Line data Source code
1 : #include "c.h"
2 :
3 : #include <sys/stat.h>
4 :
5 : #include "pgtar.h"
6 :
7 : /*
8 : * Print a numeric field in a tar header. The field starts at *s and is of
9 : * length len; val is the value to be written.
10 : *
11 : * Per POSIX, the way to write a number is in octal with leading zeroes and
12 : * one trailing space (or NUL, but we use space) at the end of the specified
13 : * field width.
14 : *
15 : * However, the given value may not fit in the available space in octal form.
16 : * If that's true, we use the GNU extension of writing \200 followed by the
17 : * number in base-256 form (ie, stored in binary MSB-first). (Note: here we
18 : * support only non-negative numbers, so we don't worry about the GNU rules
19 : * for handling negative numbers.)
20 : */
21 : void
22 1480248 : print_tar_number(char *s, int len, uint64 val)
23 : {
24 1480248 : if (val < (((uint64) 1) << ((len - 1) * 3)))
25 : {
26 : /* Use octal with trailing space */
27 1480248 : s[--len] = ' ';
28 13322264 : while (len)
29 : {
30 11842016 : s[--len] = (val & 7) + '0';
31 11842016 : val >>= 3;
32 : }
33 : }
34 : else
35 : {
36 : /* Use base-256 with leading \200 */
37 0 : s[0] = '\200';
38 0 : while (len > 1)
39 : {
40 0 : s[--len] = (val & 255);
41 0 : val >>= 8;
42 : }
43 : }
44 1480248 : }
45 :
46 :
47 : /*
48 : * Read a numeric field in a tar header. The field starts at *s and is of
49 : * length len.
50 : *
51 : * The POSIX-approved format for a number is octal, ending with a space or
52 : * NUL. However, for values that don't fit, we recognize the GNU extension
53 : * of \200 followed by the number in base-256 form (ie, stored in binary
54 : * MSB-first). (Note: here we support only non-negative numbers, so we don't
55 : * worry about the GNU rules for handling negative numbers.)
56 : */
57 : uint64
58 936298 : read_tar_number(const char *s, int len)
59 : {
60 936298 : uint64 result = 0;
61 :
62 936298 : if (*s == '\200')
63 : {
64 : /* base-256 */
65 0 : while (--len)
66 : {
67 0 : result <<= 8;
68 0 : result |= (unsigned char) (*++s);
69 : }
70 : }
71 : else
72 : {
73 : /* octal */
74 8231908 : while (len-- && *s >= '0' && *s <= '7')
75 : {
76 7295610 : result <<= 3;
77 7295610 : result |= (*s - '0');
78 7295610 : s++;
79 : }
80 : }
81 936298 : return result;
82 : }
83 :
84 :
85 : /*
86 : * Calculate the tar checksum for a header. The header is assumed to always
87 : * be 512 bytes, per the tar standard.
88 : */
89 : int
90 372353 : tarChecksum(const char *header)
91 : {
92 : int i,
93 : sum;
94 :
95 : /*
96 : * Per POSIX, the checksum is the simple sum of all bytes in the header,
97 : * treating the bytes as unsigned, and treating the checksum field (at
98 : * offset TAR_OFFSET_CHECKSUM) as though it contained 8 spaces.
99 : */
100 372353 : sum = 8 * ' '; /* presumed value for checksum field */
101 191017089 : for (i = 0; i < TAR_BLOCK_SIZE; i++)
102 190644736 : if (i < TAR_OFFSET_CHECKSUM || i >= TAR_OFFSET_CHECKSUM + 8)
103 187665912 : sum += 0xFF & header[i];
104 372353 : return sum;
105 : }
106 :
107 : /*
108 : * Check validity of a tar header (assumed to be 512 bytes long).
109 : * We verify the checksum and the magic number / version.
110 : */
111 : bool
112 187238 : isValidTarHeader(const char *header)
113 : {
114 : int sum;
115 187238 : int chk = tarChecksum(header);
116 :
117 187238 : sum = read_tar_number(&header[TAR_OFFSET_CHECKSUM], 8);
118 :
119 187238 : if (sum != chk)
120 0 : return false;
121 :
122 : /* POSIX tar format */
123 187238 : if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar\0", 6) == 0 &&
124 187238 : memcmp(&header[TAR_OFFSET_VERSION], "00", 2) == 0)
125 187238 : return true;
126 : /* GNU tar format */
127 0 : if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar \0", 8) == 0)
128 0 : return true;
129 : /* not-quite-POSIX format written by pre-9.3 pg_dump */
130 0 : if (memcmp(&header[TAR_OFFSET_MAGIC], "ustar00\0", 8) == 0)
131 0 : return true;
132 :
133 0 : return false;
134 : }
135 :
136 :
137 : /*
138 : * Fill in the buffer pointed to by h with a tar format header. This buffer
139 : * must always have space for 512 characters, which is a requirement of
140 : * the tar format.
141 : */
142 : enum tarError
143 185028 : tarCreateHeader(char *h, const char *filename, const char *linktarget,
144 : pgoff_t size, mode_t mode, uid_t uid, gid_t gid, time_t mtime)
145 : {
146 185028 : if (strlen(filename) > 99)
147 1 : return TAR_NAME_TOO_LONG;
148 :
149 185027 : if (linktarget && strlen(linktarget) > 99)
150 0 : return TAR_SYMLINK_TOO_LONG;
151 :
152 185027 : memset(h, 0, TAR_BLOCK_SIZE);
153 :
154 : /* Name 100 */
155 185027 : strlcpy(&h[TAR_OFFSET_NAME], filename, 100);
156 185027 : if (linktarget != NULL || S_ISDIR(mode))
157 : {
158 : /*
159 : * We only support symbolic links to directories, and this is
160 : * indicated in the tar format by adding a slash at the end of the
161 : * name, the same as for regular directories.
162 : */
163 4578 : int flen = strlen(filename);
164 :
165 4578 : flen = Min(flen, 99);
166 4578 : h[flen] = '/';
167 4578 : h[flen + 1] = '\0';
168 : }
169 :
170 : /* Mode 8 - this doesn't include the file type bits (S_IFMT) */
171 185027 : print_tar_number(&h[TAR_OFFSET_MODE], 8, (mode & 07777));
172 :
173 : /* User ID 8 */
174 185027 : print_tar_number(&h[TAR_OFFSET_UID], 8, uid);
175 :
176 : /* Group 8 */
177 185027 : print_tar_number(&h[TAR_OFFSET_GID], 8, gid);
178 :
179 : /* File size 12 */
180 185027 : if (linktarget != NULL || S_ISDIR(mode))
181 : /* Symbolic link or directory has size zero */
182 4578 : print_tar_number(&h[TAR_OFFSET_SIZE], 12, 0);
183 : else
184 180449 : print_tar_number(&h[TAR_OFFSET_SIZE], 12, size);
185 :
186 : /* Mod Time 12 */
187 185027 : print_tar_number(&h[TAR_OFFSET_MTIME], 12, mtime);
188 :
189 : /* Checksum 8 cannot be calculated until we've filled all other fields */
190 :
191 185027 : if (linktarget != NULL)
192 : {
193 : /* Type - Symbolic link */
194 16 : h[TAR_OFFSET_TYPEFLAG] = TAR_FILETYPE_SYMLINK;
195 : /* Link Name 100 */
196 16 : strlcpy(&h[TAR_OFFSET_LINKNAME], linktarget, 100);
197 : }
198 185011 : else if (S_ISDIR(mode))
199 : {
200 : /* Type - directory */
201 4562 : h[TAR_OFFSET_TYPEFLAG] = TAR_FILETYPE_DIRECTORY;
202 : }
203 : else
204 : {
205 : /* Type - regular file */
206 180449 : h[TAR_OFFSET_TYPEFLAG] = TAR_FILETYPE_PLAIN;
207 : }
208 :
209 : /* Magic 6 */
210 185027 : strcpy(&h[TAR_OFFSET_MAGIC], "ustar");
211 :
212 : /* Version 2 */
213 185027 : memcpy(&h[TAR_OFFSET_VERSION], "00", 2);
214 :
215 : /* User 32 */
216 : /* XXX: Do we need to care about setting correct username? */
217 185027 : strlcpy(&h[TAR_OFFSET_UNAME], "postgres", 32);
218 :
219 : /* Group 32 */
220 : /* XXX: Do we need to care about setting correct group name? */
221 185027 : strlcpy(&h[TAR_OFFSET_GNAME], "postgres", 32);
222 :
223 : /* Major Dev 8 */
224 185027 : print_tar_number(&h[TAR_OFFSET_DEVMAJOR], 8, 0);
225 :
226 : /* Minor Dev 8 */
227 185027 : print_tar_number(&h[TAR_OFFSET_DEVMINOR], 8, 0);
228 :
229 : /* Prefix 155 - not used, leave as nulls */
230 :
231 : /* Finally, compute and insert the checksum */
232 185027 : print_tar_number(&h[TAR_OFFSET_CHECKSUM], 8, tarChecksum(h));
233 :
234 185027 : return TAR_OK;
235 : }
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