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    Contents of /trunk/mkinitrd-magellan/busybox/libbb/update_passwd.c

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    Revision 816 - (show annotations) (download)
    Fri Apr 24 18:33:46 2009 UTC (15 years, 1 month ago) by niro
    File MIME type: text/plain
    File size: 3877 byte(s) 
    -updated to busybox-1.13.4
    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
    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
    39 int FAST_FUNC 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;
    46 char *fnamesfx;
    47 char *sfx_char;
    48 unsigned user_len;
    49 int old_fd;
    50 int new_fd;
    51 int i;
    52 int cnt = 0;
    53 int ret = -1; /* failure */
    54
    55 filename = xmalloc_follow_symlinks(filename);
    56 if (filename == NULL)
    57 return -1;
    58
    59 check_selinux_update_passwd(username);
    60
    61 /* New passwd file, "/etc/passwd+" for now */
    62 fnamesfx = xasprintf("%s+", filename);
    63 sfx_char = &fnamesfx[strlen(fnamesfx)-1];
    64 username = xasprintf("%s:", username);
    65 user_len = strlen(username);
    66
    67 old_fp = fopen(filename, "r+");
    68 if (!old_fp)
    69 goto free_mem;
    70 old_fd = fileno(old_fp);
    71
    72 selinux_preserve_fcontext(old_fd);
    73
    74 /* Try to create "/etc/passwd+". Wait if it exists. */
    75 i = 30;
    76 do {
    77 // FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
    78 new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600);
    79 if (new_fd >= 0) goto created;
    80 if (errno != EEXIST) break;
    81 usleep(100000); /* 0.1 sec */
    82 } while (--i);
    83 bb_perror_msg("cannot create '%s'", fnamesfx);
    84 goto close_old_fp;
    85
    86 created:
    87 if (!fstat(old_fd, &sb)) {
    88 fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
    89 fchown(new_fd, sb.st_uid, sb.st_gid);
    90 }
    91 new_fp = fdopen(new_fd, "w");
    92 if (!new_fp) {
    93 close(new_fd);
    94 goto unlink_new;
    95 }
    96
    97 /* Backup file is "/etc/passwd-" */
    98 *sfx_char = '-';
    99 /* Delete old backup */
    100 i = (unlink(fnamesfx) && errno != ENOENT);
    101 /* Create backup as a hardlink to current */
    102 if (i || link(filename, fnamesfx))
    103 bb_perror_msg("warning: cannot create backup copy '%s'", fnamesfx);
    104 *sfx_char = '+';
    105
    106 /* Lock the password file before updating */
    107 lock.l_type = F_WRLCK;
    108 lock.l_whence = SEEK_SET;
    109 lock.l_start = 0;
    110 lock.l_len = 0;
    111 if (fcntl(old_fd, F_SETLK, &lock) < 0)
    112 bb_perror_msg("warning: cannot lock '%s'", filename);
    113 lock.l_type = F_UNLCK;
    114
    115 /* Read current password file, write updated /etc/passwd+ */
    116 while (1) {
    117 char *line = xmalloc_fgets(old_fp);
    118 if (!line) break; /* EOF/error */
    119 if (strncmp(username, line, user_len) == 0) {
    120 /* we have a match with "username:"... */
    121 const char *cp = line + user_len;
    122 /* now cp -> old passwd, skip it: */
    123 cp = strchrnul(cp, ':');
    124 /* now cp -> ':' after old passwd or -> "" */
    125 fprintf(new_fp, "%s%s%s", username, new_pw, cp);
    126 cnt++;
    127 } else
    128 fputs(line, new_fp);
    129 free(line);
    130 }
    131 fcntl(old_fd, F_SETLK, &lock);
    132
    133 /* We do want all of them to execute, thus | instead of || */
    134 if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
    135 || rename(fnamesfx, filename)
    136 ) {
    137 /* At least one of those failed */
    138 goto unlink_new;
    139 }
    140 ret = cnt; /* whee, success! */
    141
    142 unlink_new:
    143 if (ret < 0) unlink(fnamesfx);
    144
    145 close_old_fp:
    146 fclose(old_fp);
    147
    148 free_mem:
    149 free(fnamesfx);
    150 free((char *)filename);
    151 free((char *)username);
    152 return ret;
    153 }