1 /*
2  * This is free and unencumbered software released into the public domain.
3  */
4 
5 #include <sys/mman.h>
6 
7 #include <endian.h>
8 #include <err.h>
9 #include <fcntl.h>
10 #include <limits.h>
11 #include <stdint.h>
12 #include <stdio.h>
13 #include <string.h>
14 #include <unistd.h>
15 #include <zlib.h>
16 
17 #define MIN(a, b) ((a) < (b) ? (a) : (b))
18 
19 void *
20 find_central_directory(uint8_t *addr, size_t len)
21 {
22 	uint32_t	 offset;
23 	uint16_t	 clen;
24 	uint8_t		*p, *end;
25 
26 	/*
27 	 * At -22 bytes from the end there is the end of the central
28 	 * directory assuming an empty comment.  It's a sensible place
29 	 * from which start.
30 	 */
31 	if (len < 22)
32 		return NULL;
33 	end = addr + len;
34 	p = end - 22;
35 
36 again:
37 	for (; p > addr; --p)
38 		if (memcmp(p, "\x50\x4b\x05\x06", 4) == 0)
39 			break;
40 
41 	if (p == addr)
42 		return NULL;
43 
44 	/* read comment length */
45 	memcpy(&clen, p + 20, sizeof(clen));
46 	clen = le16toh(clen);
47 
48 	/* false signature inside a comment? */
49 	if (clen + 22 != end - p) {
50 		p--;
51 		goto again;
52 	}
53 
54 	/* read the offset for the central directory */
55 	memcpy(&offset, p + 16, sizeof(offset));
56 	offset = le32toh(offset);
57 
58 	if (addr + offset > p)
59 		return NULL;
60 
61 	return addr + offset;
62 }
63 
64 void
65 ls(uint8_t *zip, size_t len, uint8_t *cd)
66 {
67 	uint16_t	 flen, xlen, clen;
68 	uint8_t		*end;
69 	char		 filename[PATH_MAX];
70 
71 	end = zip + len;
72 	while (cd < end - 46 && memcmp(cd, "\x50\x4b\x01\x02", 4) == 0) {
73 		memcpy(&flen, cd + 28, sizeof(flen));
74 		memcpy(&xlen, cd + 28 + 2, sizeof(xlen));
75 		memcpy(&clen, cd + 28 + 2 + 2, sizeof(clen));
76 
77 		flen = le16toh(flen);
78 		xlen = le16toh(xlen);
79 		clen = le16toh(clen);
80 
81 		memset(filename, 0, sizeof(filename));
82 		memcpy(filename, cd + 46, MIN(sizeof(filename)-1, flen));
83 
84 		printf("%s\n", filename);
85 
86 		cd += 46 + flen + xlen + clen;
87 	}
88 }
89 
90 void *
91 map_file(int fd, size_t *len)
92 {
93 	off_t	 jump;
94 	void	*addr;
95 
96 	if ((jump = lseek(fd, 0, SEEK_END)) == -1)
97 		err(1, "lseek");
98 
99 	if (lseek(fd, 0, SEEK_SET) == -1)
100 		err(1, "lseek");
101 
102 	if ((addr = mmap(NULL, jump, PROT_READ, MAP_PRIVATE, fd, 0))
103 	    == MAP_FAILED)
104                 err(1, "mmap");
105 
106 	*len = jump;
107 	return addr;
108 }
109 
110 int
111 main(int argc, char **argv)
112 {
113 	int	 fd;
114 	void	*zip, *cd;
115 	size_t	 len;
116 
117 	if (argc != 2)
118 		errx(1, "missing file to inspect");
119 
120 	if ((fd = open(argv[1], O_RDONLY)) == -1)
121 		err(1, "can't open %s", argv[1]);
122 
123 	zip = map_file(fd, &len);
124 	if ((cd = find_central_directory(zip, len)) == NULL)
125 		errx(1, "can't find the central directory");
126 
127 	ls(zip, len, cd);
128 
129 	munmap(zip, len);
130 	close(fd);
131 
132 	return 0;
133 }