libhal ====== ## Overview ## This library combines a set of low-level API functions which talk to the Cryptech FPGA cores with a set of higher-level functions providing various cryptographic services. There's some overlap between the low-level code here and the low-level code in core/platform/novena, which will need sorting out some day, but at the time this library forked that code, the core/platform/novena code was all written to support a test harness rather than a higher-level API. Current contents of the library: * Low-level I/O code (EIM and I2C). * An implementation of AES Key Wrap using the Cryptech AES core. * An interface to the Cryptech CSPRNG. * An interface to the Cryptech hash cores, including HMAC. * An implementation of PBKDF2. * An implementation of RSA using the Cryptech ModExp core. * An implementation of ECDSA, currently entirely in software. * Test code for all of the above. Most of these are fairly well self-contained, although the PBKDF2 implementation uses the hash-core-based HMAC implementation. The major exceptions are the RSA and ECDSA implementations, which uses an external bignum implementation (libtfm) to handle a lot of the arithmetic. In the long run, much or all of this may end up being implemented in Verilog, but for the moment all of the RSA math except for modular exponentiation is happening in software, as is all of the math for ECDSA. ## RSA ## The RSA implementation includes a compile-time option to bypass the ModExp core and do everything in software, because the ModExp core is a tad slow at the moment (others are hard at work fixing this). The RSA implementation includes optional blinding (enabled by default) and just enough ASN.1 code to read and write private keys; the expectation is that the latter will be used in combination with the AES Key Wrap code. ## ECDSA ## The ECDSA implementation is specific to the NIST prime curves P-256, P-384, and P-521. The ECDSA implementation includes a compile-time option to allow test code to bypass the CSPRNG in order to test against known test vectors. Do **NOT** enable this in production builds, as ECDSA depends on good random numbers not just for private keys but for individual signatures, and an attacker who knows the random number used for a particular signature can use this to recover the private key. Arguably, this option should be removed from the code entirely, once the implementation is stable. The ECDSA implementation includes enough ASN.1 to read and write ECDSA signatures and ECDSA private keys in RFC 5915 format; the expectation is that the latter will be used in combination with AES Key Wrap. The ECDSA implementation attempts to be constant-time, to reduce the risk of timing channel attacks. The algorithms chosen for the point arithmetic are a tradeoff between speed and code complexity, and can probably be improved upon even in software; reimplementing at least the field arithmetic in hardware would probably also help. The current point addition and point doubling algorithms come from the [EFD][]. At least at the moment, we're only interested in ECDSA with the NIST prime curves, so we use algorithms optimized for a=-3. The point multiplication algorithm is a straightforward double-and-add loop, which is not the fastest possible algorithm, but is relatively easy to confirm by inspection as being constant-time within the limits imposed by the NIST curves. Point multiplication could probably be made faster by using a non-adjacent form (NAF) representation for the scalar, but the author doesn't yet understand that well enough to implement it as a constant-time algorithm. In theory, changing to a NAF representation could be done without any change to the public API. Points stored in keys and curve parameters are in affine format, but point arithmetic is performed in Jacobian projective coordinates, with the coordinates themselves in Montgomery form; final mapping back to affine coordinates also handles the final Montgomery reduction. ## API ## Yeah, we ought to document the API, Real Soon Now, perhaps using [Doxygen][]. For the moment, see the function prototypes in hal.h and comments in the code. [EFD]: http://www.hyperelliptic.org/EFD/g1p/auto-shortw-jacobian-3.html [Doxygen]: http://www.doxygen.org/ id='n34' href='#n34'>34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 66 67 68 69 70 71 72 73 74 75 76 77 78 79 80 81 82 83 84 85 86 87 88 89 90 91 92 93 94 95 96 97 98 99 100 101 102 103 104 105 106 107 108 109 110 111 112 113 114 115 116 117 118 119 120 121 122 123 124 125 126 127 128 129 130 131 132 133 134 135 136 137 138 139 140 141 142 143 144 145 146 147 148 149 150 151 152 153 154 155 156 157 158 159 160 161 162 163 164 165 166 167 168 169 170 171 172 173 174 175 176 177 178 179 180 181 182 183 184 185 186 187 188 189 190 191 192 193 194 195 196 197 198 199 200 201 202 203 204 205 206 207 208 209 210 211 212 213 214 215 216 217 218 219 220 221 222 223 224 225 226 227 228 229 230 231 232 233 234 235 236 237 238 239 240 241 242 243 244 
/*
 * rpc_misc.c
 * ----------
 * RPC interface to TRNG and PIN functions
 *
 * Authors: Rob Austein
 * Copyright (c) 2015, NORDUnet A/S All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions are
 * met:
 * - Redistributions of source code must retain the above copyright notice,
 *   this list of conditions and the following disclaimer.
 *
 * - Redistributions in binary form must reproduce the above copyright
 *   notice, this list of conditions and the following disclaimer in the
 *   documentation and/or other materials provided with the distribution.
 *
 * - Neither the name of the NORDUnet nor the names of its contributors may
 *   be used to endorse or promote products derived from this software
 *   without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS
 * IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A
 * PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
 * HOLDER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
 * SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED
 * TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
 * PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
 * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
 * NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
 * SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 */

#include <assert.h>

#include "hal.h"
#include "hal_internal.h"

static hal_error_t get_version(uint32_t *version)
{
  *version = RPC_VERSION;
  return HAL_OK;
}

static hal_error_t get_random(void *buffer, const size_t length)
{
  assert(buffer != NULL && length > 0);

  return hal_get_random(NULL, buffer, length);
}

/*
 * PINs, salt, and iteration count live in the keystore.
 *
 * We also need a client table in conventional memory (here, probably)
 * to record login status.
 *
 * The USER and SO PINs correspond to PKCS #11.
 *
 * The WHEEL PIN is the one that's allowed to change the SO PIN.
 *
 * It's a bit unclear how we should manage changes to the WHEEL PIN.
 * Implementing a factory default would be easy enough (just
 * pre-compute and compile in a const hal_ks_pin_t), question is
 * whether doing so provides anything useful.  Certainly adds no real
 * security, question is whether it would help prevent accidently
 * bricking the HSM right out of the shrink wrap.
 *
 * More interesting question is whether we should ever allow the WHEEL
 * PIN to be changed a second time without toasting the keystore.
 */

typedef struct {
  hal_client_handle_t handle;
  hal_user_t logged_in;
} client_slot_t;

#ifndef HAL_PIN_MINIMUM_ITERATIONS
#define HAL_PIN_MINIMUM_ITERATIONS 10000
#endif

#ifndef HAL_PIN_DEFAULT_ITERATIONS
#define HAL_PIN_DEFAULT_ITERATIONS 20000
#endif

#ifndef HAL_STATIC_CLIENT_STATE_BLOCKS
#define HAL_STATIC_CLIENT_STATE_BLOCKS	10
#endif

#if HAL_STATIC_CLIENT_STATE_BLOCKS > 0
static client_slot_t client_handle[HAL_STATIC_CLIENT_STATE_BLOCKS];
#endif

/*
 * Client handles are supplied by the application, we don't get to
 * pick them, we just store them and associate a login state with
 * them.  HAL_USER_NONE indicates an empty slot in the table.
 */

static inline client_slot_t *alloc_slot(void)
{
#if HAL_STATIC_CLIENT_STATE_BLOCKS > 0
  for (int i = 0; i < sizeof(client_handle)/sizeof(*client_handle); i++)
    if (client_handle[i].logged_in == HAL_USER_NONE)
      return &client_handle[i];
#endif

  return NULL;
}

static inline client_slot_t *find_handle(const hal_client_handle_t handle)
{
#if HAL_STATIC_CLIENT_STATE_BLOCKS > 0
  for (int i = 0; i < sizeof(client_handle)/sizeof(*client_handle); i++)
    if (client_handle[i].logged_in != HAL_USER_NONE && client_handle[i].handle.handle == handle.handle)
      return &client_handle[i];
#endif

  return NULL;
}

static hal_error_t login(const hal_client_handle_t client,
                         const hal_user_t user,
                         const char * const pin, const size_t pin_len)
{
  assert(pin != NULL && pin_len != 0);
  assert(user == HAL_USER_NORMAL || user == HAL_USER_SO || user == HAL_USER_WHEEL);

  const hal_ks_pin_t *p;
  hal_error_t err;

  if ((err = hal_ks_get_pin(user, &p)) != HAL_OK)
    return err;

  uint8_t buf[sizeof(p->pin)];
  const uint32_t iterations = p->iterations == 0 ? HAL_PIN_DEFAULT_ITERATIONS : p->iterations;

  if ((err = hal_pbkdf2(NULL, hal_hash_sha256, (const uint8_t *) pin, pin_len,
                        p->salt, sizeof(p->salt), buf, sizeof(buf), iterations)) != HAL_OK)
    return err;

  unsigned diff = 0;
  for (int i = 0; i < sizeof(buf); i++)
    diff |= buf[i] ^ p->pin[i];

  if (diff != 0)
    return HAL_ERROR_PIN_INCORRECT;

  client_slot_t *slot = find_handle(client);

  if (slot == NULL && (slot = alloc_slot()) == NULL)
    return HAL_ERROR_NO_CLIENT_SLOTS_AVAILABLE;

  slot->handle = client;
  slot->logged_in = user;

  return HAL_OK;
}

static hal_error_t is_logged_in(const hal_client_handle_t client,
                                const hal_user_t user)
{
  assert(user == HAL_USER_NORMAL || user == HAL_USER_SO || user == HAL_USER_WHEEL);

  client_slot_t *slot = find_handle(client);

  if (slot == NULL || slot->logged_in != user)
    return HAL_ERROR_FORBIDDEN;

  return HAL_OK;
}

static hal_error_t logout(const hal_client_handle_t client)
{
  client_slot_t *slot = find_handle(client);

  if (slot != NULL)
    slot->logged_in = HAL_USER_NONE;

  return HAL_OK;
}

static hal_error_t logout_all(void)
{
#if HAL_STATIC_CLIENT_STATE_BLOCKS > 0
  for (int i = 0; i < sizeof(client_handle)/sizeof(*client_handle); i++)
    client_handle[i].logged_in = HAL_USER_NONE;
#endif

  return HAL_OK;
}

static hal_error_t set_pin(const hal_client_handle_t client,
                           const hal_user_t user,
                           const char * const newpin, const size_t newpin_len)
{
  assert(newpin != NULL && newpin_len >= hal_rpc_min_pin_length && newpin_len <= hal_rpc_max_pin_length);

  if ((user != HAL_USER_NORMAL || is_logged_in(client, HAL_USER_SO) != HAL_OK) &&
      is_logged_in(client, HAL_USER_WHEEL) != HAL_OK)
    return HAL_ERROR_FORBIDDEN;

  const hal_ks_pin_t *pp;
  hal_error_t err;

  if ((err = hal_ks_get_pin(user, &pp)) != HAL_OK)
    return err;

  hal_ks_pin_t p = *pp;

  /*
   * Another all-zeros vs all-ones disagreement between drivers.
   */
  if (p.iterations == 0x00000000 || p.iterations == 0xffffffff)
    p.iterations = HAL_PIN_DEFAULT_ITERATIONS;

  if ((err = hal_get_random(NULL, p.salt, sizeof(p.salt)))      != HAL_OK ||
      (err = hal_pbkdf2(NULL, hal_hash_sha256,
                        (const uint8_t *) newpin, newpin_len,
                        p.salt, sizeof(p.salt),
                        p.pin,  sizeof(p.pin), p.iterations))   != HAL_OK ||
      (err = hal_ks_set_pin(user, &p))                          != HAL_OK)
    return err;

  return HAL_OK;
}

const hal_rpc_misc_dispatch_t hal_rpc_local_misc_dispatch = {
  set_pin,
  login,
  logout,
  logout_all,
  is_logged_in,
  get_random,
  get_version
};

/*
 * Local variables:
 * indent-tabs-mode: nil
 * End:
 */
generated by cgit v1.2.3 (git 2.25.1) at 2024-11-13 01:14:40 +0000