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/* Find how deeply inside an .RPM the real data is */
/* kept, and report the offset in bytes */
/* Wouldn't it be a lot more sane if we could just untar these things? */
#ifndef _GNU_SOURCE
# define _GNU_SOURCE
#endif
#include <stdint.h>
#include <stdio.h>
#include <string.h>
#ifndef ARRAY_SIZE
# define ARRAY_SIZE(a) (sizeof(a) / sizeof((a)[0]))
#endif
#ifndef BUFSIZ
# define BUFSIZ 8192
#endif
#if !defined(__GLIBC__)
static void *rp_memmem(const void *buf, size_t buflen, const void *pattern, size_t len)
{
char *bf = (char *)buf, *pt = (char *)pattern, *p = bf;
while (len <= (buflen - (p - bf))) {
if (NULL != (p = memchr(p, (int)(*pt), buflen - (p - bf)))) {
if (0 == memcmp(p, pattern, len))
return p;
else
++p;
}
else
break;
}
return NULL;
}
#define memmem(a,b,c,d) rp_memmem(a,b,c,d)
#endif
typedef struct {
const char *type;
const unsigned char *magic;
const size_t len;
} magic_t;
/* LZMA is some fuzzy crap */
int is_magic_lzma(const char *buf)
{
const unsigned char *ubuf = (const void *)buf;
return (ubuf[0] == 0x5d && ubuf[4] < 0x20) &&
(!memcmp(buf + 10, "\x00\x00\x00", 3) ||
!memcmp(buf + 5, "\xFF\xFF\xFF\xFF\xFF\xFF\xFF\xFF", 8));
}
#define magic_lzma_len 13
static const unsigned char magic_gzip[] = { '\037', '\213', '\010' };
static const unsigned char magic_bzip2[] = { 'B', 'Z', 'h' };
static const unsigned char magic_xz[] = { 0xFD, '7', 'z', 'X', 'Z', 0x00 };
static const unsigned char magic_zstd[] = { 0x28, 0xB5, 0x2F, 0xFD };
static const magic_t magics[] = {
#define DECLARE_MAGIC_T(t) { .type = #t, .magic = magic_##t, .len = sizeof(magic_##t), },
DECLARE_MAGIC_T(gzip)
DECLARE_MAGIC_T(bzip2)
DECLARE_MAGIC_T(xz)
DECLARE_MAGIC_T(zstd)
#undef DECLARE_MAGIC_T
};
#define MAGIC_SIZE_MIN 3
#define MAGIC_SIZE_MAX 13
static int show_magic;
static int magic_finish(const char *magic, size_t offset)
{
if (show_magic)
printf("%s ", magic);
printf("%zu\n", offset);
return 0;
}
int main(int argc, char *argv[])
{
size_t i, read_cnt, offset, left, lzma_offset;
FILE *fp = stdin;
char p[BUFSIZ];
if (argc == 2 && !strcmp(argv[1], "-v")) {
show_magic = 1;
--argc;
}
if (argc != 1) {
puts("Usage: rpmoffset < rpmfile");
return 1;
}
/* fp = fopen(argv[1], "r"); */
lzma_offset = 0;
offset = left = 0;
while (1) {
read_cnt = fread(p + left, 1, sizeof(p) - left, fp);
if (read_cnt + left < MAGIC_SIZE_MIN)
break;
for (i = 0; i < ARRAY_SIZE(magics); ++i) {
const char *needle;
if (read_cnt + left < magics[i].len)
continue;
needle = memmem(p, sizeof(p), magics[i].magic, magics[i].len);
if (needle)
return magic_finish(magics[i].type, offset + (needle - p));
}
/* Scan for LZMA magic, but don't return yet ... */
if (!lzma_offset && read_cnt + left >= magic_lzma_len) {
for (i = 0; i <= read_cnt + left - magic_lzma_len; ++i)
if (is_magic_lzma(p + i)) {
lzma_offset = offset + i;
break;
}
}
memmove(p, p + left + read_cnt - MAGIC_SIZE_MIN + 1, MAGIC_SIZE_MIN - 1);
offset += read_cnt;
if (left == 0) {
offset -= MAGIC_SIZE_MIN - 1;
left = MAGIC_SIZE_MIN - 1;
}
}
/* Delay till the end for LZMA archives since it is too fuzzy */
if (lzma_offset)
return magic_finish("lzma", lzma_offset);
if (ferror(stdin))
perror(argv[0]);
return 1;
}
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