login: define shell to log in to with -s or --shell

The -s and --shell options allow a user to define a shell
to log in to other than the one defined it the passwd entry
or _PATH_BSHELL.

Addresses: #3855
Signed-off-by: Christian Goeschel Ndjomouo <cgoesc2@wgu.edu>

diff --git a/login-utils/login.c b/login-utils/login.c
index 402e178201e45f943a0088f3d251508e57615ff6..3cd1d528bed6ce93d017a9f5697cfa94b4dd20e1 100644 (file)
--- a/login-utils/login.c
+++ b/login-utils/login.c
@@ -111,6 +111,8 @@ struct login_context {
        const char      *tty_number;    /* end of the tty_path */
        mode_t          tty_mode;       /* chmod() mode */
 
+       char            *shell_arg;     /* command line argument defining the login shell */
+
        const char      *username;      /* points to PAM, pwd or cmd_username */
        char            *cmd_username;  /* username specified on command line */
 
@@ -1282,17 +1284,18 @@ static void init_remote_info(struct login_context *cxt, char *remotehost)
 static void __attribute__((__noreturn__)) usage(void)
 {
        fputs(USAGE_HEADER, stdout);
-       printf(_(" %s [-p] [-h <host>] [-H] [[-f] <username>]\n"), program_invocation_short_name);
+       printf(_(" %s [-p] [-s <shell>] [-h <host>] [-H] [[-f] <username>]\n"), program_invocation_short_name);
        fputs(USAGE_SEPARATOR, stdout);
        fputs(_("Begin a session on the system.\n"), stdout);
 
        fputs(USAGE_OPTIONS, stdout);
-       puts(_(" -p             do not destroy the environment"));
-       puts(_(" -f             skip a login authentication"));
-       puts(_(" -h <host>      hostname to be used for utmp logging"));
-       puts(_(" -H             suppress hostname in the login prompt"));
-       printf("     --help     %s\n", USAGE_OPTSTR_HELP);
-       printf(" -V, --version  %s\n", USAGE_OPTSTR_VERSION);
+       puts(_(" -p                  do not destroy the environment"));
+       puts(_(" -f                  skip a login authentication"));
+       puts(_(" -h <host>           hostname to be used for utmp logging"));
+       puts(_(" -H                  suppress hostname in the login prompt"));
+       puts(_(" -s, --shell <path>  define the shell to log in to"));
+       printf("     --help          %s\n", USAGE_OPTSTR_HELP);
+       printf(" -V, --version       %s\n", USAGE_OPTSTR_VERSION);
        printf(USAGE_MAN_TAIL("login(1)"));
        exit(EXIT_SUCCESS);
 }
@@ -1328,6 +1331,7 @@ static void initialize(int argc, char **argv, struct login_context *cxt)
        /* the only two longopts to satisfy UL standards */
        enum { HELP_OPTION = CHAR_MAX + 1 };
        const struct option longopts[] = {
+               {"shell", required_argument, NULL, 's'},
                {"help", no_argument, NULL, HELP_OPTION},
                {"version", no_argument, NULL, 'V'},
                {NULL, 0, NULL, 0}
@@ -1356,7 +1360,7 @@ static void initialize(int argc, char **argv, struct login_context *cxt)
 
        load_credentials(cxt);
 
-       while ((c = getopt_long(argc, argv, "fHh:pV", longopts, NULL)) != -1)
+       while ((c = getopt_long(argc, argv, "fHh:ps:V", longopts, NULL)) != -1)
                switch (c) {
                case 'f':
                        cxt->noauth = 1;
@@ -1379,6 +1383,10 @@ static void initialize(int argc, char **argv, struct login_context *cxt)
                        cxt->keep_env = 1;
                        break;
 
+               case 's':
+                       cxt->shell_arg = optarg;
+                       break;
+
                case 'V':
                        print_version(EXIT_SUCCESS);
                case HELP_OPTION:
@@ -1580,8 +1588,11 @@ int main(int argc, char **argv)
                exit(EXIT_FAILURE);
        }
 
-       if (pwd->pw_shell == NULL || *pwd->pw_shell == '\0')
+       if (cxt.shell_arg && *cxt.shell_arg != '\0') {
+               pwd->pw_shell = cxt.shell_arg;
+       } else if (pwd->pw_shell == NULL || *pwd->pw_shell == '\0') {
                pwd->pw_shell = _PATH_BSHELL;
+       }
 
        init_environ(&cxt);             /* init $HOME, $TERM ... */