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#include "pam_modutil_private.h"
#include <security/pam_ext.h>
#include <stdio.h>
#include <string.h>
#include <syslog.h>
int
pam_modutil_check_user_in_passwd(pam_handle_t *pamh,
const char *user_name,
const char *file_name)
{
int rc, c = EOF;
FILE *fp;
/* Validate the user name. */
if (user_name[0] == '\0') {
pam_syslog(pamh, LOG_NOTICE, "user name is not valid");
return PAM_SERVICE_ERR;
}
if (strchr(user_name, ':') != NULL) {
/*
* "root:x" is not a local user name even if the passwd file
* contains a line starting with "root:x:".
*/
return PAM_PERM_DENIED;
}
/* Open the passwd file. */
if (file_name == NULL) {
file_name = "/etc/passwd";
}
if ((fp = fopen(file_name, "r")) == NULL) {
pam_syslog(pamh, LOG_ERR, "error opening %s: %m", file_name);
return PAM_SERVICE_ERR;
}
/*
* Scan the file using fgetc() instead of fgetpwent_r() because
* the latter is not flexible enough in handling long lines
* in passwd files.
*/
rc = PAM_PERM_DENIED;
do {
const char *p;
/*
* Does this line start with the user name
* followed by a colon?
*/
for (p = user_name; *p != '\0'; p++) {
c = fgetc(fp);
if (c == EOF || c == '\n' || (char)c != *p)
break;
}
if (c != EOF && c != '\n')
c = fgetc(fp);
if (*p == '\0' && c == ':') {
rc = PAM_SUCCESS;
/*
* Continue reading the file to avoid timing attacks.
*/
}
/* Read till the end of this line. */
while (c != EOF && c != '\n')
c = fgetc(fp);
/* Continue with the next line. */
} while (c != EOF);
fclose(fp);
return rc;
}
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