1  /*
  2   * Copyright (c) 1997 - 2001 Kungliga Tekniska Högskolan
  3   * (Royal Institute of Technology, Stockholm, Sweden).
  4   * 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   *
 10   * 1. Redistributions of source code must retain the above copyright
 11   *    notice, this list of conditions and the following disclaimer.
 12   *
 13   * 2. Redistributions in binary form must reproduce the above copyright
 14   *    notice, this list of conditions and the following disclaimer in the
 15   *    documentation and/or other materials provided with the distribution.
 16   *
 17   * 3. Neither the name of the Institute nor the names of its contributors
 18   *    may be used to endorse or promote products derived from this software
 19   *    without specific prior written permission.
 20   *
 21   * THIS SOFTWARE IS PROVIDED BY THE INSTITUTE AND CONTRIBUTORS ``AS IS'' AND
 22   * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 23   * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 24   * ARE DISCLAIMED.  IN NO EVENT SHALL THE INSTITUTE OR CONTRIBUTORS BE LIABLE
 25   * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 26   * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 27   * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 28   * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 29   * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 30   * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 31   * SUCH DAMAGE.
 32   */
 33  
 34  #include "gsskrb5_locl.h"
 35  
 36  /*
 37   * return the length of the mechanism in token or -1
 38   * (which implies that the token was bad - GSS_S_DEFECTIVE_TOKEN
 39   */
 40  
 41  ssize_t
 42  _gsskrb5_get_mech (const u_char *ptr,
 43  		      size_t total_len,
 44  		      const u_char **mech_ret)
 45  {
 46      size_t len, len_len, mech_len, foo;
 47      const u_char *p = ptr;
 48      int e;
 49  
 50      if (total_len < 1)
 51  	return -1;
 52      if (*p++ != 0x60)
 53  	return -1;
 54      e = der_get_length (p, total_len - 1, &len, &len_len);
 55      if (e || 1 + len_len + len != total_len)
 56  	return -1;
 57      p += len_len;
 58      if (*p++ != 0x06)
 59  	return -1;
 60      e = der_get_length (p, total_len - 1 - len_len - 1,
 61  			&mech_len, &foo);
 62      if (e)
 63  	return -1;
 64      p += foo;
 65      *mech_ret = p;
 66      return mech_len;
 67  }
 68  
 69  OM_uint32
 70  _gssapi_verify_mech_header(u_char **str,
 71  			   size_t total_len,
 72  			   gss_OID mech)
 73  {
 74      const u_char *p;
 75      ssize_t mech_len;
 76  
 77      mech_len = _gsskrb5_get_mech (*str, total_len, &p);
 78      if (mech_len < 0)
 79  	return GSS_S_DEFECTIVE_TOKEN;
 80  
 81      if (mech_len != (ssize_t)mech->length)
 82  	return GSS_S_BAD_MECH;
 83      if (memcmp(p,
 84  	       mech->elements,
 85  	       mech->length) != 0)
 86  	return GSS_S_BAD_MECH;
 87      p += mech_len;
 88      *str = rk_UNCONST(p);
 89      return GSS_S_COMPLETE;
 90  }
 91  
 92  OM_uint32
 93  _gsskrb5_verify_header(u_char **str,
 94  			  size_t total_len,
 95  			  const void *type,
 96  			  gss_OID oid)
 97  {
 98      OM_uint32 ret;
 99      size_t len;
100      u_char *p = *str;
101  
102      ret = _gssapi_verify_mech_header(str, total_len, oid);
103      if (ret)
104  	return ret;
105  
106      len = total_len - (*str - p);
107  
108      if (len < 2)
109  	return GSS_S_DEFECTIVE_TOKEN;
110  
111      if (memcmp (*str, type, 2) != 0)
112  	return GSS_S_DEFECTIVE_TOKEN;
113      *str += 2;
114  
115      return 0;
116  }
117  
118  /*
119   * Remove the GSS-API wrapping from `in_token' giving `out_data.
120   * Does not copy data, so just free `in_token'.
121   */
122  
123  OM_uint32
124  _gssapi_decapsulate(OM_uint32 *minor_status,
125  		    gss_buffer_t input_token_buffer,
126  		    uint8_t type[2],
127  		    krb5_data *out_data,
128  		    const gss_OID mech)
129  {
130      OM_uint32 ret;
131      size_t len;
132      u_char *p;
133  
134      p = input_token_buffer->value;
135      ret = _gssapi_verify_mech_header(&p,
136  				    input_token_buffer->length,
137  				    mech);
138      if (ret) {
139  	*minor_status = 0;
140  	return ret;
141      }
142      
143      len = input_token_buffer->length -
144  	(p - (u_char *)input_token_buffer->value);
145  
146      if (len < 2) {
147  	*minor_status = 0;
148  	return GSS_S_DEFECTIVE_TOKEN;
149      }
150  
151      memcpy(type, p, 2);
152  
153      out_data->length = len - 2;
154      out_data->data   = p + 2;
155      return GSS_S_COMPLETE;
156  }
157  
158  /*
159   * Remove the GSS-API wrapping from `in_token' giving `out_data.
160   * Does not copy data, so just free `in_token'.
161   */
162  
163  OM_uint32
164  _gsskrb5_decapsulate(OM_uint32 *minor_status,
165  			gss_buffer_t input_token_buffer,
166  			krb5_data *out_data,
167  			const void *type,
168  			gss_OID oid)
169  {
170      u_char *p;
171      OM_uint32 ret;
172  
173      p = input_token_buffer->value;
174      ret = _gsskrb5_verify_header(&p,
175  				 input_token_buffer->length,
176  				 type,
177  				 oid);
178      if (ret) {
179  	*minor_status = 0;
180  	return ret;
181      }
182  
183      out_data->length = input_token_buffer->length -
184  	(p - (u_char *)input_token_buffer->value);
185      out_data->data   = p;
186      return GSS_S_COMPLETE;
187  }
188  
189  /*
190   * Verify padding of a gss wrapped message and return its length.
191   */
192  
193  OM_uint32
194  _gssapi_verify_pad(gss_buffer_t wrapped_token,
195  		   size_t datalen,
196  		   size_t *padlen)
197  {
198      u_char *pad;
199      size_t padlength;
200      size_t i;
201  
202      pad = (u_char *)wrapped_token->value + wrapped_token->length - 1;
203      padlength = *pad;
204  
205      if (padlength > datalen)
206  	return GSS_S_BAD_MECH;
207  
208      for (i = padlength; i > 0 && *pad == padlength; i--, pad--)
209  	;
210      if (i != 0)
211  	return GSS_S_BAD_MIC;
212  
213      *padlen = padlength;
214  
215      return 0;
216  }