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1307 lines
35 KiB
C
1307 lines
35 KiB
C
/*
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* Author: Tatu Ylonen <ylo@cs.hut.fi>
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* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
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* All rights reserved
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* Code to connect to a remote host, and to perform the client side of the
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* login (authentication) dialog.
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*
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* As far as I am concerned, the code I have written for this software
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* can be used freely for any purpose. Any derived versions of this
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* software must be clearly marked as such, and if the derived work is
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* incompatible with the protocol description in the RFC file, it must be
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* called by a name other than "ssh" or "Secure Shell".
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*/
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#include "includes.h"
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RCSID("$OpenBSD: sshconnect1.c,v 1.53 2003/04/08 20:21:29 itojun Exp $");
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#include <openssl/bn.h>
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#include <openssl/md5.h>
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#ifdef KRB4
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#include <krb.h>
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#endif
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#ifdef KRB5
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#include <krb5.h>
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#ifndef HEIMDAL
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#define krb5_get_err_text(context,code) error_message(code)
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#endif /* !HEIMDAL */
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#endif
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#ifdef AFS
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#include <kafs.h>
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#include "radix.h"
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#endif
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#include "ssh.h"
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#include "ssh1.h"
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#include "xmalloc.h"
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#include "rsa.h"
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#include "buffer.h"
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#include "packet.h"
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#include "mpaux.h"
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#include "uidswap.h"
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#include "log.h"
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#include "readconf.h"
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#include "key.h"
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#include "authfd.h"
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#include "sshconnect.h"
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#include "authfile.h"
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#include "readpass.h"
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#include "cipher.h"
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#include "canohost.h"
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#include "auth.h"
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/* Session id for the current session. */
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u_char session_id[16];
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u_int supported_authentications = 0;
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extern Options options;
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extern char *__progname;
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/*
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* Checks if the user has an authentication agent, and if so, tries to
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* authenticate using the agent.
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*/
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static int
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try_agent_authentication(void)
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{
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int type;
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char *comment;
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AuthenticationConnection *auth;
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u_char response[16];
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u_int i;
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Key *key;
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BIGNUM *challenge;
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/* Get connection to the agent. */
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auth = ssh_get_authentication_connection();
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if (!auth)
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return 0;
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if ((challenge = BN_new()) == NULL)
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fatal("try_agent_authentication: BN_new failed");
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/* Loop through identities served by the agent. */
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for (key = ssh_get_first_identity(auth, &comment, 1);
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key != NULL;
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key = ssh_get_next_identity(auth, &comment, 1)) {
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/* Try this identity. */
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debug("Trying RSA authentication via agent with '%.100s'", comment);
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xfree(comment);
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/* Tell the server that we are willing to authenticate using this key. */
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packet_start(SSH_CMSG_AUTH_RSA);
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packet_put_bignum(key->rsa->n);
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packet_send();
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packet_write_wait();
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/* Wait for server's response. */
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type = packet_read();
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/* The server sends failure if it doesn\'t like our key or
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does not support RSA authentication. */
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if (type == SSH_SMSG_FAILURE) {
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debug("Server refused our key.");
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key_free(key);
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continue;
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}
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/* Otherwise it should have sent a challenge. */
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if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
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packet_disconnect("Protocol error during RSA authentication: %d",
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type);
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packet_get_bignum(challenge);
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packet_check_eom();
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debug("Received RSA challenge from server.");
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/* Ask the agent to decrypt the challenge. */
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if (!ssh_decrypt_challenge(auth, key, challenge, session_id, 1, response)) {
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/*
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* The agent failed to authenticate this identifier
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* although it advertised it supports this. Just
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* return a wrong value.
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*/
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logit("Authentication agent failed to decrypt challenge.");
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memset(response, 0, sizeof(response));
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}
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key_free(key);
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debug("Sending response to RSA challenge.");
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/* Send the decrypted challenge back to the server. */
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packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
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for (i = 0; i < 16; i++)
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packet_put_char(response[i]);
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packet_send();
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packet_write_wait();
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/* Wait for response from the server. */
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type = packet_read();
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/* The server returns success if it accepted the authentication. */
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if (type == SSH_SMSG_SUCCESS) {
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ssh_close_authentication_connection(auth);
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BN_clear_free(challenge);
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debug("RSA authentication accepted by server.");
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return 1;
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}
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/* Otherwise it should return failure. */
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if (type != SSH_SMSG_FAILURE)
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packet_disconnect("Protocol error waiting RSA auth response: %d",
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type);
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}
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ssh_close_authentication_connection(auth);
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BN_clear_free(challenge);
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debug("RSA authentication using agent refused.");
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return 0;
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}
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/*
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* Computes the proper response to a RSA challenge, and sends the response to
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* the server.
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*/
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static void
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respond_to_rsa_challenge(BIGNUM * challenge, RSA * prv)
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{
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u_char buf[32], response[16];
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MD5_CTX md;
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int i, len;
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/* Decrypt the challenge using the private key. */
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/* XXX think about Bleichenbacher, too */
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if (rsa_private_decrypt(challenge, challenge, prv) <= 0)
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packet_disconnect(
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"respond_to_rsa_challenge: rsa_private_decrypt failed");
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/* Compute the response. */
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/* The response is MD5 of decrypted challenge plus session id. */
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len = BN_num_bytes(challenge);
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if (len <= 0 || len > sizeof(buf))
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packet_disconnect(
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"respond_to_rsa_challenge: bad challenge length %d", len);
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memset(buf, 0, sizeof(buf));
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BN_bn2bin(challenge, buf + sizeof(buf) - len);
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MD5_Init(&md);
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MD5_Update(&md, buf, 32);
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MD5_Update(&md, session_id, 16);
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MD5_Final(response, &md);
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debug("Sending response to host key RSA challenge.");
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/* Send the response back to the server. */
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packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
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for (i = 0; i < 16; i++)
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packet_put_char(response[i]);
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packet_send();
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packet_write_wait();
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memset(buf, 0, sizeof(buf));
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memset(response, 0, sizeof(response));
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memset(&md, 0, sizeof(md));
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}
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/*
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* Checks if the user has authentication file, and if so, tries to authenticate
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* the user using it.
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*/
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static int
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try_rsa_authentication(int idx)
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{
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BIGNUM *challenge;
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Key *public, *private;
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char buf[300], *passphrase, *comment, *authfile;
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int i, type, quit;
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public = options.identity_keys[idx];
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authfile = options.identity_files[idx];
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comment = xstrdup(authfile);
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debug("Trying RSA authentication with key '%.100s'", comment);
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/* Tell the server that we are willing to authenticate using this key. */
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packet_start(SSH_CMSG_AUTH_RSA);
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packet_put_bignum(public->rsa->n);
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packet_send();
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packet_write_wait();
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/* Wait for server's response. */
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type = packet_read();
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/*
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* The server responds with failure if it doesn\'t like our key or
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* doesn\'t support RSA authentication.
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*/
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if (type == SSH_SMSG_FAILURE) {
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debug("Server refused our key.");
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xfree(comment);
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return 0;
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}
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/* Otherwise, the server should respond with a challenge. */
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if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
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packet_disconnect("Protocol error during RSA authentication: %d", type);
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/* Get the challenge from the packet. */
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if ((challenge = BN_new()) == NULL)
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fatal("try_rsa_authentication: BN_new failed");
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packet_get_bignum(challenge);
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packet_check_eom();
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debug("Received RSA challenge from server.");
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/*
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* If the key is not stored in external hardware, we have to
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* load the private key. Try first with empty passphrase; if it
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* fails, ask for a passphrase.
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*/
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if (public->flags & KEY_FLAG_EXT)
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private = public;
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else
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private = key_load_private_type(KEY_RSA1, authfile, "", NULL);
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if (private == NULL && !options.batch_mode) {
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snprintf(buf, sizeof(buf),
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"Enter passphrase for RSA key '%.100s': ", comment);
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for (i = 0; i < options.number_of_password_prompts; i++) {
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passphrase = read_passphrase(buf, 0);
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if (strcmp(passphrase, "") != 0) {
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private = key_load_private_type(KEY_RSA1,
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authfile, passphrase, NULL);
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quit = 0;
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} else {
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debug2("no passphrase given, try next key");
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quit = 1;
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}
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memset(passphrase, 0, strlen(passphrase));
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xfree(passphrase);
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if (private != NULL || quit)
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break;
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debug2("bad passphrase given, try again...");
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}
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}
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/* We no longer need the comment. */
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xfree(comment);
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if (private == NULL) {
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if (!options.batch_mode)
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error("Bad passphrase.");
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/* Send a dummy response packet to avoid protocol error. */
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packet_start(SSH_CMSG_AUTH_RSA_RESPONSE);
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for (i = 0; i < 16; i++)
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packet_put_char(0);
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packet_send();
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packet_write_wait();
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/* Expect the server to reject it... */
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packet_read_expect(SSH_SMSG_FAILURE);
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BN_clear_free(challenge);
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return 0;
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}
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/* Compute and send a response to the challenge. */
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respond_to_rsa_challenge(challenge, private->rsa);
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/* Destroy the private key unless it in external hardware. */
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if (!(private->flags & KEY_FLAG_EXT))
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key_free(private);
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/* We no longer need the challenge. */
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BN_clear_free(challenge);
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/* Wait for response from the server. */
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type = packet_read();
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if (type == SSH_SMSG_SUCCESS) {
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debug("RSA authentication accepted by server.");
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return 1;
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}
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if (type != SSH_SMSG_FAILURE)
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packet_disconnect("Protocol error waiting RSA auth response: %d", type);
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debug("RSA authentication refused.");
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return 0;
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}
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/*
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* Tries to authenticate the user using combined rhosts or /etc/hosts.equiv
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* authentication and RSA host authentication.
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*/
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static int
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try_rhosts_rsa_authentication(const char *local_user, Key * host_key)
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{
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int type;
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BIGNUM *challenge;
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debug("Trying rhosts or /etc/hosts.equiv with RSA host authentication.");
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/* Tell the server that we are willing to authenticate using this key. */
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packet_start(SSH_CMSG_AUTH_RHOSTS_RSA);
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packet_put_cstring(local_user);
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packet_put_int(BN_num_bits(host_key->rsa->n));
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packet_put_bignum(host_key->rsa->e);
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packet_put_bignum(host_key->rsa->n);
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packet_send();
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packet_write_wait();
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/* Wait for server's response. */
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type = packet_read();
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/* The server responds with failure if it doesn't admit our
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.rhosts authentication or doesn't know our host key. */
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if (type == SSH_SMSG_FAILURE) {
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debug("Server refused our rhosts authentication or host key.");
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return 0;
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}
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/* Otherwise, the server should respond with a challenge. */
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if (type != SSH_SMSG_AUTH_RSA_CHALLENGE)
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packet_disconnect("Protocol error during RSA authentication: %d", type);
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/* Get the challenge from the packet. */
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if ((challenge = BN_new()) == NULL)
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fatal("try_rhosts_rsa_authentication: BN_new failed");
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packet_get_bignum(challenge);
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packet_check_eom();
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debug("Received RSA challenge for host key from server.");
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/* Compute a response to the challenge. */
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respond_to_rsa_challenge(challenge, host_key->rsa);
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/* We no longer need the challenge. */
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BN_clear_free(challenge);
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/* Wait for response from the server. */
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type = packet_read();
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if (type == SSH_SMSG_SUCCESS) {
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debug("Rhosts or /etc/hosts.equiv with RSA host authentication accepted by server.");
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return 1;
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}
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if (type != SSH_SMSG_FAILURE)
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packet_disconnect("Protocol error waiting RSA auth response: %d", type);
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debug("Rhosts or /etc/hosts.equiv with RSA host authentication refused.");
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return 0;
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}
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#ifdef KRB4
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static int
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try_krb4_authentication(void)
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{
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KTEXT_ST auth; /* Kerberos data */
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char *reply;
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char inst[INST_SZ];
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char *realm;
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CREDENTIALS cred;
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int r, type;
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socklen_t slen;
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Key_schedule schedule;
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u_long checksum, cksum;
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MSG_DAT msg_data;
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struct sockaddr_in local, foreign;
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struct stat st;
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/* Don't do anything if we don't have any tickets. */
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if (stat(tkt_string(), &st) < 0)
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return 0;
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strlcpy(inst, (char *)krb_get_phost(get_canonical_hostname(1)),
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INST_SZ);
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realm = (char *)krb_realmofhost(get_canonical_hostname(1));
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if (!realm) {
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debug("Kerberos v4: no realm for %s", get_canonical_hostname(1));
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return 0;
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}
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/* This can really be anything. */
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checksum = (u_long)getpid();
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r = krb_mk_req(&auth, KRB4_SERVICE_NAME, inst, realm, checksum);
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if (r != KSUCCESS) {
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debug("Kerberos v4 krb_mk_req failed: %s", krb_err_txt[r]);
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return 0;
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}
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/* Get session key to decrypt the server's reply with. */
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r = krb_get_cred(KRB4_SERVICE_NAME, inst, realm, &cred);
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if (r != KSUCCESS) {
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debug("get_cred failed: %s", krb_err_txt[r]);
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return 0;
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}
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des_key_sched((des_cblock *) cred.session, schedule);
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/* Send authentication info to server. */
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packet_start(SSH_CMSG_AUTH_KERBEROS);
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packet_put_string((char *) auth.dat, auth.length);
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packet_send();
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packet_write_wait();
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/* Zero the buffer. */
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(void) memset(auth.dat, 0, MAX_KTXT_LEN);
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slen = sizeof(local);
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memset(&local, 0, sizeof(local));
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if (getsockname(packet_get_connection_in(),
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(struct sockaddr *)&local, &slen) < 0)
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debug("getsockname failed: %s", strerror(errno));
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slen = sizeof(foreign);
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memset(&foreign, 0, sizeof(foreign));
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if (getpeername(packet_get_connection_in(),
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(struct sockaddr *)&foreign, &slen) < 0) {
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debug("getpeername failed: %s", strerror(errno));
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fatal_cleanup();
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}
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/* Get server reply. */
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type = packet_read();
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switch (type) {
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case SSH_SMSG_FAILURE:
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/* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
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debug("Kerberos v4 authentication failed.");
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return 0;
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break;
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case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
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/* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
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debug("Kerberos v4 authentication accepted.");
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/* Get server's response. */
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reply = packet_get_string((u_int *) &auth.length);
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if (auth.length >= MAX_KTXT_LEN)
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fatal("Kerberos v4: Malformed response from server");
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memcpy(auth.dat, reply, auth.length);
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xfree(reply);
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packet_check_eom();
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/*
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* If his response isn't properly encrypted with the session
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* key, and the decrypted checksum fails to match, he's
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* bogus. Bail out.
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*/
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r = krb_rd_priv(auth.dat, auth.length, schedule, &cred.session,
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&foreign, &local, &msg_data);
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if (r != KSUCCESS) {
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debug("Kerberos v4 krb_rd_priv failed: %s",
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krb_err_txt[r]);
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packet_disconnect("Kerberos v4 challenge failed!");
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}
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/* Fetch the (incremented) checksum that we supplied in the request. */
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memcpy((char *)&cksum, (char *)msg_data.app_data,
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sizeof(cksum));
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cksum = ntohl(cksum);
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/* If it matches, we're golden. */
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if (cksum == checksum + 1) {
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debug("Kerberos v4 challenge successful.");
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return 1;
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} else
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packet_disconnect("Kerberos v4 challenge failed!");
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break;
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default:
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packet_disconnect("Protocol error on Kerberos v4 response: %d", type);
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}
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return 0;
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}
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#endif /* KRB4 */
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#ifdef KRB5
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static int
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try_krb5_authentication(krb5_context *context, krb5_auth_context *auth_context)
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{
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krb5_error_code problem;
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const char *tkfile;
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struct stat buf;
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krb5_ccache ccache = NULL;
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const char *remotehost;
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krb5_data ap;
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int type;
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krb5_ap_rep_enc_part *reply = NULL;
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int ret;
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memset(&ap, 0, sizeof(ap));
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|
|
problem = krb5_init_context(context);
|
|
if (problem) {
|
|
debug("Kerberos v5: krb5_init_context failed");
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
problem = krb5_auth_con_init(*context, auth_context);
|
|
if (problem) {
|
|
debug("Kerberos v5: krb5_auth_con_init failed");
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
#ifndef HEIMDAL
|
|
problem = krb5_auth_con_setflags(*context, *auth_context,
|
|
KRB5_AUTH_CONTEXT_RET_TIME);
|
|
if (problem) {
|
|
debug("Keberos v5: krb5_auth_con_setflags failed");
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
#endif
|
|
|
|
tkfile = krb5_cc_default_name(*context);
|
|
if (strncmp(tkfile, "FILE:", 5) == 0)
|
|
tkfile += 5;
|
|
|
|
if (stat(tkfile, &buf) == 0 && getuid() != buf.st_uid) {
|
|
debug("Kerberos v5: could not get default ccache (permission denied).");
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
problem = krb5_cc_default(*context, &ccache);
|
|
if (problem) {
|
|
debug("Kerberos v5: krb5_cc_default failed: %s",
|
|
krb5_get_err_text(*context, problem));
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
remotehost = get_canonical_hostname(1);
|
|
|
|
problem = krb5_mk_req(*context, auth_context, AP_OPTS_MUTUAL_REQUIRED,
|
|
"host", remotehost, NULL, ccache, &ap);
|
|
if (problem) {
|
|
debug("Kerberos v5: krb5_mk_req failed: %s",
|
|
krb5_get_err_text(*context, problem));
|
|
ret = 0;
|
|
goto out;
|
|
}
|
|
|
|
packet_start(SSH_CMSG_AUTH_KERBEROS);
|
|
packet_put_string((char *) ap.data, ap.length);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
xfree(ap.data);
|
|
ap.length = 0;
|
|
|
|
type = packet_read();
|
|
switch (type) {
|
|
case SSH_SMSG_FAILURE:
|
|
/* Should really be SSH_SMSG_AUTH_KERBEROS_FAILURE */
|
|
debug("Kerberos v5 authentication failed.");
|
|
ret = 0;
|
|
break;
|
|
|
|
case SSH_SMSG_AUTH_KERBEROS_RESPONSE:
|
|
/* SSH_SMSG_AUTH_KERBEROS_SUCCESS */
|
|
debug("Kerberos v5 authentication accepted.");
|
|
|
|
/* Get server's response. */
|
|
ap.data = packet_get_string((unsigned int *) &ap.length);
|
|
packet_check_eom();
|
|
/* XXX je to dobre? */
|
|
|
|
problem = krb5_rd_rep(*context, *auth_context, &ap, &reply);
|
|
if (problem) {
|
|
ret = 0;
|
|
}
|
|
ret = 1;
|
|
break;
|
|
|
|
default:
|
|
packet_disconnect("Protocol error on Kerberos v5 response: %d",
|
|
type);
|
|
ret = 0;
|
|
break;
|
|
|
|
}
|
|
|
|
out:
|
|
if (ccache != NULL)
|
|
krb5_cc_close(*context, ccache);
|
|
if (reply != NULL)
|
|
krb5_free_ap_rep_enc_part(*context, reply);
|
|
if (ap.length > 0)
|
|
#ifdef HEIMDAL
|
|
krb5_data_free(&ap);
|
|
#else
|
|
krb5_free_data_contents(*context, &ap);
|
|
#endif
|
|
|
|
return (ret);
|
|
}
|
|
|
|
static void
|
|
send_krb5_tgt(krb5_context context, krb5_auth_context auth_context)
|
|
{
|
|
int fd, type;
|
|
krb5_error_code problem;
|
|
krb5_data outbuf;
|
|
krb5_ccache ccache = NULL;
|
|
krb5_creds creds;
|
|
#ifdef HEIMDAL
|
|
krb5_kdc_flags flags;
|
|
#else
|
|
int forwardable;
|
|
#endif
|
|
const char *remotehost;
|
|
|
|
memset(&creds, 0, sizeof(creds));
|
|
memset(&outbuf, 0, sizeof(outbuf));
|
|
|
|
fd = packet_get_connection_in();
|
|
|
|
#ifdef HEIMDAL
|
|
problem = krb5_auth_con_setaddrs_from_fd(context, auth_context, &fd);
|
|
#else
|
|
problem = krb5_auth_con_genaddrs(context, auth_context, fd,
|
|
KRB5_AUTH_CONTEXT_GENERATE_REMOTE_FULL_ADDR |
|
|
KRB5_AUTH_CONTEXT_GENERATE_LOCAL_FULL_ADDR);
|
|
#endif
|
|
if (problem)
|
|
goto out;
|
|
|
|
problem = krb5_cc_default(context, &ccache);
|
|
if (problem)
|
|
goto out;
|
|
|
|
problem = krb5_cc_get_principal(context, ccache, &creds.client);
|
|
if (problem)
|
|
goto out;
|
|
|
|
remotehost = get_canonical_hostname(1);
|
|
|
|
#ifdef HEIMDAL
|
|
problem = krb5_build_principal(context, &creds.server,
|
|
strlen(creds.client->realm), creds.client->realm,
|
|
"krbtgt", creds.client->realm, NULL);
|
|
#else
|
|
problem = krb5_build_principal(context, &creds.server,
|
|
creds.client->realm.length, creds.client->realm.data,
|
|
"host", remotehost, NULL);
|
|
#endif
|
|
if (problem)
|
|
goto out;
|
|
|
|
creds.times.endtime = 0;
|
|
|
|
#ifdef HEIMDAL
|
|
flags.i = 0;
|
|
flags.b.forwarded = 1;
|
|
flags.b.forwardable = krb5_config_get_bool(context, NULL,
|
|
"libdefaults", "forwardable", NULL);
|
|
problem = krb5_get_forwarded_creds(context, auth_context,
|
|
ccache, flags.i, remotehost, &creds, &outbuf);
|
|
#else
|
|
forwardable = 1;
|
|
problem = krb5_fwd_tgt_creds(context, auth_context, remotehost,
|
|
creds.client, creds.server, ccache, forwardable, &outbuf);
|
|
#endif
|
|
|
|
if (problem)
|
|
goto out;
|
|
|
|
packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
|
|
packet_put_string((char *)outbuf.data, outbuf.length);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
type = packet_read();
|
|
|
|
if (type == SSH_SMSG_SUCCESS) {
|
|
char *pname;
|
|
|
|
krb5_unparse_name(context, creds.client, &pname);
|
|
debug("Kerberos v5 TGT forwarded (%s).", pname);
|
|
xfree(pname);
|
|
} else
|
|
debug("Kerberos v5 TGT forwarding failed.");
|
|
|
|
return;
|
|
|
|
out:
|
|
if (problem)
|
|
debug("Kerberos v5 TGT forwarding failed: %s",
|
|
krb5_get_err_text(context, problem));
|
|
if (creds.client)
|
|
krb5_free_principal(context, creds.client);
|
|
if (creds.server)
|
|
krb5_free_principal(context, creds.server);
|
|
if (ccache)
|
|
krb5_cc_close(context, ccache);
|
|
if (outbuf.data)
|
|
xfree(outbuf.data);
|
|
}
|
|
#endif /* KRB5 */
|
|
|
|
#ifdef AFS
|
|
static void
|
|
send_krb4_tgt(void)
|
|
{
|
|
CREDENTIALS *creds;
|
|
struct stat st;
|
|
char buffer[4096], pname[ANAME_SZ], pinst[INST_SZ], prealm[REALM_SZ];
|
|
int problem, type;
|
|
|
|
/* Don't do anything if we don't have any tickets. */
|
|
if (stat(tkt_string(), &st) < 0)
|
|
return;
|
|
|
|
creds = xmalloc(sizeof(*creds));
|
|
|
|
problem = krb_get_tf_fullname(TKT_FILE, pname, pinst, prealm);
|
|
if (problem)
|
|
goto out;
|
|
|
|
problem = krb_get_cred("krbtgt", prealm, prealm, creds);
|
|
if (problem)
|
|
goto out;
|
|
|
|
if (time(0) > krb_life_to_time(creds->issue_date, creds->lifetime)) {
|
|
problem = RD_AP_EXP;
|
|
goto out;
|
|
}
|
|
creds_to_radix(creds, (u_char *)buffer, sizeof(buffer));
|
|
|
|
packet_start(SSH_CMSG_HAVE_KERBEROS_TGT);
|
|
packet_put_cstring(buffer);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
type = packet_read();
|
|
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
debug("Kerberos v4 TGT forwarded (%s%s%s@%s).",
|
|
creds->pname, creds->pinst[0] ? "." : "",
|
|
creds->pinst, creds->realm);
|
|
else
|
|
debug("Kerberos v4 TGT rejected.");
|
|
|
|
xfree(creds);
|
|
return;
|
|
|
|
out:
|
|
debug("Kerberos v4 TGT passing failed: %s", krb_err_txt[problem]);
|
|
xfree(creds);
|
|
}
|
|
|
|
static void
|
|
send_afs_tokens(void)
|
|
{
|
|
CREDENTIALS creds;
|
|
struct ViceIoctl parms;
|
|
struct ClearToken ct;
|
|
int i, type, len;
|
|
char buf[2048], *p, *server_cell;
|
|
char buffer[8192];
|
|
|
|
/* Move over ktc_GetToken, here's something leaner. */
|
|
for (i = 0; i < 100; i++) { /* just in case */
|
|
parms.in = (char *) &i;
|
|
parms.in_size = sizeof(i);
|
|
parms.out = buf;
|
|
parms.out_size = sizeof(buf);
|
|
if (k_pioctl(0, VIOCGETTOK, &parms, 0) != 0)
|
|
break;
|
|
p = buf;
|
|
|
|
/* Get secret token. */
|
|
memcpy(&creds.ticket_st.length, p, sizeof(u_int));
|
|
if (creds.ticket_st.length > MAX_KTXT_LEN)
|
|
break;
|
|
p += sizeof(u_int);
|
|
memcpy(creds.ticket_st.dat, p, creds.ticket_st.length);
|
|
p += creds.ticket_st.length;
|
|
|
|
/* Get clear token. */
|
|
memcpy(&len, p, sizeof(len));
|
|
if (len != sizeof(struct ClearToken))
|
|
break;
|
|
p += sizeof(len);
|
|
memcpy(&ct, p, len);
|
|
p += len;
|
|
p += sizeof(len); /* primary flag */
|
|
server_cell = p;
|
|
|
|
/* Flesh out our credentials. */
|
|
strlcpy(creds.service, "afs", sizeof(creds.service));
|
|
creds.instance[0] = '\0';
|
|
strlcpy(creds.realm, server_cell, REALM_SZ);
|
|
memcpy(creds.session, ct.HandShakeKey, DES_KEY_SZ);
|
|
creds.issue_date = ct.BeginTimestamp;
|
|
creds.lifetime = krb_time_to_life(creds.issue_date,
|
|
ct.EndTimestamp);
|
|
creds.kvno = ct.AuthHandle;
|
|
snprintf(creds.pname, sizeof(creds.pname), "AFS ID %d", ct.ViceId);
|
|
creds.pinst[0] = '\0';
|
|
|
|
/* Encode token, ship it off. */
|
|
if (creds_to_radix(&creds, (u_char *)buffer,
|
|
sizeof(buffer)) <= 0)
|
|
break;
|
|
packet_start(SSH_CMSG_HAVE_AFS_TOKEN);
|
|
packet_put_cstring(buffer);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
/* Roger, Roger. Clearance, Clarence. What's your vector,
|
|
Victor? */
|
|
type = packet_read();
|
|
|
|
if (type == SSH_SMSG_FAILURE)
|
|
debug("AFS token for cell %s rejected.", server_cell);
|
|
else if (type != SSH_SMSG_SUCCESS)
|
|
packet_disconnect("Protocol error on AFS token response: %d", type);
|
|
}
|
|
}
|
|
|
|
#endif /* AFS */
|
|
|
|
/*
|
|
* Tries to authenticate with any string-based challenge/response system.
|
|
* Note that the client code is not tied to s/key or TIS.
|
|
*/
|
|
static int
|
|
try_challenge_response_authentication(void)
|
|
{
|
|
int type, i;
|
|
u_int clen;
|
|
char prompt[1024];
|
|
char *challenge, *response;
|
|
|
|
debug("Doing challenge response authentication.");
|
|
|
|
for (i = 0; i < options.number_of_password_prompts; i++) {
|
|
/* request a challenge */
|
|
packet_start(SSH_CMSG_AUTH_TIS);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
type = packet_read();
|
|
if (type != SSH_SMSG_FAILURE &&
|
|
type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
|
|
packet_disconnect("Protocol error: got %d in response "
|
|
"to SSH_CMSG_AUTH_TIS", type);
|
|
}
|
|
if (type != SSH_SMSG_AUTH_TIS_CHALLENGE) {
|
|
debug("No challenge.");
|
|
return 0;
|
|
}
|
|
challenge = packet_get_string(&clen);
|
|
packet_check_eom();
|
|
snprintf(prompt, sizeof prompt, "%s%s", challenge,
|
|
strchr(challenge, '\n') ? "" : "\nResponse: ");
|
|
xfree(challenge);
|
|
if (i != 0)
|
|
error("Permission denied, please try again.");
|
|
if (options.cipher == SSH_CIPHER_NONE)
|
|
logit("WARNING: Encryption is disabled! "
|
|
"Response will be transmitted in clear text.");
|
|
response = read_passphrase(prompt, 0);
|
|
if (strcmp(response, "") == 0) {
|
|
xfree(response);
|
|
break;
|
|
}
|
|
packet_start(SSH_CMSG_AUTH_TIS_RESPONSE);
|
|
ssh_put_password(response);
|
|
memset(response, 0, strlen(response));
|
|
xfree(response);
|
|
packet_send();
|
|
packet_write_wait();
|
|
type = packet_read();
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
return 1;
|
|
if (type != SSH_SMSG_FAILURE)
|
|
packet_disconnect("Protocol error: got %d in response "
|
|
"to SSH_CMSG_AUTH_TIS_RESPONSE", type);
|
|
}
|
|
/* failure */
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* Tries to authenticate with plain passwd authentication.
|
|
*/
|
|
static int
|
|
try_password_authentication(char *prompt)
|
|
{
|
|
int type, i;
|
|
char *password;
|
|
|
|
debug("Doing password authentication.");
|
|
if (options.cipher == SSH_CIPHER_NONE)
|
|
logit("WARNING: Encryption is disabled! Password will be transmitted in clear text.");
|
|
for (i = 0; i < options.number_of_password_prompts; i++) {
|
|
if (i != 0)
|
|
error("Permission denied, please try again.");
|
|
password = read_passphrase(prompt, 0);
|
|
packet_start(SSH_CMSG_AUTH_PASSWORD);
|
|
ssh_put_password(password);
|
|
memset(password, 0, strlen(password));
|
|
xfree(password);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
type = packet_read();
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
return 1;
|
|
if (type != SSH_SMSG_FAILURE)
|
|
packet_disconnect("Protocol error: got %d in response to passwd auth", type);
|
|
}
|
|
/* failure */
|
|
return 0;
|
|
}
|
|
|
|
/*
|
|
* SSH1 key exchange
|
|
*/
|
|
void
|
|
ssh_kex(char *host, struct sockaddr *hostaddr)
|
|
{
|
|
int i;
|
|
BIGNUM *key;
|
|
Key *host_key, *server_key;
|
|
int bits, rbits;
|
|
int ssh_cipher_default = SSH_CIPHER_3DES;
|
|
u_char session_key[SSH_SESSION_KEY_LENGTH];
|
|
u_char cookie[8];
|
|
u_int supported_ciphers;
|
|
u_int server_flags, client_flags;
|
|
u_int32_t rand = 0;
|
|
|
|
debug("Waiting for server public key.");
|
|
|
|
/* Wait for a public key packet from the server. */
|
|
packet_read_expect(SSH_SMSG_PUBLIC_KEY);
|
|
|
|
/* Get cookie from the packet. */
|
|
for (i = 0; i < 8; i++)
|
|
cookie[i] = packet_get_char();
|
|
|
|
/* Get the public key. */
|
|
server_key = key_new(KEY_RSA1);
|
|
bits = packet_get_int();
|
|
packet_get_bignum(server_key->rsa->e);
|
|
packet_get_bignum(server_key->rsa->n);
|
|
|
|
rbits = BN_num_bits(server_key->rsa->n);
|
|
if (bits != rbits) {
|
|
logit("Warning: Server lies about size of server public key: "
|
|
"actual size is %d bits vs. announced %d.", rbits, bits);
|
|
logit("Warning: This may be due to an old implementation of ssh.");
|
|
}
|
|
/* Get the host key. */
|
|
host_key = key_new(KEY_RSA1);
|
|
bits = packet_get_int();
|
|
packet_get_bignum(host_key->rsa->e);
|
|
packet_get_bignum(host_key->rsa->n);
|
|
|
|
rbits = BN_num_bits(host_key->rsa->n);
|
|
if (bits != rbits) {
|
|
logit("Warning: Server lies about size of server host key: "
|
|
"actual size is %d bits vs. announced %d.", rbits, bits);
|
|
logit("Warning: This may be due to an old implementation of ssh.");
|
|
}
|
|
|
|
/* Get protocol flags. */
|
|
server_flags = packet_get_int();
|
|
packet_set_protocol_flags(server_flags);
|
|
|
|
supported_ciphers = packet_get_int();
|
|
supported_authentications = packet_get_int();
|
|
packet_check_eom();
|
|
|
|
debug("Received server public key (%d bits) and host key (%d bits).",
|
|
BN_num_bits(server_key->rsa->n), BN_num_bits(host_key->rsa->n));
|
|
|
|
if (verify_host_key(host, hostaddr, host_key) == -1)
|
|
fatal("Host key verification failed.");
|
|
|
|
client_flags = SSH_PROTOFLAG_SCREEN_NUMBER | SSH_PROTOFLAG_HOST_IN_FWD_OPEN;
|
|
|
|
compute_session_id(session_id, cookie, host_key->rsa->n, server_key->rsa->n);
|
|
|
|
/* Generate a session key. */
|
|
arc4random_stir();
|
|
|
|
/*
|
|
* Generate an encryption key for the session. The key is a 256 bit
|
|
* random number, interpreted as a 32-byte key, with the least
|
|
* significant 8 bits being the first byte of the key.
|
|
*/
|
|
for (i = 0; i < 32; i++) {
|
|
if (i % 4 == 0)
|
|
rand = arc4random();
|
|
session_key[i] = rand & 0xff;
|
|
rand >>= 8;
|
|
}
|
|
|
|
/*
|
|
* According to the protocol spec, the first byte of the session key
|
|
* is the highest byte of the integer. The session key is xored with
|
|
* the first 16 bytes of the session id.
|
|
*/
|
|
if ((key = BN_new()) == NULL)
|
|
fatal("respond_to_rsa_challenge: BN_new failed");
|
|
BN_set_word(key, 0);
|
|
for (i = 0; i < SSH_SESSION_KEY_LENGTH; i++) {
|
|
BN_lshift(key, key, 8);
|
|
if (i < 16)
|
|
BN_add_word(key, session_key[i] ^ session_id[i]);
|
|
else
|
|
BN_add_word(key, session_key[i]);
|
|
}
|
|
|
|
/*
|
|
* Encrypt the integer using the public key and host key of the
|
|
* server (key with smaller modulus first).
|
|
*/
|
|
if (BN_cmp(server_key->rsa->n, host_key->rsa->n) < 0) {
|
|
/* Public key has smaller modulus. */
|
|
if (BN_num_bits(host_key->rsa->n) <
|
|
BN_num_bits(server_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
|
|
fatal("respond_to_rsa_challenge: host_key %d < server_key %d + "
|
|
"SSH_KEY_BITS_RESERVED %d",
|
|
BN_num_bits(host_key->rsa->n),
|
|
BN_num_bits(server_key->rsa->n),
|
|
SSH_KEY_BITS_RESERVED);
|
|
}
|
|
rsa_public_encrypt(key, key, server_key->rsa);
|
|
rsa_public_encrypt(key, key, host_key->rsa);
|
|
} else {
|
|
/* Host key has smaller modulus (or they are equal). */
|
|
if (BN_num_bits(server_key->rsa->n) <
|
|
BN_num_bits(host_key->rsa->n) + SSH_KEY_BITS_RESERVED) {
|
|
fatal("respond_to_rsa_challenge: server_key %d < host_key %d + "
|
|
"SSH_KEY_BITS_RESERVED %d",
|
|
BN_num_bits(server_key->rsa->n),
|
|
BN_num_bits(host_key->rsa->n),
|
|
SSH_KEY_BITS_RESERVED);
|
|
}
|
|
rsa_public_encrypt(key, key, host_key->rsa);
|
|
rsa_public_encrypt(key, key, server_key->rsa);
|
|
}
|
|
|
|
/* Destroy the public keys since we no longer need them. */
|
|
key_free(server_key);
|
|
key_free(host_key);
|
|
|
|
if (options.cipher == SSH_CIPHER_NOT_SET) {
|
|
if (cipher_mask_ssh1(1) & supported_ciphers & (1 << ssh_cipher_default))
|
|
options.cipher = ssh_cipher_default;
|
|
} else if (options.cipher == SSH_CIPHER_ILLEGAL ||
|
|
!(cipher_mask_ssh1(1) & (1 << options.cipher))) {
|
|
logit("No valid SSH1 cipher, using %.100s instead.",
|
|
cipher_name(ssh_cipher_default));
|
|
options.cipher = ssh_cipher_default;
|
|
}
|
|
/* Check that the selected cipher is supported. */
|
|
if (!(supported_ciphers & (1 << options.cipher)))
|
|
fatal("Selected cipher type %.100s not supported by server.",
|
|
cipher_name(options.cipher));
|
|
|
|
debug("Encryption type: %.100s", cipher_name(options.cipher));
|
|
|
|
/* Send the encrypted session key to the server. */
|
|
packet_start(SSH_CMSG_SESSION_KEY);
|
|
packet_put_char(options.cipher);
|
|
|
|
/* Send the cookie back to the server. */
|
|
for (i = 0; i < 8; i++)
|
|
packet_put_char(cookie[i]);
|
|
|
|
/* Send and destroy the encrypted encryption key integer. */
|
|
packet_put_bignum(key);
|
|
BN_clear_free(key);
|
|
|
|
/* Send protocol flags. */
|
|
packet_put_int(client_flags);
|
|
|
|
/* Send the packet now. */
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
debug("Sent encrypted session key.");
|
|
|
|
/* Set the encryption key. */
|
|
packet_set_encryption_key(session_key, SSH_SESSION_KEY_LENGTH, options.cipher);
|
|
|
|
/* We will no longer need the session key here. Destroy any extra copies. */
|
|
memset(session_key, 0, sizeof(session_key));
|
|
|
|
/*
|
|
* Expect a success message from the server. Note that this message
|
|
* will be received in encrypted form.
|
|
*/
|
|
packet_read_expect(SSH_SMSG_SUCCESS);
|
|
|
|
debug("Received encrypted confirmation.");
|
|
}
|
|
|
|
/*
|
|
* Authenticate user
|
|
*/
|
|
void
|
|
ssh_userauth1(const char *local_user, const char *server_user, char *host,
|
|
Sensitive *sensitive)
|
|
{
|
|
#ifdef KRB5
|
|
krb5_context context = NULL;
|
|
krb5_auth_context auth_context = NULL;
|
|
#endif
|
|
int i, type;
|
|
|
|
if (supported_authentications == 0)
|
|
fatal("ssh_userauth1: server supports no auth methods");
|
|
|
|
/* Send the name of the user to log in as on the server. */
|
|
packet_start(SSH_CMSG_USER);
|
|
packet_put_cstring(server_user);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
/*
|
|
* The server should respond with success if no authentication is
|
|
* needed (the user has no password). Otherwise the server responds
|
|
* with failure.
|
|
*/
|
|
type = packet_read();
|
|
|
|
/* check whether the connection was accepted without authentication. */
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
goto success;
|
|
if (type != SSH_SMSG_FAILURE)
|
|
packet_disconnect("Protocol error: got %d in response to SSH_CMSG_USER", type);
|
|
|
|
#ifdef KRB5
|
|
if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
|
|
options.kerberos_authentication) {
|
|
debug("Trying Kerberos v5 authentication.");
|
|
|
|
if (try_krb5_authentication(&context, &auth_context)) {
|
|
type = packet_read();
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
goto success;
|
|
if (type != SSH_SMSG_FAILURE)
|
|
packet_disconnect("Protocol error: got %d in response to Kerberos v5 auth", type);
|
|
}
|
|
}
|
|
#endif /* KRB5 */
|
|
|
|
#ifdef KRB4
|
|
if ((supported_authentications & (1 << SSH_AUTH_KERBEROS)) &&
|
|
options.kerberos_authentication) {
|
|
debug("Trying Kerberos v4 authentication.");
|
|
|
|
if (try_krb4_authentication()) {
|
|
type = packet_read();
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
goto success;
|
|
if (type != SSH_SMSG_FAILURE)
|
|
packet_disconnect("Protocol error: got %d in response to Kerberos v4 auth", type);
|
|
}
|
|
}
|
|
#endif /* KRB4 */
|
|
|
|
/*
|
|
* Use rhosts authentication if running in privileged socket and we
|
|
* do not wish to remain anonymous.
|
|
*/
|
|
if ((supported_authentications & (1 << SSH_AUTH_RHOSTS)) &&
|
|
options.rhosts_authentication) {
|
|
debug("Trying rhosts authentication.");
|
|
packet_start(SSH_CMSG_AUTH_RHOSTS);
|
|
packet_put_cstring(local_user);
|
|
packet_send();
|
|
packet_write_wait();
|
|
|
|
/* The server should respond with success or failure. */
|
|
type = packet_read();
|
|
if (type == SSH_SMSG_SUCCESS)
|
|
goto success;
|
|
if (type != SSH_SMSG_FAILURE)
|
|
packet_disconnect("Protocol error: got %d in response to rhosts auth",
|
|
type);
|
|
}
|
|
/*
|
|
* Try .rhosts or /etc/hosts.equiv authentication with RSA host
|
|
* authentication.
|
|
*/
|
|
if ((supported_authentications & (1 << SSH_AUTH_RHOSTS_RSA)) &&
|
|
options.rhosts_rsa_authentication) {
|
|
for (i = 0; i < sensitive->nkeys; i++) {
|
|
if (sensitive->keys[i] != NULL &&
|
|
sensitive->keys[i]->type == KEY_RSA1 &&
|
|
try_rhosts_rsa_authentication(local_user,
|
|
sensitive->keys[i]))
|
|
goto success;
|
|
}
|
|
}
|
|
/* Try RSA authentication if the server supports it. */
|
|
if ((supported_authentications & (1 << SSH_AUTH_RSA)) &&
|
|
options.rsa_authentication) {
|
|
/*
|
|
* Try RSA authentication using the authentication agent. The
|
|
* agent is tried first because no passphrase is needed for
|
|
* it, whereas identity files may require passphrases.
|
|
*/
|
|
if (try_agent_authentication())
|
|
goto success;
|
|
|
|
/* Try RSA authentication for each identity. */
|
|
for (i = 0; i < options.num_identity_files; i++)
|
|
if (options.identity_keys[i] != NULL &&
|
|
options.identity_keys[i]->type == KEY_RSA1 &&
|
|
try_rsa_authentication(i))
|
|
goto success;
|
|
}
|
|
/* Try challenge response authentication if the server supports it. */
|
|
if ((supported_authentications & (1 << SSH_AUTH_TIS)) &&
|
|
options.challenge_response_authentication && !options.batch_mode) {
|
|
if (try_challenge_response_authentication())
|
|
goto success;
|
|
}
|
|
/* Try password authentication if the server supports it. */
|
|
if ((supported_authentications & (1 << SSH_AUTH_PASSWORD)) &&
|
|
options.password_authentication && !options.batch_mode) {
|
|
char prompt[80];
|
|
|
|
snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
|
|
server_user, host);
|
|
if (try_password_authentication(prompt))
|
|
goto success;
|
|
}
|
|
/* All authentication methods have failed. Exit with an error message. */
|
|
fatal("Permission denied.");
|
|
/* NOTREACHED */
|
|
|
|
success:
|
|
#ifdef KRB5
|
|
/* Try Kerberos v5 TGT passing. */
|
|
if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
|
|
options.kerberos_tgt_passing && context && auth_context) {
|
|
if (options.cipher == SSH_CIPHER_NONE)
|
|
logit("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
|
|
send_krb5_tgt(context, auth_context);
|
|
}
|
|
if (auth_context)
|
|
krb5_auth_con_free(context, auth_context);
|
|
if (context)
|
|
krb5_free_context(context);
|
|
#endif
|
|
|
|
#ifdef AFS
|
|
/* Try Kerberos v4 TGT passing if the server supports it. */
|
|
if ((supported_authentications & (1 << SSH_PASS_KERBEROS_TGT)) &&
|
|
options.kerberos_tgt_passing) {
|
|
if (options.cipher == SSH_CIPHER_NONE)
|
|
logit("WARNING: Encryption is disabled! Ticket will be transmitted in the clear!");
|
|
send_krb4_tgt();
|
|
}
|
|
/* Try AFS token passing if the server supports it. */
|
|
if ((supported_authentications & (1 << SSH_PASS_AFS_TOKEN)) &&
|
|
options.afs_token_passing && k_hasafs()) {
|
|
if (options.cipher == SSH_CIPHER_NONE)
|
|
logit("WARNING: Encryption is disabled! Token will be transmitted in the clear!");
|
|
send_afs_tokens();
|
|
}
|
|
#endif /* AFS */
|
|
|
|
return; /* need statement after label */
|
|
}
|