[openssl.org #2711] Fix possible NULL dereference on bad MIME headers

[Tomas Mraz via RT]

In some cases when a S/MIME message with broken MIME headers is
processed a NULL dereference in mime_hdr_cmp can happen. The attached
patch guards against this dereference.
-- 
Tomas Mraz
No matter how far down the wrong road you've gone, turn back.
                                              Turkish proverb


diff -up openssl-0.9.8j/crypto/asn1/asn_mime.c.bad-mime openssl-0.9.8j/crypto/asn1/asn_mime.c
--- openssl-0.9.8j/crypto/asn1/asn_mime.c.bad-mime	2008-08-05 17:56:11.000000000 +0200
+++ openssl-0.9.8j/crypto/asn1/asn_mime.c	2009-01-14 22:08:34.000000000 +0100
@@ -792,6 +792,10 @@ static int mime_hdr_addparam(MIME_HEADER
 static int mime_hdr_cmp(const MIME_HEADER * const *a,
 			const MIME_HEADER * const *b)
 {
+	if ((*a)->name == NULL || (*b)->name == NULL)
+		return (*a)->name - (*b)->name < 0 ? -1 :
+			(*a)->name - (*b)->name > 0 ? 1 : 0;
+
 	return(strcmp((*a)->name, (*b)->name));
 }