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      1 /* $OpenBSD: gss-genr.c,v 1.24 2016/09/12 01:22:38 deraadt Exp $ */
      2 
      3 /*
      4  * Copyright (c) 2001-2007 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 
     27 #include "includes.h"
     28 
     29 #ifdef GSSAPI
     30 
     31 #include <sys/types.h>
     32 
     33 #include <limits.h>
     34 #include <stdarg.h>
     35 #include <string.h>
     36 #include <signal.h>
     37 #include <unistd.h>
     38 
     39 #include "xmalloc.h"
     40 #include "buffer.h"
     41 #include "log.h"
     42 #include "ssh2.h"
     43 
     44 #include "ssh-gss.h"
     45 
     46 extern u_char *session_id2;
     47 extern u_int session_id2_len;
     48 
     49 /* Check that the OID in a data stream matches that in the context */
     50 int
     51 ssh_gssapi_check_oid(Gssctxt *ctx, void *data, size_t len)
     52 {
     53 	return (ctx != NULL && ctx->oid != GSS_C_NO_OID &&
     54 	    ctx->oid->length == len &&
     55 	    memcmp(ctx->oid->elements, data, len) == 0);
     56 }
     57 
     58 /* Set the contexts OID from a data stream */
     59 void
     60 ssh_gssapi_set_oid_data(Gssctxt *ctx, void *data, size_t len)
     61 {
     62 	if (ctx->oid != GSS_C_NO_OID) {
     63 		free(ctx->oid->elements);
     64 		free(ctx->oid);
     65 	}
     66 	ctx->oid = xcalloc(1, sizeof(gss_OID_desc));
     67 	ctx->oid->length = len;
     68 	ctx->oid->elements = xmalloc(len);
     69 	memcpy(ctx->oid->elements, data, len);
     70 }
     71 
     72 /* Set the contexts OID */
     73 void
     74 ssh_gssapi_set_oid(Gssctxt *ctx, gss_OID oid)
     75 {
     76 	ssh_gssapi_set_oid_data(ctx, oid->elements, oid->length);
     77 }
     78 
     79 /* All this effort to report an error ... */
     80 void
     81 ssh_gssapi_error(Gssctxt *ctxt)
     82 {
     83 	char *s;
     84 
     85 	s = ssh_gssapi_last_error(ctxt, NULL, NULL);
     86 	debug("%s", s);
     87 	free(s);
     88 }
     89 
     90 char *
     91 ssh_gssapi_last_error(Gssctxt *ctxt, OM_uint32 *major_status,
     92     OM_uint32 *minor_status)
     93 {
     94 	OM_uint32 lmin;
     95 	gss_buffer_desc msg = GSS_C_EMPTY_BUFFER;
     96 	OM_uint32 ctx;
     97 	Buffer b;
     98 	char *ret;
     99 
    100 	buffer_init(&b);
    101 
    102 	if (major_status != NULL)
    103 		*major_status = ctxt->major;
    104 	if (minor_status != NULL)
    105 		*minor_status = ctxt->minor;
    106 
    107 	ctx = 0;
    108 	/* The GSSAPI error */
    109 	do {
    110 		gss_display_status(&lmin, ctxt->major,
    111 		    GSS_C_GSS_CODE, ctxt->oid, &ctx, &msg);
    112 
    113 		buffer_append(&b, msg.value, msg.length);
    114 		buffer_put_char(&b, '\n');
    115 
    116 		gss_release_buffer(&lmin, &msg);
    117 	} while (ctx != 0);
    118 
    119 	/* The mechanism specific error */
    120 	do {
    121 		gss_display_status(&lmin, ctxt->minor,
    122 		    GSS_C_MECH_CODE, ctxt->oid, &ctx, &msg);
    123 
    124 		buffer_append(&b, msg.value, msg.length);
    125 		buffer_put_char(&b, '\n');
    126 
    127 		gss_release_buffer(&lmin, &msg);
    128 	} while (ctx != 0);
    129 
    130 	buffer_put_char(&b, '\0');
    131 	ret = xmalloc(buffer_len(&b));
    132 	buffer_get(&b, ret, buffer_len(&b));
    133 	buffer_free(&b);
    134 	return (ret);
    135 }
    136 
    137 /*
    138  * Initialise our GSSAPI context. We use this opaque structure to contain all
    139  * of the data which both the client and server need to persist across
    140  * {accept,init}_sec_context calls, so that when we do it from the userauth
    141  * stuff life is a little easier
    142  */
    143 void
    144 ssh_gssapi_build_ctx(Gssctxt **ctx)
    145 {
    146 	*ctx = xcalloc(1, sizeof (Gssctxt));
    147 	(*ctx)->context = GSS_C_NO_CONTEXT;
    148 	(*ctx)->name = GSS_C_NO_NAME;
    149 	(*ctx)->oid = GSS_C_NO_OID;
    150 	(*ctx)->creds = GSS_C_NO_CREDENTIAL;
    151 	(*ctx)->client = GSS_C_NO_NAME;
    152 	(*ctx)->client_creds = GSS_C_NO_CREDENTIAL;
    153 }
    154 
    155 /* Delete our context, providing it has been built correctly */
    156 void
    157 ssh_gssapi_delete_ctx(Gssctxt **ctx)
    158 {
    159 	OM_uint32 ms;
    160 
    161 	if ((*ctx) == NULL)
    162 		return;
    163 	if ((*ctx)->context != GSS_C_NO_CONTEXT)
    164 		gss_delete_sec_context(&ms, &(*ctx)->context, GSS_C_NO_BUFFER);
    165 	if ((*ctx)->name != GSS_C_NO_NAME)
    166 		gss_release_name(&ms, &(*ctx)->name);
    167 	if ((*ctx)->oid != GSS_C_NO_OID) {
    168 		free((*ctx)->oid->elements);
    169 		free((*ctx)->oid);
    170 		(*ctx)->oid = GSS_C_NO_OID;
    171 	}
    172 	if ((*ctx)->creds != GSS_C_NO_CREDENTIAL)
    173 		gss_release_cred(&ms, &(*ctx)->creds);
    174 	if ((*ctx)->client != GSS_C_NO_NAME)
    175 		gss_release_name(&ms, &(*ctx)->client);
    176 	if ((*ctx)->client_creds != GSS_C_NO_CREDENTIAL)
    177 		gss_release_cred(&ms, &(*ctx)->client_creds);
    178 
    179 	free(*ctx);
    180 	*ctx = NULL;
    181 }
    182 
    183 /*
    184  * Wrapper to init_sec_context
    185  * Requires that the context contains:
    186  *	oid
    187  *	server name (from ssh_gssapi_import_name)
    188  */
    189 OM_uint32
    190 ssh_gssapi_init_ctx(Gssctxt *ctx, int deleg_creds, gss_buffer_desc *recv_tok,
    191     gss_buffer_desc* send_tok, OM_uint32 *flags)
    192 {
    193 	int deleg_flag = 0;
    194 
    195 	if (deleg_creds) {
    196 		deleg_flag = GSS_C_DELEG_FLAG;
    197 		debug("Delegating credentials");
    198 	}
    199 
    200 	ctx->major = gss_init_sec_context(&ctx->minor,
    201 	    GSS_C_NO_CREDENTIAL, &ctx->context, ctx->name, ctx->oid,
    202 	    GSS_C_MUTUAL_FLAG | GSS_C_INTEG_FLAG | deleg_flag,
    203 	    0, NULL, recv_tok, NULL, send_tok, flags, NULL);
    204 
    205 	if (GSS_ERROR(ctx->major))
    206 		ssh_gssapi_error(ctx);
    207 
    208 	return (ctx->major);
    209 }
    210 
    211 /* Create a service name for the given host */
    212 OM_uint32
    213 ssh_gssapi_import_name(Gssctxt *ctx, const char *host)
    214 {
    215 	gss_buffer_desc gssbuf;
    216 	char *val;
    217 
    218 	xasprintf(&val, "host@%s", host);
    219 	gssbuf.value = val;
    220 	gssbuf.length = strlen(gssbuf.value);
    221 
    222 	if ((ctx->major = gss_import_name(&ctx->minor,
    223 	    &gssbuf, GSS_C_NT_HOSTBASED_SERVICE, &ctx->name)))
    224 		ssh_gssapi_error(ctx);
    225 
    226 	free(gssbuf.value);
    227 	return (ctx->major);
    228 }
    229 
    230 OM_uint32
    231 ssh_gssapi_sign(Gssctxt *ctx, gss_buffer_t buffer, gss_buffer_t hash)
    232 {
    233 	if ((ctx->major = gss_get_mic(&ctx->minor, ctx->context,
    234 	    GSS_C_QOP_DEFAULT, buffer, hash)))
    235 		ssh_gssapi_error(ctx);
    236 
    237 	return (ctx->major);
    238 }
    239 
    240 void
    241 ssh_gssapi_buildmic(Buffer *b, const char *user, const char *service,
    242     const char *context)
    243 {
    244 	buffer_init(b);
    245 	buffer_put_string(b, session_id2, session_id2_len);
    246 	buffer_put_char(b, SSH2_MSG_USERAUTH_REQUEST);
    247 	buffer_put_cstring(b, user);
    248 	buffer_put_cstring(b, service);
    249 	buffer_put_cstring(b, context);
    250 }
    251 
    252 int
    253 ssh_gssapi_check_mechanism(Gssctxt **ctx, gss_OID oid, const char *host)
    254 {
    255 	gss_buffer_desc token = GSS_C_EMPTY_BUFFER;
    256 	OM_uint32 major, minor;
    257 	gss_OID_desc spnego_oid = {6, (void *)"\x2B\x06\x01\x05\x05\x02"};
    258 
    259 	/* RFC 4462 says we MUST NOT do SPNEGO */
    260 	if (oid->length == spnego_oid.length &&
    261 	    (memcmp(oid->elements, spnego_oid.elements, oid->length) == 0))
    262 		return 0; /* false */
    263 
    264 	ssh_gssapi_build_ctx(ctx);
    265 	ssh_gssapi_set_oid(*ctx, oid);
    266 	major = ssh_gssapi_import_name(*ctx, host);
    267 	if (!GSS_ERROR(major)) {
    268 		major = ssh_gssapi_init_ctx(*ctx, 0, GSS_C_NO_BUFFER, &token,
    269 		    NULL);
    270 		gss_release_buffer(&minor, &token);
    271 		if ((*ctx)->context != GSS_C_NO_CONTEXT)
    272 			gss_delete_sec_context(&minor, &(*ctx)->context,
    273 			    GSS_C_NO_BUFFER);
    274 	}
    275 
    276 	if (GSS_ERROR(major))
    277 		ssh_gssapi_delete_ctx(ctx);
    278 
    279 	return (!GSS_ERROR(major));
    280 }
    281 
    282 #endif /* GSSAPI */
    283