| 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 |
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| 12 | #include "libbb.h"
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| 13 |
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| 14 | int update_passwd(const char *filename, const char *username,
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| 15 | const char *new_pw)
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| 16 | {
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| 17 | struct stat sb;
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| 18 | struct flock lock;
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| 19 | FILE *old_fp;
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| 20 | FILE *new_fp;
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| 21 | char *fnamesfx;
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| 22 | char *sfx_char;
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| 23 | unsigned user_len;
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| 24 | int old_fd;
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| 25 | int new_fd;
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| 26 | int i;
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| 27 | int cnt = 0;
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| 28 | int ret = -1; /* failure */
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| 29 |
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| 30 | /* New passwd file, "/etc/passwd+" for now */
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| 31 | fnamesfx = xasprintf("%s+", filename);
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| 32 | sfx_char = &fnamesfx[strlen(fnamesfx)-1];
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| 33 | username = xasprintf("%s:", username);
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| 34 | user_len = strlen(username);
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| 35 |
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| 36 | old_fp = fopen(filename, "r+");
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| 37 | if (!old_fp)
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| 38 | goto free_mem;
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| 39 | old_fd = fileno(old_fp);
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| 40 |
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| 41 | /* Try to create "/etc/passwd+". Wait if it exists. */
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| 42 | i = 30;
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| 43 | do {
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| 44 | // FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
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| 45 | new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600);
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| 46 | if (new_fd >= 0) goto created;
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| 47 | if (errno != EEXIST) break;
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| 48 | usleep(100000); /* 0.1 sec */
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| 49 | } while (--i);
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| 50 | bb_perror_msg("cannot create '%s'", fnamesfx);
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| 51 | goto close_old_fp;
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| 52 |
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| 53 | created:
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| 54 | if (!fstat(old_fd, &sb)) {
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| 55 | fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
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| 56 | fchown(new_fd, sb.st_uid, sb.st_gid);
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| 57 | }
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| 58 | new_fp = fdopen(new_fd, "w");
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| 59 | if (!new_fp) {
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| 60 | close(new_fd);
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| 61 | goto unlink_new;
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| 62 | }
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| 63 |
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| 64 | /* Backup file is "/etc/passwd-" */
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| 65 | *sfx_char = '-';
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| 66 | /* Delete old backup */
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| 67 | i = (unlink(fnamesfx) && errno != ENOENT);
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| 68 | /* Create backup as a hardlink to current */
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| 69 | if (i || link(filename, fnamesfx))
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| 70 | bb_perror_msg("warning: cannot create backup copy '%s'", fnamesfx);
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| 71 | *sfx_char = '+';
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| 72 |
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| 73 | /* Lock the password file before updating */
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| 74 | lock.l_type = F_WRLCK;
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| 75 | lock.l_whence = SEEK_SET;
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| 76 | lock.l_start = 0;
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| 77 | lock.l_len = 0;
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| 78 | if (fcntl(old_fd, F_SETLK, &lock) < 0)
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| 79 | bb_perror_msg("warning: cannot lock '%s'", filename);
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| 80 | lock.l_type = F_UNLCK;
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| 81 |
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| 82 | /* Read current password file, write updated /etc/passwd+ */
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| 83 | while (1) {
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| 84 | char *line = xmalloc_fgets(old_fp);
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| 85 | if (!line) break; /* EOF/error */
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| 86 | if (strncmp(username, line, user_len) == 0) {
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| 87 | /* we have a match with "username:"... */
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| 88 | const char *cp = line + user_len;
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| 89 | /* now cp -> old passwd, skip it: */
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| 90 | cp = strchrnul(cp, ':');
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| 91 | /* now cp -> ':' after old passwd or -> "" */
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| 92 | fprintf(new_fp, "%s%s%s", username, new_pw, cp);
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| 93 | cnt++;
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| 94 | } else
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| 95 | fputs(line, new_fp);
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| 96 | free(line);
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| 97 | }
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| 98 | fcntl(old_fd, F_SETLK, &lock);
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| 99 |
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| 100 | /* We do want all of them to execute, thus | instead of || */
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| 101 | if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
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| 102 | || rename(fnamesfx, filename)
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| 103 | ) {
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| 104 | /* At least one of those failed */
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| 105 | goto unlink_new;
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| 106 | }
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| 107 | ret = cnt; /* whee, success! */
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| 108 |
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| 109 | unlink_new:
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| 110 | if (ret < 0) unlink(fnamesfx);
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| 111 |
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| 112 | close_old_fp:
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| 113 | fclose(old_fp);
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| 114 |
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| 115 | free_mem:
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| 116 | free(fnamesfx);
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| 117 | free((char*)username);
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| 118 | return ret;
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| 119 | }
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