gpg: Revamp structure of PKT_symkey_enc.

* g10/packet.h (PKT_symkey_enc): Allocate the session key so that we
have a fixed length for this struct.
* g10/free-packet.c (free_symkey_enc): Adjust for this change
* g10/parse-packet.c (parse_symkeyenc): Ditto.
* g10/encrypt.c (encrypt_simple, write_symkey_enc): Ditto.

5 files changed, 35 insertions, 12 deletions

diff --git a/g10/encrypt.c b/g10/encrypt.c
index b67d8039d..b305ce938 100644
--- a/g10/encrypt.c
+++ b/g10/encrypt.c
@@ -572,7 +572,7 @@ encrypt_simple (const char *filename, int mode, int use_seskey)
   if ( s2k )
     {
       /* Fixme: This is quite similar to write_symkey_enc.  */
-      PKT_symkey_enc *enc = xmalloc_clear (sizeof *enc + enckeylen);
+      PKT_symkey_enc *enc = xmalloc_clear (sizeof *enc);
       enc->version = cfx.dek->use_aead ? 5 : 4;
       enc->cipher_algo = cfx.dek->algo;
       enc->aead_algo = cfx.dek->use_aead;
@@ -580,13 +580,14 @@ encrypt_simple (const char *filename, int mode, int use_seskey)
       if (enckeylen)
         {
           enc->seskeylen = enckeylen;
+          enc->seskey = xmalloc (enckeylen);
           memcpy (enc->seskey, enckey, enckeylen);
         }
       pkt.pkttype = PKT_SYMKEY_ENC;
       pkt.pkt.symkey_enc = enc;
       if ((rc = build_packet( out, &pkt )))
         log_error("build symkey packet failed: %s\n", gpg_strerror (rc) );
-      xfree (enc);
+      free_symkey_enc (enc);
       xfree (enckey);
       enckey = NULL;
     }
@@ -777,7 +778,7 @@ write_symkey_enc (STRING2KEY *symkey_s2k, aead_algo_t aead_algo,
   rc = encrypt_seskey (symkey_dek, aead_algo, &dek, &enckey, &enckeylen);
   if (rc)
     return rc;
-  enc = xtrycalloc (1, sizeof (PKT_symkey_enc) + enckeylen);
+  enc = xtrycalloc (1, sizeof (PKT_symkey_enc));
   if (!enc)
     {
       rc = gpg_error_from_syserror ();
@@ -790,6 +791,14 @@ write_symkey_enc (STRING2KEY *symkey_s2k, aead_algo_t aead_algo,
   enc->aead_algo = aead_algo;
   enc->s2k = *symkey_s2k;
   enc->seskeylen = enckeylen;
+  enc->seskey = xtrymalloc (enckeylen);
+  if (!enc->seskey)
+    {
+      rc = gpg_error_from_syserror ();
+      xfree (enc);
+      xfree (enckey);
+      return rc;
+    }
   memcpy (enc->seskey, enckey, enckeylen);
   xfree (enckey);
 
@@ -799,7 +808,7 @@ write_symkey_enc (STRING2KEY *symkey_s2k, aead_algo_t aead_algo,
   if ((rc=build_packet(out,&pkt)))
     log_error("build symkey_enc packet failed: %s\n",gpg_strerror (rc));
 
-  xfree (enc);
+  free_symkey_enc (enc);
   return rc;
 }
 
diff --git a/g10/free-packet.c b/g10/free-packet.c
index f742022f5..fc4e9d26b 100644
--- a/g10/free-packet.c
+++ b/g10/free-packet.c
@@ -49,9 +49,12 @@ my_mpi_copy (gcry_mpi_t a)
 void
 free_symkey_enc( PKT_symkey_enc *enc )
 {
-    xfree(enc);
+  if (enc)
+    xfree (enc->seskey);
+  xfree(enc);
 }
 
+
 /* This is the core of free_pubkey_enc but does only release the
  * allocated members of ENC.  */
 void
diff --git a/g10/packet.h b/g10/packet.h
index 8b4c3d9c2..60446a417 100644
--- a/g10/packet.h
+++ b/g10/packet.h
@@ -147,9 +147,9 @@ typedef struct {
      S2K function on the password is the session key. See RFC 4880,
      Section 5.3.)  */
   byte seskeylen;
-  /* The session key as encrypted by the S2K specifier.  For AEAD this
-   * includes the nonce and the authentication tag.  */
-  byte seskey[1];
+  /* The malloced session key as encrypted by the S2K specifier.  For
+   * AEAD this includes the nonce and the authentication tag.  */
+  byte *seskey;
 } PKT_symkey_enc;
 
 /* A public-key encrypted session key packet as defined in RFC 4880,
@@ -177,7 +177,7 @@ typedef struct {
 struct seskey_enc_list
 {
   struct seskey_enc_list *next;
-  int result;
+  int result; /* The error code decrypting the session key.  */
   int u_sym;  /* Use the sym member.  */
   union {
     PKT_pubkey_enc pub;
diff --git a/g10/parse-packet.c b/g10/parse-packet.c
index ac784b7fb..32ec46b6f 100644
--- a/g10/parse-packet.c
+++ b/g10/parse-packet.c
@@ -1376,8 +1376,7 @@ parse_symkeyenc (IOBUF inp, int pkttype, unsigned long pktlen,
       goto leave;
     }
   seskeylen = pktlen - minlen;
-  k = packet->pkt.symkey_enc = xmalloc_clear (sizeof *packet->pkt.symkey_enc
-					      + seskeylen - 1);
+  k = packet->pkt.symkey_enc = xmalloc_clear (sizeof *packet->pkt.symkey_enc);
   k->version = version;
   k->cipher_algo = cipher_algo;
   k->aead_algo = aead_algo;
@@ -1396,6 +1395,7 @@ parse_symkeyenc (IOBUF inp, int pkttype, unsigned long pktlen,
   k->seskeylen = seskeylen;
   if (k->seskeylen)
     {
+      k->seskey = xcalloc (1, seskeylen);
       for (i = 0; i < seskeylen && pktlen; i++, pktlen--)
 	k->seskey[i] = iobuf_get_noeof (inp);
 
diff --git a/g10/sign.c b/g10/sign.c
index f0bf9b671..9ef032e74 100644
--- a/g10/sign.c
+++ b/g10/sign.c
@@ -1728,7 +1728,18 @@ sign_symencrypt_file (ctrl_t ctrl, const char *fname, strlist_t locusr)
   /* Write the symmetric key packet */
   /* (current filters: armor)*/
   {
-    PKT_symkey_enc *enc = xmalloc_clear( sizeof *enc );
+    PKT_symkey_enc *enc = xmalloc_clear (sizeof *enc);
+
+    /* FIXME: seskeylen is 0, thus we directly encrypt the session key:
+     *
+     *     ...then the S2K algorithm applied to the passphrase produces
+     *    the session key for decrypting the file, using the symmetric
+     *    cipher algorithm from the Symmetric-Key Encrypted Session Key
+     *    packet.
+     *
+     * The problem is that this does not allow us to add additional
+     * encrypted session keys.
+     */
 
     enc->version = cfx.dek->use_aead ? 5 : 4;
     enc->cipher_algo = cfx.dek->algo;