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#define _GNU_SOURCE
#include <dirent.h>
#include <errno.h>
#include <fcntl.h>
#include <stdbool.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/stat.h>
#include <unistd.h>
#include "bloom.h"
#define PAM_BLOOM_FILTER_DIR "/etc/security/pam_bloom/filters.d"
#define MAX_PASSWORD_LENGTH 4096
static bool
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(int fd, const char *filename)
{
struct stat st;
if (fstat(fd, &st) < 0) {
perror(filename);
return -1;
}
if (!S_ISREG(st.st_mode)) {
fprintf(stderr, "%s: not a regular file\n", filename);
return -1;
}
if (st.st_uid != 0) {
fprintf(stderr, "%s: not owned by root\n", filename);
return -1;
}
if (st.st_mode & (S_IWGRP | S_IWOTH)) {
fprintf(stderr, "%s: writable by group or others\n", filename);
return -1;
}
return 0;
}
static int
validate_filter_directory(int dirfd, const char *directory)
{
struct stat st;
if (fstat(dirfd, &st) < 0) {
perror(directory);
return -1;
}
if (!S_ISDIR(st.st_mode)) {
fprintf(stderr, "%s: not a directory\n", directory);
return -1;
}
if (st.st_uid != 0) {
fprintf(stderr, "%s: not owned by root\n", directory);
return -1;
}
if (st.st_mode & (S_IWGRP | S_IWOTH)) {
fprintf(stderr, "%s: writable by group or others\n", directory);
return -1;
}
return 0;
}
/*
* Returns:
* 1 password matched a filter
* 0 password did not match
* -1 error
*/
static int
check_filters(const char *directory, const char *password, size_t password_len)
{
int dirfd = open(directory, O_RDONLY | O_DIRECTORY | O_CLOEXEC | O_NOFOLLOW);
if (dirfd < 0) {
perror(directory);
return -1;
}
if (validate_filter_directory(dirfd, directory) < 0) {
close(dirfd);
return -1;
}
DIR *dir = fdopendir(dirfd);
if (dir == NULL) {
perror(directory);
close(dirfd);
return -1;
}
bool saw_filter = false;
int result = 0;
for (;;) {
errno = 0;
struct dirent *entry = readdir(dir);
if (entry == NULL) {
if (errno != 0) {
perror("readdir");
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) {
perror(entry->d_name);
result = -1;
break;
}
if (validate_filter_fd(fd, entry->d_name) < 0) {
close(fd);
result = -1;
break;
}
bloomfilter_mapped bf = {0};
bloom_error_t err = bloom_map_fd(&bf, fd);
if (err != BF_SUCCESS) {
fprintf(stderr, "%s: %s\n", entry->d_name, bloom_strerror(err));
close(fd);
result = -1;
break;
}
bool found = bloom_mapped_lookup(&bf, password, password_len);
if (found) {
fprintf(stderr, "password matches filter: %s\n",
(const char *)bf.header->name);
}
bloom_unmap(&bf);
close(fd);
if (found) {
result = 1;
break;
}
}
if (result == 0 && !saw_filter) {
fprintf(stderr, "warning: no Bloom filters found in %s\n", directory);
}
if (closedir(dir) != 0 && result == 0) {
perror("closedir");
result = -1;
}
return result;
}
int
main(void)
{
char password[MAX_PASSWORD_LENGTH + 2];
if (fgets(password, sizeof(password), stdin) == NULL) {
if (ferror(stdin)) {
perror("stdin");
} else {
fprintf(stderr, "no password provided\n");
}
return 2;
}
size_t len = strlen(password);
if (len > 0 && password[len - 1] == '\n') {
password[--len] = '\0';
}
if (len > 0 && password[len - 1] == '\r') {
password[--len] = '\0';
}
/*
* If fgets() filled the buffer without seeing a newline, reject the
* input rather than silently checking a truncated password.
*/
if (len == MAX_PASSWORD_LENGTH + 1) {
fprintf(stderr, "password exceeds maximum length\n");
return 2;
}
int result = check_filters(PAM_BLOOM_FILTER_DIR, password, len);
/* zero the plaintext password in memory. */
explicit_bzero(password, sizeof(password));
if (result < 0) return 2;
if (result > 0) return 1;
return 0;
}
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