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openssh/sshconnect2.c
Ben Lindstrom b9be60a722 - markus@cvs.openbsd.org 2001/03/10 17:51:04 
[kex.c match.c match.h readconf.c readconf.h sshconnect2.c]
     add PreferredAuthentications
2001-03-11 01:49:19 +00:00

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/*
* 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 "includes.h"
RCSID("$OpenBSD: sshconnect2.c,v 1.53 2001/03/10 17:51:04 markus Exp $");
#include <openssl/bn.h>
#include <openssl/md5.h>
#include <openssl/dh.h>
#include <openssl/hmac.h>
#include "ssh.h"
#include "ssh2.h"
#include "xmalloc.h"
#include "rsa.h"
#include "buffer.h"
#include "packet.h"
#include "uidswap.h"
#include "compat.h"
#include "bufaux.h"
#include "cipher.h"
#include "kex.h"
#include "myproposal.h"
#include "key.h"
#include "sshconnect.h"
#include "authfile.h"
#include "cli.h"
#include "dispatch.h"
#include "authfd.h"
#include "log.h"
#include "readconf.h"
#include "readpass.h"
#include "match.h"
void ssh_dh1_client(Kex *, char *, struct sockaddr *, Buffer *, Buffer *);
void ssh_dhgex_client(Kex *, char *, struct sockaddr *, Buffer *, Buffer *);
/* import */
extern char *client_version_string;
extern char *server_version_string;
extern Options options;
/*
* SSH2 key exchange
*/
u_char *session_id2 = NULL;
int session_id2_len = 0;
void
ssh_kex2(char *host, struct sockaddr *hostaddr)
{
int i, plen;
Kex *kex;
Buffer *client_kexinit, *server_kexinit;
char *sprop[PROPOSAL_MAX];
if (options.ciphers == (char *)-1) {
log("No valid ciphers for protocol version 2 given, using defaults.");
options.ciphers = NULL;
}
if (options.ciphers != NULL) {
myproposal[PROPOSAL_ENC_ALGS_CTOS] =
myproposal[PROPOSAL_ENC_ALGS_STOC] = options.ciphers;
}
if (options.compression) {
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] = "zlib";
} else {
myproposal[PROPOSAL_COMP_ALGS_CTOS] =
myproposal[PROPOSAL_COMP_ALGS_STOC] = "none";
}
if (options.macs != NULL) {
myproposal[PROPOSAL_MAC_ALGS_CTOS] =
myproposal[PROPOSAL_MAC_ALGS_STOC] = options.macs;
}
/* buffers with raw kexinit messages */
server_kexinit = xmalloc(sizeof(*server_kexinit));
buffer_init(server_kexinit);
client_kexinit = kex_init(myproposal);
/* algorithm negotiation */
kex_exchange_kexinit(client_kexinit, server_kexinit, sprop);
kex = kex_choose_conf(myproposal, sprop, 0);
for (i = 0; i < PROPOSAL_MAX; i++)
xfree(sprop[i]);
/* server authentication and session key agreement */
switch(kex->kex_type) {
case DH_GRP1_SHA1:
ssh_dh1_client(kex, host, hostaddr,
client_kexinit, server_kexinit);
break;
case DH_GEX_SHA1:
ssh_dhgex_client(kex, host, hostaddr, client_kexinit,
server_kexinit);
break;
default:
fatal("Unsupported key exchange %d", kex->kex_type);
}
buffer_free(client_kexinit);
buffer_free(server_kexinit);
xfree(client_kexinit);
xfree(server_kexinit);
debug("Wait SSH2_MSG_NEWKEYS.");
packet_read_expect(&plen, SSH2_MSG_NEWKEYS);
packet_done();
debug("GOT SSH2_MSG_NEWKEYS.");
debug("send SSH2_MSG_NEWKEYS.");
packet_start(SSH2_MSG_NEWKEYS);
packet_send();
packet_write_wait();
debug("done: send SSH2_MSG_NEWKEYS.");
#ifdef DEBUG_KEXDH
/* send 1st encrypted/maced/compressed message */
packet_start(SSH2_MSG_IGNORE);
packet_put_cstring("markus");
packet_send();
packet_write_wait();
#endif
debug("done: KEX2.");
}
/* diffie-hellman-group1-sha1 */
void
ssh_dh1_client(Kex *kex, char *host, struct sockaddr *hostaddr,
Buffer *client_kexinit, Buffer *server_kexinit)
{
#ifdef DEBUG_KEXDH
int i;
#endif
int plen, dlen;
u_int klen, kout;
char *signature = NULL;
u_int slen;
char *server_host_key_blob = NULL;
Key *server_host_key;
u_int sbloblen;
DH *dh;
BIGNUM *dh_server_pub = 0;
BIGNUM *shared_secret = 0;
u_char *kbuf;
u_char *hash;
debug("Sending SSH2_MSG_KEXDH_INIT.");
/* generate and send 'e', client DH public key */
dh = dh_new_group1();
dh_gen_key(dh, kex->we_need * 8);
packet_start(SSH2_MSG_KEXDH_INIT);
packet_put_bignum2(dh->pub_key);
packet_send();
packet_write_wait();
#ifdef DEBUG_KEXDH
fprintf(stderr, "\np= ");
BN_print_fp(stderr, dh->p);
fprintf(stderr, "\ng= ");
BN_print_fp(stderr, dh->g);
fprintf(stderr, "\npub= ");
BN_print_fp(stderr, dh->pub_key);
fprintf(stderr, "\n");
DHparams_print_fp(stderr, dh);
#endif
debug("Wait SSH2_MSG_KEXDH_REPLY.");
packet_read_expect(&plen, SSH2_MSG_KEXDH_REPLY);
debug("Got SSH2_MSG_KEXDH_REPLY.");
/* key, cert */
server_host_key_blob = packet_get_string(&sbloblen);
server_host_key = key_from_blob(server_host_key_blob, sbloblen);
if (server_host_key == NULL)
fatal("cannot decode server_host_key_blob");
check_host_key(host, hostaddr, server_host_key,
options.user_hostfile2, options.system_hostfile2);
/* DH paramter f, server public DH key */
dh_server_pub = BN_new();
if (dh_server_pub == NULL)
fatal("dh_server_pub == NULL");
packet_get_bignum2(dh_server_pub, &dlen);
#ifdef DEBUG_KEXDH
fprintf(stderr, "\ndh_server_pub= ");
BN_print_fp(stderr, dh_server_pub);
fprintf(stderr, "\n");
debug("bits %d", BN_num_bits(dh_server_pub));
#endif
/* signed H */
signature = packet_get_string(&slen);
packet_done();
if (!dh_pub_is_valid(dh, dh_server_pub))
packet_disconnect("bad server public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
debug("shared secret: len %d/%d", klen, kout);
fprintf(stderr, "shared secret == ");
for (i = 0; i< kout; i++)
fprintf(stderr, "%02x", (kbuf[i])&0xff);
fprintf(stderr, "\n");
#endif
shared_secret = BN_new();
BN_bin2bn(kbuf, kout, shared_secret);
memset(kbuf, 0, klen);
xfree(kbuf);
/* calc and verify H */
hash = kex_hash(
client_version_string,
server_version_string,
buffer_ptr(client_kexinit), buffer_len(client_kexinit),
buffer_ptr(server_kexinit), buffer_len(server_kexinit),
server_host_key_blob, sbloblen,
dh->pub_key,
dh_server_pub,
shared_secret
);
xfree(server_host_key_blob);
DH_free(dh);
BN_free(dh_server_pub);
#ifdef DEBUG_KEXDH
fprintf(stderr, "hash == ");
for (i = 0; i< 20; i++)
fprintf(stderr, "%02x", (hash[i])&0xff);
fprintf(stderr, "\n");
#endif
if (key_verify(server_host_key, (u_char *)signature, slen, hash, 20) != 1)
fatal("key_verify failed for server_host_key");
key_free(server_host_key);
xfree(signature);
kex_derive_keys(kex, hash, shared_secret);
BN_clear_free(shared_secret);
packet_set_kex(kex);
/* save session id */
session_id2_len = 20;
session_id2 = xmalloc(session_id2_len);
memcpy(session_id2, hash, session_id2_len);
}
/* diffie-hellman-group-exchange-sha1 */
/*
* Estimates the group order for a Diffie-Hellman group that has an
* attack complexity approximately the same as O(2**bits). Estimate
* with: O(exp(1.9223 * (ln q)^(1/3) (ln ln q)^(2/3)))
*/
int
dh_estimate(int bits)
{
if (bits < 64)
return (512); /* O(2**63) */
if (bits < 128)
return (1024); /* O(2**86) */
if (bits < 192)
return (2048); /* O(2**116) */
return (4096); /* O(2**156) */
}
void
ssh_dhgex_client(Kex *kex, char *host, struct sockaddr *hostaddr,
Buffer *client_kexinit, Buffer *server_kexinit)
{
#ifdef DEBUG_KEXDH
int i;
#endif
int plen, dlen;
u_int klen, kout;
char *signature = NULL;
u_int slen, nbits;
char *server_host_key_blob = NULL;
Key *server_host_key;
u_int sbloblen;
DH *dh;
BIGNUM *dh_server_pub = 0;
BIGNUM *shared_secret = 0;
BIGNUM *p = 0, *g = 0;
u_char *kbuf;
u_char *hash;
nbits = dh_estimate(kex->we_need * 8);
debug("Sending SSH2_MSG_KEX_DH_GEX_REQUEST.");
packet_start(SSH2_MSG_KEX_DH_GEX_REQUEST);
packet_put_int(nbits);
packet_send();
packet_write_wait();
#ifdef DEBUG_KEXDH
fprintf(stderr, "\nnbits = %d", nbits);
#endif
debug("Wait SSH2_MSG_KEX_DH_GEX_GROUP.");
packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_GROUP);
debug("Got SSH2_MSG_KEX_DH_GEX_GROUP.");
if ((p = BN_new()) == NULL)
fatal("BN_new");
packet_get_bignum2(p, &dlen);
if ((g = BN_new()) == NULL)
fatal("BN_new");
packet_get_bignum2(g, &dlen);
dh = dh_new_group(g, p);
dh_gen_key(dh, kex->we_need * 8);
#ifdef DEBUG_KEXDH
fprintf(stderr, "\np= ");
BN_print_fp(stderr, dh->p);
fprintf(stderr, "\ng= ");
BN_print_fp(stderr, dh->g);
fprintf(stderr, "\npub= ");
BN_print_fp(stderr, dh->pub_key);
fprintf(stderr, "\n");
DHparams_print_fp(stderr, dh);
#endif
debug("Sending SSH2_MSG_KEX_DH_GEX_INIT.");
/* generate and send 'e', client DH public key */
packet_start(SSH2_MSG_KEX_DH_GEX_INIT);
packet_put_bignum2(dh->pub_key);
packet_send();
packet_write_wait();
debug("Wait SSH2_MSG_KEX_DH_GEX_REPLY.");
packet_read_expect(&plen, SSH2_MSG_KEX_DH_GEX_REPLY);
debug("Got SSH2_MSG_KEXDH_REPLY.");
/* key, cert */
server_host_key_blob = packet_get_string(&sbloblen);
server_host_key = key_from_blob(server_host_key_blob, sbloblen);
if (server_host_key == NULL)
fatal("cannot decode server_host_key_blob");
check_host_key(host, hostaddr, server_host_key,
options.user_hostfile2, options.system_hostfile2);
/* DH paramter f, server public DH key */
dh_server_pub = BN_new();
if (dh_server_pub == NULL)
fatal("dh_server_pub == NULL");
packet_get_bignum2(dh_server_pub, &dlen);
#ifdef DEBUG_KEXDH
fprintf(stderr, "\ndh_server_pub= ");
BN_print_fp(stderr, dh_server_pub);
fprintf(stderr, "\n");
debug("bits %d", BN_num_bits(dh_server_pub));
#endif
/* signed H */
signature = packet_get_string(&slen);
packet_done();
if (!dh_pub_is_valid(dh, dh_server_pub))
packet_disconnect("bad server public DH value");
klen = DH_size(dh);
kbuf = xmalloc(klen);
kout = DH_compute_key(kbuf, dh_server_pub, dh);
#ifdef DEBUG_KEXDH
debug("shared secret: len %d/%d", klen, kout);
fprintf(stderr, "shared secret == ");
for (i = 0; i< kout; i++)
fprintf(stderr, "%02x", (kbuf[i])&0xff);
fprintf(stderr, "\n");
#endif
shared_secret = BN_new();
BN_bin2bn(kbuf, kout, shared_secret);
memset(kbuf, 0, klen);
xfree(kbuf);
/* calc and verify H */
hash = kex_hash_gex(
client_version_string,
server_version_string,
buffer_ptr(client_kexinit), buffer_len(client_kexinit),
buffer_ptr(server_kexinit), buffer_len(server_kexinit),
server_host_key_blob, sbloblen,
nbits, dh->p, dh->g,
dh->pub_key,
dh_server_pub,
shared_secret
);
xfree(server_host_key_blob);
DH_free(dh);
BN_free(dh_server_pub);
#ifdef DEBUG_KEXDH
fprintf(stderr, "hash == ");
for (i = 0; i< 20; i++)
fprintf(stderr, "%02x", (hash[i])&0xff);
fprintf(stderr, "\n");
#endif
if (key_verify(server_host_key, (u_char *)signature, slen, hash, 20) != 1)
fatal("key_verify failed for server_host_key");
key_free(server_host_key);
xfree(signature);
kex_derive_keys(kex, hash, shared_secret);
BN_clear_free(shared_secret);
packet_set_kex(kex);
/* save session id */
session_id2_len = 20;
session_id2 = xmalloc(session_id2_len);
memcpy(session_id2, hash, session_id2_len);
}
/*
* Authenticate user
*/
typedef struct Authctxt Authctxt;
typedef struct Authmethod Authmethod;
typedef int sign_cb_fn(
Authctxt *authctxt, Key *key,
u_char **sigp, int *lenp, u_char *data, int datalen);
struct Authctxt {
const char *server_user;
const char *host;
const char *service;
AuthenticationConnection *agent;
Authmethod *method;
int success;
char *authlist;
Key *last_key;
sign_cb_fn *last_key_sign;
int last_key_hint;
};
struct Authmethod {
char *name; /* string to compare against server's list */
int (*userauth)(Authctxt *authctxt);
int *enabled; /* flag in option struct that enables method */
int *batch_flag; /* flag in option struct that disables method */
};
void input_userauth_success(int type, int plen, void *ctxt);
void input_userauth_failure(int type, int plen, void *ctxt);
void input_userauth_banner(int type, int plen, void *ctxt);
void input_userauth_error(int type, int plen, void *ctxt);
void input_userauth_info_req(int type, int plen, void *ctxt);
void input_userauth_pk_ok(int type, int plen, void *ctxt);
int userauth_none(Authctxt *authctxt);
int userauth_pubkey(Authctxt *authctxt);
int userauth_passwd(Authctxt *authctxt);
int userauth_kbdint(Authctxt *authctxt);
void userauth(Authctxt *authctxt, char *authlist);
int
sign_and_send_pubkey(Authctxt *authctxt, Key *k,
sign_cb_fn *sign_callback);
void clear_auth_state(Authctxt *authctxt);
Authmethod *authmethod_get(char *authlist);
Authmethod *authmethod_lookup(const char *name);
char *authmethods_get(void);
Authmethod authmethods[] = {
{"publickey",
userauth_pubkey,
&options.pubkey_authentication,
NULL},
{"password",
userauth_passwd,
&options.password_authentication,
&options.batch_mode},
{"keyboard-interactive",
userauth_kbdint,
&options.kbd_interactive_authentication,
&options.batch_mode},
{"none",
userauth_none,
NULL,
NULL},
{NULL, NULL, NULL, NULL}
};
void
ssh_userauth2(const char *server_user, char *host)
{
Authctxt authctxt;
int type;
int plen;
if (options.challenge_reponse_authentication)
options.kbd_interactive_authentication = 1;
debug("send SSH2_MSG_SERVICE_REQUEST");
packet_start(SSH2_MSG_SERVICE_REQUEST);
packet_put_cstring("ssh-userauth");
packet_send();
packet_write_wait();
type = packet_read(&plen);
if (type != SSH2_MSG_SERVICE_ACCEPT) {
fatal("denied SSH2_MSG_SERVICE_ACCEPT: %d", type);
}
if (packet_remaining() > 0) {
char *reply = packet_get_string(&plen);
debug("service_accept: %s", reply);
xfree(reply);
} else {
debug("buggy server: service_accept w/o service");
}
packet_done();
debug("got SSH2_MSG_SERVICE_ACCEPT");
if (options.preferred_authentications == NULL)
options.preferred_authentications = authmethods_get();
/* setup authentication context */
authctxt.agent = ssh_get_authentication_connection();
authctxt.server_user = server_user;
authctxt.host = host;
authctxt.service = "ssh-connection"; /* service name */
authctxt.success = 0;
authctxt.method = authmethod_lookup("none");
authctxt.authlist = NULL;
if (authctxt.method == NULL)
fatal("ssh_userauth2: internal error: cannot send userauth none request");
/* initial userauth request */
userauth_none(&authctxt);
dispatch_init(&input_userauth_error);
dispatch_set(SSH2_MSG_USERAUTH_SUCCESS, &input_userauth_success);
dispatch_set(SSH2_MSG_USERAUTH_FAILURE, &input_userauth_failure);
dispatch_set(SSH2_MSG_USERAUTH_BANNER, &input_userauth_banner);
dispatch_run(DISPATCH_BLOCK, &authctxt.success, &authctxt); /* loop until success */
if (authctxt.agent != NULL)
ssh_close_authentication_connection(authctxt.agent);
debug("ssh-userauth2 successful: method %s", authctxt.method->name);
}
void
userauth(Authctxt *authctxt, char *authlist)
{
if (authlist == NULL) {
authlist = authctxt->authlist;
} else {
if (authctxt->authlist)
xfree(authctxt->authlist);
authctxt->authlist = authlist;
}
for (;;) {
Authmethod *method = authmethod_get(authlist);
if (method == NULL)
fatal("Permission denied (%s).", authlist);
authctxt->method = method;
if (method->userauth(authctxt) != 0) {
debug2("we sent a %s packet, wait for reply", method->name);
break;
} else {
debug2("we did not send a packet, disable method");
method->enabled = NULL;
}
}
}
void
input_userauth_error(int type, int plen, void *ctxt)
{
fatal("input_userauth_error: bad message during authentication: "
"type %d", type);
}
void
input_userauth_banner(int type, int plen, void *ctxt)
{
char *msg, *lang;
debug3("input_userauth_banner");
msg = packet_get_string(NULL);
lang = packet_get_string(NULL);
fprintf(stderr, "%s", msg);
xfree(msg);
xfree(lang);
}
void
input_userauth_success(int type, int plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
if (authctxt == NULL)
fatal("input_userauth_success: no authentication context");
if (authctxt->authlist)
xfree(authctxt->authlist);
clear_auth_state(authctxt);
authctxt->success = 1; /* break out */
}
void
input_userauth_failure(int type, int plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
char *authlist = NULL;
int partial;
if (authctxt == NULL)
fatal("input_userauth_failure: no authentication context");
authlist = packet_get_string(NULL);
partial = packet_get_char();
packet_done();
if (partial != 0)
log("Authenticated with partial success.");
debug("authentications that can continue: %s", authlist);
clear_auth_state(authctxt);
userauth(authctxt, authlist);
}
void
input_userauth_pk_ok(int type, int plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
Key *key = NULL;
Buffer b;
int alen, blen, pktype, sent = 0;
char *pkalg, *pkblob;
if (authctxt == NULL)
fatal("input_userauth_pk_ok: no authentication context");
if (datafellows & SSH_BUG_PKOK) {
/* this is similar to SSH_BUG_PKAUTH */
debug2("input_userauth_pk_ok: SSH_BUG_PKOK");
pkblob = packet_get_string(&blen);
buffer_init(&b);
buffer_append(&b, pkblob, blen);
pkalg = buffer_get_string(&b, &alen);
buffer_free(&b);
} else {
pkalg = packet_get_string(&alen);
pkblob = packet_get_string(&blen);
}
packet_done();
debug("input_userauth_pk_ok: pkalg %s blen %d lastkey %p hint %d",
pkalg, blen, authctxt->last_key, authctxt->last_key_hint);
do {
if (authctxt->last_key == NULL ||
authctxt->last_key_sign == NULL) {
debug("no last key or no sign cb");
break;
}
debug2("last_key %s", key_fingerprint(authctxt->last_key));
if ((pktype = key_type_from_name(pkalg)) == KEY_UNSPEC) {
debug("unknown pkalg %s", pkalg);
break;
}
if ((key = key_from_blob(pkblob, blen)) == NULL) {
debug("no key from blob. pkalg %s", pkalg);
break;
}
debug2("input_userauth_pk_ok: fp %s", key_fingerprint(key));
if (!key_equal(key, authctxt->last_key)) {
debug("key != last_key");
break;
}
sent = sign_and_send_pubkey(authctxt, key,
authctxt->last_key_sign);
} while(0);
if (key != NULL)
key_free(key);
xfree(pkalg);
xfree(pkblob);
/* unregister */
clear_auth_state(authctxt);
dispatch_set(SSH2_MSG_USERAUTH_PK_OK, NULL);
/* try another method if we did not send a packet*/
if (sent == 0)
userauth(authctxt, NULL);
}
int
userauth_none(Authctxt *authctxt)
{
/* initial userauth request */
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_cstring(authctxt->server_user);
packet_put_cstring(authctxt->service);
packet_put_cstring(authctxt->method->name);
packet_send();
return 1;
}
int
userauth_passwd(Authctxt *authctxt)
{
static int attempt = 0;
char prompt[80];
char *password;
if (attempt++ >= options.number_of_password_prompts)
return 0;
if(attempt != 1)
error("Permission denied, please try again.");
snprintf(prompt, sizeof(prompt), "%.30s@%.128s's password: ",
authctxt->server_user, authctxt->host);
password = read_passphrase(prompt, 0);
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_cstring(authctxt->server_user);
packet_put_cstring(authctxt->service);
packet_put_cstring(authctxt->method->name);
packet_put_char(0);
packet_put_cstring(password);
memset(password, 0, strlen(password));
xfree(password);
packet_inject_ignore(64);
packet_send();
return 1;
}
void
clear_auth_state(Authctxt *authctxt)
{
/* XXX clear authentication state */
if (authctxt->last_key != NULL && authctxt->last_key_hint == -1) {
debug3("clear_auth_state: key_free %p", authctxt->last_key);
key_free(authctxt->last_key);
}
authctxt->last_key = NULL;
authctxt->last_key_hint = -2;
authctxt->last_key_sign = NULL;
}
int
sign_and_send_pubkey(Authctxt *authctxt, Key *k, sign_cb_fn *sign_callback)
{
Buffer b;
u_char *blob, *signature;
int bloblen, slen;
int skip = 0;
int ret = -1;
int have_sig = 1;
debug3("sign_and_send_pubkey");
if (key_to_blob(k, &blob, &bloblen) == 0) {
/* we cannot handle this key */
debug3("sign_and_send_pubkey: cannot handle key");
return 0;
}
/* data to be signed */
buffer_init(&b);
if (datafellows & SSH_OLD_SESSIONID) {
buffer_append(&b, session_id2, session_id2_len);
skip = session_id2_len;
} else {
buffer_put_string(&b, session_id2, session_id2_len);
skip = buffer_len(&b);
}
buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
buffer_put_cstring(&b, authctxt->server_user);
buffer_put_cstring(&b,
datafellows & SSH_BUG_PKSERVICE ?
"ssh-userauth" :
authctxt->service);
if (datafellows & SSH_BUG_PKAUTH) {
buffer_put_char(&b, have_sig);
} else {
buffer_put_cstring(&b, authctxt->method->name);
buffer_put_char(&b, have_sig);
buffer_put_cstring(&b, key_ssh_name(k));
}
buffer_put_string(&b, blob, bloblen);
/* generate signature */
ret = (*sign_callback)(authctxt, k, &signature, &slen,
buffer_ptr(&b), buffer_len(&b));
if (ret == -1) {
xfree(blob);
buffer_free(&b);
return 0;
}
#ifdef DEBUG_PK
buffer_dump(&b);
#endif
if (datafellows & SSH_BUG_PKSERVICE) {
buffer_clear(&b);
buffer_append(&b, session_id2, session_id2_len);
skip = session_id2_len;
buffer_put_char(&b, SSH2_MSG_USERAUTH_REQUEST);
buffer_put_cstring(&b, authctxt->server_user);
buffer_put_cstring(&b, authctxt->service);
buffer_put_cstring(&b, authctxt->method->name);
buffer_put_char(&b, have_sig);
if (!(datafellows & SSH_BUG_PKAUTH))
buffer_put_cstring(&b, key_ssh_name(k));
buffer_put_string(&b, blob, bloblen);
}
xfree(blob);
/* append signature */
buffer_put_string(&b, signature, slen);
xfree(signature);
/* skip session id and packet type */
if (buffer_len(&b) < skip + 1)
fatal("userauth_pubkey: internal error");
buffer_consume(&b, skip + 1);
/* put remaining data from buffer into packet */
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_raw(buffer_ptr(&b), buffer_len(&b));
buffer_free(&b);
packet_send();
return 1;
}
int
send_pubkey_test(Authctxt *authctxt, Key *k, sign_cb_fn *sign_callback,
int hint)
{
u_char *blob;
int bloblen, have_sig = 0;
debug3("send_pubkey_test");
if (key_to_blob(k, &blob, &bloblen) == 0) {
/* we cannot handle this key */
debug3("send_pubkey_test: cannot handle key");
return 0;
}
/* register callback for USERAUTH_PK_OK message */
authctxt->last_key_sign = sign_callback;
authctxt->last_key_hint = hint;
authctxt->last_key = k;
dispatch_set(SSH2_MSG_USERAUTH_PK_OK, &input_userauth_pk_ok);
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_cstring(authctxt->server_user);
packet_put_cstring(authctxt->service);
packet_put_cstring(authctxt->method->name);
packet_put_char(have_sig);
if (!(datafellows & SSH_BUG_PKAUTH))
packet_put_cstring(key_ssh_name(k));
packet_put_string(blob, bloblen);
xfree(blob);
packet_send();
return 1;
}
Key *
load_identity_file(char *filename)
{
Key *private;
char prompt[300], *passphrase;
int success = 0, quit, i;
struct stat st;
if (stat(filename, &st) < 0) {
debug3("no such identity: %s", filename);
return NULL;
}
private = key_new(KEY_UNSPEC);
if (!load_private_key(filename, "", private, NULL)) {
if (options.batch_mode) {
key_free(private);
return NULL;
}
snprintf(prompt, sizeof prompt,
"Enter passphrase for key '%.100s': ", filename);
for (i = 0; i < options.number_of_password_prompts; i++) {
passphrase = read_passphrase(prompt, 0);
if (strcmp(passphrase, "") != 0) {
success = load_private_key(filename,
passphrase, private, NULL);
quit = 0;
} else {
debug2("no passphrase given, try next key");
quit = 1;
}
memset(passphrase, 0, strlen(passphrase));
xfree(passphrase);
if (success || quit)
break;
debug2("bad passphrase given, try again...");
}
if (!success) {
key_free(private);
return NULL;
}
}
return private;
}
int
identity_sign_cb(Authctxt *authctxt, Key *key, u_char **sigp, int *lenp,
u_char *data, int datalen)
{
Key *private;
int idx, ret;
idx = authctxt->last_key_hint;
if (idx < 0)
return -1;
private = load_identity_file(options.identity_files[idx]);
if (private == NULL)
return -1;
ret = key_sign(private, sigp, lenp, data, datalen);
key_free(private);
return ret;
}
int agent_sign_cb(Authctxt *authctxt, Key *key, u_char **sigp, int *lenp,
u_char *data, int datalen)
{
return ssh_agent_sign(authctxt->agent, key, sigp, lenp, data, datalen);
}
int key_sign_cb(Authctxt *authctxt, Key *key, u_char **sigp, int *lenp,
u_char *data, int datalen)
{
return key_sign(key, sigp, lenp, data, datalen);
}
int
userauth_pubkey_agent(Authctxt *authctxt)
{
static int called = 0;
int ret = 0;
char *comment;
Key *k;
if (called == 0) {
if (ssh_get_num_identities(authctxt->agent, 2) == 0)
debug2("userauth_pubkey_agent: no keys at all");
called = 1;
}
k = ssh_get_next_identity(authctxt->agent, &comment, 2);
if (k == NULL) {
debug2("userauth_pubkey_agent: no more keys");
} else {
debug("userauth_pubkey_agent: testing agent key %s", comment);
xfree(comment);
ret = send_pubkey_test(authctxt, k, agent_sign_cb, -1);
if (ret == 0)
key_free(k);
}
if (ret == 0)
debug2("userauth_pubkey_agent: no message sent");
return ret;
}
int
userauth_pubkey(Authctxt *authctxt)
{
static int idx = 0;
int sent = 0;
Key *key;
char *filename;
if (authctxt->agent != NULL) {
do {
sent = userauth_pubkey_agent(authctxt);
} while(!sent && authctxt->agent->howmany > 0);
}
while (!sent && idx < options.num_identity_files) {
key = options.identity_keys[idx];
filename = options.identity_files[idx];
if (key == NULL) {
debug("try privkey: %s", filename);
key = load_identity_file(filename);
if (key != NULL) {
sent = sign_and_send_pubkey(authctxt, key,
key_sign_cb);
key_free(key);
}
} else if (key->type != KEY_RSA1) {
debug("try pubkey: %s", filename);
sent = send_pubkey_test(authctxt, key,
identity_sign_cb, idx);
}
idx++;
}
return sent;
}
/*
* Send userauth request message specifying keyboard-interactive method.
*/
int
userauth_kbdint(Authctxt *authctxt)
{
static int attempt = 0;
if (attempt++ >= options.number_of_password_prompts)
return 0;
debug2("userauth_kbdint");
packet_start(SSH2_MSG_USERAUTH_REQUEST);
packet_put_cstring(authctxt->server_user);
packet_put_cstring(authctxt->service);
packet_put_cstring(authctxt->method->name);
packet_put_cstring(""); /* lang */
packet_put_cstring(options.kbd_interactive_devices ?
options.kbd_interactive_devices : "");
packet_send();
dispatch_set(SSH2_MSG_USERAUTH_INFO_REQUEST, &input_userauth_info_req);
return 1;
}
/*
* parse INFO_REQUEST, prompt user and send INFO_RESPONSE
*/
void
input_userauth_info_req(int type, int plen, void *ctxt)
{
Authctxt *authctxt = ctxt;
char *name, *inst, *lang, *prompt, *response;
u_int num_prompts, i;
int echo = 0;
debug2("input_userauth_info_req");
if (authctxt == NULL)
fatal("input_userauth_info_req: no authentication context");
name = packet_get_string(NULL);
inst = packet_get_string(NULL);
lang = packet_get_string(NULL);
if (strlen(name) > 0)
cli_mesg(name);
if (strlen(inst) > 0)
cli_mesg(inst);
xfree(name);
xfree(inst);
xfree(lang);
num_prompts = packet_get_int();
/*
* Begin to build info response packet based on prompts requested.
* We commit to providing the correct number of responses, so if
* further on we run into a problem that prevents this, we have to
* be sure and clean this up and send a correct error response.
*/
packet_start(SSH2_MSG_USERAUTH_INFO_RESPONSE);
packet_put_int(num_prompts);
for (i = 0; i < num_prompts; i++) {
prompt = packet_get_string(NULL);
echo = packet_get_char();
response = cli_prompt(prompt, echo);
packet_put_cstring(response);
memset(response, 0, strlen(response));
xfree(response);
xfree(prompt);
}
packet_done(); /* done with parsing incoming message. */
packet_inject_ignore(64);
packet_send();
}
/* find auth method */
/*
* given auth method name, if configurable options permit this method fill
* in auth_ident field and return true, otherwise return false.
*/
int
authmethod_is_enabled(Authmethod *method)
{
if (method == NULL)
return 0;
/* return false if options indicate this method is disabled */
if (method->enabled == NULL || *method->enabled == 0)
return 0;
/* return false if batch mode is enabled but method needs interactive mode */
if (method->batch_flag != NULL && *method->batch_flag != 0)
return 0;
return 1;
}
Authmethod *
authmethod_lookup(const char *name)
{
Authmethod *method = NULL;
if (name != NULL)
for (method = authmethods; method->name != NULL; method++)
if (strcmp(name, method->name) == 0)
return method;
debug2("Unrecognized authentication method name: %s", name ? name : "NULL");
return NULL;
}
/* XXX internal state */
static Authmethod *current = NULL;
static char *supported = NULL;
static char *preferred = NULL;
/*
* Given the authentication method list sent by the server, return the
* next method we should try. If the server initially sends a nil list,
* use a built-in default list.
*/
Authmethod *
authmethod_get(char *authlist)
{
char *name = NULL;
int next;
/* Use a suitable default if we're passed a nil list. */
if (authlist == NULL || strlen(authlist) == 0)
authlist = options.preferred_authentications;
if (supported == NULL || strcmp(authlist, supported) != 0) {
debug3("start over, passed a different list %s", authlist);
if (supported != NULL)
xfree(supported);
supported = xstrdup(authlist);
preferred = options.preferred_authentications;
debug3("preferred %s", preferred);
current = NULL;
} else if (current != NULL && authmethod_is_enabled(current))
return current;
for (;;) {
if ((name = match_list(preferred, supported, &next)) == NULL) {
debug("no more auth methods to try");
current = NULL;
return NULL;
}
preferred += next;
debug3("authmethod_lookup %s", name);
debug3("remaining preferred: %s", preferred);
if ((current = authmethod_lookup(name)) != NULL &&
authmethod_is_enabled(current)) {
debug3("authmethod_is_enabled %s", name);
debug("next auth method to try is %s", name);
return current;
}
}
}
#define DELIM ","
char *
authmethods_get(void)
{
Authmethod *method = NULL;
char buf[1024];
buf[0] = '\0';
for (method = authmethods; method->name != NULL; method++) {
if (authmethod_is_enabled(method)) {
if (buf[0] != '\0')
strlcat(buf, DELIM, sizeof buf);
strlcat(buf, method->name, sizeof buf);
}
}
return xstrdup(buf);
}
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