path: root/openssl/agent/pkcs11/private-key.cxx

// file      : openssl/agent/pkcs11/private-key.cxx -*- C++ -*-
// license   : MIT; see accompanying LICENSE file

#include <openssl/agent/pkcs11/private-key.hxx>

#include <cstring> // memset(), strlen()

#include <openssl/agent/pkcs11/pkcs11.hxx>

#define API_STRING(S) api_string (S, sizeof (S))

namespace openssl
{
  namespace agent
  {
    namespace pkcs11
    {
      using namespace std;

      static void
      close_session (CK_SESSION_HANDLE* p)
      {
        if (p != nullptr)
        {
          api ()->C_CloseSession (*p);
          delete p;
        }
      }

      private_key::
      private_key (): session_ (nullptr, close_session)
      {
      }

      private_key::
      private_key (private_key&& k): private_key ()
      {
        *this = move (k);
      }

      private_key& private_key::
      operator= (private_key&& k)
      {
        description = move (k.description);
        session_    = move (k.session_);
        handle_     = k.handle_;
        simulate_   = move (k.simulate_);
        return *this;
      }

      private_key::
      private_key (const identity& idn,
                   const access& acc,
                   const char* pin,
                   optional<simulate_outcome> sim)
          : private_key ()
      {
        simulate_ = move (sim); // Can't initialize because of delegate ctor.

        // Verify the identity and access attributes.
        //
        if (idn.type && *idn.type != "private")
          throw invalid_argument ("unexpected object type " + *idn.type);

        if (pin == nullptr && acc.pin_value)
          pin = acc.pin_value->c_str ();

        if (pin == nullptr)
          throw invalid_argument ("PIN is required");

        auto no_key = [] ()
        {
          throw runtime_error ("no matching private key found");
        };

        auto simulate = [this, &no_key] ()
        {
          assert (simulate_ && session_ == nullptr);

          switch (*simulate_)
          {
          case simulate_outcome::success:
            {
              description = "simulated private key";
              return;
            }
          case simulate_outcome::failure:
            {
              no_key ();
            }
          }
        };

        // Get the Cryptoki functions pointer.
        //
        CK_FUNCTION_LIST* fs;
        {
          path p;

          if (acc.module_path)
          {
            if (acc.module_name)
              p = *acc.module_path / (*acc.module_name + ".so");
            else if (file_exists (*acc.module_path))
              p = *acc.module_path;
            else
              p = *acc.module_path / "opensc-pkcs11.so";
          }
          else if (acc.module_name)
            p = *acc.module_name + ".so";
          else
            p = path ("opensc-pkcs11.so");

          // Ignore non-existent PKCS#11 module in the simulated mode. Note
          // that if the module exists we will simulate as far as possible,
          // up to opening token sessions (but not logging into them).
          //
          fs = api (p, simulate_.has_value ());

          if (fs == nullptr)
          {
            assert (simulate_);
            simulate ();
            return;
          }
        }

        // Search for the private key.
        //
        // The overall plan is to match the PKCS#11 module, go though all the
        // matching slots it provides, log into all the matching tokens these
        // slots may contain and see if the tokens contain a matching RSA
        // private keys. Fail if unable to log into the matching tokens or
        // none or multiple private keys match. Otherwise keep both the
        // matching token session and the key handle.
        //
        auto mult_keys = [] ()
        {
          throw runtime_error ("multiple private keys match");
        };

        auto match = [] (const auto& attr, const auto& value)
        {
          return !attr || *attr == value;
        };

        // Match the module.
        //
        CK_INFO pi;
        CK_RV r (fs->C_GetInfo (&pi));

        if (r != CKR_OK)
          throw_api_error (r, "unable to obtain PKCS#11 module info");

        if (!match (idn.library_manufacturer,
                    API_STRING (pi.manufacturerID))            ||

            !match (idn.library_version,
                    library_version (pi.libraryVersion.major,
                                     pi.libraryVersion.minor)) ||

            !match (idn.library_description,
                    API_STRING (pi.libraryDescription)))
          no_key ();

        // Traverse through slots.
        //
        // In the PKCS#11 terminology a slot is something that may have token
        // be inserted into it. Not to be confused with Yubikey's 9a, 9c, etc
        // slots.
        //
        // Note that a set of slots is checked at the time when
        // C_GetSlotList() is called to obtain slots count (pSlotList argument
        // is NULL and the tokenPresent argument is false).
        //
        CK_ULONG nslots;
        r = fs->C_GetSlotList (false /* tokenPresent */,
                               nullptr /* pSlotList */,
                               &nslots);

        if (r != CKR_OK)
          throw_api_error (r, "unable to obtain slots count");

        vector<CK_SLOT_ID> slot_ids (nslots);
        r = fs->C_GetSlotList (false /* tokenPresent */,
                               slot_ids.data (),
                               &nslots);

        if (r != CKR_OK)
          throw_api_error (r, "unable to obtain slot ids");

        for (CK_SLOT_ID sid: slot_ids)
        {
          // Match the slot information.
          //
          if (!match (idn.slot_id, sid))
            continue;

          CK_SLOT_INFO si;
          r = fs->C_GetSlotInfo (sid, &si);

          if (r != CKR_OK)
            throw_api_error (
              r, "unable to obtain slot " + to_string (sid) + " info");

          if ((si.flags & CKF_TOKEN_PRESENT) == 0                            ||
              !match (idn.slot_manufacturer, API_STRING (si.manufacturerID)) ||
              !match (idn.slot_description, API_STRING (si.slotDescription)))
            continue;

          auto slot_desc = [&sid, &si] ()
          {
            string d (API_STRING (si.slotDescription));
            return "slot " + to_string (sid) + " (" +
                   (!d.empty () ? d : API_STRING (si.manufacturerID)) + ")";
          };

          // Match the token information.
          //
          CK_TOKEN_INFO ti;
          r = fs->C_GetTokenInfo (sid, &ti);

          if (r == CKR_TOKEN_NOT_PRESENT || r == CKR_TOKEN_NOT_RECOGNIZED)
            continue;

          if (r != CKR_OK)
            throw_api_error (
              r, "unable to obtain token info for " + slot_desc ());

          if ((ti.flags & CKF_TOKEN_INITIALIZED)             == 0 ||
              (ti.flags & CKF_USER_PIN_INITIALIZED)          == 0 ||
              (ti.flags & CKF_LOGIN_REQUIRED)                == 0 ||
              (ti.flags & CKF_PROTECTED_AUTHENTICATION_PATH) != 0 || // Pinpad?

              !match (idn.serial,       API_STRING (ti.serialNumber))  ||
              !match (idn.token,        API_STRING (ti.label))         ||
              !match (idn.model,        API_STRING (ti.model))         ||
              !match (idn.manufacturer, API_STRING (ti.manufacturerID)))
            continue;

          auto token_desc = [&ti] ()
          {
            string r ("token ");
            string l (API_STRING (ti.label));

            r += !l.empty ()
            ? "'" + l + "'"
            : "'" + API_STRING (ti.model) + "' by " +
              API_STRING (ti.manufacturerID);

            return r;
          };

          // Search for the matching RSA private key in the token.
          //
          // Open the read-only session with the token. Note that we can't see
          // private objects until login.
          //
          CK_SESSION_HANDLE sh;
          r = fs->C_OpenSession (sid,
                                 CKF_SERIAL_SESSION,
                                 nullptr /* pApplication */,
                                 nullptr /* Notify */,
                                 &sh);

          if (r == CKR_DEVICE_REMOVED    ||
              r == CKR_TOKEN_NOT_PRESENT ||
              r == CKR_TOKEN_NOT_RECOGNIZED)
            continue;

          if (r != CKR_OK)
            throw_api_error (
              r, "unable to open session with " + token_desc ());

          session_ptr session (new CK_SESSION_HANDLE (sh), close_session);

          // Log into the token unless simulating.
          //
          if (simulate_)
            continue;

          // Note that all sessions with a token share login, so need to login
          // once per all token sessions.
          //
          // Also note that there is no need to logout explicitly if you want
          // to keep all token sessions logged in during their lifetime.
          //
          r = fs->C_Login (
            *session,
            CKU_USER,
            reinterpret_cast<unsigned char*> (const_cast<char*> (pin)),
            strlen (pin));

          // We can fail because of the wrong PIN or trying to apply the PIN
          // to a wrong token. Should we just skip the token if that's the
          // case? Probably we should throw. Otherwise who knows how many pins
          // we will reset going forward.
          //
          if (r != CKR_USER_ALREADY_LOGGED_IN && r != CKR_OK)
            throw_api_error (r, "unable to login to " + token_desc ());

          // Search for the private key.
          //
          // Fill the search attributes.
          //
          CK_OBJECT_CLASS oc (CKO_PRIVATE_KEY);
          CK_KEY_TYPE     kt (CKK_RSA);

          vector<CK_ATTRIBUTE> sa ({{CKA_CLASS,    &oc, sizeof (oc)},
                                    {CKA_KEY_TYPE, &kt, sizeof (kt)}});
          if (idn.id)
            sa.push_back (
              CK_ATTRIBUTE {CKA_ID,
                  const_cast<unsigned char*> (idn.id->data ()),
                  idn.id->size ()});

          if (idn.object)
            sa.push_back (CK_ATTRIBUTE {CKA_LABEL,
                  const_cast<char*> (idn.object->c_str ()),
                  idn.object->size ()});

          // Initialize the search.
          //
          r = fs->C_FindObjectsInit (*session, sa.data (), sa.size ());

          if (r != CKR_OK)
            throw_api_error (
              r, "unable to enumerate private keys in " + token_desc ());

          // Finally, search for the key.
          //
          // Note that we will query 2 keys to handle the 'multiple keys
          // match' case.
          //
          CK_OBJECT_HANDLE key (0);
          {
            session_ptr search_deleter (
              session.get (),
              [] (CK_SESSION_HANDLE* p) {api ()->C_FindObjectsFinal (*p);});

            CK_ULONG n;
            CK_OBJECT_HANDLE keys[2];
            r = fs->C_FindObjects (*session,
                                   keys,
                                   2 /* ulMaxObjectCount */,
                                   &n);

            if (r != CKR_OK)
              throw_api_error (
                r,
                "unable to obtain private key handles from " + token_desc ());

            if (n == 1)
              key = keys[0]; // Exactly one key matches.
            else if (n == 0)
              continue;      // No key matches.
            else
              mult_keys ();  // Multiple keys match.
          }

          if (session_ != nullptr)
            mult_keys ();

          // Produce description for the found key.
          //
          description = "private key ";
          {
            CK_ATTRIBUTE attr {CKA_LABEL, nullptr, 0};
            r = fs->C_GetAttributeValue (*session,
                                         key,
                                         &attr,
                                         1 /* ulCount */);

            if (r == CKR_OK && attr.ulValueLen != 0)
            {
              vector<char> label (attr.ulValueLen);
              attr.pValue = label.data ();

              r = fs->C_GetAttributeValue (*session,
                                           key,
                                           &attr,
                                           1 /* ulCount */);
              if (r == CKR_OK)
                description += "'" + string (label.data (), label.size ()) +
                               "' ";
            }
          }

          description += "in " + token_desc ();

          // Note that for Yubikey 4 we cannot rely on the key's
          // CKA_ALWAYS_AUTHENTICATE attribute value for detecting if
          // authentication is required for the sign operation. For the
          // private key imported into the 9c (SIGN key) slot with the
          // --pin-policy=never option the sign operation doesn't require
          // authentication but the CKA_ALWAYS_AUTHENTICATE value is still on.
          // This seems to be some yubico-piv-tool issue (or deliberate
          // behavior) as for the 9a (PIV AUTH key) slot the sign
          // authentication is not required and the CKA_ALWAYS_AUTHENTICATE
          // value is off. This issue makes it impossible to evaluate if the
          // key requires sign authentication before the sign attempt. This is
          // probably not a big deal as, if we want, we can always check this
          // using some dummy data.
          //
#if 0
          CK_BBOOL always_auth (CK_FALSE);

          CK_ATTRIBUTE attr {
            CKA_ALWAYS_AUTHENTICATE, &always_auth, sizeof (always_auth)};

          r = fs->C_GetAttributeValue (*session,
                                       key,
                                       &attr,
                                       1 /* ulCount */);

          if (r != CKR_OK)
            throw_api_error (
              r,
              "unable to obtain 'always auth' attribute for " + description);
#endif

          // Despite the fact that the key is found we will continue to iterate
          // over slots to make sure that a single key matches the identity
          // attributes.
          //
          session_ = move (session);
          handle_ = key;
        }

        if (simulate_)
          simulate ();
        else if (session_ == nullptr)
          no_key ();
      }

      vector<char> private_key::
      sign (const vector<char>& data, const optional<simulate_outcome>& sim)
      {
        assert (!empty ());

        if (sim && *sim == simulate_outcome::failure)
          throw runtime_error ("unable to sign using " + description);

        if (sim || simulate_)
        {
          // Otherwise would fail in the private_key constructor.
          //
          assert (!simulate_ || *simulate_ == simulate_outcome::success);

          return vector<char> ({
              's', 'i', 'g', 'n', 'a', 't', 'u', 'r', 'e', '\n'});
        }

        CK_FUNCTION_LIST* fs (api ());

        CK_MECHANISM mech;
        memset (&mech, 0, sizeof (mech));
        mech.mechanism = CKM_RSA_PKCS;

        CK_RV r (fs->C_SignInit (*session_, &mech, handle_));

        if (r != CKR_OK)
          throw_api_error (
            r, "unable to init sign operation using " + description);

        for (vector<char> signature; true; signature_size_ *= 2)
        {
          signature.resize (signature_size_);

          CK_ULONG n (signature_size_);

          r = fs->C_Sign (*session_,
                          reinterpret_cast<unsigned char*> (
                            const_cast<char*> (data.data ())),
                          data.size (),
                          reinterpret_cast<unsigned char*> (
                            signature.data ()),
                          &n);

          if (r == CKR_BUFFER_TOO_SMALL)
            continue;

          if (r != CKR_OK)
            throw_api_error (r, "unable to sign using " + description);

          assert (n != 0 && n <= signature_size_);

          signature.resize (n);
          return signature;
        }
      }
    }
  }
}