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Diffstat (limited to 'kexgsss.c')
-rw-r--r-- | kexgsss.c | 256 |
1 files changed, 256 insertions, 0 deletions
diff --git a/kexgsss.c b/kexgsss.c new file mode 100644 index 000000000..6447dc97b --- /dev/null +++ b/kexgsss.c | |||
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1 | /* | ||
2 | * Copyright (c) 2001-2005 Simon Wilkinson. All rights reserved. | ||
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 | |||
29 | #include <openssl/crypto.h> | ||
30 | #include <openssl/bn.h> | ||
31 | |||
32 | #include "xmalloc.h" | ||
33 | #include "buffer.h" | ||
34 | #include "bufaux.h" | ||
35 | #include "kex.h" | ||
36 | #include "log.h" | ||
37 | #include "packet.h" | ||
38 | #include "dh.h" | ||
39 | #include "ssh2.h" | ||
40 | #include "ssh-gss.h" | ||
41 | #include "monitor_wrap.h" | ||
42 | |||
43 | void | ||
44 | kexgss_server(Kex *kex) | ||
45 | { | ||
46 | OM_uint32 maj_status, min_status; | ||
47 | |||
48 | /* | ||
49 | * Some GSSAPI implementations use the input value of ret_flags (an | ||
50 | * output variable) as a means of triggering mechanism specific | ||
51 | * features. Initializing it to zero avoids inadvertently | ||
52 | * activating this non-standard behaviour. | ||
53 | */ | ||
54 | |||
55 | OM_uint32 ret_flags = 0; | ||
56 | gss_buffer_desc gssbuf, recv_tok, msg_tok; | ||
57 | gss_buffer_desc send_tok = GSS_C_EMPTY_BUFFER; | ||
58 | Gssctxt *ctxt = NULL; | ||
59 | u_int slen, klen, kout, hashlen; | ||
60 | u_char *kbuf, *hash; | ||
61 | DH *dh; | ||
62 | int min = -1, max = -1, nbits = -1; | ||
63 | BIGNUM *shared_secret = NULL; | ||
64 | BIGNUM *dh_client_pub = NULL; | ||
65 | int type = 0; | ||
66 | int gex; | ||
67 | gss_OID oid; | ||
68 | |||
69 | /* Initialise GSSAPI */ | ||
70 | |||
71 | /* If we're rekeying, privsep means that some of the private structures | ||
72 | * in the GSSAPI code are no longer available. This kludges them back | ||
73 | * into life | ||
74 | */ | ||
75 | if (!ssh_gssapi_oid_table_ok()) | ||
76 | ssh_gssapi_server_mechanisms(); | ||
77 | |||
78 | debug2("%s: Identifying %s", __func__, kex->name); | ||
79 | oid = ssh_gssapi_id_kex(NULL, kex->name, &gex); | ||
80 | if (oid == NULL) | ||
81 | fatal("Unknown gssapi mechanism"); | ||
82 | |||
83 | debug2("%s: Acquiring credentials", __func__); | ||
84 | |||
85 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt, oid)))) | ||
86 | fatal("Unable to acquire credentials for the server"); | ||
87 | |||
88 | if (gex) { | ||
89 | debug("Doing group exchange"); | ||
90 | packet_read_expect(SSH2_MSG_KEXGSS_GROUPREQ); | ||
91 | min = packet_get_int(); | ||
92 | nbits = packet_get_int(); | ||
93 | max = packet_get_int(); | ||
94 | min = MAX(DH_GRP_MIN, min); | ||
95 | max = MIN(DH_GRP_MAX, max); | ||
96 | packet_check_eom(); | ||
97 | if (max < min || nbits < min || max < nbits) | ||
98 | fatal("GSS_GEX, bad parameters: %d !< %d !< %d", | ||
99 | min, nbits, max); | ||
100 | dh = PRIVSEP(choose_dh(min, nbits, max)); | ||
101 | if (dh == NULL) | ||
102 | packet_disconnect("Protocol error: no matching group found"); | ||
103 | |||
104 | packet_start(SSH2_MSG_KEXGSS_GROUP); | ||
105 | packet_put_bignum2(dh->p); | ||
106 | packet_put_bignum2(dh->g); | ||
107 | packet_send(); | ||
108 | |||
109 | packet_write_wait(); | ||
110 | |||
111 | } else { | ||
112 | dh = dh_new_group1(); | ||
113 | } | ||
114 | dh_gen_key(dh, kex->we_need * 8); | ||
115 | |||
116 | do { | ||
117 | debug("Wait SSH2_MSG_GSSAPI_INIT"); | ||
118 | type = packet_read(); | ||
119 | switch(type) { | ||
120 | case SSH2_MSG_KEXGSS_INIT: | ||
121 | if (dh_client_pub != NULL) | ||
122 | fatal("Received KEXGSS_INIT after initialising"); | ||
123 | recv_tok.value = packet_get_string(&slen); | ||
124 | recv_tok.length = slen; | ||
125 | |||
126 | if ((dh_client_pub = BN_new()) == NULL) | ||
127 | fatal("dh_client_pub == NULL"); | ||
128 | |||
129 | packet_get_bignum2(dh_client_pub); | ||
130 | |||
131 | /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */ | ||
132 | break; | ||
133 | case SSH2_MSG_KEXGSS_CONTINUE: | ||
134 | recv_tok.value = packet_get_string(&slen); | ||
135 | recv_tok.length = slen; | ||
136 | break; | ||
137 | default: | ||
138 | packet_disconnect( | ||
139 | "Protocol error: didn't expect packet type %d", | ||
140 | type); | ||
141 | } | ||
142 | |||
143 | maj_status = PRIVSEP(ssh_gssapi_accept_ctx(ctxt, &recv_tok, | ||
144 | &send_tok, &ret_flags)); | ||
145 | |||
146 | xfree(recv_tok.value); | ||
147 | |||
148 | if (maj_status != GSS_S_COMPLETE && send_tok.length == 0) | ||
149 | fatal("Zero length token output when incomplete"); | ||
150 | |||
151 | if (dh_client_pub == NULL) | ||
152 | fatal("No client public key"); | ||
153 | |||
154 | if (maj_status & GSS_S_CONTINUE_NEEDED) { | ||
155 | debug("Sending GSSAPI_CONTINUE"); | ||
156 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | ||
157 | packet_put_string(send_tok.value, send_tok.length); | ||
158 | packet_send(); | ||
159 | gss_release_buffer(&min_status, &send_tok); | ||
160 | } | ||
161 | } while (maj_status & GSS_S_CONTINUE_NEEDED); | ||
162 | |||
163 | if (GSS_ERROR(maj_status)) { | ||
164 | if (send_tok.length > 0) { | ||
165 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | ||
166 | packet_put_string(send_tok.value, send_tok.length); | ||
167 | packet_send(); | ||
168 | } | ||
169 | fatal("accept_ctx died"); | ||
170 | } | ||
171 | |||
172 | if (!(ret_flags & GSS_C_MUTUAL_FLAG)) | ||
173 | fatal("Mutual Authentication flag wasn't set"); | ||
174 | |||
175 | if (!(ret_flags & GSS_C_INTEG_FLAG)) | ||
176 | fatal("Integrity flag wasn't set"); | ||
177 | |||
178 | if (!dh_pub_is_valid(dh, dh_client_pub)) | ||
179 | packet_disconnect("bad client public DH value"); | ||
180 | |||
181 | klen = DH_size(dh); | ||
182 | kbuf = xmalloc(klen); | ||
183 | kout = DH_compute_key(kbuf, dh_client_pub, dh); | ||
184 | |||
185 | shared_secret = BN_new(); | ||
186 | BN_bin2bn(kbuf, kout, shared_secret); | ||
187 | memset(kbuf, 0, klen); | ||
188 | xfree(kbuf); | ||
189 | |||
190 | if (gex) { | ||
191 | kexgex_hash( | ||
192 | kex->evp_md, | ||
193 | kex->client_version_string, kex->server_version_string, | ||
194 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | ||
195 | buffer_ptr(&kex->my), buffer_len(&kex->my), | ||
196 | NULL, 0, | ||
197 | min, nbits, max, | ||
198 | dh->p, dh->g, | ||
199 | dh_client_pub, | ||
200 | dh->pub_key, | ||
201 | shared_secret, | ||
202 | &hash, &hashlen | ||
203 | ); | ||
204 | } | ||
205 | else { | ||
206 | /* The GSSAPI hash is identical to the Diffie Helman one */ | ||
207 | kex_dh_hash( | ||
208 | kex->client_version_string, kex->server_version_string, | ||
209 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | ||
210 | buffer_ptr(&kex->my), buffer_len(&kex->my), | ||
211 | NULL, 0, /* Change this if we start sending host keys */ | ||
212 | dh_client_pub, dh->pub_key, shared_secret, | ||
213 | &hash, &hashlen | ||
214 | ); | ||
215 | } | ||
216 | BN_free(dh_client_pub); | ||
217 | |||
218 | if (kex->session_id == NULL) { | ||
219 | kex->session_id_len = hashlen; | ||
220 | kex->session_id = xmalloc(kex->session_id_len); | ||
221 | memcpy(kex->session_id, hash, kex->session_id_len); | ||
222 | } | ||
223 | |||
224 | gssbuf.value = hash; | ||
225 | gssbuf.length = hashlen; | ||
226 | |||
227 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok)))) | ||
228 | fatal("Couldn't get MIC"); | ||
229 | |||
230 | packet_start(SSH2_MSG_KEXGSS_COMPLETE); | ||
231 | packet_put_bignum2(dh->pub_key); | ||
232 | packet_put_string((char *)msg_tok.value,msg_tok.length); | ||
233 | |||
234 | if (send_tok.length != 0) { | ||
235 | packet_put_char(1); /* true */ | ||
236 | packet_put_string((char *)send_tok.value, send_tok.length); | ||
237 | } else { | ||
238 | packet_put_char(0); /* false */ | ||
239 | } | ||
240 | packet_send(); | ||
241 | |||
242 | gss_release_buffer(&min_status, &send_tok); | ||
243 | gss_release_buffer(&min_status, &msg_tok); | ||
244 | |||
245 | if (gss_kex_context == NULL) | ||
246 | gss_kex_context = ctxt; | ||
247 | else | ||
248 | ssh_gssapi_delete_ctx(&ctxt); | ||
249 | |||
250 | DH_free(dh); | ||
251 | |||
252 | kex_derive_keys(kex, hash, hashlen, shared_secret); | ||
253 | BN_clear_free(shared_secret); | ||
254 | kex_finish(kex); | ||
255 | } | ||
256 | #endif /* GSSAPI */ | ||