Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 330 insertions, 0 deletions

diff --git a/src/shared/pager.c b/src/shared/pager.c
new file mode 100644
index 0000000..19deefa
--- /dev/null
+++ b/src/shared/pager.c
@@ -0,0 +1,330 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <errno.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/prctl.h>
+#include <unistd.h>
+
+#include "sd-login.h"
+
+#include "copy.h"
+#include "env-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "io-util.h"
+#include "locale-util.h"
+#include "log.h"
+#include "macro.h"
+#include "pager.h"
+#include "process-util.h"
+#include "rlimit-util.h"
+#include "signal-util.h"
+#include "string-util.h"
+#include "strv.h"
+#include "terminal-util.h"
+
+static pid_t pager_pid = 0;
+
+static int stored_stdout = -1;
+static int stored_stderr = -1;
+static bool stdout_redirected = false;
+static bool stderr_redirected = false;
+
+_noreturn_ static void pager_fallback(void) {
+        int r;
+
+        r = copy_bytes(STDIN_FILENO, STDOUT_FILENO, UINT64_MAX, 0);
+        if (r < 0) {
+                log_error_errno(r, "Internal pager failed: %m");
+                _exit(EXIT_FAILURE);
+        }
+
+        _exit(EXIT_SUCCESS);
+}
+
+static int no_quit_on_interrupt(int exe_name_fd, const char *less_opts) {
+        _cleanup_fclose_ FILE *file = NULL;
+        _cleanup_free_ char *line = NULL;
+        int r;
+
+        assert(exe_name_fd >= 0);
+        assert(less_opts);
+
+        /* This takes ownership of exe_name_fd */
+        file = fdopen(exe_name_fd, "r");
+        if (!file) {
+                safe_close(exe_name_fd);
+                return log_error_errno(errno, "Failed to create FILE object: %m");
+        }
+
+        /* Find the last line */
+        for (;;) {
+                _cleanup_free_ char *t = NULL;
+
+                r = read_line(file, LONG_LINE_MAX, &t);
+                if (r < 0)
+                        return log_error_errno(r, "Failed to read from socket: %m");
+                if (r == 0)
+                        break;
+
+                free_and_replace(line, t);
+        }
+
+        /* We only treat "less" specially.
+         * Return true whenever option K is *not* set. */
+        r = streq_ptr(line, "less") && !strchr(less_opts, 'K');
+
+        log_debug("Pager executable is \"%s\", options \"%s\", quit_on_interrupt: %s",
+                  strnull(line), less_opts, yes_no(!r));
+        return r;
+}
+
+void pager_open(PagerFlags flags) {
+        _cleanup_close_pair_ int fd[2] = EBADF_PAIR, exe_name_pipe[2] = EBADF_PAIR;
+        _cleanup_strv_free_ char **pager_args = NULL;
+        _cleanup_free_ char *l = NULL;
+        const char *pager, *less_opts;
+        int r;
+
+        if (flags & PAGER_DISABLE)
+                return;
+
+        if (pager_pid > 0)
+                return;
+
+        if (terminal_is_dumb())
+                return;
+
+        if (!is_main_thread())
+                return (void) log_error_errno(SYNTHETIC_ERRNO(EPERM), "Pager invoked from wrong thread.");
+
+        pager = getenv("SYSTEMD_PAGER");
+        if (!pager)
+                pager = getenv("PAGER");
+
+        if (pager) {
+                pager_args = strv_split(pager, WHITESPACE);
+                if (!pager_args)
+                        return (void) log_oom();
+
+                /* If the pager is explicitly turned off, honour it */
+                if (strv_isempty(pager_args) || strv_equal(pager_args, STRV_MAKE("cat")))
+                        return;
+        }
+
+        /* Determine and cache number of columns/lines before we spawn the pager so that we get the value from the
+         * actual tty */
+        (void) columns();
+        (void) lines();
+
+        if (pipe2(fd, O_CLOEXEC) < 0)
+                return (void) log_error_errno(errno, "Failed to create pager pipe: %m");
+
+        /* This is a pipe to feed the name of the executed pager binary into the parent */
+        if (pipe2(exe_name_pipe, O_CLOEXEC) < 0)
+                return (void) log_error_errno(errno, "Failed to create exe_name pipe: %m");
+
+        /* Initialize a good set of less options */
+        less_opts = getenv("SYSTEMD_LESS");
+        if (!less_opts)
+                less_opts = "FRSXMK";
+        if (flags & PAGER_JUMP_TO_END) {
+                l = strjoin(less_opts, " +G");
+                if (!l)
+                        return (void) log_oom();
+                less_opts = l;
+        }
+
+        /* We set SIGINT as PR_DEATHSIG signal here, to match the "K" parameter we set in $LESS, which enables SIGINT behaviour. */
+        r = safe_fork("(pager)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGINT|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pager_pid);
+        if (r < 0)
+                return;
+        if (r == 0) {
+                const char *less_charset;
+
+                /* In the child start the pager */
+
+                if (dup2(fd[0], STDIN_FILENO) < 0) {
+                        log_error_errno(errno, "Failed to duplicate file descriptor to STDIN: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                safe_close_pair(fd);
+
+                if (setenv("LESS", less_opts, 1) < 0) {
+                        log_error_errno(errno, "Failed to set environment variable LESS: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                /* Initialize a good charset for less. This is particularly important if we output UTF-8
+                 * characters. */
+                less_charset = getenv("SYSTEMD_LESSCHARSET");
+                if (!less_charset && is_locale_utf8())
+                        less_charset = "utf-8";
+                if (less_charset &&
+                    setenv("LESSCHARSET", less_charset, 1) < 0) {
+                        log_error_errno(errno, "Failed to set environment variable LESSCHARSET: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                /* People might invoke us from sudo, don't needlessly allow less to be a way to shell out
+                 * privileged stuff. If the user set $SYSTEMD_PAGERSECURE, trust their configuration of the
+                 * pager. If they didn't, use secure mode when under euid is changed. If $SYSTEMD_PAGERSECURE
+                 * wasn't explicitly set, and we autodetect the need for secure mode, only use the pager we
+                 * know to be good. */
+                int use_secure_mode = getenv_bool_secure("SYSTEMD_PAGERSECURE");
+                bool trust_pager = use_secure_mode >= 0;
+                if (use_secure_mode == -ENXIO) {
+                        uid_t uid;
+
+                        r = sd_pid_get_owner_uid(0, &uid);
+                        if (r < 0)
+                                log_debug_errno(r, "sd_pid_get_owner_uid() failed, enabling pager secure mode: %m");
+
+                        use_secure_mode = r < 0 || uid != geteuid();
+
+                } else if (use_secure_mode < 0) {
+                        log_warning_errno(use_secure_mode, "Unable to parse $SYSTEMD_PAGERSECURE, assuming true: %m");
+                        use_secure_mode = true;
+                }
+
+                /* We generally always set variables used by less, even if we end up using a different pager.
+                 * They shouldn't hurt in any case, and ideally other pagers would look at them too. */
+                r = set_unset_env("LESSSECURE", use_secure_mode ? "1" : NULL, true);
+                if (r < 0) {
+                        log_error_errno(r, "Failed to adjust environment variable LESSSECURE: %m");
+                        _exit(EXIT_FAILURE);
+                }
+
+                if (trust_pager && pager_args) { /* The pager config might be set globally, and we cannot
+                                                  * know if the user adjusted it to be appropriate for the
+                                                  * secure mode. Thus, start the pager specified through
+                                                  * envvars only when $SYSTEMD_PAGERSECURE was explicitly set
+                                                  * as well. */
+                        r = loop_write(exe_name_pipe[1], pager_args[0], strlen(pager_args[0]) + 1);
+                        if (r < 0) {
+                                log_error_errno(r, "Failed to write pager name to socket: %m");
+                                _exit(EXIT_FAILURE);
+                        }
+
+                        execvp(pager_args[0], pager_args);
+                        log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno,
+                                       "Failed to execute '%s', using fallback pagers: %m", pager_args[0]);
+                }
+
+                /* Debian's alternatives command for pagers is called 'pager'. Note that we do not call
+                 * sensible-pagers here, since that is just a shell script that implements a logic that is
+                 * similar to this one anyway, but is Debian-specific. */
+                static const char* pagers[] = { "pager", "less", "more", "(built-in)" };
+
+                for (unsigned i = 0; i < ELEMENTSOF(pagers); i++) {
+                        /* Only less (and our trivial fallback) implement secure mode right now. */
+                        if (use_secure_mode && !STR_IN_SET(pagers[i], "less", "(built-in)"))
+                                continue;
+
+                        r = loop_write(exe_name_pipe[1], pagers[i], strlen(pagers[i]) + 1);
+                        if (r < 0) {
+                                log_error_errno(r, "Failed to write pager name to socket: %m");
+                                _exit(EXIT_FAILURE);
+                        }
+
+                        if (i < ELEMENTSOF(pagers) - 1) {
+                                execlp(pagers[i], pagers[i], NULL);
+                                log_full_errno(errno == ENOENT ? LOG_DEBUG : LOG_WARNING, errno,
+                                               "Failed to execute '%s', will try '%s' next: %m", pagers[i], pagers[i+1]);
+                        } else {
+                                /* Close pipe to signal the parent to start sending data */
+                                safe_close_pair(exe_name_pipe);
+                                pager_fallback();
+                                assert_not_reached();
+                        }
+                }
+        }
+
+        /* Return in the parent */
+        stored_stdout = fcntl(STDOUT_FILENO, F_DUPFD_CLOEXEC, 3);
+        if (dup2(fd[1], STDOUT_FILENO) < 0) {
+                stored_stdout = safe_close(stored_stdout);
+                return (void) log_error_errno(errno, "Failed to duplicate pager pipe: %m");
+        }
+        stdout_redirected = true;
+
+        stored_stderr = fcntl(STDERR_FILENO, F_DUPFD_CLOEXEC, 3);
+        if (dup2(fd[1], STDERR_FILENO) < 0) {
+                stored_stderr = safe_close(stored_stderr);
+                return (void) log_error_errno(errno, "Failed to duplicate pager pipe: %m");
+        }
+        stderr_redirected = true;
+
+        exe_name_pipe[1] = safe_close(exe_name_pipe[1]);
+
+        r = no_quit_on_interrupt(TAKE_FD(exe_name_pipe[0]), less_opts);
+        if (r > 0)
+                (void) ignore_signals(SIGINT);
+}
+
+void pager_close(void) {
+
+        if (pager_pid <= 0)
+                return;
+
+        /* Inform pager that we are done */
+        (void) fflush(stdout);
+        if (stdout_redirected)
+                if (stored_stdout < 0 || dup2(stored_stdout, STDOUT_FILENO) < 0)
+                        (void) close(STDOUT_FILENO);
+        stored_stdout = safe_close(stored_stdout);
+        (void) fflush(stderr);
+        if (stderr_redirected)
+                if (stored_stderr < 0 || dup2(stored_stderr, STDERR_FILENO) < 0)
+                        (void) close(STDERR_FILENO);
+        stored_stderr = safe_close(stored_stderr);
+        stdout_redirected = stderr_redirected = false;
+
+        (void) kill(pager_pid, SIGCONT);
+        (void) wait_for_terminate(TAKE_PID(pager_pid), NULL);
+        pager_pid = 0;
+}
+
+bool pager_have(void) {
+        return pager_pid > 0;
+}
+
+int show_man_page(const char *desc, bool null_stdio) {
+        const char *args[4] = { "man", NULL, NULL, NULL };
+        char *e = NULL;
+        pid_t pid;
+        size_t k;
+        int r;
+
+        k = strlen(desc);
+
+        if (desc[k-1] == ')')
+                e = strrchr(desc, '(');
+
+        if (e) {
+                char *page = NULL, *section = NULL;
+
+                page = strndupa_safe(desc, e - desc);
+                section = strndupa_safe(e + 1, desc + k - e - 2);
+
+                args[1] = section;
+                args[2] = page;
+        } else
+                args[1] = desc;
+
+        r = safe_fork("(man)", FORK_RESET_SIGNALS|FORK_DEATHSIG_SIGTERM|(null_stdio ? FORK_REARRANGE_STDIO : 0)|FORK_RLIMIT_NOFILE_SAFE|FORK_LOG, &pid);
+        if (r < 0)
+                return r;
+        if (r == 0) {
+                /* Child */
+                execvp(args[0], (char**) args);
+                log_error_errno(errno, "Failed to execute man: %m");
+                _exit(EXIT_FAILURE);
+        }
+
+        return wait_for_terminate_and_check(NULL, pid, 0);
+}