implementing client library for talking to the crypto helper process

contrib/gana

@@ -1 +1 @@
-Subproject commit 05da9c93fc7fff258e54a9413d11ea72a82fe03f
+Subproject commit e5ae01eeb4dedd8599473e64e098ea97fb7dadde

src/include/taler_crypto_lib.h

@@ -24,7 +24,7 @@
 
 #include <gnunet/gnunet_util_lib.h>
 #include "taler_util.h"
-
+#include "taler_error_codes.h"
 #include <gcrypt.h>
 
 
@@ -737,6 +737,123 @@ TALER_refresh_get_commitment (struct TALER_RefreshCommitmentP *rc,
                               const struct TALER_CoinSpendPublicKeyP *coin_pub,
                               const struct TALER_Amount *amount_with_fee);
 
+/* **************** Helper-based RSA operations **************** */
+
+/**
+ * Handle for talking to an Denomination key signing helper.
+ */
+struct TALER_CRYPTO_DenominationHelper;
+
+/**
+ * Function called with information about available keys for signing.  Usually
+ * only called once per key upon connect. Also called again in case a key is
+ * being revoked, in that case with an @a end_time of zero.
+ *
+ * @param cls closure
+ * @param section_name name of the denomination type in the configuration;
+ *                 NULL if the key has been revoked or purged
+ * @param start_time when does the key become available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param validity_duration how long does the key remain available for signing;
+ *                 zero if the key has been revoked or purged
+ * @param h_denom_pub hash of the @a denom_pub that is available (or was purged)
+ * @param denom_pub the public key itself, NULL if the key was revoked or purged
+ */
+typedef void
+(*TALER_CRYPTO_DenominationKeyStatusCallback)(
+  void *cls,
+  const char *section_name,
+  struct GNUNET_TIME_Absolute start_time,
+  struct GNUNET_TIME_Relative validity_duration,
+  const struct GNUNET_HashCode *h_denom_pub,
+  const struct TALER_DenominationPublicKey *denom_pub);
+
+
+/**
+ * Initiate connection to an denomination key helper.
+ *
+ * @param cfg configuration to use
+ * @param dkc function to call with key information
+ * @param dkc_cls closure for @a dkc
+ * @return NULL on error (such as bad @a cfg).
+ */
+struct TALER_CRYPTO_DenominationHelper *
+TALER_CRYPTO_helper_denom_connect (
+  const struct GNUNET_CONFIGURATION_Handle *cfg,
+  TALER_CRYPTO_DenominationKeyStatusCallback dkc,
+  void *dkc_cls);
+
+
+/**
+ * Function to call to 'poll' for updates to the available key material.
+ * Should be called whenever it is important that the key material status is
+ * current, like when handling a "/keys" request.  This function basically
+ * briefly checks if there are messages from the helper announcing changes to
+ * denomination keys.
+ *
+ * @param dh helper process connection
+ */
+void
+TALER_CRYPTO_helper_poll (struct TALER_CRYPTO_DenominationHelper *dh);
+
+
+/**
+ * Request helper @a dh to sign @a msg using the public key corresponding to
+ * @a h_denom_pub.
+ *
+ * This operation will block until the signature has been obtained.  Should
+ * this process receive a signal (that is not ignored) while the operation is
+ * pending, the operation will fail.  Note that the helper may still believe
+ * that it created the signature. Thus, signals may result in a small
+ * differences in the signature counters.  Retrying in this case may work.
+ *
+ * @param dh helper process connection
+ * @param h_denom_pub hash of the public key to use to sign
+ * @param msg message to sign
+ * @param msg_size number of bytes in @a msg
+ * @param[out] ec set to the error code (or #TALER_EC_NONE on success)
+ * @return signature, the value inside the structure will be NULL on failure,
+ *         see @a ec for details about the failure
+ */
+struct TALER_DenominationSignature
+TALER_CRYPTO_helper_denom_sign (
+  struct TALER_CRYPTO_DenominationHelper *dh,
+  const struct GNUNET_HashCode *h_denom_pub,
+  const void *msg,
+  size_t msg_size,
+  enum TALER_ErrorCode *ec);
+
+
+/**
+ * Ask the helper to revoke the public key associated with @param h_denom_pub.
+ * Will cause the helper to tell all clients that the key is now unavailable,
+ * and to create a replacement key.
+ *
+ * This operation will block until the revocation request has been
+ * transmitted.  Should this process receive a signal (that is not ignored)
+ * while the operation is pending, the operation may fail. If the key is
+ * unknown, this function will also appear to have succeeded. To be sure that
+ * the revocation worked, clients must watch the denomination key status
+ * callback.
+ *
+ * @param dh helper to process connection
+ * @param h_denom_pub hash of the public key to revoke
+ */
+void
+TALER_CRYPTO_helper_denom_revoke (
+  struct TALER_CRYPTO_DenominationHelper *dh,
+  const struct GNUNET_HashCode *h_denom_pub);
+
+
+/**
+ * Close connection to @a dh.
+ *
+ * @param[in] dh connection to close
+ */
+void
+TALER_CRYPTO_helper_denom_disconnect (
+  struct TALER_CRYPTO_DenominationHelper *dh);
+
 
 /* **************** /wire account offline signing **************** */
 

src/util/Makefile.am

@@ -50,6 +50,7 @@ libtalerutil_la_SOURCES = \
   amount.c \
   config.c \
   crypto.c \
+  crypto_helper.c \
   crypto_wire.c \
   getopt.c \
   lang.c \

src/util/crypto_helper.c

@@ -0,0 +1,406 @@
+/*
+  This file is part of TALER
+  Copyright (C) 2020 Taler Systems SA
+
+  TALER is free software; you can redistribute it and/or modify it under the
+  terms of the GNU General Public License as published by the Free Software
+  Foundation; either version 3, or (at your option) any later version.
+
+  TALER is distributed in the hope that it will be useful, but WITHOUT ANY
+  WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
+  A PARTICULAR PURPOSE.  See the GNU General Public License for more details.
+
+  You should have received a copy of the GNU General Public License along with
+  TALER; see the file COPYING.  If not, see <http://www.gnu.org/licenses/>
+*/
+/**
+ * @file util/crypto_helper.c
+ * @brief utility functions for running out-of-process private key operations
+ * @author Christian Grothoff
+ */
+#include "platform.h"
+#include "taler_util.h"
+#include "taler-helper-crypto-rsa.h"
+
+
+struct TALER_CRYPTO_DenominationHelper
+{
+  /**
+   * Function to call with updates to available key material.
+   */
+  TALER_CRYPTO_DenominationKeyStatusCallback dkc;
+
+  /**
+   * Closure for @e dkc
+   */
+  void *dkc_cls;
+
+  /**
+   * Socket address of the denomination helper process.
+   * Used to reconnect if the connection breaks.
+   */
+  struct sockaddr_un sa;
+
+  /**
+   * The UNIX domain socket, -1 if we are currently not connected.
+   */
+  int sock;
+};
+
+
+/**
+ * Disconnect from the helper process.  Updates
+ * @e sock field in @a dh.
+ *
+ * @param[in,out] dh handle to tear down connection of
+ */
+static void
+do_disconnect (struct TALER_CRYPTO_DenominationHelper *dh)
+{
+  GNUNET_break (0 == close (dh->sock));
+  dh->sock = -1;
+}
+
+
+/**
+ * Try to connect to the helper process.  Updates
+ * @e sock field in @a dh.
+ *
+ * @param[in,out] dh handle to establish connection for
+ */
+static void
+try_connect (struct TALER_CRYPTO_DenominationHelper *dh)
+{
+  if (-1 != dh->sock)
+    return;
+  dh->sock = socket (AF_UNIX,
+                     SOCK_DGRAM,
+                     0);
+  if (-1 == dh->sock)
+  {
+    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
+                         "socket");
+    return;
+  }
+  if (0 != connect (dh->sock,
+                    (const struct sockaddr *) &dh->sa,
+                    sizeof (dh->sa)))
+  {
+    if (EINPROGRESS != dh->sock)
+    {
+      GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
+                           "connect");
+      do_disconnect (dh);
+      return;
+    }
+  }
+}
+
+
+struct TALER_CRYPTO_DenominationHelper *
+TALER_CRYPTO_helper_denom_connect (
+  const struct GNUNET_CONFIGURATION_Handle *cfg,
+  TALER_CRYPTO_DenominationKeyStatusCallback dkc,
+  void *dkc_cls)
+{
+  struct TALER_CRYPTO_DenominationHelper *dh;
+  char *unixpath;
+
+  if (GNUNET_OK !=
+      GNUNET_CONFIGURATION_get_value_filename (cfg,
+                                               "taler-helper-crypto-rsa",
+                                               "UNIXPATH",
+                                               &unixpath))
+  {
+    GNUNET_log_config_missing (GNUNET_ERROR_TYPE_ERROR,
+                               "taler-helper-crypto-rsa",
+                               "UNIXPATH");
+    return NULL;
+  }
+  if (strlen (unixpath) > sizeof (dh->sa.sun_path))
+  {
+    GNUNET_log_config_invalid (GNUNET_ERROR_TYPE_ERROR,
+                               "taler-helper-crypto-rsa",
+                               "UNIXPATH",
+                               "path too long");
+    GNUNET_free (unixpath);
+    return NULL;
+  }
+  dh = GNUNET_new (struct TALER_CRYPTO_DenominationHelper);
+  dh->dkc = dkc;
+  dh->dkc_cls = dkc_cls;
+  strncpy (dh->sa.sun_path,
+           unixpath,
+           sizeof (dh->sa.sun_path));
+  dh->sock = -1;
+  TALER_CRYPTO_helper_poll (dh);
+  return dh;
+}
+
+
+void
+TALER_CRYPTO_helper_poll (struct TALER_CRYPTO_DenominationHelper *dh)
+{
+  char buf[UINT16_MAX];
+  ssize_t ret;
+  const struct GNUNET_MessageHeader *hdr
+    = (const struct GNUNET_MessageHeader *) buf;
+
+  try_connect (dh);
+  if (-1 == dh->sock)
+    return; /* give up */
+  while (1)
+  {
+    ret = recv (dh->sock,
+                buf,
+                sizeof (buf),
+                MSG_DONTWAIT);
+    if (ret < 0)
+    {
+      GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
+                           "recv");
+      do_disconnect (dh);
+      return;
+    }
+
+    if ( (ret < sizeof (struct GNUNET_MessageHeader)) ||
+         (ret != ntohs (hdr->size)) )
+    {
+      GNUNET_break_op (0);
+      do_disconnect (dh);
+      return;
+    }
+    switch (ntohs (hdr->type))
+    {
+    case TALER_HELPER_RSA_MT_AVAIL:
+      {
+        const struct TALER_CRYPTO_RsaKeyAvailableNotification *kan
+          = (const struct TALER_CRYPTO_RsaKeyAvailableNotification *) buf;
+        const char *section_name;
+        struct TALER_DenominationPublicKey denom_pub;
+        struct GNUNET_HashCode h_denom_pub;
+
+        if ( (sizeof (*kan) < ret) ||
+             (sizeof (*kan) + ntohs (kan->pub_size) + ntohs (
+                kan->section_name_len)) ||
+             ('\0' != buf[ret - 1]) )
+        {
+          GNUNET_break_op (0);
+          do_disconnect (dh);
+          return;
+        }
+        denom_pub.rsa_public_key
+          = GNUNET_CRYPTO_rsa_public_key_decode (&buf[sizeof (*kan)],
+                                                 ntohs (kan->pub_size));
+        if (NULL == denom_pub.rsa_public_key)
+        {
+          GNUNET_break_op (0);
+          do_disconnect (dh);
+          return;
+        }
+        section_name = &buf[sizeof (*kan) + ntohs (kan->pub_size)];
+        GNUNET_CRYPTO_rsa_public_key_hash (denom_pub.rsa_public_key,
+                                           &h_denom_pub);
+        dh->dkc (dh->dkc_cls,
+                 section_name,
+                 GNUNET_TIME_absolute_ntoh (kan->anchor_time),
+                 GNUNET_TIME_relative_ntoh (kan->duration_withdraw),
+                 &h_denom_pub,
+                 &denom_pub);
+        GNUNET_CRYPTO_rsa_public_key_free (denom_pub.rsa_public_key);
+      }
+      break;
+    case TALER_HELPER_RSA_MT_PURGE:
+      {
+        const struct TALER_CRYPTO_RsaKeyPurgeNotification *pn
+          = (const struct TALER_CRYPTO_RsaKeyPurgeNotification *) buf;
+
+        if (sizeof (*pn) != ret)
+        {
+          GNUNET_break_op (0);
+          do_disconnect (dh);
+          return;
+        }
+
+        dh->dkc (dh->dkc_cls,
+                 NULL,
+                 GNUNET_TIME_UNIT_ZERO_ABS,
+                 GNUNET_TIME_UNIT_ZERO,
+                 &pn->h_denom_pub,
+                 NULL);
+      }
+      break;
+    default:
+      GNUNET_break_op (0);
+      do_disconnect (dh);
+      return;
+    }
+  }
+}
+
+
+struct TALER_DenominationSignature
+TALER_CRYPTO_helper_denom_sign (
+  struct TALER_CRYPTO_DenominationHelper *dh,
+  const struct GNUNET_HashCode *h_denom_pub,
+  const void *msg,
+  size_t msg_size,
+  enum TALER_ErrorCode *ec)
+{
+  struct TALER_DenominationSignature ds = { NULL };
+  {
+    char buf[sizeof (struct TALER_CRYPTO_SignRequest) + msg_size];
+    struct TALER_CRYPTO_SignRequest *sr
+      = (struct TALER_CRYPTO_SignRequest *) buf;
+    ssize_t ret;
+
+    try_connect (dh);
+    if (-1 == dh->sock)
+    {
+      *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_UNAVAILABLE;
+      return ds;
+    }
+    sr->header.size = htons (sizeof (buf));
+    sr->header.type = htons (TALER_HELPER_RSA_MT_REQ_SIGN);
+    sr->reserved = htonl (0);
+    sr->h_denom_pub = *h_denom_pub;
+    memcpy (&sr[1],
+            msg,
+            msg_size);
+    ret = send (dh->sock,
+                buf,
+                sizeof (buf),
+                0);
+    if (ret < 0)
+    {
+      GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
+                           "send");
+      do_disconnect (dh);
+      *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_UNAVAILABLE;
+      return ds;
+    }
+    /* We are using SOCK_DGRAM, partial writes should not be possible */
+    GNUNET_break (((size_t) ret) == sizeof (buf));
+  }
+
+  {
+    char buf[UINT16_MAX];
+    ssize_t ret;
+    const struct GNUNET_MessageHeader *hdr
+      = (const struct GNUNET_MessageHeader *) buf;
+
+    ret = recv (dh->sock,
+                buf,
+                sizeof (buf),
+                MSG_DONTWAIT);
+    if (ret < 0)
+    {
+      GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
+                           "recv");
+      do_disconnect (dh);
+      *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_UNAVAILABLE;
+      return ds;
+    }
+    if ( (ret < sizeof (struct GNUNET_MessageHeader)) ||
+         (ret != ntohs (hdr->size)) )
+    {
+      GNUNET_break_op (0);
+      do_disconnect (dh);
+      *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_BUG;
+      return ds;
+    }
+    switch (ntohs (hdr->type))
+    {
+    case TALER_HELPER_RSA_MT_RES_SIGNATURE:
+      if (ret < sizeof (struct TALER_CRYPTO_SignResponse))
+      {
+        GNUNET_break_op (0);
+        do_disconnect (dh);
+        *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_BUG;
+        break;
+      }
+      {
+        const struct TALER_CRYPTO_SignResponse *sr =
+          (const struct TALER_CRYPTO_SignResponse *) buf;
+        struct GNUNET_CRYPTO_RsaSignature *rsa_signature;
+
+        rsa_signature = GNUNET_CRYPTO_rsa_signature_decode (&sr[1],
+                                                            ret - sizeof (*sr));
+        if (NULL == rsa_signature)
+        {
+          GNUNET_break_op (0);
+          do_disconnect (dh);
+          *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_BUG;
+          break;
+        }
+        *ec = TALER_EC_NONE;
+        ds.rsa_signature = rsa_signature;
+        return ds;
+      }
+    case TALER_HELPER_RSA_MT_RES_SIGN_FAILURE:
+      if (ret != sizeof (struct TALER_CRYPTO_SignFailure))
+      {
+        GNUNET_break_op (0);
+        do_disconnect (dh);
+        *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_BUG;
+        break;
+      }
+      {
+        const struct TALER_CRYPTO_SignFailure *sf =
+          (const struct TALER_CRYPTO_SignFailure *) buf;
+
+        *ec = (enum TALER_ErrorCode) ntohl (sf->ec);
+        break;
+      }
+    default:
+      GNUNET_break_op (0);
+      do_disconnect (dh);
+      *ec = TALER_EC_EXCHANGE_DENOMINATION_HELPER_BUG;
+      break;
+    }
+  }
+  return ds;
+}
+
+
+void
+TALER_CRYPTO_helper_denom_revoke (
+  struct TALER_CRYPTO_DenominationHelper *dh,
+  const struct GNUNET_HashCode *h_denom_pub)
+{
+  struct TALER_CRYPTO_RevokeRequest rr = {
+    .header.size = htons (sizeof (rr)),
+    .header.type = htons (TALER_HELPER_RSA_MT_REQ_REVOKE),
+    .h_denom_pub = *h_denom_pub
+  };
+  ssize_t ret;
+
+  try_connect (dh);
+  if (-1 == dh->sock)
+    return; /* give up */
+  ret = send (dh->sock,
+              &rr,
+              sizeof (rr),
+              0);
+  if (ret < 0)
+  {
+    GNUNET_log_strerror (GNUNET_ERROR_TYPE_WARNING,
+                         "send");
+    do_disconnect (dh);
+    return;
+  }
+  /* We are using SOCK_DGRAM, partial writes should not be possible */
+  GNUNET_break (((size_t) ret) == sizeof (rr));
+}
+
+
+void
+TALER_CRYPTO_helper_denom_disconnect (
+  struct TALER_CRYPTO_DenominationHelper *dh)
+{
+  do_disconnect (dh);
+  GNUNET_free (dh);
+}
+
+
+/* end of crypto_helper.c */

src/util/taler-helper-crypto-rsa.h

@@ -99,7 +99,7 @@ struct TALER_CRYPTO_RsaKeyPurgeNotification
 struct TALER_CRYPTO_SignRequest
 {
   /**
-   * Type is #TALER_HELPER_RSA_MT_SIGN.
+   * Type is #TALER_HELPER_RSA_MT_REQ_SIGN.
    */
   struct GNUNET_MessageHeader header;
 
@@ -123,7 +123,7 @@ struct TALER_CRYPTO_SignRequest
 struct TALER_CRYPTO_RevokeRequest
 {
   /**
-   * Type is #TALER_HELPER_RSA_MT_REVOKE.
+   * Type is #TALER_HELPER_RSA_MT_REQ_REVOKE.
    */
   struct GNUNET_MessageHeader header;