aboutsummaryrefslogtreecommitdiff
path: root/lib/tar/write_header.c
blob: e4d4d3833355763bbf832e70296aa32044e1037e (plain)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
/* SPDX-License-Identifier: GPL-3.0-or-later */
/*
 * write_header.c
 *
 * Copyright (C) 2019 David Oberhollenzer <goliath@infraroot.at>
 */
#include "config.h"

#include "internal.h"

static void write_binary(char *dst, uint64_t value, int digits)
{
	memset(dst, 0, digits);

	while (digits > 0) {
		((unsigned char *)dst)[digits - 1] = value & 0xFF;
		--digits;
		value >>= 8;
	}

	((unsigned char *)dst)[0] |= 0x80;
}

static void write_number(char *dst, uint64_t value, int digits)
{
	uint64_t mask = 0;
	char buffer[64];
	int i;

	for (i = 0; i < (digits - 1); ++i)
		mask = (mask << 3) | 7;

	if (value <= mask) {
		sprintf(buffer, "%0*o ", digits - 1, (unsigned int)value);
		memcpy(dst, buffer, digits);
	} else if (value <= ((mask << 3) | 7)) {
		sprintf(buffer, "%0*o", digits, (unsigned int)value);
		memcpy(dst, buffer, digits);
	} else {
		write_binary(dst, value, digits);
	}
}

static void write_number_signed(char *dst, int64_t value, int digits)
{
	uint64_t neg;

	if (value < 0) {
		neg = -value;
		write_binary(dst, ~neg + 1, digits);
	} else {
		write_number(dst, value, digits);
	}
}

static int write_header(int fd, const struct stat *sb, const char *name,
			const char *slink_target, int type)
{
	int maj = 0, min = 0;
	uint64_t size = 0;
	tar_header_t hdr;

	if (S_ISCHR(sb->st_mode) || S_ISBLK(sb->st_mode)) {
		maj = major(sb->st_rdev);
		min = minor(sb->st_rdev);
	}

	if (S_ISREG(sb->st_mode))
		size = sb->st_size;

	memset(&hdr, 0, sizeof(hdr));

	strncpy(hdr.name, name, sizeof(hdr.name) - 1);
	write_number(hdr.mode, sb->st_mode & ~S_IFMT, sizeof(hdr.mode));
	write_number(hdr.uid, sb->st_uid, sizeof(hdr.uid));
	write_number(hdr.gid, sb->st_gid, sizeof(hdr.gid));
	write_number(hdr.size, size, sizeof(hdr.size));
	write_number_signed(hdr.mtime, sb->st_mtime, sizeof(hdr.mtime));
	hdr.typeflag = type;
	if (slink_target != NULL)
		memcpy(hdr.linkname, slink_target, sb->st_size);
	memcpy(hdr.magic, TAR_MAGIC_OLD, sizeof(hdr.magic));
	memcpy(hdr.version, TAR_VERSION_OLD, sizeof(hdr.version));
	sprintf(hdr.uname, "%u", sb->st_uid);
	sprintf(hdr.gname, "%u", sb->st_gid);
	write_number(hdr.devmajor, maj, sizeof(hdr.devmajor));
	write_number(hdr.devminor, min, sizeof(hdr.devminor));

	update_checksum(&hdr);

	return write_data("writing tar header record", fd, &hdr, sizeof(hdr));
}

static int write_gnu_header(int fd, const struct stat *orig,
			    const char *payload, size_t payload_len,
			    int type, const char *name)
{
	struct stat sb;

	sb = *orig;
	sb.st_mode = S_IFREG | 0644;
	sb.st_size = payload_len;

	if (write_header(fd, &sb, name, NULL, type))
		return -1;

	if (write_data("writing GNU extension header",
		       fd, payload, payload_len)) {
		return -1;
	}

	return padd_file(fd, payload_len, 512);
}

int write_tar_header(int fd, const struct stat *sb, const char *name,
		     const char *slink_target, unsigned int counter)
{
	const char *reason;
	char buffer[64];
	int type;

	if (!S_ISLNK(sb->st_mode))
		slink_target = NULL;

	if (S_ISLNK(sb->st_mode) && sb->st_size >= 100) {
		sprintf(buffer, "gnu/target%u", counter);
		if (write_gnu_header(fd, sb, slink_target, sb->st_size,
				     TAR_TYPE_GNU_SLINK, buffer))
			return -1;
		slink_target = NULL;
	}

	if (strlen(name) >= 100) {
		sprintf(buffer, "gnu/name%u", counter);

		if (write_gnu_header(fd, sb, name, strlen(name),
				     TAR_TYPE_GNU_PATH, buffer)) {
			return -1;
		}

		sprintf(buffer, "gnu/data%u", counter);
		name = buffer;
	}

	switch (sb->st_mode & S_IFMT) {
	case S_IFCHR: type = TAR_TYPE_CHARDEV; break;
	case S_IFBLK: type = TAR_TYPE_BLOCKDEV; break;
	case S_IFLNK: type = TAR_TYPE_SLINK; break;
	case S_IFREG: type = TAR_TYPE_FILE; break;
	case S_IFDIR: type = TAR_TYPE_DIR; break;
	case S_IFIFO: type = TAR_TYPE_FIFO; break;
	case S_IFSOCK:
		reason = "cannot pack socket";
		goto out_skip;
	default:
		reason = "unknown type";
		goto out_skip;
	}

	return write_header(fd, sb, name, slink_target, type);
out_skip:
	fprintf(stderr, "WARNING: %s: %s\n", name, reason);
	return 1;
}