source: branches/2.2.5/mindi-busybox/libbb/update_passwd.c @ 1765

Last change on this file since 1765 was 1765, checked in by Bruno Cornec, 13 years ago

Update to busybox 1.7.2

  • Property svn:eol-style set to native
File size: 2.9 KB
Line 
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
14int update_passwd(const char *filename, const char *username,
15            const char *new_pw)
16{
17    struct stat sb;
18    struct flock lock;
19    FILE *old_fp;
20    FILE *new_fp;
21    char *fnamesfx;
22    char *sfx_char;
23    unsigned user_len;
24    int old_fd;
25    int new_fd;
26    int i;
27    int cnt = 0;
28    int ret = -1; /* failure */
29
30    /* New passwd file, "/etc/passwd+" for now */
31    fnamesfx = xasprintf("%s+", filename);
32    sfx_char = &fnamesfx[strlen(fnamesfx)-1];
33    username = xasprintf("%s:", username);
34    user_len = strlen(username);
35
36    old_fp = fopen(filename, "r+");
37    if (!old_fp)
38        goto free_mem;
39    old_fd = fileno(old_fp);
40
41    /* Try to create "/etc/passwd+". Wait if it exists. */
42    i = 30;
43    do {
44        // FIXME: on last iteration try w/o O_EXCL but with O_TRUNC?
45        new_fd = open(fnamesfx, O_WRONLY|O_CREAT|O_EXCL, 0600);
46        if (new_fd >= 0) goto created;
47        if (errno != EEXIST) break;
48        usleep(100000); /* 0.1 sec */
49    } while (--i);
50    bb_perror_msg("cannot create '%s'", fnamesfx);
51    goto close_old_fp;
52
53 created:
54    if (!fstat(old_fd, &sb)) {
55        fchmod(new_fd, sb.st_mode & 0777); /* ignore errors */
56        fchown(new_fd, sb.st_uid, sb.st_gid);
57    }
58    new_fp = fdopen(new_fd, "w");
59    if (!new_fp) {
60        close(new_fd);
61        goto unlink_new;
62    }
63
64    /* Backup file is "/etc/passwd-" */
65    *sfx_char = '-';
66    /* Delete old backup */
67    i = (unlink(fnamesfx) && errno != ENOENT);
68    /* Create backup as a hardlink to current */
69    if (i || link(filename, fnamesfx))
70        bb_perror_msg("warning: cannot create backup copy '%s'", fnamesfx);
71    *sfx_char = '+';
72
73    /* Lock the password file before updating */
74    lock.l_type = F_WRLCK;
75    lock.l_whence = SEEK_SET;
76    lock.l_start = 0;
77    lock.l_len = 0;
78    if (fcntl(old_fd, F_SETLK, &lock) < 0)
79        bb_perror_msg("warning: cannot lock '%s'", filename);
80    lock.l_type = F_UNLCK;
81
82    /* Read current password file, write updated /etc/passwd+ */
83    while (1) {
84        char *line = xmalloc_fgets(old_fp);
85        if (!line) break; /* EOF/error */
86        if (strncmp(username, line, user_len) == 0) {
87            /* we have a match with "username:"... */
88            const char *cp = line + user_len;
89            /* now cp -> old passwd, skip it: */
90            cp = strchrnul(cp, ':');
91            /* now cp -> ':' after old passwd or -> "" */
92            fprintf(new_fp, "%s%s%s", username, new_pw, cp);
93            cnt++;
94        } else
95            fputs(line, new_fp);
96        free(line);
97    }
98    fcntl(old_fd, F_SETLK, &lock);
99
100    /* We do want all of them to execute, thus | instead of || */
101    if ((ferror(old_fp) | fflush(new_fp) | fsync(new_fd) | fclose(new_fp))
102     || rename(fnamesfx, filename)
103    ) {
104        /* At least one of those failed */
105        goto unlink_new;
106    }
107    ret = cnt; /* whee, success! */
108
109 unlink_new:
110    if (ret < 0) unlink(fnamesfx);
111
112 close_old_fp:
113    fclose(old_fp);
114
115 free_mem:
116    free(fnamesfx);
117    free((char*)username);
118    return ret;
119}
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