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         return;
  80 }
  81
  82 /**
  83  * Session key parameter generation is deferred until here because if privacy
  84  * mode is enabled the session key parameter generation can take a while
  85  * depending on the key size used and prepare is called before returning
  86  * from the request_key upcall by lgss_keyring
  87  */
  88 static int lgss_sk_using_cred(struct lgss_cred *cred)
  89 {
  90         struct sk_cred *skc = cred->lc_mech_cred;
  91         gss_buffer_desc bufs[SK_INIT_BUFFERS];
  92         uint32_t version;
  93         uint32_t flags;
  94         int rc;
  95
  96         rc = sk_gen_params(skc);
  97         if (rc)
  98                 return rc;
  99
 100         /* HMAC is generated in this order */
 101         version = htobe32(SK_MSG_VERSION);
 102         bufs[SK_INIT_VERSION].value = &version;
 103         bufs[SK_INIT_VERSION].length = sizeof(version);
 104         bufs[SK_INIT_RANDOM].value = &skc->sc_kctx.skc_host_random;
 105         bufs[SK_INIT_RANDOM].length = sizeof(skc->sc_kctx.skc_host_random);
 106         bufs[SK_INIT_PUB_KEY] = skc->sc_pub_key;
 107         bufs[SK_INIT_P] = skc->sc_p;
 108         bufs[SK_INIT_TARGET] = skc->sc_tgt;
 109         bufs[SK_INIT_NODEMAP] = skc->sc_nodemap_hash;
 110         flags = htobe32(skc->sc_flags);
 111         bufs[SK_INIT_FLAGS].value = &flags;
 112         bufs[SK_INIT_FLAGS].length = sizeof(flags);
 113
 114         /* sign all the bufs except HMAC */
 115         rc = sk_sign_bufs(&skc->sc_kctx.skc_shared_key, bufs,
 116                           SK_INIT_BUFFERS - 1, EVP_sha256(),
 117                           &skc->sc_hmac);
 118         if (rc)
 119                 return rc;
 120
 121         bufs[SK_INIT_HMAC] = skc->sc_hmac;
 122         rc = sk_encode_netstring(bufs, SK_INIT_BUFFERS, &cred->lc_mech_token);
 123         if (rc)
 124                 return rc;
 125
 126         printerr(2, "Created netstring of %zd bytes\n",
 127                  cred->lc_mech_token.length);
 128
 129         return 0;
 130 }
 131
 132 static int lgss_sk_validate_cred(struct lgss_cred *cred, gss_buffer_desc *token,
 133                                  gss_buffer_desc *ctx_token)
 134 {
 135         struct sk_cred *skc = cred->lc_mech_cred;
 136         gss_buffer_desc bufs[SK_RESP_BUFFERS];
 137         uint32_t version;
 138         int i;
 139         uint32_t rc;
 140
 141         /* Decode responder buffers and validate */
 142         i = sk_decode_netstring(bufs, SK_RESP_BUFFERS, token);
 143         if (i != SK_RESP_BUFFERS) {
 144                 printerr(0, "Invalid token received\n");
 145                 return -EINVAL;
 146         }
 147
 148         rc = sk_verify_hmac(skc, bufs, SK_RESP_BUFFERS - 1, EVP_sha256(),
 149                             &bufs[SK_RESP_HMAC]);
 150         if (rc != GSS_S_COMPLETE) {
 151                 printerr(0, "Invalid HMAC receieved: 0x%x\n", rc);
 152                 return -EINVAL;
 153         }
 154
 155         if (bufs[SK_RESP_VERSION].length != sizeof(version)) {
 156                 printerr(0, "Invalid version received (wrong size)\n");
 157                 return -EINVAL;
 158         }
 159         memcpy(&version, bufs[SK_RESP_VERSION].value, sizeof(version));
 160         version = be32toh(version);
 161         if (version != SK_MSG_VERSION) {
 162                 printerr(0, "Invalid version received: %d\n", version);
 163                 return -EINVAL;
 164         }
 165
 166         /* In the rare event that both the random values are equal the
 167          * client has the responsability to retry the connection attempt
 168          * otherwise we would leak information about the plain text by
 169          * reuusing IVs as both peer and host use the same values other
 170          * than the nonce. */
 171         memcpy(&skc->sc_kctx.skc_peer_random, bufs[SK_RESP_RANDOM].value,
 172                sizeof(skc->sc_kctx.skc_peer_random));
 173         if (skc->sc_kctx.skc_host_random == skc->sc_kctx.skc_peer_random) {
 174                 printerr(0, "Host and peer randoms are equal, must retry to "
 175                          "ensure unique value for nonce\n");
 176                 return -EAGAIN;
 177         }
 178
 179         rc = sk_compute_dh_key(skc, &bufs[SK_RESP_PUB_KEY]);
 180         if (rc == GSS_S_DEFECTIVE_TOKEN) {
 181                 /* Defective token for short key means we need to retry
 182                  * because there is a chance that the parameters generated
 183                  * resulted in a key that is 1 byte short */
 184                 printerr(0, "Short key computed, must retry\n");
 185                 return -EAGAIN;
 186         } else if (rc != GSS_S_COMPLETE) {
 187                 printerr(0, "Failed to compute session key: 0x%x\n", rc);
 188                 return -EINVAL;
 189         }
 190
 191         rc = sk_session_kdf(skc, cred->lc_self_nid, &cred->lc_mech_token,
 192                             token);
 193         if (rc) {
 194                 printerr(0, "Failed to calulate derived key\n");
 195                 return -EINVAL;
 196         }
 197
 198         rc = sk_compute_keys(skc);
 199         if (rc) {
 200                 printerr(0, "Failed to compute HMAC and session key\n");
 201                 return -EINVAL;
 202         }
 203
 204         if (sk_serialize_kctx(skc, ctx_token)) {
 205                 printerr(0, "Failed to serialize context for kernel\n");
 206                 return -EINVAL;
 207         }
 208
 209         return 0;
 210 }
 211
 212 struct lgss_mech_type lgss_mech_sk = {
 213         .lmt_name               = "sk",
 214         .lmt_mech_n             = LGSS_MECH_SK,
 215         .lmt_prepare_cred       = lgss_sk_prepare_cred,
 216         .lmt_release_cred       = lgss_sk_release_cred,
 217         .lmt_using_cred         = lgss_sk_using_cred,
 218         .lmt_validate_cred      = lgss_sk_validate_cred,
 219 };