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git.ipfire.org Git - thirdparty/systemd.git/blob - src/shared/pager.c
1 /* SPDX-License-Identifier: LGPL-2.1-or-later */
18 #include "locale-util.h"
22 #include "process-util.h"
23 #include "rlimit-util.h"
24 #include "signal-util.h"
25 #include "string-util.h"
27 #include "terminal-util.h"
29 static pid_t pager_pid
= 0;
31 static int stored_stdout
= -1;
32 static int stored_stderr
= -1;
33 static bool stdout_redirected
= false;
34 static bool stderr_redirected
= false;
36 _noreturn_
static void pager_fallback(void) {
39 r
= copy_bytes(STDIN_FILENO
, STDOUT_FILENO
, UINT64_MAX
, 0);
41 log_error_errno(r
, "Internal pager failed: %m");
48 static int no_quit_on_interrupt(int exe_name_fd
, const char *less_opts
) {
49 _cleanup_fclose_
FILE *file
= NULL
;
50 _cleanup_free_
char *line
= NULL
;
53 assert(exe_name_fd
>= 0);
56 /* This takes ownership of exe_name_fd */
57 file
= fdopen(exe_name_fd
, "r");
59 safe_close(exe_name_fd
);
60 return log_error_errno(errno
, "Failed to create FILE object: %m");
63 /* Find the last line */
65 _cleanup_free_
char *t
= NULL
;
67 r
= read_line(file
, LONG_LINE_MAX
, &t
);
69 return log_error_errno(r
, "Failed to read from socket: %m");
73 free_and_replace(line
, t
);
76 /* We only treat "less" specially.
77 * Return true whenever option K is *not* set. */
78 r
= streq_ptr(line
, "less") && !strchr(less_opts
, 'K');
80 log_debug("Pager executable is \"%s\", options \"%s\", quit_on_interrupt: %s",
81 strnull(line
), less_opts
, yes_no(!r
));
85 void pager_open(PagerFlags flags
) {
86 _cleanup_close_pair_
int fd
[2] = EBADF_PAIR
, exe_name_pipe
[2] = EBADF_PAIR
;
87 _cleanup_strv_free_
char **pager_args
= NULL
;
88 _cleanup_free_
char *l
= NULL
;
89 const char *pager
, *less_opts
;
92 if (flags
& PAGER_DISABLE
)
98 if (terminal_is_dumb())
101 if (!is_main_thread())
102 return (void) log_error_errno(SYNTHETIC_ERRNO(EPERM
), "Pager invoked from wrong thread.");
104 pager
= getenv("SYSTEMD_PAGER");
106 pager
= getenv("PAGER");
109 pager_args
= strv_split(pager
, WHITESPACE
);
111 return (void) log_oom();
113 /* If the pager is explicitly turned off, honour it */
114 if (strv_isempty(pager_args
) || strv_equal(pager_args
, STRV_MAKE("cat")))
118 /* Determine and cache number of columns/lines before we spawn the pager so that we get the value from the
123 if (pipe2(fd
, O_CLOEXEC
) < 0)
124 return (void) log_error_errno(errno
, "Failed to create pager pipe: %m");
126 /* This is a pipe to feed the name of the executed pager binary into the parent */
127 if (pipe2(exe_name_pipe
, O_CLOEXEC
) < 0)
128 return (void) log_error_errno(errno
, "Failed to create exe_name pipe: %m");
130 /* Initialize a good set of less options */
131 less_opts
= getenv("SYSTEMD_LESS");
133 less_opts
= "FRSXMK";
134 if (flags
& PAGER_JUMP_TO_END
) {
135 l
= strjoin(less_opts
, " +G");
137 return (void) log_oom();
141 /* We set SIGINT as PR_DEATHSIG signal here, to match the "K" parameter we set in $LESS, which enables SIGINT behaviour. */
142 r
= safe_fork("(pager)", FORK_RESET_SIGNALS
|FORK_DEATHSIG_SIGINT
|FORK_RLIMIT_NOFILE_SAFE
|FORK_LOG
, &pager_pid
);
146 const char *less_charset
;
148 /* In the child start the pager */
150 if (dup2(fd
[0], STDIN_FILENO
) < 0) {
151 log_error_errno(errno
, "Failed to duplicate file descriptor to STDIN: %m");
157 if (setenv("LESS", less_opts
, 1) < 0) {
158 log_error_errno(errno
, "Failed to set environment variable LESS: %m");
162 /* Initialize a good charset for less. This is particularly important if we output UTF-8
164 less_charset
= getenv("SYSTEMD_LESSCHARSET");
165 if (!less_charset
&& is_locale_utf8())
166 less_charset
= "utf-8";
168 setenv("LESSCHARSET", less_charset
, 1) < 0) {
169 log_error_errno(errno
, "Failed to set environment variable LESSCHARSET: %m");
173 /* People might invoke us from sudo, don't needlessly allow less to be a way to shell out
174 * privileged stuff. If the user set $SYSTEMD_PAGERSECURE, trust their configuration of the
175 * pager. If they didn't, use secure mode when under euid is changed. If $SYSTEMD_PAGERSECURE
176 * wasn't explicitly set, and we autodetect the need for secure mode, only use the pager we
177 * know to be good. */
178 int use_secure_mode
= secure_getenv_bool("SYSTEMD_PAGERSECURE");
179 bool trust_pager
= use_secure_mode
>= 0;
180 if (use_secure_mode
== -ENXIO
) {
183 r
= sd_pid_get_owner_uid(0, &uid
);
185 log_debug_errno(r
, "sd_pid_get_owner_uid() failed, enabling pager secure mode: %m");
187 use_secure_mode
= r
< 0 || uid
!= geteuid();
189 } else if (use_secure_mode
< 0) {
190 log_warning_errno(use_secure_mode
, "Unable to parse $SYSTEMD_PAGERSECURE, assuming true: %m");
191 use_secure_mode
= true;
194 /* We generally always set variables used by less, even if we end up using a different pager.
195 * They shouldn't hurt in any case, and ideally other pagers would look at them too. */
196 r
= set_unset_env("LESSSECURE", use_secure_mode
? "1" : NULL
, true);
198 log_error_errno(r
, "Failed to adjust environment variable LESSSECURE: %m");
202 if (trust_pager
&& pager_args
) { /* The pager config might be set globally, and we cannot
203 * know if the user adjusted it to be appropriate for the
204 * secure mode. Thus, start the pager specified through
205 * envvars only when $SYSTEMD_PAGERSECURE was explicitly set
207 r
= loop_write(exe_name_pipe
[1], pager_args
[0], strlen(pager_args
[0]) + 1);
209 log_error_errno(r
, "Failed to write pager name to socket: %m");
213 execvp(pager_args
[0], pager_args
);
214 log_full_errno(errno
== ENOENT
? LOG_DEBUG
: LOG_WARNING
, errno
,
215 "Failed to execute '%s', using fallback pagers: %m", pager_args
[0]);
218 /* Debian's alternatives command for pagers is called 'pager'. Note that we do not call
219 * sensible-pagers here, since that is just a shell script that implements a logic that is
220 * similar to this one anyway, but is Debian-specific. */
221 static const char* pagers
[] = { "pager", "less", "more", "(built-in)" };
223 for (unsigned i
= 0; i
< ELEMENTSOF(pagers
); i
++) {
224 /* Only less (and our trivial fallback) implement secure mode right now. */
225 if (use_secure_mode
&& !STR_IN_SET(pagers
[i
], "less", "(built-in)"))
228 r
= loop_write(exe_name_pipe
[1], pagers
[i
], strlen(pagers
[i
]) + 1);
230 log_error_errno(r
, "Failed to write pager name to socket: %m");
234 if (i
< ELEMENTSOF(pagers
) - 1) {
235 execlp(pagers
[i
], pagers
[i
], NULL
);
236 log_full_errno(errno
== ENOENT
? LOG_DEBUG
: LOG_WARNING
, errno
,
237 "Failed to execute '%s', will try '%s' next: %m", pagers
[i
], pagers
[i
+1]);
239 /* Close pipe to signal the parent to start sending data */
240 safe_close_pair(exe_name_pipe
);
242 assert_not_reached();
247 /* Return in the parent */
248 stored_stdout
= fcntl(STDOUT_FILENO
, F_DUPFD_CLOEXEC
, 3);
249 if (dup2(fd
[1], STDOUT_FILENO
) < 0) {
250 stored_stdout
= safe_close(stored_stdout
);
251 return (void) log_error_errno(errno
, "Failed to duplicate pager pipe: %m");
253 stdout_redirected
= true;
255 stored_stderr
= fcntl(STDERR_FILENO
, F_DUPFD_CLOEXEC
, 3);
256 if (dup2(fd
[1], STDERR_FILENO
) < 0) {
257 stored_stderr
= safe_close(stored_stderr
);
258 return (void) log_error_errno(errno
, "Failed to duplicate pager pipe: %m");
260 stderr_redirected
= true;
262 exe_name_pipe
[1] = safe_close(exe_name_pipe
[1]);
264 r
= no_quit_on_interrupt(TAKE_FD(exe_name_pipe
[0]), less_opts
);
266 (void) ignore_signals(SIGINT
);
269 void pager_close(void) {
274 /* Inform pager that we are done */
275 (void) fflush(stdout
);
276 if (stdout_redirected
)
277 if (stored_stdout
< 0 || dup2(stored_stdout
, STDOUT_FILENO
) < 0)
278 (void) close(STDOUT_FILENO
);
279 stored_stdout
= safe_close(stored_stdout
);
280 (void) fflush(stderr
);
281 if (stderr_redirected
)
282 if (stored_stderr
< 0 || dup2(stored_stderr
, STDERR_FILENO
) < 0)
283 (void) close(STDERR_FILENO
);
284 stored_stderr
= safe_close(stored_stderr
);
285 stdout_redirected
= stderr_redirected
= false;
287 (void) kill(pager_pid
, SIGCONT
);
288 (void) wait_for_terminate(TAKE_PID(pager_pid
), NULL
);
292 bool pager_have(void) {
293 return pager_pid
> 0;
296 int show_man_page(const char *desc
, bool null_stdio
) {
297 const char *args
[4] = { "man", NULL
, NULL
, NULL
};
305 if (desc
[k
-1] == ')')
306 e
= strrchr(desc
, '(');
309 char *page
= NULL
, *section
= NULL
;
311 page
= strndupa_safe(desc
, e
- desc
);
312 section
= strndupa_safe(e
+ 1, desc
+ k
- e
- 2);
319 r
= safe_fork("(man)", FORK_RESET_SIGNALS
|FORK_DEATHSIG_SIGTERM
|(null_stdio
? FORK_REARRANGE_STDIO
: 0)|FORK_RLIMIT_NOFILE_SAFE
|FORK_LOG
, &pid
);
324 execvp(args
[0], (char**) args
);
325 log_error_errno(errno
, "Failed to execute man: %m");
329 return wait_for_terminate_and_check(NULL
, pid
, 0);