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/*
* Dropbear SSH
*
* Copyright (c) 2004 Martin Carlsson
* Portions (c) 2004 Matt Johnston
* All rights reserved.
*
* Permission is hereby granted, free of charge, to any person obtaining a copy
* of this software and associated documentation files (the "Software"), to deal
* in the Software without restriction, including without limitation the rights
* to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
* copies of the Software, and to permit persons to whom the Software is
* furnished to do so, subject to the following conditions:
*
* The above copyright notice and this permission notice shall be included in
* all copies or substantial portions of the Software.
*
* THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
* IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
* FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
* AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
* LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
* OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
* SOFTWARE. */
/* Validates a user password using PAM */
#include "includes.h"
#include "session.h"
#include "buffer.h"
#include "dbutil.h"
#include "auth.h"
#ifdef ENABLE_SVR_PAM_AUTH
#if defined(HAVE_SECURITY_PAM_APPL_H)
#include <security/pam_appl.h>
#elif defined (HAVE_PAM_PAM_APPL_H)
#include <pam/pam_appl.h>
#endif
struct UserDataS {
char* user;
char* passwd;
};
/* PAM conversation function - for now we only handle one message */
int
pamConvFunc(int num_msg,
const struct pam_message **msg,
struct pam_response **respp,
void *appdata_ptr) {
int rc = PAM_SUCCESS;
struct pam_response* resp = NULL;
struct UserDataS* userDatap = (struct UserDataS*) appdata_ptr;
unsigned int msg_len = 0;
unsigned int i = 0;
const char* message = (*msg)->msg;
/* make a copy we can strip */
char * compare_message = m_strdup(message);
TRACE(("enter pamConvFunc"))
if (num_msg != 1) {
/* If you're getting here - Dropbear probably can't support your pam
* modules. This whole file is a bit of a hack around lack of
* asynchronocity in PAM anyway. */
dropbear_log(LOG_INFO, "pamConvFunc() called with >1 messages: not supported.");
return PAM_CONV_ERR;
}
TRACE(("msg_style is %d", (*msg)->msg_style))
if (compare_message) {
TRACE(("message is '%s'", compare_message))
} else {
TRACE(("null message"))
}
/* Make the string lowercase. */
msg_len = strlen(compare_message);
for (i = 0; i < msg_len; i++) {
compare_message[i] = tolower(compare_message[i]);
}
/* If the string ends with ": ", remove the space.
ie "login: " vs "login:" */
if (msg_len > 2
&& compare_message[msg_len-2] == ':'
&& compare_message[msg_len-1] == ' ') {
compare_message[msg_len-1] = '\0';
}
switch((*msg)->msg_style) {
case PAM_PROMPT_ECHO_OFF:
if (!(strcmp(compare_message, "password:") == 0)) {
/* We don't recognise the prompt as asking for a password,
so can't handle it. Add more above as required for
different pam modules/implementations */
dropbear_log(LOG_NOTICE, "PAM unknown prompt %s (no echo)",
compare_message);
rc = PAM_CONV_ERR;
break;
}
/* You have to read the PAM module-writers' docs (do we look like
* module writers? no.) to find out that the module will
* free the pam_response and its resp element - ie we _must_ malloc
* it here */
resp = (struct pam_response*) m_malloc(sizeof(struct pam_response));
memset(resp, 0, sizeof(struct pam_response));
resp->resp = m_strdup(userDatap->passwd);
m_burn(userDatap->passwd, strlen(userDatap->passwd));
(*respp) = resp;
break;
case PAM_PROMPT_ECHO_ON:
if (!((strcmp(compare_message, "login:" ) == 0)
|| (strcmp(compare_message, "please enter username:") == 0))) {
/* We don't recognise the prompt as asking for a username,
so can't handle it. Add more above as required for
different pam modules/implementations */
dropbear_log(LOG_NOTICE, "PAM unknown prompt %s (with echo)",
compare_message);
rc = PAM_CONV_ERR;
break;
}
/* You have to read the PAM module-writers' docs (do we look like
* module writers? no.) to find out that the module will
* free the pam_response and its resp element - ie we _must_ malloc
* it here */
resp = (struct pam_response*) m_malloc(sizeof(struct pam_response));
memset(resp, 0, sizeof(struct pam_response));
resp->resp = m_strdup(userDatap->user);
TRACE(("userDatap->user='%s'", userDatap->user))
(*respp) = resp;
break;
default:
TRACE(("Unknown message type"))
rc = PAM_CONV_ERR;
break;
}
m_free(compare_message);
TRACE(("leave pamConvFunc, rc %d", rc))
return rc;
}
/* Process a password auth request, sending success or failure messages as
* appropriate. To the client it looks like it's doing normal password auth (as
* opposed to keyboard-interactive or something), so the pam module has to be
* fairly standard (ie just "what's your username, what's your password, OK").
*
* Keyboard interactive would be a lot nicer, but since PAM is synchronous, it
* gets very messy trying to send the interactive challenges, and read the
* interactive responses, over the network. */
void svr_auth_pam() {
struct UserDataS userData = {NULL, NULL};
struct pam_conv pamConv = {
pamConvFunc,
&userData /* submitted to pamvConvFunc as appdata_ptr */
};
pam_handle_t* pamHandlep = NULL;
unsigned char * password = NULL;
unsigned int passwordlen;
int rc = PAM_SUCCESS;
unsigned char changepw;
/* check if client wants to change password */
changepw = buf_getbool(ses.payload);
if (changepw) {
/* not implemented by this server */
send_msg_userauth_failure(0, 1);
goto cleanup;
}
password = buf_getstring(ses.payload, &passwordlen);
/* used to pass data to the PAM conversation function - don't bother with
* strdup() etc since these are touched only by our own conversation
* function (above) which takes care of it */
userData.user = ses.authstate.printableuser;
userData.passwd = password;
/* Init pam */
if ((rc = pam_start("sshd", NULL, &pamConv, &pamHandlep)) != PAM_SUCCESS) {
dropbear_log(LOG_WARNING, "pam_start() failed, rc=%d, %s\n",
rc, pam_strerror(pamHandlep, rc));
goto cleanup;
}
/* just to set it to something */
if ((rc = pam_set_item(pamHandlep, PAM_TTY, "ssh") != PAM_SUCCESS)) {
dropbear_log(LOG_WARNING, "pam_set_item() failed, rc=%d, %s\n",
rc, pam_strerror(pamHandlep, rc));
goto cleanup;
}
(void) pam_fail_delay(pamHandlep, 0 /* musec_delay */);
/* (void) pam_set_item(pamHandlep, PAM_FAIL_DELAY, (void*) pamDelayFunc); */
if ((rc = pam_authenticate(pamHandlep, 0)) != PAM_SUCCESS) {
dropbear_log(LOG_WARNING, "pam_authenticate() failed, rc=%d, %s\n",
rc, pam_strerror(pamHandlep, rc));
dropbear_log(LOG_WARNING,
"bad PAM password attempt for '%s' from %s",
ses.authstate.printableuser,
svr_ses.addrstring);
send_msg_userauth_failure(0, 1);
goto cleanup;
}
if ((rc = pam_acct_mgmt(pamHandlep, 0)) != PAM_SUCCESS) {
dropbear_log(LOG_WARNING, "pam_acct_mgmt() failed, rc=%d, %s\n",
rc, pam_strerror(pamHandlep, rc));
dropbear_log(LOG_WARNING,
"bad PAM password attempt for '%s' from %s",
ses.authstate.printableuser,
svr_ses.addrstring);
send_msg_userauth_failure(0, 1);
goto cleanup;
}
/* successful authentication */
dropbear_log(LOG_NOTICE, "PAM password auth succeeded for '%s' from %s",
ses.authstate.printableuser,
svr_ses.addrstring);
send_msg_userauth_success();
cleanup:
if (password != NULL) {
m_burn(password, passwordlen);
m_free(password);
}
if (pamHandlep != NULL) {
TRACE(("pam_end"))
(void) pam_end(pamHandlep, 0 /* pam_status */);
}
}
#endif /* ENABLE_SVR_PAM_AUTH */
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