1 files changed, 382 insertions, 0 deletions
diff --git a/auth2-chall.c b/auth2-chall.c
new file mode 100644
index 0000000..021df82
--- /dev/null
+++ b/auth2-chall.c
@@ -0,0 +1,382 @@
+/* $OpenBSD: auth2-chall.c,v 1.54 2020/10/18 11:32:01 djm Exp $ */
+/*
+ * Copyright (c) 2001 Markus Friedl.  All rights reserved.
+ * Copyright (c) 2001 Per Allansson.  All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ * 1. Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ * 2. Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in the
+ *    documentation and/or other materials provided with the distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
+ * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
+ * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
+ * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
+ * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
+ * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
+ * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
+ * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
+ * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
+ */
+
+#include "includes.h"
+
+#include <sys/types.h>
+
+#include <stdlib.h>
+#include <stdio.h>
+#include <string.h>
+#include <stdarg.h>
+
+#include "xmalloc.h"
+#include "ssh2.h"
+#include "sshkey.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "sshbuf.h"
+#include "packet.h"
+#include "dispatch.h"
+#include "ssherr.h"
+#include "log.h"
+#include "misc.h"
+#include "servconf.h"
+
+/* import */
+extern ServerOptions options;
+
+static int auth2_challenge_start(struct ssh *);
+static int send_userauth_info_request(struct ssh *);
+static int input_userauth_info_response(int, u_int32_t, struct ssh *);
+
+#ifdef BSD_AUTH
+extern KbdintDevice bsdauth_device;
+#else
+#ifdef USE_PAM
+extern KbdintDevice sshpam_device;
+#endif
+#endif
+
+KbdintDevice *devices[] = {
+#ifdef BSD_AUTH
+	&bsdauth_device,
+#else
+#ifdef USE_PAM
+	&sshpam_device,
+#endif
+#endif
+	NULL
+};
+
+typedef struct KbdintAuthctxt KbdintAuthctxt;
+struct KbdintAuthctxt
+{
+	char *devices;
+	void *ctxt;
+	KbdintDevice *device;
+	u_int nreq;
+	u_int devices_done;
+};
+
+#ifdef USE_PAM
+void
+remove_kbdint_device(const char *devname)
+{
+	int i, j;
+
+	for (i = 0; devices[i] != NULL; i++)
+		if (strcmp(devices[i]->name, devname) == 0) {
+			for (j = i; devices[j] != NULL; j++)
+				devices[j] = devices[j+1];
+			i--;
+		}
+}
+#endif
+
+static KbdintAuthctxt *
+kbdint_alloc(const char *devs)
+{
+	KbdintAuthctxt *kbdintctxt;
+	struct sshbuf *b;
+	int i, r;
+
+#ifdef USE_PAM
+	if (!options.use_pam)
+		remove_kbdint_device("pam");
+#endif
+
+	kbdintctxt = xcalloc(1, sizeof(KbdintAuthctxt));
+	if (strcmp(devs, "") == 0) {
+		if ((b = sshbuf_new()) == NULL)
+			fatal_f("sshbuf_new failed");
+		for (i = 0; devices[i]; i++) {
+			if ((r = sshbuf_putf(b, "%s%s",
+			    sshbuf_len(b) ? "," : "", devices[i]->name)) != 0)
+				fatal_fr(r, "buffer error");
+		}
+		if ((kbdintctxt->devices = sshbuf_dup_string(b)) == NULL)
+			fatal_f("sshbuf_dup_string failed");
+		sshbuf_free(b);
+	} else {
+		kbdintctxt->devices = xstrdup(devs);
+	}
+	debug("kbdint_alloc: devices '%s'", kbdintctxt->devices);
+	kbdintctxt->ctxt = NULL;
+	kbdintctxt->device = NULL;
+	kbdintctxt->nreq = 0;
+
+	return kbdintctxt;
+}
+static void
+kbdint_reset_device(KbdintAuthctxt *kbdintctxt)
+{
+	if (kbdintctxt->ctxt) {
+		kbdintctxt->device->free_ctx(kbdintctxt->ctxt);
+		kbdintctxt->ctxt = NULL;
+	}
+	kbdintctxt->device = NULL;
+}
+static void
+kbdint_free(KbdintAuthctxt *kbdintctxt)
+{
+	if (kbdintctxt->device)
+		kbdint_reset_device(kbdintctxt);
+	free(kbdintctxt->devices);
+	freezero(kbdintctxt, sizeof(*kbdintctxt));
+}
+/* get next device */
+static int
+kbdint_next_device(Authctxt *authctxt, KbdintAuthctxt *kbdintctxt)
+{
+	size_t len;
+	char *t;
+	int i;
+
+	if (kbdintctxt->device)
+		kbdint_reset_device(kbdintctxt);
+	do {
+		len = kbdintctxt->devices ?
+		    strcspn(kbdintctxt->devices, ",") : 0;
+
+		if (len == 0)
+			break;
+		for (i = 0; devices[i]; i++) {
+			if ((kbdintctxt->devices_done & (1 << i)) != 0 ||
+			    !auth2_method_allowed(authctxt,
+			    "keyboard-interactive", devices[i]->name))
+				continue;
+			if (strncmp(kbdintctxt->devices, devices[i]->name,
+			    len) == 0) {
+				kbdintctxt->device = devices[i];
+				kbdintctxt->devices_done |= 1 << i;
+			}
+		}
+		t = kbdintctxt->devices;
+		kbdintctxt->devices = t[len] ? xstrdup(t+len+1) : NULL;
+		free(t);
+		debug2("kbdint_next_device: devices %s", kbdintctxt->devices ?
+		    kbdintctxt->devices : "<empty>");
+	} while (kbdintctxt->devices && !kbdintctxt->device);
+
+	return kbdintctxt->device ? 1 : 0;
+}
+
+/*
+ * try challenge-response, set authctxt->postponed if we have to
+ * wait for the response.
+ */
+int
+auth2_challenge(struct ssh *ssh, char *devs)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	debug("auth2_challenge: user=%s devs=%s",
+	    authctxt->user ? authctxt->user : "<nouser>",
+	    devs ? devs : "<no devs>");
+
+	if (authctxt->user == NULL || !devs)
+		return 0;
+	if (authctxt->kbdintctxt == NULL)
+		authctxt->kbdintctxt = kbdint_alloc(devs);
+	return auth2_challenge_start(ssh);
+}
+
+/* unregister kbd-int callbacks and context */
+void
+auth2_challenge_stop(struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	/* unregister callback */
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE, NULL);
+	if (authctxt->kbdintctxt != NULL) {
+		kbdint_free(authctxt->kbdintctxt);
+		authctxt->kbdintctxt = NULL;
+	}
+}
+
+/* side effect: sets authctxt->postponed if a reply was sent*/
+static int
+auth2_challenge_start(struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	KbdintAuthctxt *kbdintctxt = authctxt->kbdintctxt;
+
+	debug2("auth2_challenge_start: devices %s",
+	    kbdintctxt->devices ?  kbdintctxt->devices : "<empty>");
+
+	if (kbdint_next_device(authctxt, kbdintctxt) == 0) {
+		auth2_challenge_stop(ssh);
+		return 0;
+	}
+	debug("auth2_challenge_start: trying authentication method '%s'",
+	    kbdintctxt->device->name);
+
+	if ((kbdintctxt->ctxt = kbdintctxt->device->init_ctx(authctxt)) == NULL) {
+		auth2_challenge_stop(ssh);
+		return 0;
+	}
+	if (send_userauth_info_request(ssh) == 0) {
+		auth2_challenge_stop(ssh);
+		return 0;
+	}
+	ssh_dispatch_set(ssh, SSH2_MSG_USERAUTH_INFO_RESPONSE,
+	    &input_userauth_info_response);
+
+	authctxt->postponed = 1;
+	return 0;
+}
+
+static int
+send_userauth_info_request(struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	KbdintAuthctxt *kbdintctxt;
+	char *name, *instr, **prompts;
+	u_int r, i, *echo_on;
+
+	kbdintctxt = authctxt->kbdintctxt;
+	if (kbdintctxt->device->query(kbdintctxt->ctxt,
+	    &name, &instr, &kbdintctxt->nreq, &prompts, &echo_on))
+		return 0;
+
+	if ((r = sshpkt_start(ssh, SSH2_MSG_USERAUTH_INFO_REQUEST)) != 0 ||
+	    (r = sshpkt_put_cstring(ssh, name)) != 0 ||
+	    (r = sshpkt_put_cstring(ssh, instr)) != 0 ||
+	    (r = sshpkt_put_cstring(ssh, "")) != 0 ||	/* language not used */
+	    (r = sshpkt_put_u32(ssh, kbdintctxt->nreq)) != 0)
+		fatal_fr(r, "start packet");
+	for (i = 0; i < kbdintctxt->nreq; i++) {
+		if ((r = sshpkt_put_cstring(ssh, prompts[i])) != 0 ||
+		    (r = sshpkt_put_u8(ssh, echo_on[i])) != 0)
+			fatal_fr(r, "assemble packet");
+	}
+	if ((r = sshpkt_send(ssh)) != 0 ||
+	    (r = ssh_packet_write_wait(ssh)) != 0)
+		fatal_fr(r, "send packet");
+
+	for (i = 0; i < kbdintctxt->nreq; i++)
+		free(prompts[i]);
+	free(prompts);
+	free(echo_on);
+	free(name);
+	free(instr);
+	return 1;
+}
+
+static int
+input_userauth_info_response(int type, u_int32_t seq, struct ssh *ssh)
+{
+	Authctxt *authctxt = ssh->authctxt;
+	KbdintAuthctxt *kbdintctxt;
+	int authenticated = 0, res;
+	int r;
+	u_int i, nresp;
+	const char *devicename = NULL;
+	char **response = NULL;
+
+	if (authctxt == NULL)
+		fatal_f("no authctxt");
+	kbdintctxt = authctxt->kbdintctxt;
+	if (kbdintctxt == NULL || kbdintctxt->ctxt == NULL)
+		fatal_f("no kbdintctxt");
+	if (kbdintctxt->device == NULL)
+		fatal_f("no device");
+
+	authctxt->postponed = 0;	/* reset */
+	if ((r = sshpkt_get_u32(ssh, &nresp)) != 0)
+		fatal_fr(r, "parse packet");
+	if (nresp != kbdintctxt->nreq)
+		fatal_f("wrong number of replies");
+	if (nresp > 100)
+		fatal_f("too many replies");
+	if (nresp > 0) {
+		response = xcalloc(nresp, sizeof(char *));
+		for (i = 0; i < nresp; i++) {
+			if ((r = sshpkt_get_cstring(ssh, &response[i], NULL)) != 0)
+				fatal_fr(r, "parse response");
+		}
+	}
+	if ((r = sshpkt_get_end(ssh)) != 0)
+		fatal_fr(r, "parse packet");
+
+	res = kbdintctxt->device->respond(kbdintctxt->ctxt, nresp, response);
+
+	for (i = 0; i < nresp; i++) {
+		explicit_bzero(response[i], strlen(response[i]));
+		free(response[i]);
+	}
+	free(response);
+
+	switch (res) {
+	case 0:
+		/* Success! */
+		authenticated = authctxt->valid ? 1 : 0;
+		break;
+	case 1:
+		/* Authentication needs further interaction */
+		if (send_userauth_info_request(ssh) == 1)
+			authctxt->postponed = 1;
+		break;
+	default:
+		/* Failure! */
+		break;
+	}
+	devicename = kbdintctxt->device->name;
+	if (!authctxt->postponed) {
+		if (authenticated) {
+			auth2_challenge_stop(ssh);
+		} else {
+			/* start next device */
+			/* may set authctxt->postponed */
+			auth2_challenge_start(ssh);
+		}
+	}
+	userauth_finish(ssh, authenticated, "keyboard-interactive",
+	    devicename);
+	return 0;
+}
+
+void
+privsep_challenge_enable(void)
+{
+#if defined(BSD_AUTH) || defined(USE_PAM)
+	int n = 0;
+#endif
+#ifdef BSD_AUTH
+	extern KbdintDevice mm_bsdauth_device;
+#endif
+#ifdef USE_PAM
+	extern KbdintDevice mm_sshpam_device;
+#endif
+
+#ifdef BSD_AUTH
+	devices[n++] = &mm_bsdauth_device;
+#else
+#ifdef USE_PAM
+	devices[n++] = &mm_sshpam_device;
+#endif
+#endif
+}