gpg: Some support to allow Kyber decryption.

* g10/call-agent.c (agent_pkdecrypt): Support dual keygrips and switch
to KEM mode.
* g10/ecdh.c (pk_ecdh_decrypt): Add an extra length check.
* g10/keyid.c (do_hash_public_key): Fix Kyber fingerprint computation.

* g10/mainproc.c (release_list): Free all 4 data elements.
(proc_pubkey_enc): Copy all 4 data elements.
* g10/misc.c (openpgp_pk_test_algo2): Map Kyber to KEM.

* g10/parse-packet.c (parse_pubkeyenc): Fix Kyber parser.
* g10/pubkey-enc.c (get_session_key): Allow Kyber.
(get_it): Support Kyber.
--

GnuPG-bug-id: 6815

7 files changed, 67 insertions, 15 deletions

diff --git a/g10/call-agent.c b/g10/call-agent.c
index a49c987fa..31943d7df 100644
--- a/g10/call-agent.c
+++ b/g10/call-agent.c
@@ -2878,6 +2878,7 @@ agent_pkdecrypt (ctrl_t ctrl, const char *keygrip, const char *desc,
   membuf_t data;
   size_t n, len;
   char *p, *buf, *endp;
+  const char *keygrip2 = NULL;
   struct default_inq_parm_s dfltparm;
 
   memset (&dfltparm, 0, sizeof dfltparm);
@@ -2886,13 +2887,26 @@ agent_pkdecrypt (ctrl_t ctrl, const char *keygrip, const char *desc,
   dfltparm.keyinfo.mainkeyid   = mainkeyid;
   dfltparm.keyinfo.pubkey_algo = pubkey_algo;
 
-  if (!keygrip || strlen(keygrip) != 40
-      || !s_ciphertext || !r_buf || !r_buflen || !r_padding)
+  if (!keygrip || !s_ciphertext || !r_buf || !r_buflen || !r_padding)
     return gpg_error (GPG_ERR_INV_VALUE);
 
   *r_buf = NULL;
   *r_padding = -1;
 
+  /* Parse the keygrip in case of a dual algo.  */
+  keygrip2 = strchr (keygrip, ',');
+  if (!keygrip2)
+    keygrip2 = keygrip + strlen (keygrip);
+  if (keygrip2 - keygrip != 40)
+    return gpg_error (GPG_ERR_INV_VALUE);
+  if (*keygrip2)
+    {
+      keygrip2++;
+      if (strlen (keygrip2) != 40)
+        return gpg_error (GPG_ERR_INV_VALUE);
+    }
+
+
   err = start_agent (ctrl, 0);
   if (err)
     return err;
@@ -2903,11 +2917,19 @@ agent_pkdecrypt (ctrl_t ctrl, const char *keygrip, const char *desc,
   if (err)
     return err;
 
-  snprintf (line, sizeof line, "SETKEY %s", keygrip);
+  snprintf (line, sizeof line, "SETKEY %.40s", keygrip);
   err = assuan_transact (agent_ctx, line, NULL, NULL, NULL, NULL, NULL, NULL);
   if (err)
     return err;
 
+  if (*keygrip2)
+    {
+      snprintf (line, sizeof line, "SETKEY --another %.40s", keygrip2);
+      err = assuan_transact (agent_ctx, line, NULL, NULL,NULL,NULL,NULL,NULL);
+      if (err)
+        return err;
+    }
+
   if (desc)
     {
       snprintf (line, DIM(line), "SETKEYDESC %s", desc);
@@ -2926,7 +2948,8 @@ agent_pkdecrypt (ctrl_t ctrl, const char *keygrip, const char *desc,
     err = make_canon_sexp (s_ciphertext, &parm.ciphertext, &parm.ciphertextlen);
     if (err)
       return err;
-    err = assuan_transact (agent_ctx, "PKDECRYPT",
+    err = assuan_transact (agent_ctx,
+                           *keygrip2? "PKDECRYPT --kem=PQC-PGP":"PKDECRYPT",
                            put_membuf_cb, &data,
                            inq_ciphertext_cb, &parm,
                            padding_info_cb, r_padding);
diff --git a/g10/ecdh.c b/g10/ecdh.c
index 4938e419d..279508bec 100644
--- a/g10/ecdh.c
+++ b/g10/ecdh.c
@@ -537,7 +537,7 @@ pk_ecdh_decrypt (gcry_mpi_t *r_result, const byte sk_fp[MAX_FINGERPRINT_LEN],
   nbytes = (nbits+7)/8;
 
   data_buf_size = nbytes;
-  if ((data_buf_size & 7) != 1)
+  if ((data_buf_size & 7) != 1 || data_buf_size <= 1 + 8)
     {
       log_error ("can't use a shared secret of %d bytes for ecdh\n",
                  data_buf_size);
diff --git a/g10/keyid.c b/g10/keyid.c
index 09940cbfe..08f684829 100644
--- a/g10/keyid.c
+++ b/g10/keyid.c
@@ -336,17 +336,24 @@ do_hash_public_key (gcry_md_hd_t md, PKT_public_key *pk, int use_v5)
             {
               /* Ugly: We need to re-construct the wire format of the
                * key parameter.  It would be easier to use a second
-               * second index for pp and nn which could bump
-               * independet of i.  */
+               * index for pp and nn which we could bump independet of
+               * i.  */
               const char *p;
 
               p = gcry_mpi_get_opaque (pk->pkey[i], &nbits);
-              pp[i] = xmalloc ((nbits+7)/8 + 1);
+              nn[i] = (nbits+7)/8;
+              pp[i] = xmalloc (4 + nn[i] + 1);
               if (p)
-                memcpy (pp[i], p, (nbits+7)/8);
+                {
+                  pp[i][0] = nn[i] >> 24;
+                  pp[i][1] = nn[i] >> 16;
+                  pp[i][2] = nn[i] >> 8;
+                  pp[i][3] = nn[i];
+                  memcpy (pp[i] + 4 , p, nn[i]);
+                  nn[i] += 4;
+                }
               else
                 pp[i] = NULL;
-              nn[i] = (nbits+7)/8;
               n += nn[i];
             }
           else if (gcry_mpi_get_flag (pk->pkey[i], GCRYMPI_FLAG_OPAQUE))
diff --git a/g10/mainproc.c b/g10/mainproc.c
index d2e00514f..6f3254e88 100644
--- a/g10/mainproc.c
+++ b/g10/mainproc.c
@@ -143,6 +143,8 @@ release_list( CTX c )
 
       mpi_release (c->pkenc_list->data[0]);
       mpi_release (c->pkenc_list->data[1]);
+      mpi_release (c->pkenc_list->data[2]);
+      mpi_release (c->pkenc_list->data[3]);
       xfree (c->pkenc_list);
       c->pkenc_list = tmp;
     }
@@ -527,11 +529,13 @@ proc_pubkey_enc (CTX c, PACKET *pkt)
       x->keyid[1] = enc->keyid[1];
       x->pubkey_algo = enc->pubkey_algo;
       x->result = -1;
-      x->data[0] = x->data[1] = NULL;
+      x->data[0] = x->data[1] = x->data[2] = x->data[3] = NULL;
       if (enc->data[0])
         {
           x->data[0] = mpi_copy (enc->data[0]);
           x->data[1] = mpi_copy (enc->data[1]);
+          x->data[2] = mpi_copy (enc->data[2]);
+          x->data[3] = mpi_copy (enc->data[3]);
         }
       x->next = c->pkenc_list;
       c->pkenc_list = x;
diff --git a/g10/misc.c b/g10/misc.c
index 432fe1760..ce0c04b3b 100644
--- a/g10/misc.c
+++ b/g10/misc.c
@@ -750,6 +750,8 @@ openpgp_pk_test_algo2 (pubkey_algo_t algo, unsigned int use)
         ga = GCRY_PK_ELG;
       break;
 
+    case PUBKEY_ALGO_KYBER:     ga = GCRY_PK_KEM; break;
+
     default:
       break;
     }
diff --git a/g10/parse-packet.c b/g10/parse-packet.c
index 2163787cb..c55bb1b71 100644
--- a/g10/parse-packet.c
+++ b/g10/parse-packet.c
@@ -1444,6 +1444,7 @@ parse_symkeyenc (IOBUF inp, int pkttype, unsigned long pktlen,
 }
 
 
+/* Parse a public key encrypted packet (Tag 1).  */
 static int
 parse_pubkeyenc (IOBUF inp, int pkttype, unsigned long pktlen,
 		 PACKET * packet)
@@ -1514,9 +1515,14 @@ parse_pubkeyenc (IOBUF inp, int pkttype, unsigned long pktlen,
     {
       log_assert (ndata == 4);
       /* Get the ephemeral public key.  */
-      rc = read_octet_string (inp, &pktlen, 4, 0, 0, k->data + 0);
-      if (rc)
-        goto leave;
+      n = pktlen;
+      k->data[0] = sos_read (inp, &n, 0);
+      pktlen -= n;
+      if (!k->data[0])
+        {
+          rc = gpg_error (GPG_ERR_INV_PACKET);
+          goto leave;
+        }
       /* Get the Kyber ciphertext.  */
       rc = read_octet_string (inp, &pktlen, 4, 0, 0, k->data + 1);
       if (rc)
diff --git a/g10/pubkey-enc.c b/g10/pubkey-enc.c
index 3e9daa963..873b864b5 100644
--- a/g10/pubkey-enc.c
+++ b/g10/pubkey-enc.c
@@ -117,6 +117,7 @@ get_session_key (ctrl_t ctrl, struct pubkey_enc_list *list, DEK *dek)
         {
           if (!(k->pubkey_algo == PUBKEY_ALGO_ELGAMAL_E
                 || k->pubkey_algo == PUBKEY_ALGO_ECDH
+                || k->pubkey_algo == PUBKEY_ALGO_KYBER
                 || k->pubkey_algo == PUBKEY_ALGO_RSA
                 || k->pubkey_algo == PUBKEY_ALGO_RSA_E
                 || k->pubkey_algo == PUBKEY_ALGO_ELGAMAL))
@@ -237,6 +238,16 @@ get_it (ctrl_t ctrl,
         err = gcry_sexp_build (&s_data, NULL, "(enc-val(ecdh(s%m)(e%m)))",
                                enc->data[1], enc->data[0]);
     }
+  else if (sk->pubkey_algo == PUBKEY_ALGO_KYBER)
+    {
+      if (!enc->data[0] || !enc->data[1] || !enc->data[2] || !enc->data[3])
+        err = gpg_error (GPG_ERR_BAD_MPI);
+      else
+        err = gcry_sexp_build (&s_data, NULL,
+                               "(enc-val(pqc(e%m)(k%m)(s%m)(fixed-info%s)))",
+                               enc->data[0], enc->data[1], enc->data[3],
+                               "\x1d" /*PUBKEY_ALGO_KYBER*/);
+    }
   else
     err = gpg_error (GPG_ERR_BUG);
 
@@ -249,7 +260,6 @@ get_it (ctrl_t ctrl,
   /* Decrypt. */
   desc = gpg_format_keydesc (ctrl, sk, FORMAT_KEYDESC_NORMAL, 1);
 
-  /*FIXME: Support dual keys.  */
   err = agent_pkdecrypt (NULL, keygrip,
                          desc, sk->keyid, sk->main_keyid, sk->pubkey_algo,
                          s_data, &frame, &nframe, &padding);