARMAG+1];
struct ar_hdr arh;
off_t mem_len;
int len = strlen(name);
if (len > sizeof(arh.ar_name)) {
ds_printf(DS_LEV_DEBUG, "findMember: '%s' is too long to be an archive member name",
name);
return 0;
}
/* This shouldn't happen, but... */
if (deb_fs == NULL)
ds_fail_printf(DS_FAIL_INTERNAL, "findMember: called while deb_fs == NULL");
rewind(deb_fs);
if (!fgets(magic,sizeof(magic),deb_fs))
ds_fail_printf(DS_FAIL_INTERNAL, "findMember: failure to read package (%s)",
strerror(errno));
/* We will fail in main() with this one */
if (strcmp(magic,ARMAG)) {
ds_printf(DS_LEV_DEBUG, "findMember: archive has bad magic");
return 0;
}
while(!feof(deb_fs)) {
if (fread(&arh, 1, sizeof(arh),deb_fs) != sizeof(arh)) {
if (ferror(deb_fs))
ds_fail_printf(DS_FAIL_INTERNAL, "findMember: error while parsing archive header (%s)",
strerror(errno));
return 0;
}
if (dpkg_ar_member_is_illegal(&arh))
ds_fail_printf(DS_FAIL_INTERNAL, "findMember: archive appears to be corrupt, fmag incorrect");
dpkg_ar_normalize_name(&arh);
mem_len = dpkg_ar_member_get_size(deb, &arh);
/*
* If all looks well, then we return the length of the member, and
* leave the file pointer where it is (at the start of the data).
* The logic here is based on the ar spec. The ar_name field is
* padded with spaces to get the full length. The actual name may
* also be suffixed with '/' (dpkg-deb creates .deb's without the
* trailing '/' in the member names, but binutils ar does, so we
* try to be compatible, like dpkg does). We don't support the
* "extended naming" scheme that binutils does.
*/
if (strncmp(arh.ar_name, name, len) == 0 &&
strnlen(arh.ar_name, sizeof(arh.ar_name)) == len)
return mem_len;
/* fseek to the start of the next member, and try again */
if (fseek(deb_fs, mem_len + (mem_len & 1), SEEK_CUR) == -1 && ferror(deb_fs))
ds_fail_printf(DS_FAIL_INTERNAL,
"findMember: error during file seek (%s)", strerror(errno));
}
/* well, nothing found, so let's pass on the bad news */
return 0;
}
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