diff options
Diffstat (limited to 'modules/pam_motd/pam_motd.c')
| -rw-r--r-- | modules/pam_motd/pam_motd.c | 445 |
1 files changed, 445 insertions, 0 deletions
diff --git a/modules/pam_motd/pam_motd.c b/modules/pam_motd/pam_motd.c new file mode 100644 index 0000000..6ac8cba --- /dev/null +++ b/modules/pam_motd/pam_motd.c @@ -0,0 +1,445 @@ +/* + * pam_motd module + * + * Modified for pam_motd by Ben Collins <bcollins@debian.org> + * Written by Michael K. Johnson <johnsonm@redhat.com> 1996/10/24 + */ + +#include "config.h" + +#include <stdio.h> +#include <string.h> +#include <stdlib.h> +#include <unistd.h> +#include <fcntl.h> +#include <dirent.h> +#include <sys/types.h> +#include <sys/stat.h> +#include <pwd.h> +#include <syslog.h> +#include <errno.h> + +#include <security/_pam_macros.h> +#include <security/pam_ext.h> +#include <security/pam_modules.h> +#include <security/pam_modutil.h> +#include "pam_inline.h" + +#define DEFAULT_MOTD "/etc/motd:/run/motd:/usr/lib/motd" +#define DEFAULT_MOTD_D "/etc/motd.d:/run/motd.d:/usr/lib/motd.d" + +/* --- session management functions (only) --- */ + +int +pam_sm_close_session (pam_handle_t *pamh UNUSED, int flags UNUSED, + int argc UNUSED, const char **argv UNUSED) +{ + return PAM_IGNORE; +} + +static const char default_motd[] = DEFAULT_MOTD; +static const char default_motd_dir[] = DEFAULT_MOTD_D; + +static void try_to_display_fd(pam_handle_t *pamh, int fd) +{ + struct stat st; + char *mtmp = NULL; + + /* fill in message buffer with contents of motd */ + if ((fstat(fd, &st) < 0) || !st.st_size || st.st_size > 0x10000) + return; + + if (!(mtmp = malloc(st.st_size+1))) + return; + + if (pam_modutil_read(fd, mtmp, st.st_size) == st.st_size) { + if (mtmp[st.st_size-1] == '\n') + mtmp[st.st_size-1] = '\0'; + else + mtmp[st.st_size] = '\0'; + + pam_info (pamh, "%s", mtmp); + } + + _pam_drop(mtmp); +} + +/* + * Split a DELIM-separated string ARG into an array. + * Outputs a newly allocated array of strings OUT_ARG_SPLIT + * and the number of strings OUT_NUM_STRS. + * Returns 0 in case of error, 1 in case of success. + */ +static int pam_split_string(const pam_handle_t *pamh, char *arg, char delim, + char ***out_arg_split, unsigned int *out_num_strs) +{ + char *arg_extracted = NULL; + const char *arg_ptr = arg; + char **arg_split = NULL; + char delim_str[2]; + unsigned int i = 0; + unsigned int num_strs = 0; + int retval = 0; + + delim_str[0] = delim; + delim_str[1] = '\0'; + + if (arg == NULL) { + goto out; + } + + while (arg_ptr != NULL) { + num_strs++; + arg_ptr = strchr(arg_ptr + sizeof(const char), delim); + } + + arg_split = calloc(num_strs, sizeof(*arg_split)); + if (arg_split == NULL) { + pam_syslog(pamh, LOG_CRIT, "failed to allocate string array"); + goto out; + } + + arg_extracted = strtok_r(arg, delim_str, &arg); + while (arg_extracted != NULL && i < num_strs) { + arg_split[i++] = arg_extracted; + arg_extracted = strtok_r(NULL, delim_str, &arg); + } + + retval = 1; + + out: + *out_num_strs = num_strs; + *out_arg_split = arg_split; + + return retval; +} + +/* Join A_STR and B_STR, inserting a "/" between them if one is not already trailing + * in A_STR or beginning B_STR. A pointer to a newly allocated string holding the + * joined string is returned in STRP_OUT. + * Returns -1 in case of error, or the number of bytes in the joined string in + * case of success. */ +static int join_dir_strings(char **strp_out, const char *a_str, const char *b_str) +{ + int has_sep = 0; + int retval = -1; + char *join_strp = NULL; + + if (strp_out == NULL || a_str == NULL || b_str == NULL) { + goto out; + } + if (strlen(a_str) == 0) { + goto out; + } + + has_sep = (a_str[strlen(a_str) - 1] == '/') || (b_str[0] == '/'); + + retval = asprintf(&join_strp, "%s%s%s", a_str, + (has_sep == 1) ? "" : "/", b_str); + + if (retval < 0) { + goto out; + } + + *strp_out = join_strp; + + out: + return retval; +} + +static int compare_strings(const void *a, const void *b) +{ + const char *a_str = *(const char * const *)a; + const char *b_str = *(const char * const *)b; + + if (a_str == NULL && b_str == NULL) { + return 0; + } + else if (a_str == NULL) { + return -1; + } + else if (b_str == NULL) { + return 1; + } + else { + return strcmp(a_str, b_str); + } +} + +static int filter_dirents(const struct dirent *d) +{ + return (d->d_type == DT_REG || d->d_type == DT_LNK); +} + +static void try_to_display_directories_with_overrides(pam_handle_t *pamh, + char **motd_dir_path_split, unsigned int num_motd_dirs, int report_missing) +{ + struct dirent ***dirscans = NULL; + unsigned int *dirscans_sizes = NULL; + unsigned int dirscans_size_total = 0; + char **dirnames_all = NULL; + unsigned int i; + int i_dirnames = 0; + + if (pamh == NULL || motd_dir_path_split == NULL) { + goto out; + } + if (num_motd_dirs < 1) { + goto out; + } + + if ((dirscans = calloc(num_motd_dirs, sizeof(*dirscans))) == NULL) { + pam_syslog(pamh, LOG_CRIT, "failed to allocate dirent arrays"); + goto out; + } + if ((dirscans_sizes = calloc(num_motd_dirs, sizeof(*dirscans_sizes))) == NULL) { + pam_syslog(pamh, LOG_CRIT, "failed to allocate dirent array sizes"); + goto out; + } + + for (i = 0; i < num_motd_dirs; i++) { + int rv; + rv = scandir(motd_dir_path_split[i], &(dirscans[i]), + filter_dirents, alphasort); + if (rv < 0) { + if (errno != ENOENT || report_missing) { + pam_syslog(pamh, LOG_ERR, "error scanning directory %s: %m", + motd_dir_path_split[i]); + } + } else { + dirscans_sizes[i] = rv; + } + dirscans_size_total += dirscans_sizes[i]; + } + + if (dirscans_size_total == 0) + goto out; + + /* Allocate space for all file names found in the directories, including duplicates. */ + if ((dirnames_all = calloc(dirscans_size_total, sizeof(*dirnames_all))) == NULL) { + pam_syslog(pamh, LOG_CRIT, "failed to allocate dirname array"); + goto out; + } + + for (i = 0; i < num_motd_dirs; i++) { + unsigned int j; + + for (j = 0; j < dirscans_sizes[i]; j++) { + dirnames_all[i_dirnames] = dirscans[i][j]->d_name; + i_dirnames++; + } + } + + qsort(dirnames_all, dirscans_size_total, + sizeof(const char *), compare_strings); + + for (i = 0; i < dirscans_size_total; i++) { + unsigned int j; + + if (dirnames_all[i] == NULL) { + continue; + } + + /* Skip duplicate file names. */ + if (i > 0 && strcmp(dirnames_all[i], dirnames_all[i - 1]) == 0) { + continue; + } + + for (j = 0; j < num_motd_dirs; j++) { + char *abs_path = NULL; + int fd; + + if (join_dir_strings(&abs_path, motd_dir_path_split[j], + dirnames_all[i]) < 0 || abs_path == NULL) { + continue; + } + + fd = open(abs_path, O_RDONLY, 0); + _pam_drop(abs_path); + + if (fd >= 0) { + try_to_display_fd(pamh, fd); + close(fd); + + /* We displayed a file, skip to the next file name. */ + break; + } + } + } + + out: + _pam_drop(dirnames_all); + if (dirscans_sizes != NULL) { + for (i = 0; i < num_motd_dirs; i++) { + unsigned int j; + + for (j = 0; j < dirscans_sizes[i]; j++) + _pam_drop(dirscans[i][j]); + _pam_drop(dirscans[i]); + } + _pam_drop(dirscans_sizes); + } + _pam_drop(dirscans); +} + +static int drop_privileges(pam_handle_t *pamh, struct pam_modutil_privs *privs) +{ + struct passwd *pw; + const char *username; + int retval; + + retval = pam_get_user(pamh, &username, NULL); + + if (retval == PAM_SUCCESS) { + pw = pam_modutil_getpwnam (pamh, username); + } else { + return PAM_SESSION_ERR; + } + + if (pw == NULL || pam_modutil_drop_priv(pamh, privs, pw)) { + return PAM_SESSION_ERR; + } + + return PAM_SUCCESS; +} + +static int try_to_display(pam_handle_t *pamh, char **motd_path_split, + unsigned int num_motd_paths, + char **motd_dir_path_split, + unsigned int num_motd_dir_paths, int report_missing) +{ + PAM_MODUTIL_DEF_PRIVS(privs); + + if (drop_privileges(pamh, &privs) != PAM_SUCCESS) { + pam_syslog(pamh, LOG_ERR, "Unable to drop privileges"); + return PAM_SESSION_ERR; + } + + if (motd_path_split != NULL) { + unsigned int i; + + for (i = 0; i < num_motd_paths; i++) { + int fd = open(motd_path_split[i], O_RDONLY, 0); + + if (fd >= 0) { + try_to_display_fd(pamh, fd); + close(fd); + + /* We found and displayed a file, + * move onto next filename. + */ + break; + } + } + } + + if (motd_dir_path_split != NULL) { + try_to_display_directories_with_overrides(pamh, + motd_dir_path_split, + num_motd_dir_paths, + report_missing); + } + + if (pam_modutil_regain_priv(pamh, &privs)) { + pam_syslog(pamh, LOG_ERR, "Unable to regain privileges"); + return PAM_SESSION_ERR; + } + + return PAM_SUCCESS; +} + +int pam_sm_open_session(pam_handle_t *pamh, int flags, + int argc, const char **argv) +{ + int retval = PAM_IGNORE; + const char *motd_path = NULL; + char *motd_path_copy = NULL; + unsigned int num_motd_paths = 0; + char **motd_path_split = NULL; + const char *motd_dir_path = NULL; + char *motd_dir_path_copy = NULL; + unsigned int num_motd_dir_paths = 0; + char **motd_dir_path_split = NULL; + int report_missing; + + if (flags & PAM_SILENT) { + return retval; + } + + for (; argc-- > 0; ++argv) { + const char *str; + if ((str = pam_str_skip_prefix(*argv, "motd=")) != NULL) { + + motd_path = str; + if (*motd_path != '\0') { + D(("set motd path: %s", motd_path)); + } else { + motd_path = NULL; + pam_syslog(pamh, LOG_ERR, + "motd= specification missing argument - ignored"); + } + } + else if ((str = pam_str_skip_prefix(*argv, "motd_dir=")) != NULL) { + + motd_dir_path = str; + if (*motd_dir_path != '\0') { + D(("set motd.d path: %s", motd_dir_path)); + } else { + motd_dir_path = NULL; + pam_syslog(pamh, LOG_ERR, + "motd_dir= specification missing argument - ignored"); + } + } + else + pam_syslog(pamh, LOG_ERR, "unknown option: %s", *argv); + } + + if (motd_path == NULL && motd_dir_path == NULL) { + motd_path = default_motd; + motd_dir_path = default_motd_dir; + report_missing = 0; + } else { + report_missing = 1; + } + + if (motd_path != NULL) { + motd_path_copy = strdup(motd_path); + } + + if (motd_path_copy != NULL) { + if (pam_split_string(pamh, motd_path_copy, ':', + &motd_path_split, &num_motd_paths) == 0) { + goto out; + } + } + + if (motd_dir_path != NULL) { + motd_dir_path_copy = strdup(motd_dir_path); + } + + if (motd_dir_path_copy != NULL) { + if (pam_split_string(pamh, motd_dir_path_copy, ':', + &motd_dir_path_split, &num_motd_dir_paths) == 0) { + goto out; + } + } + + retval = try_to_display(pamh, motd_path_split, num_motd_paths, + motd_dir_path_split, num_motd_dir_paths, + report_missing); + + out: + _pam_drop(motd_path_copy); + _pam_drop(motd_path_split); + _pam_drop(motd_dir_path_copy); + _pam_drop(motd_dir_path_split); + + if (retval == PAM_SUCCESS) { + retval = pam_putenv(pamh, "MOTD_SHOWN=pam"); + return retval == PAM_SUCCESS ? PAM_IGNORE : retval; + } else { + return retval; + } +} + +/* end of module definition */ |