| 1 | /* vi: set sw=4 ts=4: */
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| 2 | /*
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| 3 | * update_passwd
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| 4 | *
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| 5 | * update_passwd is a common function for passwd and chpasswd applets;
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| 6 | * it is responsible for updating password file (i.e. /etc/passwd or
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| 7 | * /etc/shadow) for a given user and password.
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| 8 | *
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| 9 | * Moved from loginutils/passwd.c by Alexander Shishkin <virtuoso@slind.org>
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| 10 | *
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| 11 | * Modified to be able to add or delete users, groups and users to/from groups
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| 12 | * by Tito Ragusa <farmatito@tiscali.it>
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| 13 | *
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| 14 | * Licensed under GPLv2, see file LICENSE in this source tree.
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| 15 | */
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| 16 | #include "libbb.h"
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| 17 |
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| 18 | #if ENABLE_SELINUX
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| 19 | static void check_selinux_update_passwd(const char *username)
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| 20 | {
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| 21 | security_context_t context;
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| 22 | char *seuser;
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| 23 |
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| 24 | if (getuid() != (uid_t)0 || is_selinux_enabled() == 0)
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| 25 | return; /* No need to check */
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| 26 |
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| 27 | if (getprevcon_raw(&context) < 0)
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| 28 | bb_perror_msg_and_die("getprevcon failed");
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| 29 | seuser = strtok(context, ":");
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| 30 | if (!seuser)
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| 31 | bb_error_msg_and_die("invalid context '%s'", context);
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| 32 | if (strcmp(seuser, username) != 0) {
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| 33 | if (checkPasswdAccess(PASSWD__PASSWD) != 0)
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| 34 | bb_error_msg_and_die("SELinux: access denied");
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| 35 | }
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| 36 | if (ENABLE_FEATURE_CLEAN_UP)
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| 37 | freecon(context);
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| 38 | }
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| 39 | #else
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| 40 | # define check_selinux_update_passwd(username) ((void)0)
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| 41 | #endif
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| 42 |
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| 43 | /*
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| 44 | 1) add a user: update_passwd(FILE, USER, REMAINING_PWLINE, NULL)
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| 45 | only if CONFIG_ADDUSER=y and applet_name[0] == 'a' like in adduser
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| 46 |
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| 47 | 2) add a group: update_passwd(FILE, GROUP, REMAINING_GRLINE, NULL)
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| 48 | only if CONFIG_ADDGROUP=y and applet_name[0] == 'a' like in addgroup
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| 49 |
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| 50 | 3) add a user to a group: update_passwd(FILE, GROUP, NULL, MEMBER)
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| 51 | only if CONFIG_FEATURE_ADDUSER_TO_GROUP=y, applet_name[0] == 'a'
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| 52 | like in addgroup and member != NULL
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| 53 |
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| 54 | 4) delete a user: update_passwd(FILE, USER, NULL, NULL)
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| 55 |
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| 56 | 5) delete a group: update_passwd(FILE, GROUP, NULL, NULL)
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| 57 |
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| 58 | 6) delete a user from a group: update_passwd(FILE, GROUP, NULL, MEMBER)
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| 59 | only if CONFIG_FEATURE_DEL_USER_FROM_GROUP=y and member != NULL
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| 60 |
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| 61 | 7) change user's password: update_passwd(FILE, USER, NEW_PASSWD, NULL)
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| 62 | only if CONFIG_PASSWD=y and applet_name[0] == 'p' like in passwd
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| 63 | or if CONFIG_CHPASSWD=y and applet_name[0] == 'c' like in chpasswd
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| 64 |
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| 65 | This function does not validate the arguments fed to it
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| 66 | so the calling program should take care of that.
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| 67 |
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| 68 | Returns number of lines changed, or -1 on error.
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| 69 | */
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| 70 | int FAST_FUNC update_passwd(const char *filename,
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| 71 | const char *name,
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| 72 | const char *new_passwd,
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| 73 | const char *member)
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| 74 | {
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| 75 | #if !(ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP)
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| 76 | #define member NULL
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| 77 | #endif
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| 78 | struct stat sb;
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| 79 | struct flock lock;
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| 80 | FILE *old_fp;
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| 81 | FILE *new_fp;
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| 82 | char *fnamesfx;
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| 83 | char *sfx_char;
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| 84 | char *name_colon;
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| 85 | unsigned user_len;
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| 86 | int old_fd;
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| 87 | int new_fd;
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| 88 | int i;
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| 89 | int changed_lines;
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| 90 | int ret = -1; /* failure */
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| 91 | /* used as a bool: "are we modifying /etc/shadow?" */
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| 92 | #if ENABLE_FEATURE_SHADOWPASSWDS
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| 93 | const char *shadow = strstr(filename, "shadow");
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| 94 | #else
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| 95 | # define shadow NULL
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| 96 | #endif
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| 97 |
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| 98 | filename = xmalloc_follow_symlinks(filename);
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| 99 | if (filename == NULL)
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| 100 | return ret;
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| 101 |
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| 102 | check_selinux_update_passwd(name);
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| 103 |
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| 104 | /* New passwd file, "/etc/passwd+" for now */
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| 105 | fnamesfx = xasprintf("%s+", filename);
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| 106 | sfx_char = &fnamesfx[strlen(fnamesfx)-1];
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| 107 | name_colon = xasprintf("%s:", name);
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| 108 | user_len = strlen(name_colon);
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| 109 |
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| 110 | if (shadow)
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| 111 | old_fp = fopen(filename, "r+");
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| 112 | else
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| 113 | old_fp = fopen_or_warn(filename, "r+");
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| 114 | if (!old_fp) {
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| 115 | if (shadow)
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| 116 | ret = 0; /* missing shadow is not an error */
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| 117 | goto free_mem;
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| 118 | }
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| 119 | old_fd = fileno(old_fp);
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| 120 |
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| 121 | selinux_preserve_fcontext(old_fd);
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| 122 |
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| 123 | /* Try to create "/etc/passwd+". Wait if it exists. */
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| 124 | i = 30;
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| 125 | do {
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| 126 | // FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
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| 127 | new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600);
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| 128 | if (new_fd >= 0) goto created;
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| 129 | if (errno != EEXIST) break;
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| 130 | usleep(100000); /* 0.1 sec */
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| 131 | } while (--i);
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| 132 | bb_perror_msg("can't create '%s'", fnamesfx);
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| 133 | goto close_old_fp;
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| 134 |
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| 135 | created:
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| 136 | if (fstat(old_fd, &sb) == 0) {
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| 137 | fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
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| 138 | fchown(new_fd, sb.st_uid, sb.st_gid);
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| 139 | }
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| 140 | errno = 0;
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| 141 | new_fp = xfdopen_for_write(new_fd);
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| 142 |
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| 143 | /* Backup file is "/etc/passwd-" */
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| 144 | *sfx_char = '-';
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| 145 | /* Delete old backup */
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| 146 | i = (unlink(fnamesfx) && errno != ENOENT);
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| 147 | /* Create backup as a hardlink to current */
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| 148 | if (i || link(filename, fnamesfx))
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| 149 | bb_perror_msg("warning: can't create backup copy '%s'",
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| 150 | fnamesfx);
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| 151 | *sfx_char = '+';
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| 152 |
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| 153 | /* Lock the password file before updating */
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| 154 | lock.l_type = F_WRLCK;
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| 155 | lock.l_whence = SEEK_SET;
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| 156 | lock.l_start = 0;
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| 157 | lock.l_len = 0;
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| 158 | if (fcntl(old_fd, F_SETLK, &lock) < 0)
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| 159 | bb_perror_msg("warning: can't lock '%s'", filename);
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| 160 | lock.l_type = F_UNLCK;
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| 161 |
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| 162 | /* Read current password file, write updated /etc/passwd+ */
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| 163 | changed_lines = 0;
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| 164 | while (1) {
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| 165 | char *cp, *line;
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| 166 |
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| 167 | line = xmalloc_fgetline(old_fp);
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| 168 | if (!line) /* EOF/error */
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| 169 | break;
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| 170 | if (strncmp(name_colon, line, user_len) != 0) {
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| 171 | fprintf(new_fp, "%s\n", line);
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| 172 | goto next;
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| 173 | }
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| 174 |
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| 175 | /* We have a match with "name:"... */
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| 176 | cp = line + user_len; /* move past name: */
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| 177 |
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| 178 | #if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
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| 179 | if (member) {
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| 180 | /* It's actually /etc/group+, not /etc/passwd+ */
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| 181 | if (ENABLE_FEATURE_ADDUSER_TO_GROUP
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| 182 | && applet_name[0] == 'a'
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| 183 | ) {
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| 184 | /* Add user to group */
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| 185 | fprintf(new_fp, "%s%s%s\n", line,
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| 186 | last_char_is(line, ':') ? "" : ",",
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| 187 | member);
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| 188 | changed_lines++;
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| 189 | } else if (ENABLE_FEATURE_DEL_USER_FROM_GROUP
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| 190 | /* && applet_name[0] == 'd' */
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| 191 | ) {
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| 192 | /* Delete user from group */
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| 193 | char *tmp;
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| 194 | const char *fmt = "%s";
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| 195 |
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| 196 | /* find the start of the member list: last ':' */
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| 197 | cp = strrchr(line, ':');
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| 198 | /* cut it */
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| 199 | *cp++ = '\0';
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| 200 | /* write the cut line name:passwd:gid:
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| 201 | * or name:!:: */
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| 202 | fprintf(new_fp, "%s:", line);
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| 203 | /* parse the tokens of the member list */
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| 204 | tmp = cp;
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| 205 | while ((cp = strsep(&tmp, ",")) != NULL) {
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| 206 | if (strcmp(member, cp) != 0) {
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| 207 | fprintf(new_fp, fmt, cp);
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| 208 | fmt = ",%s";
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| 209 | } else {
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| 210 | /* found member, skip it */
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| 211 | changed_lines++;
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| 212 | }
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| 213 | }
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| 214 | fprintf(new_fp, "\n");
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| 215 | }
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| 216 | } else
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| 217 | #endif
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| 218 | if ((ENABLE_PASSWD && applet_name[0] == 'p')
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| 219 | || (ENABLE_CHPASSWD && applet_name[0] == 'c')
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| 220 | ) {
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| 221 | /* Change passwd */
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| 222 | cp = strchrnul(cp, ':'); /* move past old passwd */
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| 223 |
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| 224 | if (shadow && *cp == ':') {
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| 225 | /* /etc/shadow's field 3 (passwd change date) needs updating */
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| 226 | /* move past old change date */
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| 227 | cp = strchrnul(cp + 1, ':');
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| 228 | /* "name:" + "new_passwd" + ":" + "change date" + ":rest of line" */
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| 229 | fprintf(new_fp, "%s%s:%u%s\n", name_colon, new_passwd,
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| 230 | (unsigned)(time(NULL)) / (24*60*60), cp);
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| 231 | } else {
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| 232 | /* "name:" + "new_passwd" + ":rest of line" */
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| 233 | fprintf(new_fp, "%s%s%s\n", name_colon, new_passwd, cp);
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| 234 | }
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| 235 | changed_lines++;
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| 236 | } /* else delete user or group: skip the line */
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| 237 | next:
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| 238 | free(line);
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| 239 | }
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| 240 |
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| 241 | if (changed_lines == 0) {
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| 242 | #if ENABLE_FEATURE_ADDUSER_TO_GROUP || ENABLE_FEATURE_DEL_USER_FROM_GROUP
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| 243 | if (member) {
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| 244 | if (ENABLE_ADDGROUP && applet_name[0] == 'a')
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| 245 | bb_error_msg("can't find %s in %s", name, filename);
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| 246 | if (ENABLE_DELGROUP && applet_name[0] == 'd')
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| 247 | bb_error_msg("can't find %s in %s", member, filename);
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| 248 | }
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| 249 | #endif
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| 250 | if ((ENABLE_ADDUSER || ENABLE_ADDGROUP)
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| 251 | && applet_name[0] == 'a' && !member
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| 252 | ) {
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| 253 | /* add user or group */
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| 254 | fprintf(new_fp, "%s%s\n", name_colon, new_passwd);
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| 255 | changed_lines++;
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| 256 | }
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| 257 | }
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| 258 |
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| 259 | fcntl(old_fd, F_SETLK, &lock);
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| 260 |
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| 261 | /* We do want all of them to execute, thus | instead of || */
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| 262 | errno = 0;
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| 263 | if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
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| 264 | || rename(fnamesfx, filename)
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| 265 | ) {
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| 266 | /* At least one of those failed */
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| 267 | bb_perror_nomsg();
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| 268 | goto unlink_new;
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| 269 | }
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| 270 | /* Success: ret >= 0 */
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| 271 | ret = changed_lines;
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| 272 |
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| 273 | unlink_new:
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| 274 | if (ret < 0)
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| 275 | unlink(fnamesfx);
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| 276 |
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| 277 | close_old_fp:
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| 278 | fclose(old_fp);
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| 279 |
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| 280 | free_mem:
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| 281 | free(fnamesfx);
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| 282 | free((char *)filename);
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| 283 | free(name_colon);
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| 284 | return ret;
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| 285 | }
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