OpenBSD-4.6/usr.bin/ssh/authfd.c
/* $OpenBSD: authfd.c,v 1.80 2006/08/03 03:34:41 deraadt Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
* Functions for connecting the local authentication agent.
*
* 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".
*
* SSH2 implementation,
* Copyright (c) 2000 Markus Friedl. 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 <sys/types.h>
#include <sys/un.h>
#include <sys/socket.h>
#include <openssl/evp.h>
#include <openssl/crypto.h>
#include <fcntl.h>
#include <stdlib.h>
#include <signal.h>
#include <string.h>
#include <unistd.h>
#include "xmalloc.h"
#include "ssh.h"
#include "rsa.h"
#include "buffer.h"
#include "key.h"
#include "authfd.h"
#include "cipher.h"
#include "kex.h"
#include "compat.h"
#include "log.h"
#include "atomicio.h"
#include "misc.h"
static int agent_present = 0;
/* helper */
int decode_reply(int type);
/* macro to check for "agent failure" message */
#define agent_failed(x) \
((x == SSH_AGENT_FAILURE) || (x == SSH_COM_AGENT2_FAILURE) || \
(x == SSH2_AGENT_FAILURE))
int
ssh_agent_present(void)
{
int authfd;
if (agent_present)
return 1;
if ((authfd = ssh_get_authentication_socket()) == -1)
return 0;
else {
ssh_close_authentication_socket(authfd);
return 1;
}
}
/* Returns the number of the authentication fd, or -1 if there is none. */
int
ssh_get_authentication_socket(void)
{
const char *authsocket;
int sock;
struct sockaddr_un sunaddr;
authsocket = getenv(SSH_AUTHSOCKET_ENV_NAME);
if (!authsocket)
return -1;
sunaddr.sun_family = AF_UNIX;
strlcpy(sunaddr.sun_path, authsocket, sizeof(sunaddr.sun_path));
sock = socket(AF_UNIX, SOCK_STREAM, 0);
if (sock < 0)
return -1;
/* close on exec */
if (fcntl(sock, F_SETFD, 1) == -1) {
close(sock);
return -1;
}
if (connect(sock, (struct sockaddr *)&sunaddr, sizeof sunaddr) < 0) {
close(sock);
return -1;
}
agent_present = 1;
return sock;
}
static int
ssh_request_reply(AuthenticationConnection *auth, Buffer *request, Buffer *reply)
{
u_int l, len;
char buf[1024];
/* Get the length of the message, and format it in the buffer. */
len = buffer_len(request);
put_u32(buf, len);
/* Send the length and then the packet to the agent. */
if (atomicio(vwrite, auth->fd, buf, 4) != 4 ||
atomicio(vwrite, auth->fd, buffer_ptr(request),
buffer_len(request)) != buffer_len(request)) {
error("Error writing to authentication socket.");
return 0;
}
/*
* Wait for response from the agent. First read the length of the
* response packet.
*/
if (atomicio(read, auth->fd, buf, 4) != 4) {
error("Error reading response length from authentication socket.");
return 0;
}
/* Extract the length, and check it for sanity. */
len = get_u32(buf);
if (len > 256 * 1024)
fatal("Authentication response too long: %u", len);
/* Read the rest of the response in to the buffer. */
buffer_clear(reply);
while (len > 0) {
l = len;
if (l > sizeof(buf))
l = sizeof(buf);
if (atomicio(read, auth->fd, buf, l) != l) {
error("Error reading response from authentication socket.");
return 0;
}
buffer_append(reply, buf, l);
len -= l;
}
return 1;
}
/*
* Closes the agent socket if it should be closed (depends on how it was
* obtained). The argument must have been returned by
* ssh_get_authentication_socket().
*/
void
ssh_close_authentication_socket(int sock)
{
if (getenv(SSH_AUTHSOCKET_ENV_NAME))
close(sock);
}
/*
* Opens and connects a private socket for communication with the
* authentication agent. Returns the file descriptor (which must be
* shut down and closed by the caller when no longer needed).
* Returns NULL if an error occurred and the connection could not be
* opened.
*/
AuthenticationConnection *
ssh_get_authentication_connection(void)
{
AuthenticationConnection *auth;
int sock;
sock = ssh_get_authentication_socket();
/*
* Fail if we couldn't obtain a connection. This happens if we
* exited due to a timeout.
*/
if (sock < 0)
return NULL;
auth = xmalloc(sizeof(*auth));
auth->fd = sock;
buffer_init(&auth->identities);
auth->howmany = 0;
return auth;
}
/*
* Closes the connection to the authentication agent and frees any associated
* memory.
*/
void
ssh_close_authentication_connection(AuthenticationConnection *auth)
{
buffer_free(&auth->identities);
close(auth->fd);
xfree(auth);
}
/* Lock/unlock agent */
int
ssh_lock_agent(AuthenticationConnection *auth, int lock, const char *password)
{
int type;
Buffer msg;
buffer_init(&msg);
buffer_put_char(&msg, lock ? SSH_AGENTC_LOCK : SSH_AGENTC_UNLOCK);
buffer_put_cstring(&msg, password);
if (ssh_request_reply(auth, &msg, &msg) == 0) {
buffer_free(&msg);
return 0;
}
type = buffer_get_char(&msg);
buffer_free(&msg);
return decode_reply(type);
}
/*
* Returns the first authentication identity held by the agent.
*/
int
ssh_get_num_identities(AuthenticationConnection *auth, int version)
{
int type, code1 = 0, code2 = 0;
Buffer request;
switch (version) {
case 1:
code1 = SSH_AGENTC_REQUEST_RSA_IDENTITIES;
code2 = SSH_AGENT_RSA_IDENTITIES_ANSWER;
break;
case 2:
code1 = SSH2_AGENTC_REQUEST_IDENTITIES;
code2 = SSH2_AGENT_IDENTITIES_ANSWER;
break;
default:
return 0;
}
/*
* Send a message to the agent requesting for a list of the
* identities it can represent.
*/
buffer_init(&request);
buffer_put_char(&request, code1);
buffer_clear(&auth->identities);
if (ssh_request_reply(auth, &request, &auth->identities) == 0) {
buffer_free(&request);
return 0;
}
buffer_free(&request);
/* Get message type, and verify that we got a proper answer. */
type = buffer_get_char(&auth->identities);
if (agent_failed(type)) {
return 0;
} else if (type != code2) {
fatal("Bad authentication reply message type: %d", type);
}
/* Get the number of entries in the response and check it for sanity. */
auth->howmany = buffer_get_int(&auth->identities);
if ((u_int)auth->howmany > 1024)
fatal("Too many identities in authentication reply: %d",
auth->howmany);
return auth->howmany;
}
Key *
ssh_get_first_identity(AuthenticationConnection *auth, char **comment, int version)
{
/* get number of identities and return the first entry (if any). */
if (ssh_get_num_identities(auth, version) > 0)
return ssh_get_next_identity(auth, comment, version);
return NULL;
}
Key *
ssh_get_next_identity(AuthenticationConnection *auth, char **comment, int version)
{
int keybits;
u_int bits;
u_char *blob;
u_int blen;
Key *key = NULL;
/* Return failure if no more entries. */
if (auth->howmany <= 0)
return NULL;
/*
* Get the next entry from the packet. These will abort with a fatal
* error if the packet is too short or contains corrupt data.
*/
switch (version) {
case 1:
key = key_new(KEY_RSA1);
bits = buffer_get_int(&auth->identities);
buffer_get_bignum(&auth->identities, key->rsa->e);
buffer_get_bignum(&auth->identities, key->rsa->n);
*comment = buffer_get_string(&auth->identities, NULL);
keybits = BN_num_bits(key->rsa->n);
if (keybits < 0 || bits != (u_int)keybits)
logit("Warning: identity keysize mismatch: actual %d, announced %u",
BN_num_bits(key->rsa->n), bits);
break;
case 2:
blob = buffer_get_string(&auth->identities, &blen);
*comment = buffer_get_string(&auth->identities, NULL);
key = key_from_blob(blob, blen);
xfree(blob);
break;
default:
return NULL;
}
/* Decrement the number of remaining entries. */
auth->howmany--;
return key;
}
/*
* Generates a random challenge, sends it to the agent, and waits for
* response from the agent. Returns true (non-zero) if the agent gave the
* correct answer, zero otherwise. Response type selects the style of
* response desired, with 0 corresponding to protocol version 1.0 (no longer
* supported) and 1 corresponding to protocol version 1.1.
*/
int
ssh_decrypt_challenge(AuthenticationConnection *auth,
Key* key, BIGNUM *challenge,
u_char session_id[16],
u_int response_type,
u_char response[16])
{
Buffer buffer;
int success = 0;
int i;
int type;
if (key->type != KEY_RSA1)
return 0;
if (response_type == 0) {
logit("Compatibility with ssh protocol version 1.0 no longer supported.");
return 0;
}
buffer_init(&buffer);
buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
buffer_put_int(&buffer, BN_num_bits(key->rsa->n));
buffer_put_bignum(&buffer, key->rsa->e);
buffer_put_bignum(&buffer, key->rsa->n);
buffer_put_bignum(&buffer, challenge);
buffer_append(&buffer, session_id, 16);
buffer_put_int(&buffer, response_type);
if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
buffer_free(&buffer);
return 0;
}
type = buffer_get_char(&buffer);
if (agent_failed(type)) {
logit("Agent admitted failure to authenticate using the key.");
} else if (type != SSH_AGENT_RSA_RESPONSE) {
fatal("Bad authentication response: %d", type);
} else {
success = 1;
/*
* Get the response from the packet. This will abort with a
* fatal error if the packet is corrupt.
*/
for (i = 0; i < 16; i++)
response[i] = (u_char)buffer_get_char(&buffer);
}
buffer_free(&buffer);
return success;
}
/* ask agent to sign data, returns -1 on error, 0 on success */
int
ssh_agent_sign(AuthenticationConnection *auth,
Key *key,
u_char **sigp, u_int *lenp,
u_char *data, u_int datalen)
{
extern int datafellows;
Buffer msg;
u_char *blob;
u_int blen;
int type, flags = 0;
int ret = -1;
if (key_to_blob(key, &blob, &blen) == 0)
return -1;
if (datafellows & SSH_BUG_SIGBLOB)
flags = SSH_AGENT_OLD_SIGNATURE;
buffer_init(&msg);
buffer_put_char(&msg, SSH2_AGENTC_SIGN_REQUEST);
buffer_put_string(&msg, blob, blen);
buffer_put_string(&msg, data, datalen);
buffer_put_int(&msg, flags);
xfree(blob);
if (ssh_request_reply(auth, &msg, &msg) == 0) {
buffer_free(&msg);
return -1;
}
type = buffer_get_char(&msg);
if (agent_failed(type)) {
logit("Agent admitted failure to sign using the key.");
} else if (type != SSH2_AGENT_SIGN_RESPONSE) {
fatal("Bad authentication response: %d", type);
} else {
ret = 0;
*sigp = buffer_get_string(&msg, lenp);
}
buffer_free(&msg);
return ret;
}
/* Encode key for a message to the agent. */
static void
ssh_encode_identity_rsa1(Buffer *b, RSA *key, const char *comment)
{
buffer_put_int(b, BN_num_bits(key->n));
buffer_put_bignum(b, key->n);
buffer_put_bignum(b, key->e);
buffer_put_bignum(b, key->d);
/* To keep within the protocol: p < q for ssh. in SSL p > q */
buffer_put_bignum(b, key->iqmp); /* ssh key->u */
buffer_put_bignum(b, key->q); /* ssh key->p, SSL key->q */
buffer_put_bignum(b, key->p); /* ssh key->q, SSL key->p */
buffer_put_cstring(b, comment);
}
static void
ssh_encode_identity_ssh2(Buffer *b, Key *key, const char *comment)
{
buffer_put_cstring(b, key_ssh_name(key));
switch (key->type) {
case KEY_RSA:
buffer_put_bignum2(b, key->rsa->n);
buffer_put_bignum2(b, key->rsa->e);
buffer_put_bignum2(b, key->rsa->d);
buffer_put_bignum2(b, key->rsa->iqmp);
buffer_put_bignum2(b, key->rsa->p);
buffer_put_bignum2(b, key->rsa->q);
break;
case KEY_DSA:
buffer_put_bignum2(b, key->dsa->p);
buffer_put_bignum2(b, key->dsa->q);
buffer_put_bignum2(b, key->dsa->g);
buffer_put_bignum2(b, key->dsa->pub_key);
buffer_put_bignum2(b, key->dsa->priv_key);
break;
}
buffer_put_cstring(b, comment);
}
/*
* Adds an identity to the authentication server. This call is not meant to
* be used by normal applications.
*/
int
ssh_add_identity_constrained(AuthenticationConnection *auth, Key *key,
const char *comment, u_int life, u_int confirm)
{
Buffer msg;
int type, constrained = (life || confirm);
buffer_init(&msg);
switch (key->type) {
case KEY_RSA1:
type = constrained ?
SSH_AGENTC_ADD_RSA_ID_CONSTRAINED :
SSH_AGENTC_ADD_RSA_IDENTITY;
buffer_put_char(&msg, type);
ssh_encode_identity_rsa1(&msg, key->rsa, comment);
break;
case KEY_RSA:
case KEY_DSA:
type = constrained ?
SSH2_AGENTC_ADD_ID_CONSTRAINED :
SSH2_AGENTC_ADD_IDENTITY;
buffer_put_char(&msg, type);
ssh_encode_identity_ssh2(&msg, key, comment);
break;
default:
buffer_free(&msg);
return 0;
}
if (constrained) {
if (life != 0) {
buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
buffer_put_int(&msg, life);
}
if (confirm != 0)
buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
}
if (ssh_request_reply(auth, &msg, &msg) == 0) {
buffer_free(&msg);
return 0;
}
type = buffer_get_char(&msg);
buffer_free(&msg);
return decode_reply(type);
}
int
ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment)
{
return ssh_add_identity_constrained(auth, key, comment, 0, 0);
}
/*
* Removes an identity from the authentication server. This call is not
* meant to be used by normal applications.
*/
int
ssh_remove_identity(AuthenticationConnection *auth, Key *key)
{
Buffer msg;
int type;
u_char *blob;
u_int blen;
buffer_init(&msg);
if (key->type == KEY_RSA1) {
buffer_put_char(&msg, SSH_AGENTC_REMOVE_RSA_IDENTITY);
buffer_put_int(&msg, BN_num_bits(key->rsa->n));
buffer_put_bignum(&msg, key->rsa->e);
buffer_put_bignum(&msg, key->rsa->n);
} else if (key->type == KEY_DSA || key->type == KEY_RSA) {
key_to_blob(key, &blob, &blen);
buffer_put_char(&msg, SSH2_AGENTC_REMOVE_IDENTITY);
buffer_put_string(&msg, blob, blen);
xfree(blob);
} else {
buffer_free(&msg);
return 0;
}
if (ssh_request_reply(auth, &msg, &msg) == 0) {
buffer_free(&msg);
return 0;
}
type = buffer_get_char(&msg);
buffer_free(&msg);
return decode_reply(type);
}
int
ssh_update_card(AuthenticationConnection *auth, int add,
const char *reader_id, const char *pin, u_int life, u_int confirm)
{
Buffer msg;
int type, constrained = (life || confirm);
if (add) {
type = constrained ?
SSH_AGENTC_ADD_SMARTCARD_KEY_CONSTRAINED :
SSH_AGENTC_ADD_SMARTCARD_KEY;
} else
type = SSH_AGENTC_REMOVE_SMARTCARD_KEY;
buffer_init(&msg);
buffer_put_char(&msg, type);
buffer_put_cstring(&msg, reader_id);
buffer_put_cstring(&msg, pin);
if (constrained) {
if (life != 0) {
buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_LIFETIME);
buffer_put_int(&msg, life);
}
if (confirm != 0)
buffer_put_char(&msg, SSH_AGENT_CONSTRAIN_CONFIRM);
}
if (ssh_request_reply(auth, &msg, &msg) == 0) {
buffer_free(&msg);
return 0;
}
type = buffer_get_char(&msg);
buffer_free(&msg);
return decode_reply(type);
}
/*
* Removes all identities from the agent. This call is not meant to be used
* by normal applications.
*/
int
ssh_remove_all_identities(AuthenticationConnection *auth, int version)
{
Buffer msg;
int type;
int code = (version==1) ?
SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES :
SSH2_AGENTC_REMOVE_ALL_IDENTITIES;
buffer_init(&msg);
buffer_put_char(&msg, code);
if (ssh_request_reply(auth, &msg, &msg) == 0) {
buffer_free(&msg);
return 0;
}
type = buffer_get_char(&msg);
buffer_free(&msg);
return decode_reply(type);
}
int
decode_reply(int type)
{
switch (type) {
case SSH_AGENT_FAILURE:
case SSH_COM_AGENT2_FAILURE:
case SSH2_AGENT_FAILURE:
logit("SSH_AGENT_FAILURE");
return 0;
case SSH_AGENT_SUCCESS:
return 1;
default:
fatal("Bad response from authentication agent: %d", type);
}
/* NOTREACHED */
return 0;
}