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/*
* pam_http: authenticate local users against an HTTP server
*
* See README for more documentation.
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*
* This program is distributed in the hope that it will be useful,
* but WITHOUT ANY WARRANTY; without even the implied warranty of
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
* GNU General Public License for more details.
*
* You should have received a copy of the GNU General Public License
* along with this program; if not, write to the Free Software
* Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
*/
#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#define PAM_SM_PASSWORD
#include <security/pam_modules.h>
/* we use libcURL */
#include <curl/curl.h>
#include <curl/types.h>
#include <curl/easy.h>
/* nop write function */
static size_t nop_wf(void* a, size_t x, size_t y, void* b) { return x * y; }
/* nop password ask function */
static int my_getpass(void *client, char *prompt, char *buffer, int buflen) {
buffer[0] = '\0';
return 0;
}
static int geturl(const char *url, const char *username,
const char *password, const char *cafile)
{
CURL *curl = curl_easy_init();
CURLcode res = -1;
char *userpass;
int len = strlen(username) + strlen(password) + 2;
if (!curl) return 0;
userpass = malloc(len);
if (!userpass) goto cleanup;
sprintf(userpass, "%s:%s", username, password);
curl_easy_setopt(curl, CURLOPT_URL, url);
/* discard read data */
curl_easy_setopt(curl, CURLOPT_WRITEFUNCTION, nop_wf);
curl_easy_setopt(curl, CURLOPT_USERPWD, userpass);
/* provide no progress indicator */
curl_easy_setopt(curl, CURLOPT_NOPROGRESS, 1);
/* fail on HTTP errors */
curl_easy_setopt(curl, CURLOPT_FAILONERROR, 1);
/* return an empty password if none supplied instead of the default
behavior, which is to fuck with the tty and half-assedly ask the
user for a password from somewhere in the guts of libcURL */
curl_easy_setopt(curl, CURLOPT_PASSWDFUNCTION, my_getpass);
/* seed SSL randomness from somewhere; this is really problematic
because libcurl wants to read 16 kilobytes of randomness. (Why
does it think it needs 131072 bits? Does it think someone might
spend 10^39334 universe-lifetimes to brute-force our SSL
connection?) */
curl_easy_setopt(curl, CURLOPT_RANDOM_FILE, "/dev/urandom");
/* verify SSL peer's certificate */
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYPEER, 1);
/* and also verify that its name matches the name we're calling it by */
curl_easy_setopt(curl, CURLOPT_SSL_VERIFYHOST, 2);
/* use this file for SSL cert verification */
curl_easy_setopt(curl, CURLOPT_CAINFO, cafile);
res = curl_easy_perform(curl);
memset(userpass, '\0', len);
free(userpass);
cleanup:
curl_easy_cleanup(curl);
return res == 0;
}
/* pam arguments are normally of the form name=value. This gets the
* 'value' corresponding to the passed 'name' from the argument
* list. */
static const char *getarg(const char *name, int argc, const char **argv) {
int len = strlen(name);
while (argc) {
if (strlen(*argv) > len &&
!strncmp(name, *argv, len) &&
(*argv)[len] == '=') {
return *argv + len + 1; /* 1 for the = */
}
argc--;
argv++;
}
return 0;
}
PAM_EXTERN int pam_sm_authenticate(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
struct pam_conv *item;
struct pam_message msg;
const struct pam_message *msgp;
struct pam_response *respp;
const char *username;
const char *cafile = getarg("cafile", argc, argv); /* possibly NULL */
const char *url = getarg("url", argc, argv);
int rv = PAM_SUCCESS;
if (!url) return PAM_AUTH_ERR;
msgp = &msg;
msg.msg_style = PAM_PROMPT_ECHO_OFF;
msg.msg = "Tell me a secret: ";
if (pam_get_item(pamh, PAM_CONV, (const void**)&item) != PAM_SUCCESS) {
fprintf(stderr, "Couldn't get pam_conv\n");
return PAM_AUTH_ERR;
}
if (pam_get_user(pamh, &username, 0) != PAM_SUCCESS) {
fprintf(stderr, "Couldn't get username\n");
return PAM_AUTH_ERR;
}
item->conv(1, &msgp, &respp, item->appdata_ptr);
if (!geturl(url, (char*)username, respp[0].resp, cafile))
rv = PAM_AUTH_ERR;
memset(respp[0].resp, '\0', strlen(respp[0].resp));
free(respp);
return rv;
}
PAM_EXTERN int pam_sm_setcred(pam_handle_t *pamh, int flags,
int argc, const char **argv)
{
return PAM_SUCCESS;
}
#ifdef PAM_STATIC /* untested */
struct pam_module _pam_http_modstruct = {
"pam_http",
pam_sm_authenticate,
pam_sm_setcred,
0, 0, 0, 0
};
#endif
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