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b46fa825 | 1 | /* |
f713db99 | 2 | * Copyright (c) 2001-2006 Simon Wilkinson. All rights reserved. |
b46fa825 | 3 | * |
4 | * Redistribution and use in source and binary forms, with or without | |
5 | * modification, are permitted provided that the following conditions | |
6 | * are met: | |
7 | * 1. Redistributions of source code must retain the above copyright | |
8 | * notice, this list of conditions and the following disclaimer. | |
9 | * 2. Redistributions in binary form must reproduce the above copyright | |
10 | * notice, this list of conditions and the following disclaimer in the | |
11 | * documentation and/or other materials provided with the distribution. | |
12 | * | |
13 | * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR | |
14 | * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES | |
15 | * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. | |
16 | * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, | |
17 | * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT | |
18 | * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, | |
19 | * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY | |
20 | * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT | |
21 | * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF | |
22 | * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. | |
23 | */ | |
24 | ||
25 | #include "includes.h" | |
26 | ||
27 | #ifdef GSSAPI | |
28 | ||
f713db99 | 29 | #include <string.h> |
30 | ||
b46fa825 | 31 | #include <openssl/crypto.h> |
32 | #include <openssl/bn.h> | |
33 | ||
34 | #include "xmalloc.h" | |
35 | #include "buffer.h" | |
f713db99 | 36 | #include "ssh2.h" |
30460aeb | 37 | #include "key.h" |
f713db99 | 38 | #include "cipher.h" |
b46fa825 | 39 | #include "kex.h" |
40 | #include "log.h" | |
41 | #include "packet.h" | |
42 | #include "dh.h" | |
b46fa825 | 43 | #include "ssh-gss.h" |
44 | #include "monitor_wrap.h" | |
23987cb8 | 45 | |
46 | static void kex_gss_send_error(Gssctxt *ctxt); | |
b46fa825 | 47 | |
48 | void | |
49 | kexgss_server(Kex *kex) | |
50 | { | |
b46fa825 | 51 | OM_uint32 maj_status, min_status; |
52 | ||
fe4ad273 | 53 | /* |
54 | * Some GSSAPI implementations use the input value of ret_flags (an | |
e23e524c | 55 | * output variable) as a means of triggering mechanism specific |
56 | * features. Initializing it to zero avoids inadvertently | |
fe4ad273 | 57 | * activating this non-standard behaviour. |
58 | */ | |
b46fa825 | 59 | |
60 | OM_uint32 ret_flags = 0; | |
fe4ad273 | 61 | gss_buffer_desc gssbuf, recv_tok, msg_tok; |
62 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | |
b46fa825 | 63 | Gssctxt *ctxt = NULL; |
f472818d | 64 | u_int slen, klen, kout, hashlen; |
65 | u_char *kbuf, *hash; | |
fe4ad273 | 66 | DH *dh; |
67 | int min = -1, max = -1, nbits = -1; | |
68 | BIGNUM *shared_secret = NULL; | |
69 | BIGNUM *dh_client_pub = NULL; | |
70 | int type = 0; | |
23987cb8 | 71 | gss_OID oid; |
f713db99 | 72 | |
b46fa825 | 73 | /* Initialise GSSAPI */ |
74 | ||
fe4ad273 | 75 | /* If we're rekeying, privsep means that some of the private structures |
76 | * in the GSSAPI code are no longer available. This kludges them back | |
f713db99 | 77 | * into life |
fe4ad273 | 78 | */ |
79 | if (!ssh_gssapi_oid_table_ok()) | |
80 | ssh_gssapi_server_mechanisms(); | |
81 | ||
82 | debug2("%s: Identifying %s", __func__, kex->name); | |
f713db99 | 83 | oid = ssh_gssapi_id_kex(NULL, kex->name, kex->kex_type); |
84 | if (oid == GSS_C_NO_OID) | |
fe4ad273 | 85 | fatal("Unknown gssapi mechanism"); |
86 | ||
87 | debug2("%s: Acquiring credentials", __func__); | |
88 | ||
89 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) { | |
23987cb8 | 90 | kex_gss_send_error(ctxt); |
f713db99 | 91 | fatal("Unable to acquire credentials for the server"); |
92 | } | |
93 | ||
94 | switch (kex->kex_type) { | |
95 | case KEX_GSS_GRP1_SHA1: | |
96 | dh = dh_new_group1(); | |
97 | break; | |
98 | case KEX_GSS_GRP14_SHA1: | |
99 | dh = dh_new_group14(); | |
100 | break; | |
101 | case KEX_GSS_GEX_SHA1: | |
fe4ad273 | 102 | debug("Doing group exchange"); |
103 | packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ); | |
104 | min = packet_get_int(); | |
105 | nbits = packet_get_int(); | |
106 | max = packet_get_int(); | |
107 | min = MAX(DH_GRP_MIN, min); | |
108 | max = MIN(DH_GRP_MAX, max); | |
109 | packet_check_eom(); | |
110 | if (max < min || nbits < min || max < nbits) | |
111 | fatal("GSS_GEX, bad parameters: %d !< %d !< %d", | |
112 | min, nbits, max); | |
113 | dh = PRIVSEP(choose_dh(min, nbits, max)); | |
114 | if (dh == NULL) | |
115 | packet_disconnect("Protocol error: no matching group found"); | |
116 | ||
117 | packet_start(SSH2_MSG_KEXGSS_GROUP); | |
118 | packet_put_bignum2(dh->p); | |
119 | packet_put_bignum2(dh->g); | |
120 | packet_send(); | |
121 | ||
122 | packet_write_wait(); | |
f713db99 | 123 | break; |
124 | default: | |
125 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
fe4ad273 | 126 | } |
f713db99 | 127 | |
fe4ad273 | 128 | dh_gen_key(dh, kex->we_need * 8); |
129 | ||
b46fa825 | 130 | do { |
131 | debug("Wait SSH2_MSG_GSSAPI_INIT"); | |
132 | type = packet_read(); | |
133 | switch(type) { | |
134 | case SSH2_MSG_KEXGSS_INIT: | |
fe4ad273 | 135 | if (dh_client_pub != NULL) |
136 | fatal("Received KEXGSS_INIT after initialising"); | |
137 | recv_tok.value = packet_get_string(&slen); | |
138 | recv_tok.length = slen; | |
139 | ||
140 | if ((dh_client_pub = BN_new()) == NULL) | |
141 | fatal("dh_client_pub == NULL"); | |
142 | ||
143 | packet_get_bignum2(dh_client_pub); | |
144 | ||
145 | /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */ | |
b46fa825 | 146 | break; |
147 | case SSH2_MSG_KEXGSS_CONTINUE: | |
fe4ad273 | 148 | recv_tok.value = packet_get_string(&slen); |
149 | recv_tok.length = slen; | |
b46fa825 | 150 | break; |
151 | default: | |
fe4ad273 | 152 | packet_disconnect( |
153 | "Protocol error: didn't expect packet type %d", | |
154 | type); | |
b46fa825 | 155 | } |
b46fa825 | 156 | |
fe4ad273 | 157 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok, |
158 | &send_tok, &ret_flags)); | |
159 | ||
160 | xfree(recv_tok.value); | |
161 | ||
162 | if (maj_status != GSS_S_COMPLETE && send_tok.length == 0) | |
163 | fatal("Zero length token output when incomplete"); | |
164 | ||
e23e524c | 165 | if (dh_client_pub == NULL) |
166 | fatal("No client public key"); | |
167 | ||
c045675e | 168 | if (maj_status & GSS_S_CONTINUE_NEEDED) { |
b46fa825 | 169 | debug("Sending GSSAPI_CONTINUE"); |
170 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | |
fe4ad273 | 171 | packet_put_string(send_tok.value, send_tok.length); |
b46fa825 | 172 | packet_send(); |
b46fa825 | 173 | gss_release_buffer(&min_status, &send_tok); |
174 | } | |
175 | } while (maj_status & GSS_S_CONTINUE_NEEDED); | |
176 | ||
177 | if (GSS_ERROR(maj_status)) { | |
23987cb8 | 178 | kex_gss_send_error(ctxt); |
fe4ad273 | 179 | if (send_tok.length > 0) { |
e23e524c | 180 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); |
fe4ad273 | 181 | packet_put_string(send_tok.value, send_tok.length); |
e23e524c | 182 | packet_send(); |
fe4ad273 | 183 | } |
184 | packet_disconnect("GSSAPI Key Exchange handshake failed"); | |
b46fa825 | 185 | } |
fe4ad273 | 186 | |
23987cb8 | 187 | if (!(ret_flags & GSS_C_MUTUAL_FLAG)) |
fe4ad273 | 188 | fatal("Mutual Authentication flag wasn't set"); |
189 | ||
23987cb8 | 190 | if (!(ret_flags & GSS_C_INTEG_FLAG)) |
fe4ad273 | 191 | fatal("Integrity flag wasn't set"); |
b46fa825 | 192 | |
fe4ad273 | 193 | if (!dh_pub_is_valid(dh, dh_client_pub)) |
194 | packet_disconnect("bad client public DH value"); | |
b46fa825 | 195 | |
fe4ad273 | 196 | klen = DH_size(dh); |
197 | kbuf = xmalloc(klen); | |
198 | kout = DH_compute_key(kbuf, dh_client_pub, dh); | |
b46fa825 | 199 | |
200 | shared_secret = BN_new(); | |
201 | BN_bin2bn(kbuf, kout, shared_secret); | |
202 | memset(kbuf, 0, klen); | |
203 | xfree(kbuf); | |
fe4ad273 | 204 | |
f713db99 | 205 | switch (kex->kex_type) { |
206 | case KEX_GSS_GRP1_SHA1: | |
207 | case KEX_GSS_GRP14_SHA1: | |
208 | kex_dh_hash( | |
209 | kex->client_version_string, kex->server_version_string, | |
210 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
211 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
212 | NULL, 0, /* Change this if we start sending host keys */ | |
213 | dh_client_pub, dh->pub_key, shared_secret, | |
214 | &hash, &hashlen | |
215 | ); | |
216 | break; | |
217 | case KEX_GSS_GEX_SHA1: | |
08822d99 | 218 | kexgex_hash( |
219 | kex->evp_md, | |
fe4ad273 | 220 | kex->client_version_string, kex->server_version_string, |
221 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
222 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
223 | NULL, 0, | |
224 | min, nbits, max, | |
225 | dh->p, dh->g, | |
226 | dh_client_pub, | |
227 | dh->pub_key, | |
08822d99 | 228 | shared_secret, |
229 | &hash, &hashlen | |
fe4ad273 | 230 | ); |
f713db99 | 231 | break; |
232 | default: | |
233 | fatal("%s: Unexpected KEX type %d", __func__, kex->kex_type); | |
fe4ad273 | 234 | } |
f713db99 | 235 | |
b46fa825 | 236 | BN_free(dh_client_pub); |
fe4ad273 | 237 | |
b46fa825 | 238 | if (kex->session_id == NULL) { |
d33fd7cd | 239 | kex->session_id_len = hashlen; |
b46fa825 | 240 | kex->session_id = xmalloc(kex->session_id_len); |
241 | memcpy(kex->session_id, hash, kex->session_id_len); | |
242 | } | |
fe4ad273 | 243 | |
b46fa825 | 244 | gssbuf.value = hash; |
d33fd7cd | 245 | gssbuf.length = hashlen; |
fe4ad273 | 246 | |
247 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok)))) | |
23987cb8 | 248 | fatal("Couldn't get MIC"); |
fe4ad273 | 249 | |
b46fa825 | 250 | packet_start(SSH2_MSG_KEXGSS_COMPLETE); |
251 | packet_put_bignum2(dh->pub_key); | |
252 | packet_put_string((char *)msg_tok.value,msg_tok.length); | |
253 | ||
fe4ad273 | 254 | if (send_tok.length != 0) { |
b46fa825 | 255 | packet_put_char(1); /* true */ |
fe4ad273 | 256 | packet_put_string((char *)send_tok.value, send_tok.length); |
b46fa825 | 257 | } else { |
258 | packet_put_char(0); /* false */ | |
259 | } | |
fe4ad273 | 260 | packet_send(); |
261 | ||
262 | gss_release_buffer(&min_status, &send_tok); | |
263 | gss_release_buffer(&min_status, &msg_tok); | |
264 | ||
265 | if (gss_kex_context == NULL) | |
266 | gss_kex_context = ctxt; | |
267 | else | |
268 | ssh_gssapi_delete_ctx(&ctxt); | |
269 | ||
b46fa825 | 270 | DH_free(dh); |
271 | ||
08822d99 | 272 | kex_derive_keys(kex, hash, hashlen, shared_secret); |
b46fa825 | 273 | BN_clear_free(shared_secret); |
274 | kex_finish(kex); | |
275 | } | |
276 | ||
23987cb8 | 277 | static void |
278 | kex_gss_send_error(Gssctxt *ctxt) { | |
279 | char *errstr; | |
280 | OM_uint32 maj,min; | |
281 | ||
282 | errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min)); | |
283 | if (errstr) { | |
284 | packet_start(SSH2_MSG_KEXGSS_ERROR); | |
285 | packet_put_int(maj); | |
286 | packet_put_int(min); | |
287 | packet_put_cstring(errstr); | |
288 | packet_put_cstring(""); | |
289 | packet_send(); | |
290 | packet_write_wait(); | |
291 | /* XXX - We should probably log the error locally here */ | |
292 | xfree(errstr); | |
293 | } | |
294 | } | |
b46fa825 | 295 | #endif /* GSSAPI */ |