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/*
*
* authfd.c
*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
*
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
*
* Created: Wed Mar 29 01:30:28 1995 ylo
*
* Functions for connecting the local authentication agent.
*
*/
#include "includes.h"
RCSID("$OpenBSD: authfd.c,v 1.24 2000/08/15 19:20:46 markus Exp $");
#include "ssh.h"
#include "rsa.h"
#include "buffer.h"
#include "bufaux.h"
#include "xmalloc.h"
#include "getput.h"
#include <openssl/rsa.h>
#include <openssl/dsa.h>
#include <openssl/evp.h>
#include "key.h"
#include "authfd.h"
#include "kex.h"
/* helper */
int decode_reply(int type);
/* Returns the number of the authentication fd, or -1 if there is none. */
int
ssh_get_authentication_socket()
{
const char *authsocket;
int sock, len;
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));
sunaddr.sun_len = len = SUN_LEN(&sunaddr)+1;
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, len) < 0) {
close(sock);
return -1;
}
return sock;
}
int
ssh_request_reply(AuthenticationConnection *auth,
Buffer *request, Buffer *reply)
{
int l, len;
char buf[1024];
/* Get the length of the message, and format it in the buffer. */
len = buffer_len(request);
PUT_32BIT(buf, len);
/* Send the length and then the packet to the agent. */
if (atomicio(write, auth->fd, buf, 4) != 4 ||
atomicio(write, 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.
*/
len = 4;
while (len > 0) {
l = read(auth->fd, buf + 4 - len, len);
if (l <= 0) {
error("Error reading response length from authentication socket.");
return 0;
}
len -= l;
}
/* Extract the length, and check it for sanity. */
len = GET_32BIT(buf);
if (len > 256 * 1024)
fatal("Authentication response too long: %d", 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);
l = read(auth->fd, buf, l);
if (l <= 0) {
error("Error reading response from authentication socket.");
return 0;
}
buffer_append(reply, (char *) 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()
{
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->packet);
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 *ac)
{
buffer_free(&ac->packet);
buffer_free(&ac->identities);
close(ac->fd);
xfree(ac);
}
/*
* Returns the first authentication identity held by the agent.
* Returns true if an identity is available, 0 otherwise.
* The caller must initialize the integers before the call, and free the
* comment after a successful call (before calling ssh_get_next_identity).
*/
int
ssh_get_first_identity(AuthenticationConnection *auth,
BIGNUM *e, BIGNUM *n, char **comment)
{
Buffer request;
int type;
/*
* Send a message to the agent requesting for a list of the
* identities it can represent.
*/
buffer_init(&request);
buffer_put_char(&request, SSH_AGENTC_REQUEST_RSA_IDENTITIES);
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 (type != SSH_AGENT_RSA_IDENTITIES_ANSWER)
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 (auth->howmany > 1024)
fatal("Too many identities in authentication reply: %d\n",
auth->howmany);
/* Return the first entry (if any). */
return ssh_get_next_identity(auth, e, n, comment);
}
/*
* Returns the next authentication identity for the agent. Other functions
* can be called between this and ssh_get_first_identity or two calls of this
* function. This returns 0 if there are no more identities. The caller
* must free comment after a successful return.
*/
int
ssh_get_next_identity(AuthenticationConnection *auth,
BIGNUM *e, BIGNUM *n, char **comment)
{
unsigned int bits;
/* Return failure if no more entries. */
if (auth->howmany <= 0)
return 0;
/*
* Get the next entry from the packet. These will abort with a fatal
* error if the packet is too short or contains corrupt data.
*/
bits = buffer_get_int(&auth->identities);
buffer_get_bignum(&auth->identities, e);
buffer_get_bignum(&auth->identities, n);
*comment = buffer_get_string(&auth->identities, NULL);
if (bits != BN_num_bits(n))
log("Warning: identity keysize mismatch: actual %d, announced %u",
BN_num_bits(n), bits);
/* Decrement the number of remaining entries. */
auth->howmany--;
return 1;
}
/*
* 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,
BIGNUM* e, BIGNUM *n, BIGNUM *challenge,
unsigned char session_id[16],
unsigned int response_type,
unsigned char response[16])
{
Buffer buffer;
int success = 0;
int i;
int type;
if (response_type == 0)
fatal("Compatibility with ssh protocol version "
"1.0 no longer supported.");
buffer_init(&buffer);
buffer_put_char(&buffer, SSH_AGENTC_RSA_CHALLENGE);
buffer_put_int(&buffer, BN_num_bits(n));
buffer_put_bignum(&buffer, e);
buffer_put_bignum(&buffer, n);
buffer_put_bignum(&buffer, challenge);
buffer_append(&buffer, (char *) 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 (type == SSH_AGENT_FAILURE) {
log("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] = buffer_get_char(&buffer);
}
buffer_free(&buffer);
return success;
}
/* Encode key for a message to the agent. */
void
ssh_encode_identity_rsa(Buffer *b, RSA *key, const char *comment)
{
buffer_clear(b);
buffer_put_char(b, SSH_AGENTC_ADD_RSA_IDENTITY);
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_string(b, comment, strlen(comment));
}
void
ssh_encode_identity_dsa(Buffer *b, DSA *key, const char *comment)
{
buffer_clear(b);
buffer_put_char(b, SSH2_AGENTC_ADD_IDENTITY);
buffer_put_cstring(b, KEX_DSS);
buffer_put_bignum2(b, key->p);
buffer_put_bignum2(b, key->q);
buffer_put_bignum2(b, key->g);
buffer_put_bignum2(b, key->pub_key);
buffer_put_bignum2(b, key->priv_key);
buffer_put_string(b, comment, strlen(comment));
}
/*
* Adds an identity to the authentication server. This call is not meant to
* be used by normal applications.
*/
int
ssh_add_identity(AuthenticationConnection *auth, Key *key, const char *comment)
{
Buffer buffer;
int type;
buffer_init(&buffer);
switch (key->type) {
case KEY_RSA:
ssh_encode_identity_rsa(&buffer, key->rsa, comment);
break;
case KEY_DSA:
ssh_encode_identity_dsa(&buffer, key->dsa, comment);
break;
default:
buffer_free(&buffer);
return 0;
break;
}
if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
buffer_free(&buffer);
return 0;
}
type = buffer_get_char(&buffer);
buffer_free(&buffer);
return decode_reply(type);
}
/*
* Removes an identity from the authentication server. This call is not
* meant to be used by normal applications.
*/
int
ssh_remove_identity(AuthenticationConnection *auth, RSA *key)
{
Buffer buffer;
int type;
buffer_init(&buffer);
buffer_put_char(&buffer, SSH_AGENTC_REMOVE_RSA_IDENTITY);
buffer_put_int(&buffer, BN_num_bits(key->n));
buffer_put_bignum(&buffer, key->e);
buffer_put_bignum(&buffer, key->n);
if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
buffer_free(&buffer);
return 0;
}
type = buffer_get_char(&buffer);
buffer_free(&buffer);
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)
{
Buffer buffer;
int type;
buffer_init(&buffer);
buffer_put_char(&buffer, SSH_AGENTC_REMOVE_ALL_RSA_IDENTITIES);
if (ssh_request_reply(auth, &buffer, &buffer) == 0) {
buffer_free(&buffer);
return 0;
}
type = buffer_get_char(&buffer);
buffer_free(&buffer);
return decode_reply(type);
}
int
decode_reply(int type)
{
switch (type) {
case SSH_AGENT_FAILURE:
log("SSH_AGENT_FAILURE");
return 0;
case SSH_AGENT_SUCCESS:
return 1;
default:
fatal("Bad response from authentication agent: %d", type);
}
/* NOTREACHED */
return 0;
}
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