Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 1 | /* vi: set sw=4 ts=4: */ |
| 2 | /* |
| 3 | * update_passwd |
| 4 | * |
| 5 | * update_passwd is a common function for passwd and chpasswd applets; |
| 6 | * it is responsible for updating password file (i.e. /etc/passwd or |
| 7 | * /etc/shadow) for a given user and password. |
| 8 | * |
| 9 | * Moved from loginutils/passwd.c by Alexander Shishkin <virtuoso@slind.org> |
| 10 | */ |
| 11 | |
| 12 | #include "libbb.h" |
| 13 | |
Denis Vlasenko | 2edbc2a | 2007-10-20 02:00:49 +0000 | [diff] [blame^] | 14 | #if ENABLE_SELINUX |
| 15 | static void check_selinux_update_passwd(const char *username) |
| 16 | { |
| 17 | security_context_t context; |
| 18 | char *seuser; |
| 19 | |
| 20 | if (getuid() != (uid_t)0 || is_selinux_enabled() == 0) |
| 21 | return; /* No need to check */ |
| 22 | |
| 23 | if (getprevcon_raw(&context) < 0) |
| 24 | bb_perror_msg_and_die("getprevcon failed"); |
| 25 | seuser = strtok(context, ":"); |
| 26 | if (!seuser) |
| 27 | bb_error_msg_and_die("invalid context '%s'", context); |
| 28 | if (strcmp(seuser, username) != 0) { |
| 29 | if (checkPasswdAccess(PASSWD__PASSWD) != 0) |
| 30 | bb_error_msg_and_die("SELinux: access denied"); |
| 31 | } |
| 32 | if (ENABLE_FEATURE_CLEAN_UP) |
| 33 | freecon(context); |
| 34 | } |
| 35 | #else |
| 36 | #define check_selinux_update_passwd(username) ((void)0) |
| 37 | #endif |
| 38 | |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 39 | int update_passwd(const char *filename, const char *username, |
| 40 | const char *new_pw) |
| 41 | { |
| 42 | struct stat sb; |
| 43 | struct flock lock; |
| 44 | FILE *old_fp; |
| 45 | FILE *new_fp; |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 46 | char *fnamesfx; |
| 47 | char *sfx_char; |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 48 | unsigned user_len; |
| 49 | int old_fd; |
| 50 | int new_fd; |
| 51 | int i; |
| 52 | int cnt = 0; |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 53 | int ret = -1; /* failure */ |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 54 | |
Denis Vlasenko | 2edbc2a | 2007-10-20 02:00:49 +0000 | [diff] [blame^] | 55 | check_selinux_update_passwd(username); |
| 56 | |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 57 | /* New passwd file, "/etc/passwd+" for now */ |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 58 | fnamesfx = xasprintf("%s+", filename); |
| 59 | sfx_char = &fnamesfx[strlen(fnamesfx)-1]; |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 60 | username = xasprintf("%s:", username); |
| 61 | user_len = strlen(username); |
| 62 | |
| 63 | old_fp = fopen(filename, "r+"); |
| 64 | if (!old_fp) |
| 65 | goto free_mem; |
| 66 | old_fd = fileno(old_fp); |
| 67 | |
Denis Vlasenko | 2edbc2a | 2007-10-20 02:00:49 +0000 | [diff] [blame^] | 68 | selinux_preserve_fcontext(old_fd); |
| 69 | |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 70 | /* Try to create "/etc/passwd+". Wait if it exists. */ |
| 71 | i = 30; |
| 72 | do { |
| 73 | // FIXME: on last iteration try w/o O_EXCL but with O_TRUNC? |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 74 | new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600); |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 75 | if (new_fd >= 0) goto created; |
| 76 | if (errno != EEXIST) break; |
| 77 | usleep(100000); /* 0.1 sec */ |
| 78 | } while (--i); |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 79 | bb_perror_msg("cannot create '%s'", fnamesfx); |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 80 | goto close_old_fp; |
| 81 | |
| 82 | created: |
| 83 | if (!fstat(old_fd, &sb)) { |
| 84 | fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */ |
| 85 | fchown(new_fd, sb.st_uid, sb.st_gid); |
| 86 | } |
| 87 | new_fp = fdopen(new_fd, "w"); |
| 88 | if (!new_fp) { |
| 89 | close(new_fd); |
| 90 | goto unlink_new; |
| 91 | } |
| 92 | |
| 93 | /* Backup file is "/etc/passwd-" */ |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 94 | *sfx_char = '-'; |
| 95 | /* Delete old backup */ |
| 96 | i = (unlink(fnamesfx) && errno != ENOENT); |
| 97 | /* Create backup as a hardlink to current */ |
| 98 | if (i || link(filename, fnamesfx)) |
| 99 | bb_perror_msg("warning: cannot create backup copy '%s'", fnamesfx); |
| 100 | *sfx_char = '+'; |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 101 | |
| 102 | /* Lock the password file before updating */ |
| 103 | lock.l_type = F_WRLCK; |
| 104 | lock.l_whence = SEEK_SET; |
| 105 | lock.l_start = 0; |
| 106 | lock.l_len = 0; |
| 107 | if (fcntl(old_fd, F_SETLK, &lock) < 0) |
| 108 | bb_perror_msg("warning: cannot lock '%s'", filename); |
| 109 | lock.l_type = F_UNLCK; |
| 110 | |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 111 | /* Read current password file, write updated /etc/passwd+ */ |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 112 | while (1) { |
| 113 | char *line = xmalloc_fgets(old_fp); |
| 114 | if (!line) break; /* EOF/error */ |
| 115 | if (strncmp(username, line, user_len) == 0) { |
| 116 | /* we have a match with "username:"... */ |
| 117 | const char *cp = line + user_len; |
| 118 | /* now cp -> old passwd, skip it: */ |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 119 | cp = strchrnul(cp, ':'); |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 120 | /* now cp -> ':' after old passwd or -> "" */ |
| 121 | fprintf(new_fp, "%s%s%s", username, new_pw, cp); |
| 122 | cnt++; |
| 123 | } else |
| 124 | fputs(line, new_fp); |
| 125 | free(line); |
| 126 | } |
| 127 | fcntl(old_fd, F_SETLK, &lock); |
| 128 | |
| 129 | /* We do want all of them to execute, thus | instead of || */ |
| 130 | if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp)) |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 131 | || rename(fnamesfx, filename) |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 132 | ) { |
| 133 | /* At least one of those failed */ |
| 134 | goto unlink_new; |
| 135 | } |
| 136 | ret = cnt; /* whee, success! */ |
| 137 | |
| 138 | unlink_new: |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 139 | if (ret < 0) unlink(fnamesfx); |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 140 | |
| 141 | close_old_fp: |
| 142 | fclose(old_fp); |
| 143 | |
| 144 | free_mem: |
Denis Vlasenko | 557fb71 | 2007-07-21 13:25:28 +0000 | [diff] [blame] | 145 | free(fnamesfx); |
| 146 | free((char*)username); |
Denis Vlasenko | 1ec5eae | 2007-07-20 21:29:49 +0000 | [diff] [blame] | 147 | return ret; |
| 148 | } |