CVE-2022-3437 source4/heimdal: Pass correct length to _gssapi_verify_pad()

We later subtract 8 when calculating the length of the output message
buffer. If padlength is excessively high, this calculation can underflow
and result in a very large positive value.

Now we properly constrain the value of padlength so underflow shouldn't
be possible.

BUG: https://bugzilla.samba.org/show_bug.cgi?id=15134

Signed-off-by: Joseph Sutton <josephsutton@catalyst.net.nz>
Reviewed-by: Andrew Bartlett <abartlet@samba.org>

diff --git a/selftest/knownfail.d/heimdal-des-overflow b/selftest/knownfail.d/heimdal-des-overflow
deleted file mode 100644 (file)
index a7416dc..0000000
--- a/selftest/knownfail.d/heimdal-des-overflow
+++ /dev/null
@@ -1,2 +0,0 @@
-^samba.unittests.auth.heimdal_gensec_unwrap_des.test_unwrap_with_padding_truncated_0.none
-^samba.unittests.auth.heimdal_gensec_unwrap_des.test_unwrap_with_padding_truncated_1.none

diff --git a/source4/heimdal/lib/gssapi/krb5/unwrap.c b/source4/heimdal/lib/gssapi/krb5/unwrap.c
index 70d26a75ccfc6978b95d2fa0f374fd195865da86..ed8f7d78ffab48e4cfb48e32f1c0d956341bae7b 100644 (file)
--- a/source4/heimdal/lib/gssapi/krb5/unwrap.c
+++ b/source4/heimdal/lib/gssapi/krb5/unwrap.c
@@ -124,7 +124,7 @@ unwrap_des
   } else {
     /* check pad */
     ret = _gssapi_verify_pad(input_message_buffer,
-                            input_message_buffer->length - len,
+                            input_message_buffer->length - len - 8,
                             &padlength);
     if (ret)
         return ret;
@@ -289,7 +289,7 @@ unwrap_des3
   } else {
     /* check pad */
     ret = _gssapi_verify_pad(input_message_buffer,
-                            input_message_buffer->length - len,
+                            input_message_buffer->length - len - 8,
                             &padlength);
     if (ret)
         return ret;