--- /dev/null
+/* $OpenBSD: auth1.c,v 1.75 2010/08/31 09:58:37 djm Exp $ */
+/*
+ * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
+ * All rights reserved
+ *
+ * As far as I am concerned, the code I have written for this software
+ * can be used freely for any purpose. Any derived versions of this
+ * software must be clearly marked as such, and if the derived work is
+ * incompatible with the protocol description in the RFC file, it must be
+ * called by a name other than "ssh" or "Secure Shell".
+ */
+
+#include "includes.h"
+
+#include <sys/types.h>
+
+#include <stdarg.h>
+#include <stdio.h>
+#include <string.h>
+#include <unistd.h>
+#include <pwd.h>
+
+#include "openbsd-compat/sys-queue.h"
+#include "xmalloc.h"
+#include "rsa.h"
+#include "ssh1.h"
+#include "packet.h"
+#include "buffer.h"
+#include "log.h"
+#include "servconf.h"
+#include "compat.h"
+#include "key.h"
+#include "hostfile.h"
+#include "auth.h"
+#include "channels.h"
+#include "session.h"
+#include "uidswap.h"
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+#include "monitor_wrap.h"
+#include "buffer.h"
+
+/* import */
+extern ServerOptions options;
+extern Buffer loginmsg;
+
+static int auth1_process_password(Authctxt *, char *, size_t);
+static int auth1_process_rsa(Authctxt *, char *, size_t);
+static int auth1_process_rhosts_rsa(Authctxt *, char *, size_t);
+static int auth1_process_tis_challenge(Authctxt *, char *, size_t);
+static int auth1_process_tis_response(Authctxt *, char *, size_t);
+
+static char *client_user = NULL; /* Used to fill in remote user for PAM */
+
+struct AuthMethod1 {
+ int type;
+ char *name;
+ int *enabled;
+ int (*method)(Authctxt *, char *, size_t);
+};
+
+const struct AuthMethod1 auth1_methods[] = {
+ {
+ SSH_CMSG_AUTH_PASSWORD, "password",
+ &options.password_authentication, auth1_process_password
+ },
+ {
+ SSH_CMSG_AUTH_RSA, "rsa",
+ &options.rsa_authentication, auth1_process_rsa
+ },
+ {
+ SSH_CMSG_AUTH_RHOSTS_RSA, "rhosts-rsa",
+ &options.rhosts_rsa_authentication, auth1_process_rhosts_rsa
+ },
+ {
+ SSH_CMSG_AUTH_TIS, "challenge-response",
+ &options.challenge_response_authentication,
+ auth1_process_tis_challenge
+ },
+ {
+ SSH_CMSG_AUTH_TIS_RESPONSE, "challenge-response",
+ &options.challenge_response_authentication,
+ auth1_process_tis_response
+ },
+ { -1, NULL, NULL, NULL}
+};
+
+static const struct AuthMethod1
+*lookup_authmethod1(int type)
+{
+ int i;
+
+ for (i = 0; auth1_methods[i].name != NULL; i++)
+ if (auth1_methods[i].type == type)
+ return (&(auth1_methods[i]));
+
+ return (NULL);
+}
+
+static char *
+get_authname(int type)
+{
+ const struct AuthMethod1 *a;
+ static char buf[64];
+
+ if ((a = lookup_authmethod1(type)) != NULL)
+ return (a->name);
+ snprintf(buf, sizeof(buf), "bad-auth-msg-%d", type);
+ return (buf);
+}
+
+/*ARGSUSED*/
+static int
+auth1_process_password(Authctxt *authctxt, char *info, size_t infolen)
+{
+ int authenticated = 0;
+ char *password;
+ u_int dlen;
+
+ /*
+ * Read user password. It is in plain text, but was
+ * transmitted over the encrypted channel so it is
+ * not visible to an outside observer.
+ */
+ password = packet_get_string(&dlen);
+ packet_check_eom();
+
+ /* Try authentication with the password. */
+ authenticated = PRIVSEP(auth_password(authctxt, password));
+
+ memset(password, 0, dlen);
+ xfree(password);
+
+ return (authenticated);
+}
+
+/*ARGSUSED*/
+static int
+auth1_process_rsa(Authctxt *authctxt, char *info, size_t infolen)
+{
+ int authenticated = 0;
+ BIGNUM *n;
+
+ /* RSA authentication requested. */
+ if ((n = BN_new()) == NULL)
+ fatal("do_authloop: BN_new failed");
+ packet_get_bignum(n);
+ packet_check_eom();
+ authenticated = auth_rsa(authctxt, n);
+ BN_clear_free(n);
+
+ return (authenticated);
+}
+
+/*ARGSUSED*/
+static int
+auth1_process_rhosts_rsa(Authctxt *authctxt, char *info, size_t infolen)
+{
+ int keybits, authenticated = 0;
+ u_int bits;
+ Key *client_host_key;
+ u_int ulen;
+
+ /*
+ * Get client user name. Note that we just have to
+ * trust the client; root on the client machine can
+ * claim to be any user.
+ */
+ client_user = packet_get_cstring(&ulen);
+
+ /* Get the client host key. */
+ client_host_key = key_new(KEY_RSA1);
+ bits = packet_get_int();
+ packet_get_bignum(client_host_key->rsa->e);
+ packet_get_bignum(client_host_key->rsa->n);
+
+ keybits = BN_num_bits(client_host_key->rsa->n);
+ if (keybits < 0 || bits != (u_int)keybits) {
+ verbose("Warning: keysize mismatch for client_host_key: "
+ "actual %d, announced %d",
+ BN_num_bits(client_host_key->rsa->n), bits);
+ }
+ packet_check_eom();
+
+ authenticated = auth_rhosts_rsa(authctxt, client_user,
+ client_host_key);
+ key_free(client_host_key);
+
+ snprintf(info, infolen, " ruser %.100s", client_user);
+
+ return (authenticated);
+}
+
+/*ARGSUSED*/
+static int
+auth1_process_tis_challenge(Authctxt *authctxt, char *info, size_t infolen)
+{
+ char *challenge;
+
+ if ((challenge = get_challenge(authctxt)) == NULL)
+ return (0);
+
+ debug("sending challenge '%s'", challenge);
+ packet_start(SSH_SMSG_AUTH_TIS_CHALLENGE);
+ packet_put_cstring(challenge);
+ xfree(challenge);
+ packet_send();
+ packet_write_wait();
+
+ return (-1);
+}
+
+/*ARGSUSED*/
+static int
+auth1_process_tis_response(Authctxt *authctxt, char *info, size_t infolen)
+{
+ int authenticated = 0;
+ char *response;
+ u_int dlen;
+
+ response = packet_get_string(&dlen);
+ packet_check_eom();
+ authenticated = verify_response(authctxt, response);
+ memset(response, 'r', dlen);
+ xfree(response);
+
+ return (authenticated);
+}
+
+/*
+ * read packets, try to authenticate the user and
+ * return only if authentication is successful
+ */
+static void
+do_authloop(Authctxt *authctxt)
+{
+ int authenticated = 0;
+ char info[1024];
+ int prev = 0, type = 0;
+ const struct AuthMethod1 *meth;
+
+ debug("Attempting authentication for %s%.100s.",
+ authctxt->valid ? "" : "invalid user ", authctxt->user);
+
+ /* If the user has no password, accept authentication immediately. */
+ if (options.permit_empty_passwd && options.password_authentication &&
+#ifdef KRB5
+ (!options.kerberos_authentication || options.kerberos_or_local_passwd) &&
+#endif
+ PRIVSEP(auth_password(authctxt, ""))) {
+#ifdef USE_PAM
+ if (options.use_pam && (PRIVSEP(do_pam_account())))
+#endif
+ {
+ auth_log(authctxt, 1, "without authentication", "");
+ return;
+ }
+ }
+
+ /* Indicate that authentication is needed. */
+ packet_start(SSH_SMSG_FAILURE);
+ packet_send();
+ packet_write_wait();
+
+ for (;;) {
+ /* default to fail */
+ authenticated = 0;
+
+ info[0] = '\0';
+
+ /* Get a packet from the client. */
+ prev = type;
+ type = packet_read();
+
+ /*
+ * If we started challenge-response authentication but the
+ * next packet is not a response to our challenge, release
+ * the resources allocated by get_challenge() (which would
+ * normally have been released by verify_response() had we
+ * received such a response)
+ */
+ if (prev == SSH_CMSG_AUTH_TIS &&
+ type != SSH_CMSG_AUTH_TIS_RESPONSE)
+ abandon_challenge_response(authctxt);
+
+ if (authctxt->failures >= options.max_authtries)
+ goto skip;
+ if ((meth = lookup_authmethod1(type)) == NULL) {
+ logit("Unknown message during authentication: "
+ "type %d", type);
+ goto skip;
+ }
+
+ if (!*(meth->enabled)) {
+ verbose("%s authentication disabled.", meth->name);
+ goto skip;
+ }
+
+ authenticated = meth->method(authctxt, info, sizeof(info));
+ if (authenticated == -1)
+ continue; /* "postponed" */
+
+#ifdef BSD_AUTH
+ if (authctxt->as) {
+ auth_close(authctxt->as);
+ authctxt->as = NULL;
+ }
+#endif
+ if (!authctxt->valid && authenticated)
+ fatal("INTERNAL ERROR: authenticated invalid user %s",
+ authctxt->user);
+
+#ifdef _UNICOS
+ if (authenticated && cray_access_denied(authctxt->user)) {
+ authenticated = 0;
+ fatal("Access denied for user %s.",authctxt->user);
+ }
+#endif /* _UNICOS */
+
+#ifndef HAVE_CYGWIN
+ /* Special handling for root */
+ if (authenticated && authctxt->pw->pw_uid == 0 &&
+ !auth_root_allowed(meth->name)) {
+ authenticated = 0;
+# ifdef SSH_AUDIT_EVENTS
+ PRIVSEP(audit_event(SSH_LOGIN_ROOT_DENIED));
+# endif
+ }
+#endif
+
+#ifdef USE_PAM
+ if (options.use_pam && authenticated &&
+ !PRIVSEP(do_pam_account())) {
+ char *msg;
+ size_t len;
+
+ error("Access denied for user %s by PAM account "
+ "configuration", authctxt->user);
+ len = buffer_len(&loginmsg);
+ buffer_append(&loginmsg, "\0", 1);
+ msg = buffer_ptr(&loginmsg);
+ /* strip trailing newlines */
+ if (len > 0)
+ while (len > 0 && msg[--len] == '\n')
+ msg[len] = '\0';
+ else
+ msg = "Access denied.";
+ packet_disconnect("%s", msg);
+ }
+#endif
+
+ skip:
+ /* Log before sending the reply */
+ auth_log(authctxt, authenticated, get_authname(type), info);
+
+ if (client_user != NULL) {
+ xfree(client_user);
+ client_user = NULL;
+ }
+
+ if (authenticated)
+ return;
+
+ if (++authctxt->failures >= options.max_authtries) {
+#ifdef SSH_AUDIT_EVENTS
+ PRIVSEP(audit_event(SSH_LOGIN_EXCEED_MAXTRIES));
+#endif
+ packet_disconnect(AUTH_FAIL_MSG, authctxt->user);
+ }
+
+ packet_start(SSH_SMSG_FAILURE);
+ packet_send();
+ packet_write_wait();
+ }
+}
+
+/*
+ * Performs authentication of an incoming connection. Session key has already
+ * been exchanged and encryption is enabled.
+ */
+void
+do_authentication(Authctxt *authctxt)
+{
+ u_int ulen;
+ char *user, *style = NULL;
+
+ /* Get the name of the user that we wish to log in as. */
+ packet_read_expect(SSH_CMSG_USER);
+
+ /* Get the user name. */
+ user = packet_get_cstring(&ulen);
+ packet_check_eom();
+
+ if ((style = strchr(user, ':')) != NULL)
+ *style++ = '\0';
+
+ authctxt->user = user;
+ authctxt->style = style;
+
+ /* Verify that the user is a valid user. */
+ if ((authctxt->pw = PRIVSEP(getpwnamallow(user))) != NULL)
+ authctxt->valid = 1;
+ else {
+ debug("do_authentication: invalid user %s", user);
+ authctxt->pw = fakepw();
+ }
+
+ setproctitle("%s%s", authctxt->valid ? user : "unknown",
+ use_privsep ? " [net]" : "");
+
+#ifdef USE_PAM
+ if (options.use_pam)
+ PRIVSEP(start_pam(authctxt));
+#endif
+
+ /*
+ * If we are not running as root, the user must have the same uid as
+ * the server.
+ */
+#ifndef HAVE_CYGWIN
+ if (!use_privsep && getuid() != 0 && authctxt->pw &&
+ authctxt->pw->pw_uid != getuid())
+ packet_disconnect("Cannot change user when server not running as root.");
+#endif
+
+ /*
+ * Loop until the user has been authenticated or the connection is
+ * closed, do_authloop() returns only if authentication is successful
+ */
+ do_authloop(authctxt);
+
+ /* The user has been authenticated and accepted. */
+ packet_start(SSH_SMSG_SUCCESS);
+ packet_send();
+ packet_write_wait();
+}
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