Annotation of src/usr.bin/ssh/gss-serv.c, Revision 1.26
1.26 ! djm 1: /* $OpenBSD: gss-serv.c,v 1.25 2014/02/02 03:44:31 djm Exp $ */
1.1 markus 2:
3: /*
4: * Copyright (c) 2001-2003 Simon Wilkinson. All rights reserved.
5: *
6: * Redistribution and use in source and binary forms, with or without
7: * modification, are permitted provided that the following conditions
8: * are met:
9: * 1. Redistributions of source code must retain the above copyright
10: * notice, this list of conditions and the following disclaimer.
11: * 2. Redistributions in binary form must reproduce the above copyright
12: * notice, this list of conditions and the following disclaimer in the
13: * documentation and/or other materials provided with the distribution.
14: *
15: * THIS SOFTWARE IS PROVIDED BY THE AUTHOR `AS IS'' AND ANY EXPRESS OR
16: * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17: * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18: * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19: * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20: * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21: * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22: * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23: * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24: * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25: */
26:
1.20 deraadt 27: #include <sys/types.h>
1.21 djm 28: #include <sys/param.h>
1.22 djm 29: #include <sys/queue.h>
1.1 markus 30:
31: #ifdef GSSAPI
1.19 stevesk 32:
33: #include <string.h>
1.1 markus 34:
1.20 deraadt 35: #include "xmalloc.h"
36: #include "buffer.h"
37: #include "key.h"
38: #include "hostfile.h"
1.1 markus 39: #include "auth.h"
40: #include "log.h"
41: #include "channels.h"
42: #include "session.h"
1.17 djm 43: #include "misc.h"
1.1 markus 44:
45: #include "ssh-gss.h"
46:
47: static ssh_gssapi_client gssapi_client =
48: { GSS_C_EMPTY_BUFFER, GSS_C_EMPTY_BUFFER,
1.24 djm 49: GSS_C_NO_CREDENTIAL, NULL, {NULL, NULL, NULL, NULL}};
1.1 markus 50:
51: ssh_gssapi_mech gssapi_null_mech =
52: { NULL, NULL, {0, NULL}, NULL, NULL, NULL, NULL};
53:
54: #ifdef KRB5
55: extern ssh_gssapi_mech gssapi_kerberos_mech;
56: #endif
57:
58: ssh_gssapi_mech* supported_mechs[]= {
59: #ifdef KRB5
60: &gssapi_kerberos_mech,
61: #endif
62: &gssapi_null_mech,
63: };
1.21 djm 64:
1.26 ! djm 65: /*
! 66: * ssh_gssapi_supported_oids() can cause sandbox violations, so prepare the
! 67: * list of supported mechanisms before privsep is set up.
! 68: */
! 69: static gss_OID_set supported_oids;
! 70:
! 71: void
! 72: ssh_gssapi_prepare_supported_oids(void)
! 73: {
! 74: ssh_gssapi_supported_oids(&supported_oids);
! 75: }
! 76:
! 77: OM_uint32
! 78: ssh_gssapi_test_oid_supported(OM_uint32 *ms, gss_OID member, int *present)
! 79: {
! 80: if (supported_oids == NULL)
! 81: ssh_gssapi_prepare_supported_oids();
! 82: return gss_test_oid_set_member(ms, member, supported_oids, present);
! 83: }
1.21 djm 84:
85: /*
86: * Acquire credentials for a server running on the current host.
87: * Requires that the context structure contains a valid OID
88: */
89:
90: /* Returns a GSSAPI error code */
91: /* Privileged (called from ssh_gssapi_server_ctx) */
92: static OM_uint32
93: ssh_gssapi_acquire_cred(Gssctxt *ctx)
94: {
95: OM_uint32 status;
96: char lname[MAXHOSTNAMELEN];
97: gss_OID_set oidset;
98:
99: gss_create_empty_oid_set(&status, &oidset);
100: gss_add_oid_set_member(&status, ctx->oid, &oidset);
101:
102: if (gethostname(lname, MAXHOSTNAMELEN)) {
103: gss_release_oid_set(&status, &oidset);
104: return (-1);
105: }
106:
107: if (GSS_ERROR(ssh_gssapi_import_name(ctx, lname))) {
108: gss_release_oid_set(&status, &oidset);
109: return (ctx->major);
110: }
111:
112: if ((ctx->major = gss_acquire_cred(&ctx->minor,
113: ctx->name, 0, oidset, GSS_C_ACCEPT, &ctx->creds, NULL, NULL)))
114: ssh_gssapi_error(ctx);
115:
116: gss_release_oid_set(&status, &oidset);
117: return (ctx->major);
118: }
119:
120: /* Privileged */
121: OM_uint32
122: ssh_gssapi_server_ctx(Gssctxt **ctx, gss_OID oid)
123: {
124: if (*ctx)
125: ssh_gssapi_delete_ctx(ctx);
126: ssh_gssapi_build_ctx(ctx);
127: ssh_gssapi_set_oid(*ctx, oid);
128: return (ssh_gssapi_acquire_cred(*ctx));
129: }
1.1 markus 130:
1.11 stevesk 131: /* Unprivileged */
1.1 markus 132: void
133: ssh_gssapi_supported_oids(gss_OID_set *oidset)
134: {
135: int i = 0;
136: OM_uint32 min_status;
137: int present;
138: gss_OID_set supported;
139:
140: gss_create_empty_oid_set(&min_status, oidset);
141: gss_indicate_mechs(&min_status, &supported);
142:
143: while (supported_mechs[i]->name != NULL) {
144: if (GSS_ERROR(gss_test_oid_set_member(&min_status,
145: &supported_mechs[i]->oid, supported, &present)))
146: present = 0;
147: if (present)
148: gss_add_oid_set_member(&min_status,
149: &supported_mechs[i]->oid, oidset);
150: i++;
151: }
1.15 djm 152:
153: gss_release_oid_set(&min_status, &supported);
1.1 markus 154: }
155:
156:
157: /* Wrapper around accept_sec_context
158: * Requires that the context contains:
159: * oid
160: * credentials (from ssh_gssapi_acquire_cred)
161: */
1.11 stevesk 162: /* Privileged */
1.1 markus 163: OM_uint32
164: ssh_gssapi_accept_ctx(Gssctxt *ctx, gss_buffer_desc *recv_tok,
165: gss_buffer_desc *send_tok, OM_uint32 *flags)
166: {
167: OM_uint32 status;
168: gss_OID mech;
169:
170: ctx->major = gss_accept_sec_context(&ctx->minor,
171: &ctx->context, ctx->creds, recv_tok,
172: GSS_C_NO_CHANNEL_BINDINGS, &ctx->client, &mech,
173: send_tok, flags, NULL, &ctx->client_creds);
174:
175: if (GSS_ERROR(ctx->major))
176: ssh_gssapi_error(ctx);
177:
178: if (ctx->client_creds)
179: debug("Received some client credentials");
180: else
181: debug("Got no client credentials");
182:
183: status = ctx->major;
184:
185: /* Now, if we're complete and we have the right flags, then
186: * we flag the user as also having been authenticated
187: */
188:
189: if (((flags == NULL) || ((*flags & GSS_C_MUTUAL_FLAG) &&
190: (*flags & GSS_C_INTEG_FLAG))) && (ctx->major == GSS_S_COMPLETE)) {
191: if (ssh_gssapi_getclient(ctx, &gssapi_client))
192: fatal("Couldn't convert client name");
193: }
194:
195: return (status);
196: }
197:
198: /*
199: * This parses an exported name, extracting the mechanism specific portion
200: * to use for ACL checking. It verifies that the name belongs the mechanism
201: * originally selected.
202: */
203: static OM_uint32
204: ssh_gssapi_parse_ename(Gssctxt *ctx, gss_buffer_t ename, gss_buffer_t name)
205: {
1.6 djm 206: u_char *tok;
1.1 markus 207: OM_uint32 offset;
208: OM_uint32 oidl;
1.3 markus 209:
1.13 stevesk 210: tok = ename->value;
1.3 markus 211:
212: /*
213: * Check that ename is long enough for all of the fixed length
1.1 markus 214: * header, and that the initial ID bytes are correct
215: */
216:
1.13 stevesk 217: if (ename->length < 6 || memcmp(tok, "\x04\x01", 2) != 0)
1.1 markus 218: return GSS_S_FAILURE;
219:
220: /*
221: * Extract the OID, and check it. Here GSSAPI breaks with tradition
222: * and does use the OID type and length bytes. To confuse things
223: * there are two lengths - the first including these, and the
224: * second without.
225: */
226:
1.17 djm 227: oidl = get_u16(tok+2); /* length including next two bytes */
1.1 markus 228: oidl = oidl-2; /* turn it into the _real_ length of the variable OID */
229:
230: /*
231: * Check the BER encoding for correct type and length, that the
232: * string is long enough and that the OID matches that in our context
233: */
234: if (tok[4] != 0x06 || tok[5] != oidl ||
1.3 markus 235: ename->length < oidl+6 ||
1.13 stevesk 236: !ssh_gssapi_check_oid(ctx, tok+6, oidl))
1.1 markus 237: return GSS_S_FAILURE;
238:
239: offset = oidl+6;
1.3 markus 240:
1.1 markus 241: if (ename->length < offset+4)
242: return GSS_S_FAILURE;
1.3 markus 243:
1.17 djm 244: name->length = get_u32(tok+offset);
1.1 markus 245: offset += 4;
1.3 markus 246:
1.23 markus 247: if (UINT_MAX - offset < name->length)
248: return GSS_S_FAILURE;
1.1 markus 249: if (ename->length < offset+name->length)
1.3 markus 250: return GSS_S_FAILURE;
251:
1.2 markus 252: name->value = xmalloc(name->length+1);
1.14 stevesk 253: memcpy(name->value, tok+offset, name->length);
1.2 markus 254: ((char *)name->value)[name->length] = 0;
255:
1.1 markus 256: return GSS_S_COMPLETE;
1.3 markus 257: }
1.1 markus 258:
259: /* Extract the client details from a given context. This can only reliably
260: * be called once for a context */
261:
1.11 stevesk 262: /* Privileged (called from accept_secure_ctx) */
1.1 markus 263: OM_uint32
264: ssh_gssapi_getclient(Gssctxt *ctx, ssh_gssapi_client *client)
265: {
266: int i = 0;
267:
268: gss_buffer_desc ename;
1.3 markus 269:
1.1 markus 270: client->mech = NULL;
271:
272: while (supported_mechs[i]->name != NULL) {
273: if (supported_mechs[i]->oid.length == ctx->oid->length &&
274: (memcmp(supported_mechs[i]->oid.elements,
275: ctx->oid->elements, ctx->oid->length) == 0))
276: client->mech = supported_mechs[i];
277: i++;
278: }
279:
1.3 markus 280: if (client->mech == NULL)
1.1 markus 281: return GSS_S_FAILURE;
1.3 markus 282:
283: if ((ctx->major = gss_display_name(&ctx->minor, ctx->client,
1.1 markus 284: &client->displayname, NULL))) {
1.3 markus 285: ssh_gssapi_error(ctx);
286: return (ctx->major);
1.1 markus 287: }
1.3 markus 288:
289: if ((ctx->major = gss_export_name(&ctx->minor, ctx->client,
1.1 markus 290: &ename))) {
291: ssh_gssapi_error(ctx);
292: return (ctx->major);
293: }
1.3 markus 294:
1.1 markus 295: if ((ctx->major = ssh_gssapi_parse_ename(ctx,&ename,
296: &client->exportedname))) {
297: return (ctx->major);
298: }
299:
300: /* We can't copy this structure, so we just move the pointer to it */
301: client->creds = ctx->client_creds;
302: ctx->client_creds = GSS_C_NO_CREDENTIAL;
303: return (ctx->major);
304: }
305:
1.4 markus 306: /* As user - called on fatal/exit */
1.1 markus 307: void
1.4 markus 308: ssh_gssapi_cleanup_creds(void)
1.1 markus 309: {
310: if (gssapi_client.store.filename != NULL) {
311: /* Unlink probably isn't sufficient */
1.14 stevesk 312: debug("removing gssapi cred file\"%s\"",
313: gssapi_client.store.filename);
1.1 markus 314: unlink(gssapi_client.store.filename);
315: }
316: }
317:
318: /* As user */
319: void
320: ssh_gssapi_storecreds(void)
321: {
322: if (gssapi_client.mech && gssapi_client.mech->storecreds) {
323: (*gssapi_client.mech->storecreds)(&gssapi_client);
324: } else
325: debug("ssh_gssapi_storecreds: Not a GSSAPI mechanism");
326: }
327:
328: /* This allows GSSAPI methods to do things to the childs environment based
329: * on the passed authentication process and credentials.
330: */
331: /* As user */
332: void
333: ssh_gssapi_do_child(char ***envp, u_int *envsizep)
334: {
335:
336: if (gssapi_client.store.envvar != NULL &&
337: gssapi_client.store.envval != NULL) {
338: debug("Setting %s to %s", gssapi_client.store.envvar,
1.13 stevesk 339: gssapi_client.store.envval);
1.1 markus 340: child_set_env(envp, envsizep, gssapi_client.store.envvar,
1.7 djm 341: gssapi_client.store.envval);
1.1 markus 342: }
343: }
344:
1.9 djm 345: /* Privileged */
1.1 markus 346: int
347: ssh_gssapi_userok(char *user)
348: {
1.8 djm 349: OM_uint32 lmin;
350:
1.1 markus 351: if (gssapi_client.exportedname.length == 0 ||
352: gssapi_client.exportedname.value == NULL) {
353: debug("No suitable client data");
354: return 0;
355: }
356: if (gssapi_client.mech && gssapi_client.mech->userok)
1.8 djm 357: if ((*gssapi_client.mech->userok)(&gssapi_client, user))
358: return 1;
359: else {
360: /* Destroy delegated credentials if userok fails */
361: gss_release_buffer(&lmin, &gssapi_client.displayname);
362: gss_release_buffer(&lmin, &gssapi_client.exportedname);
363: gss_release_cred(&lmin, &gssapi_client.creds);
1.25 djm 364: explicit_bzero(&gssapi_client,
365: sizeof(ssh_gssapi_client));
1.8 djm 366: return 0;
367: }
1.1 markus 368: else
369: debug("ssh_gssapi_userok: Unknown GSSAPI mechanism");
370: return (0);
1.5 markus 371: }
372:
1.11 stevesk 373: /* Privileged */
1.5 markus 374: OM_uint32
375: ssh_gssapi_checkmic(Gssctxt *ctx, gss_buffer_t gssbuf, gss_buffer_t gssmic)
376: {
377: ctx->major = gss_verify_mic(&ctx->minor, ctx->context,
378: gssbuf, gssmic, NULL);
379:
380: return (ctx->major);
1.1 markus 381: }
382:
383: #endif
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