crond: implement "SHELL=prog" in crontab. Export LOGNAME as POSIX wants

function                                             old     new   delta
fork_job                                             343     456    +113
load_crontab                                         688     777     +89
crond_main                                          1456    1434     -22
------------------------------------------------------------------------------
(add/remove: 0/0 grow/shrink: 2/1 up/down: 202/-22)           Total: 180 bytes

Signed-off-by: Denys Vlasenko <vda.linux@googlemail.com>

1 files changed, 48 insertions, 24 deletions

diff --git a/miscutils/crond.c b/miscutils/crond.c
index 210da5f47..3659b9a6f 100644
--- a/miscutils/crond.c
+++ b/miscutils/crond.c
@@ -104,6 +104,7 @@ typedef struct CronLine {
         int cl_empty_mail_size;         /* size of mail header only, 0 if no mailfile */
         char *cl_mailto;                /* whom to mail results, may be NULL */
 #endif
+        char *cl_shell;
         /* ordered by size, not in natural order. makes code smaller: */
         char cl_Dow[7];                 /* 0-6, beginning sunday */
         char cl_Mons[12];               /* 0-11 */
@@ -135,6 +136,8 @@ struct globals {
 #if SETENV_LEAKS
         char *env_var_user;
         char *env_var_home;
+        char *env_var_shell;
+        char *env_var_logname;
 #endif
 } FIX_ALIASING;
 #define G (*(struct globals*)&bb_common_bufsiz1)
@@ -397,6 +400,7 @@ static void load_crontab(const char *fileName)
 #if ENABLE_FEATURE_CROND_CALL_SENDMAIL
         char *mailTo = NULL;
 #endif
+        char *shell = NULL;
 
         delete_cronfile(fileName);
 
@@ -441,7 +445,12 @@ static void load_crontab(const char *fileName)
 #endif /* otherwise just ignore such lines */
                                 continue;
                         }
-//TODO: handle SHELL=, HOME= too? "man crontab" says:
+                        if (0 == strncmp(tokens[0], "SHELL=", 6)) {
+                                free(shell);
+                                shell = xstrdup(&tokens[0][6]);
+                                continue;
+                        }
+//TODO: handle HOME= too? "man crontab" says:
 //name = value
 //
 //where the spaces around the equal-sign (=) are optional, and any subsequent
@@ -453,6 +462,7 @@ static void load_crontab(const char *fileName)
 //SHELL is set to /bin/sh, and LOGNAME and HOME are set from the /etc/passwd
 //line of the crontab's owner. HOME and SHELL may be overridden by settings
 //in the crontab; LOGNAME may not.
+
                         /* check if a minimum of tokens is specified */
                         if (n < 6)
                                 continue;
@@ -472,9 +482,9 @@ static void load_crontab(const char *fileName)
                         /* copy mailto (can be NULL) */
                         line->cl_mailto = xstrdup(mailTo);
 #endif
+                        line->cl_shell = xstrdup(shell);
                         /* copy command */
                         line->cl_cmd = xstrdup(tokens[5]);
-                        log5(" command:%s", tokens[5]);
                         pline = &line->cl_next;
 //bb_error_msg("M[%s]F[%s][%s][%s][%s][%s][%s]", mailTo, tokens[0], tokens[1], tokens[2], tokens[3], tokens[4], tokens[5]);
                 }
@@ -484,6 +494,10 @@ static void load_crontab(const char *fileName)
                 G.cron_files = file;
         }
         config_close(parser);
+#if ENABLE_FEATURE_CROND_CALL_SENDMAIL
+        free(mailTo);
+#endif
+        free(shell);
 }
 
 static void process_cron_update_file(void)
@@ -555,19 +569,22 @@ static void safe_setenv(char **pvar_val, const char *var, const char *val)
 }
 #endif
 
-static void set_env_vars(struct passwd *pas)
+static void set_env_vars(struct passwd *pas, const char *shell)
 {
+        /* POSIX requires crond to set up at least HOME, LOGNAME, PATH, SHELL.
+         * We assume crond inherited suitable PATH.
+         */
 #if SETENV_LEAKS
+        safe_setenv(&G.env_var_logname, "LOGNAME", pas->pw_name);
         safe_setenv(&G.env_var_user, "USER", pas->pw_name);
         safe_setenv(&G.env_var_home, "HOME", pas->pw_dir);
-        /* if we want to set user's shell instead: */
-        /*safe_setenv(G.env_var_shell, "SHELL", pas->pw_shell);*/
+        safe_setenv(&G.env_var_shell, "SHELL", shell);
 #else
+        xsetenv("LOGNAME", pas->pw_name);
         xsetenv("USER", pas->pw_name);
         xsetenv("HOME", pas->pw_dir);
+        xsetenv("SHELL", shell);
 #endif
-        /* currently, we use constant one: */
-        /*setenv("SHELL", DEFAULT_SHELL, 1); - done earlier */
 }
 
 static void change_user(struct passwd *pas)
@@ -584,12 +601,11 @@ static void change_user(struct passwd *pas)
 #if ENABLE_FEATURE_CROND_CALL_SENDMAIL
 
 static pid_t
-fork_job(const char *user, int mailFd,
-                const char *prog,
-                const char *shell_cmd /* if NULL, we run sendmail */
-) {
-        smallint sv_logmode;
+fork_job(const char *user, int mailFd, CronLine *line, bool run_sendmail)
+{
         struct passwd *pas;
+        const char *shell, *prog;
+        smallint sv_logmode;
         pid_t pid;
 
         /* prepare things before vfork */
@@ -598,7 +614,11 @@ fork_job(const char *user, int mailFd,
                 bb_error_msg("can't get uid for %s", user);
                 goto err;
         }
-        set_env_vars(pas);
+
+        shell = line->cl_shell ? line->cl_shell : DEFAULT_SHELL;
+        prog = run_sendmail ? SENDMAIL : shell;
+
+        set_env_vars(pas, shell);
 
         sv_logmode = logmode;
         pid = vfork();
@@ -608,12 +628,15 @@ fork_job(const char *user, int mailFd,
                 change_user(pas);
                 log5("child running %s", prog);
                 if (mailFd >= 0) {
-                        xmove_fd(mailFd, shell_cmd ? 1 : 0);
+                        xmove_fd(mailFd, run_sendmail ? 0 : 1);
                         dup2(1, 2);
                 }
                 /* crond 3.0pl1-100 puts tasks in separate process groups */
                 bb_setpgrp();
-                execlp(prog, prog, (shell_cmd ? "-c" : SENDMAIL_ARGS), shell_cmd, (char *) NULL);
+                if (!run_sendmail)
+                        execlp(prog, prog, "-c", line->cl_cmd, (char *) NULL);
+                else
+                        execlp(prog, prog, SENDMAIL_ARGS, (char *) NULL);
                 /*
                  * I want this error message on stderr too,
                  * even if other messages go only to syslog:
@@ -662,7 +685,7 @@ static void start_one_job(const char *user, CronLine *line)
                 }
         }
 
-        line->cl_pid = fork_job(user, mailFd, DEFAULT_SHELL, line->cl_cmd);
+        line->cl_pid = fork_job(user, mailFd, line, /*sendmail?*/ 0);
         if (mailFd >= 0) {
                 if (line->cl_pid <= 0) {
                         unlink(mailFile);
@@ -718,13 +741,14 @@ static void process_finished_job(const char *user, CronLine *line)
         }
         line->cl_empty_mail_size = 0;
         /* if (line->cl_mailto) - always true if cl_empty_mail_size was nonzero */
-                line->cl_pid = fork_job(user, mailFd, SENDMAIL, NULL);
+                line->cl_pid = fork_job(user, mailFd, line, /*sendmail?*/ 1);
 }
 
 #else /* !ENABLE_FEATURE_CROND_CALL_SENDMAIL */
 
 static void start_one_job(const char *user, CronLine *line)
 {
+        const char *shell;
         struct passwd *pas;
         pid_t pid;
 
@@ -735,7 +759,8 @@ static void start_one_job(const char *user, CronLine *line)
         }
 
         /* Prepare things before vfork */
-        set_env_vars(pas);
+        shell = line->cl_shell ? line->cl_shell : DEFAULT_SHELL;
+        set_env_vars(pas, shell);
 
         /* Fork as the user in question and run program */
         pid = vfork();
@@ -743,11 +768,11 @@ static void start_one_job(const char *user, CronLine *line)
                 /* CHILD */
                 /* initgroups, setgid, setuid, and chdir to home or CRON_DIR */
                 change_user(pas);
-                log5("child running %s", DEFAULT_SHELL);
+                log5("child running %s", shell);
                 /* crond 3.0pl1-100 puts tasks in separate process groups */
                 bb_setpgrp();
-                execl(DEFAULT_SHELL, DEFAULT_SHELL, "-c", line->cl_cmd, (char *) NULL);
-                bb_error_msg_and_die("can't execute '%s' for user %s", DEFAULT_SHELL, user);
+                execl(shell, shell, "-c", line->cl_cmd, (char *) NULL);
+                bb_error_msg_and_die("can't execute '%s' for user %s", shell, user);
         }
         if (pid < 0) {
                 bb_perror_msg("vfork");
@@ -916,11 +941,10 @@ int crond_main(int argc UNUSED_PARAM, char **argv)
                 logmode = LOGMODE_SYSLOG;
         }
 
-        reopen_logfile_to_stderr();
+        //signal(SIGHUP, SIG_IGN); /* ? original crond dies on HUP... */
 
+        reopen_logfile_to_stderr();
         xchdir(G.crontab_dir_name);
-        //signal(SIGHUP, SIG_IGN); /* ? original crond dies on HUP... */
-        xsetenv("SHELL", DEFAULT_SHELL); /* once, for all future children */
         log8("crond (busybox "BB_VER") started, log level %d", G.log_level);
         rescan_crontab_dir();
         write_pidfile(CONFIG_PID_FILE_PATH "/crond.pid");