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Now passing Ticket and Authenticator between client and server
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 - tested for the KDH-only mode, without server certificate
 - including a keytab for `generic/testsrv\@tlspool.arpa2.lab@ARPA2.NET`
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@vanrein
vanrein committed Aug 25, 2016
1 parent 95eacd5 commit c78ab02
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Showing 3 changed files with 78 additions and 38 deletions.
8 changes: 4 additions & 4 deletions etc/tlspool.conf
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Original file line number Diff line number Diff line change
Expand Up @@ -335,10 +335,10 @@ dnssec_rootkey ../etc/root.key
# may have to wait for a convincing use case.
#

#ENOSYS# kerberos_client_keytab = ../testdata/kerberos-client.keytab
kerberos_server_keytab = ../testdata/kerberos-server.keytab
kerberos_client_credcache = DIR:../testdata/kerberos-client.credcache
kerberos_server_credcache = DIR:../testdata/kerberos-server.credcache
#ENOSYS# kerberos_client_keytab ../testdata/kerberos-client.keytab
kerberos_server_keytab ../testdata/kerberos-server.keytab
kerberos_client_credcache DIR:../testdata/kerberos-client.credcache
kerberos_server_credcache DIR:../testdata/kerberos-server.credcache


#
Expand Down
108 changes: 74 additions & 34 deletions src/starttls.c
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Original file line number Diff line number Diff line change
Expand Up @@ -2229,7 +2229,7 @@ static int have_key_tgt_cc (struct command *cmd, // in, session context
if (key->contents == NULL) {
if (k5err != 0) {
const char *errmsg = krb5_get_error_message (ctx, k5err);
tlog (TLOG_DAEMON, LOG_ERR, "Kerberos error: %s", errmsg);
tlog (TLOG_DAEMON, LOG_ERR, "Kerberos error in have_key_tgt_cc: %s", errmsg);
krb5_free_error_message (ctx, errmsg);
}
if (*tgt != NULL) {
Expand Down Expand Up @@ -2473,6 +2473,25 @@ uint32_t qder2b_unpack_uint32 (dercursor data5) {
}


#ifdef HAVE_TLS_KDH
/* TODO: Debugging function for printing (descr,ptr,len) ranges */
static inline void prange (char *descr, uint8_t *ptr, int len) {
fprintf (stderr, "%s #%04d: %02x %02x %02x %02x %02x %02x %02x %02x...%02x %02x %02x %02x\n",
descr, len,
ptr [0], ptr [1], ptr [2], ptr [3],
ptr [4], ptr [5], ptr [6], ptr [7],
ptr [len-4], ptr [len-3], ptr [len-2], ptr [len-1]);
}
static inline void prangefull (char *descr, uint8_t *ptr, int len) {
fprintf (stderr, "%s #%04d:", descr, len);
while (len-- > 0) {
fprintf (stderr, " %02x", *ptr++);
}
fprintf (stderr, "\n");
}
#endif


/* The callback function that retrieves a TLS-KDH "signature", which is kept
* outside of GnuTLS. The callback computes an authenticator encrypted to
* the session's Kerberos key.
Expand Down Expand Up @@ -2510,6 +2529,8 @@ static gtls_error cli_kdhsig_encode (gnutls_session_t session,
//
// Setup secure hash in authenticator (never optional for TLS-KDH)
auth.cksum.cksumtype = qder2b_pack_int32 (dercksumtype, checksum_type);
auth.cksum.checksum.derptr = hash->data;
auth.cksum.checksum.derlen = hash->size;
//
// Optionally include a subkey (namely, for KDH-Only)
peercert = gnutls_certificate_type_get_peers (session);
Expand All @@ -2525,6 +2546,7 @@ static gtls_error cli_kdhsig_encode (gnutls_session_t session,
auth.subkey.keytype = qder2b_pack_int32 (dersubkey, subkey.enctype);
auth.subkey.keyvalue.derptr = subkey.contents;
auth.subkey.keyvalue.derlen = subkey.length;
prange ("cli_K", subkey.contents, subkey.length);
}
//
// Setup the client realm and principal name
Expand Down Expand Up @@ -2557,7 +2579,8 @@ static gtls_error cli_kdhsig_encode (gnutls_session_t session,
}
der_pack ( auth_packer,
(const dercursor *) &auth,
decptr);
decptr + declen);
prangefull ("cli_A", decptr, declen);
size_t rawlen;
if (0 != krb5_c_encrypt_length (krbctx_cli,
cmd->krb_key.enctype,
Expand Down Expand Up @@ -2612,14 +2635,16 @@ static gtls_error cli_kdhsig_encode (gnutls_session_t session,
}
der_pack ( encdata_packer,
(const dercursor *) &encdata,
encptr);
encptr + enclen);
free (rawptr);
//
// Return our final verdict on the generation of the Authenticator
dec_authenticator->data = decptr;
dec_authenticator->size = declen;
enc_authenticator->data = encptr;
enc_authenticator->size = enclen;
prange ("cli_D", decptr, declen);
prange ("cli_E", encptr, enclen);
return 0;
}
#endif
Expand All @@ -2637,13 +2662,15 @@ static int srv_kdhsig_decode (gnutls_session_t session,
int32_t *checksum_type) {
//
// Variables, sanity checks and initialisation
int k5err = 0;
struct command *cmd;
static const uint8_t encdata_packer [] = {
DER_PACK_rfc4120_EncryptedData, DER_PACK_END };
static const uint8_t auth_packer [] = {
DER_PACK_rfc4120_Authenticator, DER_PACK_END };
encrypted_data_t encdata;
cmd = (struct command *) gnutls_session_get_ptr (session);
prange ("srv_E", enc_authenticator->data, enc_authenticator->size);
//
// Retrieve the session key and store it in cmd->krb_key.
//
Expand All @@ -2665,66 +2692,74 @@ static int srv_kdhsig_decode (gnutls_session_t session,
krb5_ticket *tkt;
krbcert.data = certs [0].data;
krbcert.length = certs [0].size;
prange ("srv_C", certs [0].data, certs [0].size);
if (0 != krb5_decode_ticket (&krbcert, &tkt)) {
return GNUTLS_E_NO_CERTIFICATE_FOUND;
}
bool notfound = 0;
if (cmd->krb_key.contents != NULL) {
// user-to-user mode
if (0 != krb5_decrypt_tkt_part (
krbctx_srv, &cmd->krb_key, tkt)) {
notfound = 1;
}
krb5_free_keyblock_contents (krbctx_srv, &cmd->krb_key);
k5err = krb5_decrypt_tkt_part (
krbctx_srv,
&cmd->krb_key,
tkt);
krb5_free_keyblock_contents (
krbctx_srv,
&cmd->krb_key);
} else {
// client-to-server mode
if (0 != krb5_server_decrypt_ticket_keytab (
krbctx_srv, krb_kt_srv, tkt)) {
notfound = 1;
}
k5err = krb5_server_decrypt_ticket_keytab (
krbctx_srv,
krb_kt_srv,
tkt);
}
if (0 != krb5_copy_keyblock_contents (
if (k5err == 0) {
k5err = krb5_copy_keyblock_contents (
krbctx_srv,
tkt->enc_part2->session,
&cmd->krb_key)) {
notfound = 1;
&cmd->krb_key);
}
if (0 != krb5_copy_principal ( krbctx_srv,
if (k5err == 0) {
k5err = krb5_copy_principal (
krbctx_srv,
tkt->enc_part2->client,
&cmd->krbid_cli)) {
notfound = 1;
}
if (cmd->krbid_srv->data != NULL) {
if (!krb5_principal_compare ( krbctx_srv,
tkt->server,
cmd->krbid_srv)) {
// Server name changed since u2u setup -- not permitted
notfound = 1;
}
} else {
if (0 != krb5_copy_principal ( krbctx_srv,
tkt->server,
&cmd->krbid_srv)) {
notfound = 1;
&cmd->krbid_cli);
}
if (k5err == 0) {
if (cmd->krbid_srv != NULL) {
k5err = krb5_principal_compare (
krbctx_srv,
tkt->server,
cmd->krbid_srv);
// Server name changed since u2u setup => k5err
} else {
k5err = krb5_copy_principal (
krbctx_srv,
tkt->server,
&cmd->krbid_srv);
}
}
krb5_free_ticket (krbctx_srv, tkt);
if (notfound) {
if (k5err != 0) {
const char *errmsg = krb5_get_error_message (krbctx_srv, k5err);
tlog (TLOG_DAEMON, LOG_ERR, "Kerberos error in srv_kdhsig_decode: %s", errmsg);
krb5_free_error_message (krbctx_srv, errmsg);
return GNUTLS_E_NO_CERTIFICATE_FOUND;
}
//
// Harvest the EncryptedData fields from the enc_authenticator
dercursor enctransport;
enctransport.derptr = enc_authenticator->data;
enctransport.derlen = enc_authenticator->size;
memset (&encdata, 0, sizeof (encdata));
if (0 != der_unpack ( &enctransport,
encdata_packer,
(dercursor *) &encdata,
1)) {
tlog (TLOG_DAEMON, LOG_ERR, "Failed to der_unpack(EncryptedData) in server: %s", strerror (errno));
return GNUTLS_E_DECRYPTION_FAILED;
}
if (encdata.kvno.derptr != NULL) {
return GNUTLS_E_DECRYPTION_FAILED;
//TODO//NOTYET//ANDWHY// return GNUTLS_E_DECRYPTION_FAILED;
}
int32_t etype = qder2b_unpack_int32 (encdata.etype);
//
Expand All @@ -2736,6 +2771,7 @@ static int srv_kdhsig_decode (gnutls_session_t session,
rawdata.enctype = etype;
rawdata.ciphertext.data = encdata.cipher.derptr;
rawdata.ciphertext.length = encdata.cipher.derlen;
prange ("srv_R", encdata.cipher.derptr, encdata.cipher.derlen);
decdata.data = dec_authenticator->data;
decdata.length = dec_authenticator->size;
if (0 != krb5_c_decrypt ( krbctx_srv,
Expand All @@ -2747,16 +2783,20 @@ static int srv_kdhsig_decode (gnutls_session_t session,
return GNUTLS_E_DECRYPTION_FAILED;
}
dec_authenticator->size = decdata.length;
prange ("srv_D", decdata.data, decdata.length);
//
// Unpack the decrypted Authenticator
dercursor decsyntax;
decsyntax.derptr = decdata.data;
decsyntax.derlen = decdata.length;
prangefull ("srv_A", decdata.data, decdata.length);
authenticator_t auth;
memset (&auth, 0, sizeof (auth));
if (0 != der_unpack ( &decsyntax,
auth_packer,
(dercursor *) &auth,
1)) {
tlog (TLOG_DAEMON, LOG_ERR, "Failed to der_unpack(Authenticator) in server: %s", strerror (errno));
return GNUTLS_E_DECRYPTION_FAILED;
}
//
Expand Down
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