1/*
2 * rpmunpack for busybox
3 *
4 * rpmunpack.c  -  Utility program to unpack an RPM archive
5 *
6 * Gero Kuhlmann <gero@gkminix.han.de> 1998
7 *
8 *  This program is public domain software; you can do whatever you like
9 *  with this source, including modifying and redistributing it.
10 *
11 *  This program is distributed in the hope that it will be useful,
12 *  but WITHOUT ANY WARRANTY; without even the implied warranty of
13 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.
14 */
15
16#include <fcntl.h>
17#include <unistd.h>
18#include <string.h>
19#include <stdlib.h>
20#include "busybox.h"
21
22/*
23 * Some general definitions
24 */
25
26#define RPM_MAGIC	"\355\253\356\333"
27#define GZ_MAGIC_1	'\037'
28#define GZ_MAGIC_2	'\213'
29
30/*
31 * Global variables
32 */
33static char *progname;
34static int infile, outfile;
35
36/*
37 * Read a specified number of bytes from input file
38 */
39static void myread(int num, char *buffer)
40{
41  int err;
42
43  if ((err = read(infile, buffer, num)) != num) {
44	if (err < 0)
45		perror_msg_and_die(progname);
46	else
47		error_msg_and_die("Unexpected end of input file!");
48  }
49}
50
51/*
52 * Main program
53 */
54int rpmunpack_main(int argc, char **argv)
55{
56  int len, status = 0;
57  RESERVE_BB_BUFFER(buffer, BUFSIZ);
58
59  /* Get our own program name */
60  if ((progname = strrchr(argv[0], '/')) == NULL)
61	progname = argv[0];
62  else
63	progname++;
64
65  /* Check for command line parameters */
66	if (argc>=2 && *argv[1]=='-') {
67           show_usage();
68	}
69
70  /* Open input file */
71  if (argc == 1)
72	infile = STDIN_FILENO;
73  else if ((infile = open(argv[1], O_RDONLY)) < 0)
74	perror_msg_and_die("%s", argv[1]);
75
76  /* Read magic ID and output filename */
77  myread(4, buffer);
78  if (strncmp(buffer, RPM_MAGIC, 4)) {
79	fprintf(stderr, "Input file is not in RPM format!\n");
80	exit(1);
81  }
82  myread(6, buffer);		/* Skip flags */
83  myread(64, buffer);
84  buffer[64] = '\0';
85
86  /* Open output file */
87  strcat(buffer, ".cpio.gz");
88  if (infile == STDIN_FILENO)
89	outfile = STDOUT_FILENO;
90  else if ((outfile = open(buffer, O_WRONLY | O_CREAT | O_TRUNC, 0644)) < 0)
91	  perror_msg_and_die("%s", buffer);
92
93  /*
94   * Now search for the GZIP signature. This is rather awkward, but I don't
95   * know any other way how to find out the exact starting position of the
96   * archive within the input file. There are a couple of data structures
97   * and texts (obviously descriptions, installation shell scripts etc.)
98   * coming before the archive, but even they start at different offsets
99   * with different RPM files. However, it looks like the GZIP signature
100   * never appears before offset 0x200, so we skip these first couple of
101   * bytes to make the signature scan a little more reliable.
102   */
103  myread(0x200 - 74, buffer);
104  while (status < 2) {
105	myread(1, buffer);
106	if (status == 0 && buffer[0] == GZ_MAGIC_1)
107		status++;
108	else if (status == 1 && buffer[0] == GZ_MAGIC_2)
109		status++;
110	else
111		status = 0;
112  }
113  buffer[0] = GZ_MAGIC_1;
114  buffer[1] = GZ_MAGIC_2;
115  if (write(outfile, buffer, 2) < 0)
116	perror_msg_and_die("write");
117
118  /* Now simply copy the GZIP archive into the output file */
119  while ((len = read(infile, buffer, BUFSIZ)) > 0) {
120	if (write(outfile, buffer, len) < 0)
121		perror_msg_and_die("write");
122  }
123  if (len < 0)
124    perror_msg_and_die("read");
125  return EXIT_SUCCESS;
126}
127