security-and-privacy/gnupg
security-and-privacy/gnupg
1
0
Fork 0
mirror of git://git.gnupg.org/gnupg.git synced 2025-07-02 22:46:30 +02:00
Code Activity

gpg: Implement AEAD for SKESK packets.

Browse source 
* g10/packet.h (PKT_symkey_enc): Add field aead_algo.
* g10/build-packet.c (do_symkey_enc): Support version 5 packets.
* g10/parse-packet.c (parse_symkeyenc): Ditto.
* g10/encrypt.c (encrypt_symmetric): Force using a random session
key in AEAD mode.
(encrypt_seskey): Add and support arg aead_algo.
(write_symkey_enc): Ditto.
(encrypt_simple): Adjust accordingly.
(encrypt_filter): Ditto.
* g10/gpgcompose.c (sk_esk): For now call encrypt_seskey without AEAD
support.
* g10/mainproc.c (symkey_decrypt_seskey): Support AEAD.  Nver call BUG
but return an error.
(proc_symkey_enc): Call symkey_decrypt_seskey in a bug compatible way.

* g10/import.c (check_prefs): Check AEAD preferences.
* g10/keyedit.c (show_prefs): Print AEAD preferences.
--

For easier debugging this patch also changes some diagnostics to also
print the encryption mode with the cipher algorithm.

Signed-off-by: Werner Koch <wk@gnupg.org>
This commit is contained in:
Werner Koch 2018-01-23 12:07:25 +01:00
parent da3015e3c0
commit 9aab9167bc
No known key found for this signature in database
GPG key ID: E3FDFF218E45B72B
11 changed files with 300 additions and 104 deletions
Download patch file Download diff file Expand all files Collapse all files

116
g10/mainproc.c
View file

@ -245,46 +245,102 @@ add_signature (CTX c, PACKET *pkt)
return 1;
}
static int
static gpg_error_t
symkey_decrypt_seskey (DEK *dek, byte *seskey, size_t slen)
{
gpg_error_t err;
gcry_cipher_hd_t hd;
unsigned int noncelen, keylen;
enum gcry_cipher_modes ciphermode;
byte ad[4];
if(slen < 17 || slen > 33)
if (dek->use_aead)
{
err = openpgp_aead_algo_info (dek->use_aead, &ciphermode, &noncelen);
if (err)
return err;
}
else
{
ciphermode = GCRY_CIPHER_MODE_CFB;
noncelen = 0;
}
/* Check that the session key has a size of 16 to 32 bytes. */
if ((dek->use_aead && (slen < (noncelen + 16 + 16)
|| slen > (noncelen + 32 + 16)))
|| (!dek->use_aead && (slen < 17 || slen > 33)))
{
log_error ( _("weird size for an encrypted session key (%d)\n"),
(int)slen);
return GPG_ERR_BAD_KEY;
return gpg_error (GPG_ERR_BAD_KEY);
}
if (openpgp_cipher_open (&hd, dek->algo, GCRY_CIPHER_MODE_CFB, 1))
BUG ();
if (gcry_cipher_setkey ( hd, dek->key, dek->keylen ))
BUG ();
gcry_cipher_setiv ( hd, NULL, 0 );
gcry_cipher_decrypt ( hd, seskey, slen, NULL, 0 );
gcry_cipher_close ( hd );
err = openpgp_cipher_open (&hd, dek->algo, ciphermode, GCRY_CIPHER_SECURE);
if (!err)
err = gcry_cipher_setkey (hd, dek->key, dek->keylen);
if (!err)
err = gcry_cipher_setiv (hd, noncelen? seskey : NULL, noncelen);
if (err)
goto leave;
/* Now we replace the dek components with the real session key to
decrypt the contents of the sequencing packet. */
if (dek->use_aead)
{
byte ad[4];
dek->keylen=slen-1;
dek->algo=seskey[0];
if(dek->keylen > DIM(dek->key))
BUG ();
memcpy(dek->key, seskey + 1, dek->keylen);
ad[0] = (0xc0 | PKT_SYMKEY_ENC);
ad[1] = 5;
ad[2] = dek->algo;
ad[3] = dek->use_aead;
err = gcry_cipher_authenticate (hd, ad, 4);
if (err)
goto leave;
gcry_cipher_final (hd);
keylen = slen - noncelen - 16;
err = gcry_cipher_decrypt (hd, seskey+noncelen, keylen, NULL, 0);
if (err)
goto leave;
err = gcry_cipher_checktag (hd, seskey+noncelen+keylen, 16);
if (err)
goto leave;
/* Now we replace the dek components with the real session key to
* decrypt the contents of the sequencing packet. */
if (keylen > DIM(dek->key))
{
err = gpg_error (GPG_ERR_TOO_LARGE);
goto leave;
}
dek->keylen = keylen;
memcpy (dek->key, seskey + noncelen, dek->keylen);
}
else
{
gcry_cipher_decrypt (hd, seskey, slen, NULL, 0 );
/* Now we replace the dek components with the real session key to
* decrypt the contents of the sequencing packet. */
keylen = slen-1;
if (keylen > DIM(dek->key))
{
err = gpg_error (GPG_ERR_TOO_LARGE);
goto leave;
}
dek->algo = seskey[0];
dek->keylen = keylen;
memcpy (dek->key, seskey + 1, dek->keylen);
}
/*log_hexdump( "thekey", dek->key, dek->keylen );*/
return 0;
leave:
gcry_cipher_close (hd);
return err;
}
static void
proc_symkey_enc (CTX c, PACKET *pkt)
{
gpg_error_t err;
PKT_symkey_enc *enc;
enc = pkt->pkt.symkey_enc;
@ -294,19 +350,21 @@ proc_symkey_enc (CTX c, PACKET *pkt)
{
int algo = enc->cipher_algo;
const char *s = openpgp_cipher_algo_name (algo);
const char *a = (enc->aead_algo ? openpgp_aead_algo_name (enc->aead_algo)
/**/ : "CFB");
if (!openpgp_cipher_test_algo (algo))
{
if (!opt.quiet)
{
if (enc->seskeylen)
log_info (_("%s encrypted session key\n"), s );
log_info (_("%s.%s encrypted session key\n"), s, a );
else
log_info (_("%s encrypted data\n"), s );
log_info (_("%s.%s encrypted data\n"), s, a );
}
}
else
log_error (_("encrypted with unknown algorithm %d\n"), algo);
log_error (_("encrypted with unknown algorithm %d.%s\n"), algo, a);
if (openpgp_md_test_algo (enc->s2k.hash_algo))
{
@ -334,6 +392,7 @@ proc_symkey_enc (CTX c, PACKET *pkt)
if (c->dek)
{
c->dek->symmetric = 1;
c->dek->use_aead = enc->aead_algo;
/* FIXME: This doesn't work perfectly if a symmetric key
comes before a public key in the message - if the
@ -344,9 +403,16 @@ proc_symkey_enc (CTX c, PACKET *pkt)
come later. */
if (enc->seskeylen)
{
if (symkey_decrypt_seskey (c->dek,
enc->seskey, enc->seskeylen))
err = symkey_decrypt_seskey (c->dek,
enc->seskey, enc->seskeylen);
if (err)
{
log_info ("decryption of the symmetrically encrypted"
" session key failed: %s\n",
gpg_strerror (err));
if (gpg_err_code (err) != GPG_ERR_BAD_KEY)
log_fatal ("process terminated to be bug compatible"
" with GnuPG <= 2.2\n");
xfree (c->dek);
c->dek = NULL;
}