lustre/utils/gss/lgss_sk_utils.c

   1 /*
   2  * GPL HEADER START
   3  *
   4  * DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
   5  *
   6  * This program is free software; you can redistribute it and/or modify
   7  * it under the terms of the GNU General Public License version 2 only,
   8  * as published by the Free Software Foundation.
   9  *
  10  * This program is distributed in the hope that it will be useful, but
  11  * WITHOUT ANY WARRANTY; without even the implied warranty of
  12  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13  * General Public License version 2 for more details (a copy is included
  14  * in the LICENSE file that accompanied this code).
  15  *
  16  * You should have received a copy of the GNU General Public License
  17  * version 2 along with this program; If not, see
  18  * http://www.gnu.org/licenses/gpl-2.0.html
  19  *
  20  * GPL HEADER END
  21  */
  22 /*
  23  * Copyright (C) 2015, Trustees of Indiana University
  24  *
  25  * Author: Jeremy Filizetti <jfilizet@iu.edu>
  26  */
  27
  28 #include <limits.h>
  29 #include <string.h>
  30 #include <openssl/dh.h>
  31 #include <openssl/engine.h>
  32 #include <openssl/err.h>
  33
  34 #include "sk_utils.h"
  35 #include "lgss_utils.h"
  36
  37 /**
  38  * Create the initial shared key credentials
  39  */
  40 static int lgss_sk_prepare_cred(struct lgss_cred *cred)
  41 {
  42         uint32_t flags = cred->lc_root_flags;
  43
  44         switch (cred->lc_svc_type) {
  45         case 'n':
  46                 flags |= LGSS_SVC_NULL;
  47                 break;
  48         case 'a':
  49                 flags |= LGSS_SVC_AUTH;
  50                 break;
  51         case 'i':
  52                 flags |= LGSS_SVC_INTG;
  53                 break;
  54         case 'p':
  55                 flags |= LGSS_SVC_PRIV;
  56                 break;
  57         default:
  58                 break;
  59         }
  60
  61         cred->lc_mech_cred = sk_create_cred(cred->lc_tgt_uuid, NULL, flags);
  62         if (cred->lc_mech_cred == NULL) {
  63                 printerr(0, "sk: cannot create credential: %s\n",
  64                          cred->lc_tgt_uuid);
  65                 return -ENOKEY;
  66         }
  67
  68         return 0;
  69 }
  70
  71 /* Free all the sk_cred resources */
  72 static void lgss_sk_release_cred(struct lgss_cred *cred)
  73 {
  74         struct sk_cred *skc = cred->lc_mech_cred;
  75
  76         sk_free_cred(skc);
  77         cred->lc_mech_cred = NULL;
  78         free(cred->lc_mech_token.value);
  79 }
  80
  81 /**
  82  * Session key parameter generation is deferred until here because if privacy
  83  * mode is enabled the session key parameter generation can take a while
  84  * depending on the key size used and prepare is called before returning
  85  * from the request_key upcall by lgss_keyring
  86  */
  87 static int lgss_sk_using_cred(struct lgss_cred *cred)
  88 {
  89         struct sk_cred *skc = cred->lc_mech_cred;
  90         gss_buffer_desc bufs[SK_INIT_BUFFERS];
  91         uint32_t version;
  92         uint32_t flags;
  93         int rc;
  94
  95         rc = sk_gen_params(skc, 0);
  96         if (rc)
  97                 return rc;
  98
  99         /* HMAC is generated in this order */
 100         version = htobe32(SK_MSG_VERSION);
 101         bufs[SK_INIT_VERSION].value = &version;
 102         bufs[SK_INIT_VERSION].length = sizeof(version);
 103         bufs[SK_INIT_RANDOM].value = &skc->sc_kctx.skc_host_random;
 104         bufs[SK_INIT_RANDOM].length = sizeof(skc->sc_kctx.skc_host_random);
 105         bufs[SK_INIT_PUB_KEY] = skc->sc_pub_key;
 106         bufs[SK_INIT_P] = skc->sc_p;
 107         bufs[SK_INIT_TARGET] = skc->sc_tgt;
 108         bufs[SK_INIT_NODEMAP] = skc->sc_nodemap_hash;
 109         flags = htobe32(skc->sc_flags);
 110         bufs[SK_INIT_FLAGS].value = &flags;
 111         bufs[SK_INIT_FLAGS].length = sizeof(flags);
 112
 113         /* sign all the bufs except HMAC */
 114         rc = sk_sign_bufs(&skc->sc_kctx.skc_shared_key, bufs,
 115                           SK_INIT_BUFFERS - 1, EVP_sha256(),
 116                           &skc->sc_hmac);
 117         if (rc)
 118                 return rc;
 119
 120         bufs[SK_INIT_HMAC] = skc->sc_hmac;
 121         rc = sk_encode_netstring(bufs, SK_INIT_BUFFERS, &cred->lc_mech_token);
 122         if (rc)
 123                 return rc;
 124
 125         printerr(2, "Created netstring of %zd bytes\n",
 126                  cred->lc_mech_token.length);
 127
 128         return 0;
 129 }
 130
 131 static int lgss_sk_validate_cred(struct lgss_cred *cred, gss_buffer_desc *token,
 132                                  gss_buffer_desc *ctx_token)
 133 {
 134         struct sk_cred *skc = cred->lc_mech_cred;
 135         gss_buffer_desc bufs[SK_RESP_BUFFERS];
 136         uint32_t version;
 137         int i;
 138         uint32_t rc;
 139
 140         /* Decode responder buffers and validate */
 141         i = sk_decode_netstring(bufs, SK_RESP_BUFFERS, token);
 142         if (i != SK_RESP_BUFFERS) {
 143                 printerr(0, "Invalid token received\n");
 144                 return -EINVAL;
 145         }
 146
 147         rc = sk_verify_hmac(skc, bufs, SK_RESP_BUFFERS - 1, EVP_sha256(),
 148                             &bufs[SK_RESP_HMAC]);
 149         if (rc != GSS_S_COMPLETE) {
 150                 printerr(0, "Invalid HMAC receieved: 0x%x\n", rc);
 151                 return -EINVAL;
 152         }
 153
 154         if (bufs[SK_RESP_VERSION].length != sizeof(version)) {
 155                 printerr(0, "Invalid version received (wrong size)\n");
 156                 return -EINVAL;
 157         }
 158         memcpy(&version, bufs[SK_RESP_VERSION].value, sizeof(version));
 159         version = be32toh(version);
 160         if (version != SK_MSG_VERSION) {
 161                 printerr(0, "Invalid version received: %d\n", version);
 162                 return -EINVAL;
 163         }
 164
 165         /* In the rare event that both the random values are equal the
 166          * client has the responsability to retry the connection attempt
 167          * otherwise we would leak information about the plain text by
 168          * reuusing IVs as both peer and host use the same values other
 169          * than the nonce. */
 170         memcpy(&skc->sc_kctx.skc_peer_random, bufs[SK_RESP_RANDOM].value,
 171                sizeof(skc->sc_kctx.skc_peer_random));
 172         if (skc->sc_kctx.skc_host_random == skc->sc_kctx.skc_peer_random) {
 173                 printerr(0, "Host and peer randoms are equal, must retry to "
 174                          "ensure unique value for nonce\n");
 175                 return -EAGAIN;
 176         }
 177
 178         rc = sk_compute_dh_key(skc, &bufs[SK_RESP_PUB_KEY]);
 179         if (rc == GSS_S_BAD_QOP) {
 180                 /* Defective token for short key means we need to retry
 181                  * because there is a chance that the parameters generated
 182                  * resulted in a key that is 1 byte short */
 183                 printerr(0, "Short key computed, must retry\n");
 184                 if (skc->sc_dh_shared_key.value) {
 185                         /* erase secret key before freeing memory */
 186                         memset(skc->sc_dh_shared_key.value, 0,
 187                                skc->sc_dh_shared_key.length);
 188                         free(skc->sc_dh_shared_key.value);
 189                         skc->sc_dh_shared_key.value = NULL;
 190                 }
 191                 skc->sc_dh_shared_key.length = 0;
 192                 return -EAGAIN;
 193         } else if (rc != GSS_S_COMPLETE) {
 194                 printerr(0, "Failed to compute session key: 0x%x\n", rc);
 195                 return -EINVAL;
 196         }
 197
 198         rc = sk_session_kdf(skc, cred->lc_self_nid, &cred->lc_mech_token,
 199                             token);
 200         if (rc) {
 201                 printerr(0, "Failed to calculate derived key\n");
 202                 return -EINVAL;
 203         }
 204
 205         rc = sk_compute_keys(skc);
 206         if (rc) {
 207                 printerr(0, "Failed to compute HMAC and session key\n");
 208                 return -EINVAL;
 209         }
 210
 211         if (sk_serialize_kctx(skc, ctx_token)) {
 212                 printerr(0, "Failed to serialize context for kernel\n");
 213                 return -EINVAL;
 214         }
 215
 216         return 0;
 217 }
 218
 219 struct lgss_mech_type lgss_mech_sk = {
 220         .lmt_name               = "sk",
 221         .lmt_mech_n             = LGSS_MECH_SK,
 222         .lmt_prepare_cred       = lgss_sk_prepare_cred,
 223         .lmt_release_cred       = lgss_sk_release_cred,
 224         .lmt_using_cred         = lgss_sk_using_cred,
 225         .lmt_validate_cred      = lgss_sk_validate_cred,
 226 };