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1c14df9e | 1 | /* |
88928908 | 2 | * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved. |
1c14df9e | 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" | |
88928908 | 42 | |
43 | static void kex_gss_send_error(Gssctxt *ctxt); | |
1c14df9e | 44 | |
45 | void | |
46 | kexgss_server(Kex *kex) | |
47 | { | |
1c14df9e | 48 | OM_uint32 maj_status, min_status; |
49 | ||
50 | /* Some GSSAPI implementations use the input value of ret_flags (an | |
51 | * output variable) as a means of triggering mechanism specific | |
52 | * features. Initializing it to zero avoids inadvertently | |
53 | * activating this non-standard behaviour.*/ | |
54 | ||
55 | OM_uint32 ret_flags = 0; | |
56 | gss_buffer_desc gssbuf,send_tok,recv_tok,msg_tok; | |
57 | Gssctxt *ctxt = NULL; | |
58 | unsigned int klen, kout; | |
59 | unsigned char *kbuf; | |
60 | unsigned char *hash; | |
61 | DH *dh; | |
62 | BIGNUM *shared_secret = NULL; | |
63 | BIGNUM *dh_client_pub = NULL; | |
64 | int type =0; | |
1c14df9e | 65 | u_int slen; |
88928908 | 66 | gss_OID oid; |
1c14df9e | 67 | |
68 | /* Initialise GSSAPI */ | |
69 | ||
70 | debug2("%s: Identifying %s",__func__,kex->name); | |
88928908 | 71 | oid=ssh_gssapi_server_id_kex(kex->name); |
1c14df9e | 72 | if (oid==NULL) { |
73 | packet_disconnect("Unknown gssapi mechanism"); | |
74 | } | |
75 | ||
76 | debug2("%s: Acquiring credentials",__func__); | |
77 | ||
88928908 | 78 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_server_ctx(&ctxt,oid)))) { |
79 | kex_gss_send_error(ctxt); | |
80 | packet_disconnect("Unable to acquire credentials for the server"); | |
81 | } | |
82 | ||
1c14df9e | 83 | do { |
84 | debug("Wait SSH2_MSG_GSSAPI_INIT"); | |
85 | type = packet_read(); | |
86 | switch(type) { | |
87 | case SSH2_MSG_KEXGSS_INIT: | |
88 | if (dh_client_pub!=NULL) | |
89 | packet_disconnect("Received KEXGSS_INIT after initialising"); | |
90 | recv_tok.value=packet_get_string(&slen); | |
91 | recv_tok.length=slen; /* int vs. size_t */ | |
92 | ||
93 | dh_client_pub = BN_new(); | |
94 | ||
95 | if (dh_client_pub == NULL) | |
88928908 | 96 | packet_disconnect("dh_client_pub == NULL"); |
1c14df9e | 97 | packet_get_bignum2(dh_client_pub); |
98 | ||
99 | /* Send SSH_MSG_KEXGSS_HOSTKEY here, if we want */ | |
100 | break; | |
101 | case SSH2_MSG_KEXGSS_CONTINUE: | |
1c14df9e | 102 | recv_tok.value=packet_get_string(&slen); |
103 | recv_tok.length=slen; /* int vs. size_t */ | |
104 | break; | |
105 | default: | |
106 | packet_disconnect("Protocol error: didn't expect packet type %d", | |
107 | type); | |
108 | } | |
109 | ||
110 | maj_status=PRIVSEP(ssh_gssapi_accept_ctx(ctxt,&recv_tok, | |
111 | &send_tok, &ret_flags)); | |
112 | ||
113 | gss_release_buffer(&min_status,&recv_tok); | |
88928908 | 114 | |
1c14df9e | 115 | #ifdef GSS_C_GLOBUS_LIMITED_PROXY_FLAG |
116 | if (ret_flags & GSS_C_GLOBUS_LIMITED_PROXY_FLAG) { | |
117 | packet_disconnect("Limited proxy is not allowed in gssapi key exchange."); | |
118 | } | |
119 | #endif | |
88928908 | 120 | |
121 | if (maj_status!=GSS_S_COMPLETE && send_tok.length==0) { | |
122 | fatal("Zero length token output when incomplete"); | |
123 | } | |
124 | ||
125 | if (dh_client_pub == NULL) | |
126 | fatal("No client public key"); | |
1c14df9e | 127 | |
128 | if (maj_status & GSS_S_CONTINUE_NEEDED) { | |
129 | debug("Sending GSSAPI_CONTINUE"); | |
130 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | |
131 | packet_put_string(send_tok.value,send_tok.length); | |
132 | packet_send(); | |
133 | packet_write_wait(); | |
134 | gss_release_buffer(&min_status, &send_tok); | |
135 | } | |
136 | } while (maj_status & GSS_S_CONTINUE_NEEDED); | |
137 | ||
138 | if (GSS_ERROR(maj_status)) { | |
88928908 | 139 | kex_gss_send_error(ctxt); |
140 | if (send_tok.length>0) { | |
141 | packet_start(SSH2_MSG_KEXGSS_CONTINUE); | |
142 | packet_put_string(send_tok.value,send_tok.length); | |
143 | packet_send(); | |
144 | packet_write_wait(); | |
145 | } | |
1c14df9e | 146 | packet_disconnect("gssapi key exchange handshake failed"); |
147 | } | |
88928908 | 148 | |
1c14df9e | 149 | debug("gss_complete"); |
88928908 | 150 | if (!(ret_flags & GSS_C_MUTUAL_FLAG)) |
151 | packet_disconnect("gssapi_mutual authentication failed"); | |
1c14df9e | 152 | |
88928908 | 153 | if (!(ret_flags & GSS_C_INTEG_FLAG)) |
1c14df9e | 154 | packet_disconnect("gssapi channel integrity not established"); |
88928908 | 155 | |
1c14df9e | 156 | dh = dh_new_group1(); |
157 | dh_gen_key(dh, kex->we_need * 8); | |
158 | ||
159 | if (!dh_pub_is_valid(dh, dh_client_pub)) | |
160 | packet_disconnect("bad client public DH value"); | |
161 | ||
162 | klen = DH_size(dh); | |
163 | kbuf = xmalloc(klen); | |
164 | kout = DH_compute_key(kbuf, dh_client_pub, dh); | |
165 | ||
166 | shared_secret = BN_new(); | |
167 | BN_bin2bn(kbuf, kout, shared_secret); | |
168 | memset(kbuf, 0, klen); | |
169 | xfree(kbuf); | |
170 | ||
88928908 | 171 | /* The GSSAPI hash is identical to the Diffie Helman one */ |
172 | hash = kex_dh_hash( | |
1c14df9e | 173 | kex->client_version_string, |
174 | kex->server_version_string, | |
175 | buffer_ptr(&kex->peer), buffer_len(&kex->peer), | |
176 | buffer_ptr(&kex->my), buffer_len(&kex->my), | |
177 | NULL, 0, /* Change this if we start sending host keys */ | |
178 | dh_client_pub, | |
179 | dh->pub_key, | |
180 | shared_secret | |
181 | ); | |
182 | BN_free(dh_client_pub); | |
183 | ||
184 | if (kex->session_id == NULL) { | |
185 | kex->session_id_len = 20; | |
186 | kex->session_id = xmalloc(kex->session_id_len); | |
187 | memcpy(kex->session_id, hash, kex->session_id_len); | |
188 | } | |
189 | ||
190 | gssbuf.value = hash; | |
191 | gssbuf.length = 20; /* Hashlen appears to always be 20 */ | |
192 | ||
193 | if (GSS_ERROR(PRIVSEP(ssh_gssapi_sign(ctxt,&gssbuf,&msg_tok)))) { | |
88928908 | 194 | kex_gss_send_error(ctxt); |
195 | fatal("Couldn't get MIC"); | |
1c14df9e | 196 | } |
197 | ||
198 | packet_start(SSH2_MSG_KEXGSS_COMPLETE); | |
199 | packet_put_bignum2(dh->pub_key); | |
200 | packet_put_string((char *)msg_tok.value,msg_tok.length); | |
201 | ||
202 | if (send_tok.length!=0) { | |
203 | packet_put_char(1); /* true */ | |
204 | packet_put_string((char *)send_tok.value,send_tok.length); | |
205 | } else { | |
206 | packet_put_char(0); /* false */ | |
207 | } | |
208 | packet_send(); | |
209 | packet_write_wait(); | |
210 | ||
211 | /* We used to store the client name and credentials here for later | |
212 | * use. With privsep, its easier to do this as a by product of the | |
213 | * call to accept_context, which stores delegated information when | |
214 | * the context is complete */ | |
215 | ||
216 | gss_release_buffer(&min_status, &send_tok); | |
217 | ||
218 | /* If we've got a context, delete it. It may be NULL if we've been | |
219 | * using privsep */ | |
220 | ssh_gssapi_delete_ctx(&ctxt); | |
221 | ||
222 | DH_free(dh); | |
223 | ||
224 | kex_derive_keys(kex, hash, shared_secret); | |
225 | BN_clear_free(shared_secret); | |
226 | kex_finish(kex); | |
227 | } | |
228 | ||
88928908 | 229 | static void |
230 | kex_gss_send_error(Gssctxt *ctxt) { | |
231 | char *errstr; | |
232 | OM_uint32 maj,min; | |
233 | ||
234 | errstr=PRIVSEP(ssh_gssapi_last_error(ctxt,&maj,&min)); | |
235 | if (errstr) { | |
236 | packet_start(SSH2_MSG_KEXGSS_ERROR); | |
237 | packet_put_int(maj); | |
238 | packet_put_int(min); | |
239 | packet_put_cstring(errstr); | |
240 | packet_put_cstring(""); | |
241 | packet_send(); | |
242 | packet_write_wait(); | |
243 | /* XXX - We should probably log the error locally here */ | |
244 | xfree(errstr); | |
245 | } | |
246 | } | |
1c14df9e | 247 | #endif /* GSSAPI */ |