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#define PAM_SM_PASSWORD
#include <security/pam_modules.h>
#include <security/pam_ext.h>
#include <dirent.h>
#include <stdbool.h>
#include <string.h>
#include <syslog.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>
#include <sys/stat.h>
#include "bloom.h"
#define PAM_BLOOM_FILTER_DIR "/etc/security/pam_bloom/filters.d"
static int
has_bloom_extension(const char *name)
{
size_t len = strlen(name);
return len > 6 &&
strcmp(name + len - 6, ".bloom") == 0;
}
static int
validate_filter_fd(pam_handle_t *pamh, int fd, const char *filename)
{
struct stat st;
if (fstat(fd, &st) < 0) {
pam_syslog(pamh, LOG_ERR, "unable to stat Bloom filter %s", filename);
return -1;
}
if (!S_ISREG(st.st_mode)) {
pam_syslog(pamh, LOG_ERR, "Bloom filter %s is not a regular file", filename);
return -1;
}
if (st.st_uid != 0) {
pam_syslog(pamh, LOG_ERR, "Bloom filter %s is not owned by root", filename);
return -1;
}
if (st.st_mode & (S_IWGRP | S_IWOTH)) {
pam_syslog(pamh, LOG_ERR, "Bloom filter %s is writable by group or others", filename);
return -1;
}
return 0;
}
static int
check_filter_fd(pam_handle_t *pamh, int fd, const char *filename, const char *password)
{
bloomfilter_mapped bf = {0};
bloom_error_t err = bloom_map_fd(&bf, fd);
if (err != BF_SUCCESS) {
pam_syslog(pamh, LOG_ERR,
"unable to map Bloom filter %s: %s", filename, bloom_strerror(err));
return -1;
}
bool found = bloom_mapped_lookup(&bf, password, strlen(password));
if (found) {
pam_error(pamh,
"Password rejected: it matches the %s filter.",
(const char *)bf.header->name);
}
bloom_unmap(&bf);
return found ? 1 : 0;
}
static int
validate_filter_directory(pam_handle_t *pamh, int dirfd, const char *directory)
{
struct stat st;
if (fstat(dirfd, &st) < 0) {
pam_syslog(pamh, LOG_ERR, "unable to stat Bloom filter directory %s", directory);
return -1;
}
if (!S_ISDIR(st.st_mode)) {
pam_syslog(pamh, LOG_ERR, "Bloom filter path %s is not a directory", directory);
return -1;
}
if (st.st_uid != 0) {
pam_syslog(pamh, LOG_ERR, "Bloom filter directory %s is not owned by root", directory);
return -1;
}
if (st.st_mode & (S_IWGRP | S_IWOTH)) {
pam_syslog(pamh, LOG_ERR,
"Bloom filter directory %s is writable by group or others", directory);
return -1;
}
return 0;
}
static int
check_filter_directory(pam_handle_t *pamh, const char *directory, const char *password)
{
int dirfd = open(directory, O_RDONLY | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
if (dirfd < 0) {
pam_syslog(pamh, LOG_ERR, "unable to open Bloom filter directory %s", directory);
return -1;
}
if (validate_filter_directory(pamh, dirfd, directory) < 0) {
close(dirfd);
return -1;
}
DIR *dir = fdopendir(dirfd);
if (dir == NULL) {
close(dirfd);
pam_syslog(pamh, LOG_ERR, "unable to read Bloom filter directory %s", directory);
return -1;
}
bool saw_filter = false;
int result = 0;
struct dirent *entry;
for (;;) {
errno = 0;
entry = readdir(dir);
if (entry == NULL) {
if (errno != 0) {
pam_syslog(pamh, LOG_ERR, "error reading Bloom filter directory %s", directory);
result = -1;
}
break;
}
if (!has_bloom_extension(entry->d_name)) {
continue;
}
saw_filter = true;
int fd = openat(dirfd, entry->d_name, O_RDONLY | O_CLOEXEC | O_NOFOLLOW);
if (fd < 0) {
pam_syslog(pamh, LOG_ERR, "unable to open Bloom filter %s", entry->d_name);
result = -1;
break;
}
if (validate_filter_fd(pamh, fd, entry->d_name) < 0) {
close(fd);
result = -1;
break;
}
result = check_filter_fd(pamh, fd, entry->d_name, password);
close(fd);
if (result != 0) {
break;
}
}
if (result == 0 && !saw_filter) {
pam_syslog(pamh, LOG_WARNING, "no Bloom filters found in directory %s", directory);
}
if (closedir(dir) != 0) {
pam_syslog(pamh, LOG_ERR, "error closing Bloom filter directory %s", directory);
if (result == 0) {
result = -1;
}
}
return result;
}
PAM_EXTERN int
pam_sm_chauthtok(pam_handle_t *pamh, int flags, int argc, const char **argv)
{
const char *filter_dir = PAM_BLOOM_FILTER_DIR;
bool dir_seen = false;
for (int i = 0; i < argc; i++) {
static const char prefix[] = "dir=";
if (strncmp(argv[i], prefix, sizeof(prefix) - 1) != 0) {
pam_syslog(pamh, LOG_ERR, "pam_bloom: unknown option: %s", argv[i]);
return PAM_SERVICE_ERR;
}
if (dir_seen) {
pam_syslog(pamh, LOG_ERR, "pam_bloom: duplicate dir= option");
return PAM_SERVICE_ERR;
}
dir_seen = true;
const char *value = argv[i] + sizeof(prefix) - 1;
if (*value == '\0') {
pam_syslog(pamh, LOG_ERR, "pam_bloom: empty dir= option");
return PAM_SERVICE_ERR;
}
filter_dir = value;
}
if (!(flags & PAM_UPDATE_AUTHTOK)) {
return PAM_SUCCESS;
}
const char *password = NULL;
int rc = pam_get_authtok(pamh, PAM_AUTHTOK, &password, NULL);
if (rc != PAM_SUCCESS || password == NULL) {
return PAM_AUTHTOK_ERR;
}
int result = check_filter_directory(pamh, filter_dir, password);
if (result < 0) return PAM_SERVICE_ERR;
if (result > 0) return PAM_AUTHTOK_ERR;
return PAM_SUCCESS;
}
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