Line data Source code
1 : /*-------------------------------------------------------------------------
2 : *
3 : * basebackup_to_shell.c
4 : * target base backup files to a shell command
5 : *
6 : * Copyright (c) 2016-2025, PostgreSQL Global Development Group
7 : *
8 : * contrib/basebackup_to_shell/basebackup_to_shell.c
9 : *-------------------------------------------------------------------------
10 : */
11 : #include "postgres.h"
12 :
13 : #include "access/xact.h"
14 : #include "backup/basebackup_target.h"
15 : #include "common/percentrepl.h"
16 : #include "miscadmin.h"
17 : #include "storage/fd.h"
18 : #include "utils/acl.h"
19 : #include "utils/guc.h"
20 :
21 2 : PG_MODULE_MAGIC;
22 :
23 : typedef struct bbsink_shell
24 : {
25 : /* Common information for all types of sink. */
26 : bbsink base;
27 :
28 : /* User-supplied target detail string. */
29 : char *target_detail;
30 :
31 : /* Shell command pattern being used for this backup. */
32 : char *shell_command;
33 :
34 : /* The command that is currently running. */
35 : char *current_command;
36 :
37 : /* Pipe to the running command. */
38 : FILE *pipe;
39 : } bbsink_shell;
40 :
41 : static void *shell_check_detail(char *target, char *target_detail);
42 : static bbsink *shell_get_sink(bbsink *next_sink, void *detail_arg);
43 :
44 : static void bbsink_shell_begin_archive(bbsink *sink,
45 : const char *archive_name);
46 : static void bbsink_shell_archive_contents(bbsink *sink, size_t len);
47 : static void bbsink_shell_end_archive(bbsink *sink);
48 : static void bbsink_shell_begin_manifest(bbsink *sink);
49 : static void bbsink_shell_manifest_contents(bbsink *sink, size_t len);
50 : static void bbsink_shell_end_manifest(bbsink *sink);
51 :
52 : static const bbsink_ops bbsink_shell_ops = {
53 : .begin_backup = bbsink_forward_begin_backup,
54 : .begin_archive = bbsink_shell_begin_archive,
55 : .archive_contents = bbsink_shell_archive_contents,
56 : .end_archive = bbsink_shell_end_archive,
57 : .begin_manifest = bbsink_shell_begin_manifest,
58 : .manifest_contents = bbsink_shell_manifest_contents,
59 : .end_manifest = bbsink_shell_end_manifest,
60 : .end_backup = bbsink_forward_end_backup,
61 : .cleanup = bbsink_forward_cleanup
62 : };
63 :
64 : static char *shell_command = "";
65 : static char *shell_required_role = "";
66 :
67 : void
68 2 : _PG_init(void)
69 : {
70 2 : DefineCustomStringVariable("basebackup_to_shell.command",
71 : "Shell command to be executed for each backup file.",
72 : NULL,
73 : &shell_command,
74 : "",
75 : PGC_SIGHUP,
76 : 0,
77 : NULL, NULL, NULL);
78 :
79 2 : DefineCustomStringVariable("basebackup_to_shell.required_role",
80 : "Backup user must be a member of this role to use shell backup target.",
81 : NULL,
82 : &shell_required_role,
83 : "",
84 : PGC_SIGHUP,
85 : 0,
86 : NULL, NULL, NULL);
87 :
88 2 : MarkGUCPrefixReserved("basebackup_to_shell");
89 :
90 2 : BaseBackupAddTarget("shell", shell_check_detail, shell_get_sink);
91 2 : }
92 :
93 : /*
94 : * We choose to defer sanity checking until shell_get_sink(), and so
95 : * just pass the target detail through without doing anything. However, we do
96 : * permissions checks here, before any real work has been done.
97 : */
98 : static void *
99 12 : shell_check_detail(char *target, char *target_detail)
100 : {
101 12 : if (shell_required_role[0] != '\0')
102 : {
103 : Oid roleid;
104 :
105 6 : StartTransactionCommand();
106 6 : roleid = get_role_oid(shell_required_role, true);
107 6 : if (!has_privs_of_role(GetUserId(), roleid))
108 2 : ereport(ERROR,
109 : (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
110 : errmsg("permission denied to use basebackup_to_shell")));
111 4 : CommitTransactionCommand();
112 : }
113 :
114 10 : return target_detail;
115 : }
116 :
117 : /*
118 : * Set up a bbsink to implement this base backup target.
119 : *
120 : * This is also a convenient place to sanity check that a target detail was
121 : * given if and only if %d is present.
122 : */
123 : static bbsink *
124 10 : shell_get_sink(bbsink *next_sink, void *detail_arg)
125 : {
126 : bbsink_shell *sink;
127 10 : bool has_detail_escape = false;
128 : char *c;
129 :
130 : /*
131 : * Set up the bbsink.
132 : *
133 : * We remember the current value of basebackup_to_shell.shell_command to
134 : * be certain that it can't change under us during the backup.
135 : */
136 10 : sink = palloc0(sizeof(bbsink_shell));
137 10 : *((const bbsink_ops **) &sink->base.bbs_ops) = &bbsink_shell_ops;
138 10 : sink->base.bbs_next = next_sink;
139 10 : sink->target_detail = detail_arg;
140 10 : sink->shell_command = pstrdup(shell_command);
141 :
142 : /* Reject an empty shell command. */
143 10 : if (sink->shell_command[0] == '\0')
144 2 : ereport(ERROR,
145 : errcode(ERRCODE_INVALID_PARAMETER_VALUE),
146 : errmsg("shell command for backup is not configured"));
147 :
148 : /* Determine whether the shell command we're using contains %d. */
149 824 : for (c = sink->shell_command; *c != '\0'; ++c)
150 : {
151 816 : if (c[0] == '%' && c[1] != '\0')
152 : {
153 12 : if (c[1] == 'd')
154 4 : has_detail_escape = true;
155 12 : ++c;
156 : }
157 : }
158 :
159 : /* There should be a target detail if %d was used, and not otherwise. */
160 8 : if (has_detail_escape && sink->target_detail == NULL)
161 2 : ereport(ERROR,
162 : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
163 : errmsg("a target detail is required because the configured command includes %%d"),
164 : errhint("Try \"pg_basebackup --target shell:DETAIL ...\"")));
165 6 : else if (!has_detail_escape && sink->target_detail != NULL)
166 2 : ereport(ERROR,
167 : (errcode(ERRCODE_INVALID_PARAMETER_VALUE),
168 : errmsg("a target detail is not permitted because the configured command does not include %%d")));
169 :
170 : /*
171 : * Since we're passing the string provided by the user to popen(), it will
172 : * be interpreted by the shell, which is a potential security
173 : * vulnerability, since the user invoking this module is not necessarily a
174 : * superuser. To stay out of trouble, we must disallow any shell
175 : * metacharacters here; to be conservative and keep things simple, we
176 : * allow only alphanumerics.
177 : */
178 4 : if (sink->target_detail != NULL)
179 : {
180 : char *d;
181 2 : bool scary = false;
182 :
183 8 : for (d = sink->target_detail; *d != '\0'; ++d)
184 : {
185 6 : if (*d >= 'a' && *d <= 'z')
186 6 : continue;
187 0 : if (*d >= 'A' && *d <= 'Z')
188 0 : continue;
189 0 : if (*d >= '0' && *d <= '9')
190 0 : continue;
191 0 : scary = true;
192 0 : break;
193 : }
194 :
195 2 : if (scary)
196 0 : ereport(ERROR,
197 : errcode(ERRCODE_INVALID_PARAMETER_VALUE),
198 : errmsg("target detail must contain only alphanumeric characters"));
199 : }
200 :
201 4 : return &sink->base;
202 : }
203 :
204 : /*
205 : * Construct the exact shell command that we're actually going to run,
206 : * making substitutions as appropriate for escape sequences.
207 : */
208 : static char *
209 8 : shell_construct_command(const char *base_command, const char *filename,
210 : const char *target_detail)
211 : {
212 8 : return replace_percent_placeholders(base_command, "basebackup_to_shell.command",
213 : "df", target_detail, filename);
214 : }
215 :
216 : /*
217 : * Finish executing the shell command once all data has been written.
218 : */
219 : static void
220 8 : shell_finish_command(bbsink_shell *sink)
221 : {
222 : int pclose_rc;
223 :
224 : /* There should be a command running. */
225 : Assert(sink->current_command != NULL);
226 : Assert(sink->pipe != NULL);
227 :
228 : /* Close down the pipe we opened. */
229 8 : pclose_rc = ClosePipeStream(sink->pipe);
230 8 : if (pclose_rc == -1)
231 0 : ereport(ERROR,
232 : (errcode_for_file_access(),
233 : errmsg("could not close pipe to external command: %m")));
234 8 : else if (pclose_rc != 0)
235 : {
236 0 : ereport(ERROR,
237 : (errcode(ERRCODE_EXTERNAL_ROUTINE_EXCEPTION),
238 : errmsg("shell command \"%s\" failed",
239 : sink->current_command),
240 : errdetail_internal("%s", wait_result_to_str(pclose_rc))));
241 : }
242 :
243 : /* Clean up. */
244 8 : sink->pipe = NULL;
245 8 : pfree(sink->current_command);
246 8 : sink->current_command = NULL;
247 8 : }
248 :
249 : /*
250 : * Start up the shell command, substituting %f in for the current filename.
251 : */
252 : static void
253 8 : shell_run_command(bbsink_shell *sink, const char *filename)
254 : {
255 : /* There should not be anything already running. */
256 : Assert(sink->current_command == NULL);
257 : Assert(sink->pipe == NULL);
258 :
259 : /* Construct a suitable command. */
260 16 : sink->current_command = shell_construct_command(sink->shell_command,
261 : filename,
262 8 : sink->target_detail);
263 :
264 : /* Run it. */
265 8 : sink->pipe = OpenPipeStream(sink->current_command, PG_BINARY_W);
266 8 : if (sink->pipe == NULL)
267 0 : ereport(ERROR,
268 : (errcode_for_file_access(),
269 : errmsg("could not execute command \"%s\": %m",
270 : sink->current_command)));
271 8 : }
272 :
273 : /*
274 : * Send accumulated data to the running shell command.
275 : */
276 : static void
277 10836 : shell_send_data(bbsink_shell *sink, size_t len)
278 : {
279 : /* There should be a command running. */
280 : Assert(sink->current_command != NULL);
281 : Assert(sink->pipe != NULL);
282 :
283 : /* Try to write the data. */
284 21672 : if (fwrite(sink->base.bbs_buffer, len, 1, sink->pipe) != 1 ||
285 10836 : ferror(sink->pipe))
286 : {
287 0 : if (errno == EPIPE)
288 : {
289 : /*
290 : * The error we're about to throw would shut down the command
291 : * anyway, but we may get a more meaningful error message by doing
292 : * this. If not, we'll fall through to the generic error below.
293 : */
294 0 : shell_finish_command(sink);
295 0 : errno = EPIPE;
296 : }
297 0 : ereport(ERROR,
298 : (errcode_for_file_access(),
299 : errmsg("could not write to shell backup program: %m")));
300 : }
301 10836 : }
302 :
303 : /*
304 : * At start of archive, start up the shell command and forward to next sink.
305 : */
306 : static void
307 4 : bbsink_shell_begin_archive(bbsink *sink, const char *archive_name)
308 : {
309 4 : bbsink_shell *mysink = (bbsink_shell *) sink;
310 :
311 4 : shell_run_command(mysink, archive_name);
312 4 : bbsink_forward_begin_archive(sink, archive_name);
313 4 : }
314 :
315 : /*
316 : * Send archive contents to command's stdin and forward to next sink.
317 : */
318 : static void
319 10816 : bbsink_shell_archive_contents(bbsink *sink, size_t len)
320 : {
321 10816 : bbsink_shell *mysink = (bbsink_shell *) sink;
322 :
323 10816 : shell_send_data(mysink, len);
324 10816 : bbsink_forward_archive_contents(sink, len);
325 10816 : }
326 :
327 : /*
328 : * At end of archive, shut down the shell command and forward to next sink.
329 : */
330 : static void
331 4 : bbsink_shell_end_archive(bbsink *sink)
332 : {
333 4 : bbsink_shell *mysink = (bbsink_shell *) sink;
334 :
335 4 : shell_finish_command(mysink);
336 4 : bbsink_forward_end_archive(sink);
337 4 : }
338 :
339 : /*
340 : * At start of manifest, start up the shell command and forward to next sink.
341 : */
342 : static void
343 4 : bbsink_shell_begin_manifest(bbsink *sink)
344 : {
345 4 : bbsink_shell *mysink = (bbsink_shell *) sink;
346 :
347 4 : shell_run_command(mysink, "backup_manifest");
348 4 : bbsink_forward_begin_manifest(sink);
349 4 : }
350 :
351 : /*
352 : * Send manifest contents to command's stdin and forward to next sink.
353 : */
354 : static void
355 20 : bbsink_shell_manifest_contents(bbsink *sink, size_t len)
356 : {
357 20 : bbsink_shell *mysink = (bbsink_shell *) sink;
358 :
359 20 : shell_send_data(mysink, len);
360 20 : bbsink_forward_manifest_contents(sink, len);
361 20 : }
362 :
363 : /*
364 : * At end of manifest, shut down the shell command and forward to next sink.
365 : */
366 : static void
367 4 : bbsink_shell_end_manifest(bbsink *sink)
368 : {
369 4 : bbsink_shell *mysink = (bbsink_shell *) sink;
370 :
371 4 : shell_finish_command(mysink);
372 4 : bbsink_forward_end_manifest(sink);
373 4 : }
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