Try decrypting using session key if subkey fails in tgs rep handling

Heimdal at least up through 1.2 incorrectly encrypts the TGS response
in the session key not the subkey when a subkey is supplied.  See RFC
4120 page 35.  Work around this by trying decryption using the session
key after the subkey fails.

* decode_kdc_rep.c: rename to krb5int_decode_tgs_rep; only used for
  TGS and now needs to take keyusage
* gc_via_tkt: pass in session key and appropriate usage if subkey
  fails.

Note that the dead code to process AS responses in decode_kdc_rep is
not removed by this commit.  That will be removed as FAST TGS client
support is integrated post 1.7.

ticket: 6484
Tags: pullup
Target_Version: 1.7

git-svn-id: svn://anonsvn.mit.edu/krb5/trunk@22325 dc483132-0cff-0310-8789-dd5450dbe970

diff --git a/src/include/k5-int.h b/src/include/k5-int.h
index de391a7d95cd7f27c535e18c4e5e071db55634fc..be3d1a9bf2145997488654b2c2abb13126d9551c 100644 (file)
--- a/src/include/k5-int.h
+++ b/src/include/k5-int.h
@@ -2613,10 +2613,10 @@ krb5_error_code krb5int_send_tgs
                 * in with the subkey needed to decrypt the TGS
                 * response. Otherwise it will be set to null.
                 */
-krb5_error_code krb5_decode_kdc_rep
+krb5_error_code krb5int_decode_tgs_rep
        (krb5_context,
                krb5_data *,
-         const krb5_keyblock *,
+        const krb5_keyblock *, krb5_keyusage,
                krb5_kdc_rep ** );
 krb5_error_code krb5int_find_authdata
 (krb5_context context, krb5_authdata *const * ticket_authdata,

diff --git a/src/lib/krb5/krb/decode_kdc.c b/src/lib/krb5/krb/decode_kdc.c
index a75bbf26652f6a8636c2ee2e61cd0e6968e1b922..689e2a2419d11348fb7135e00af4ca3902e2a370 100644 (file)
--- a/src/lib/krb5/krb/decode_kdc.c
+++ b/src/lib/krb5/krb/decode_kdc.c
@@ -43,17 +43,15 @@
  */
 
 krb5_error_code
-krb5_decode_kdc_rep(krb5_context context, krb5_data *enc_rep, const krb5_keyblock *key, krb5_kdc_rep **dec_rep)
+krb5int_decode_tgs_rep(krb5_context context, krb5_data *enc_rep, const krb5_keyblock *key,
+                      krb5_keyusage usage, krb5_kdc_rep **dec_rep)
 {
     krb5_error_code retval;
     krb5_kdc_rep *local_dec_rep;
-    krb5_keyusage usage;
 
     if (krb5_is_as_rep(enc_rep)) {
-       usage = KRB5_KEYUSAGE_AS_REP_ENCPART;
        retval = decode_krb5_as_rep(enc_rep, &local_dec_rep);
     } else if (krb5_is_tgs_rep(enc_rep)) {
-       usage = KRB5_KEYUSAGE_TGS_REP_ENCPART_SUBKEY;
        retval = decode_krb5_tgs_rep(enc_rep, &local_dec_rep);
     } else {
        return KRB5KRB_AP_ERR_MSG_TYPE;

diff --git a/src/lib/krb5/krb/gc_via_tkt.c b/src/lib/krb5/krb/gc_via_tkt.c
index e8dbd97fecacb69edcdb89dd93a4e1c22e298163..83c8026fcdafb181a207cdf17f86ce1aaa5043f8 100644 (file)
--- a/src/lib/krb5/krb/gc_via_tkt.c
+++ b/src/lib/krb5/krb/gc_via_tkt.c
@@ -290,9 +290,17 @@ krb5_get_cred_via_tkt (krb5_context context, krb5_creds *tkt,
        goto error_4;
     }
 
-    if ((retval = krb5_decode_kdc_rep(context, &tgsrep.response,
-                                     subkey, &dec_rep)))
-       goto error_4;
+    /* Unfortunately, Heimdal at least up through 1.2  encrypts using
+       the session key not the subsession key.  So we try both. */
+    if ((retval = krb5int_decode_tgs_rep(context, &tgsrep.response,
+                                     subkey,
+                                        KRB5_KEYUSAGE_TGS_REP_ENCPART_SUBKEY, &dec_rep))) {
+           if ((krb5int_decode_tgs_rep(context, &tgsrep.response,
+                                     &tkt->keyblock,
+                                       KRB5_KEYUSAGE_TGS_REP_ENCPART_SESSKEY, &dec_rep)) == 0)
+               retval = 0;
+           else goto error_4;
+    }
 
     if (dec_rep->msg_type != KRB5_TGS_REP) {
        retval = KRB5KRB_AP_ERR_MSG_TYPE;

diff --git a/src/lib/krb5/libkrb5.exports b/src/lib/krb5/libkrb5.exports
index 45e5002f099c3c82f6ca512d23fe971b4d6b7c3f..bd50fddb56b22990a0149f7a0c4e3e16ec56efca 100644 (file)
--- a/src/lib/krb5/libkrb5.exports
+++ b/src/lib/krb5/libkrb5.exports
@@ -185,7 +185,6 @@ krb5_copy_ticket
 krb5_create_secure_file
 krb5_crypto_us_timeofday
 krb5_decode_authdata_container
-krb5_decode_kdc_rep
 krb5_decode_ticket
 krb5_decrypt_tkt_part
 krb5_default_pwd_prompt1