SRT2003-09-11-1200 - setgid man MANPL overflow

[KF <dotslash@xxxxxxxxxxx>]

The full version of this advisory can be found at.
http://www.secnetops.com/research/advisories/SRT2003-09-11-1200.txt


Quick Summary:
************************************************************************
Advisory Number         : SRT2003-09-11-1200
Product                 : Andries Brouwer man
Version                 : Version <=1.5m1
Vendor                  : ftp://ftp.win.tue.nl/pub/linux-local/utils/man
Class                   : Local

High Level Explanation
************************************************************************
High Level Description  : MANPL variable suffers from overflow
What to do              : upgrade to man-1.5m2.tar.gz

Technical Details
************************************************************************
Proof Of Concept Status : SNO has working Poc code.
Low Level Description   :

In efforts to keep man secure most vendors include a variant of the patch
"man-1.5l-redhat-patches.patch" . This patch provides a length check on
several variables used in getenv() calls and in turn it stops at least one
overflow. This patch has been left out of vendor supplied packages on
occasion while man was still sgid. If you have compiled man yourself or
have set the sgid bit on a vendor supplied man (RH9) you may be vulnerable.

+     char *s;
+#define CHECK(p, l) s=getenv(p); if(s && (strlen(s)>l)) { fprintf(stderr,
"ERROR: Environment variable %s too long!\n", p); exit(1); }
+
+     CHECK("LANG", 32);
+     CHECK("MANPAGER", 128);
+     CHECK("PAGER", 128);
+     CHECK("SYSTEM", 64);
+     CHECK("MANROFFSEQ", 128);
+     CHECK("MANSECT", 128);
+     CHECK("MANPL", 128);
+     CHECK("MAN_HP_DIREXT", 128);
+     CHECK("LANGUAGE", 128);
+     CHECK("LC_MESSAGES", 128);

in the default man-1.5x code these checks are not present which causes an
exploitable condition.

-KF