1 files changed, 258 insertions, 0 deletions
diff --git a/svr-authpam.c b/svr-authpam.c
new file mode 100644
index 0000000..4e257ae
--- /dev/null
+++ b/svr-authpam.c
@@ -0,0 +1,258 @@
+/*
+ * 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"
+
+#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
+
+#ifdef ENABLE_SVR_PAM_AUTH
+
+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 */