From 4b7d9cd4a018898d7714ce06f3faf2626c14582b Mon Sep 17 00:00:00 2001

From: Werner Koch <wk@gnupg.org>

Date: Wed, 5 Oct 2022 14:19:06 +0200

Subject: [PATCH] Detect a possible overflow directly in the TLV parser.

* src/ber-help.c (_ksba_ber_read_tl): Check for overflow of a commonly

used sum.

--

It is quite common to have checks like

    if (ti.nhdr + ti.length >= DIM(tmpbuf))

       return gpg_error (GPG_ERR_TOO_LARGE);

This patch detects possible integer overflows immmediately when

creating the TI object.

Reported-by: ZDI-CAN-18927, ZDI-CAN-18928, ZDI-CAN-18929

---

 src/ber-help.c | 6 ++++++

 1 file changed, 6 insertions(+)

diff --git a/src/ber-help.c b/src/ber-help.c

index 81c31ed..56efb6a 100644

--- a/src/ber-help.c

+++ b/src/ber-help.c

@@ -182,6 +182,12 @@ _ksba_ber_read_tl (ksba_reader_t reader, struct tag_info *ti)

       ti->length = len;

     }

+  if (ti->length > ti->nhdr && (ti->nhdr + ti->length) < ti->length)

+    {

+      ti->err_string = "header+length would overflow";

+      return gpg_error (GPG_ERR_EOVERFLOW);

+    }

+

   /* Without this kludge some example certs can't be parsed */

   if (ti->class == CLASS_UNIVERSAL && !ti->tag)

     ti->length = 0;

-- 

2.37.3

commit f61a5ea4e0f6a80fd4b28ef0174bee77793cf070

Author: Werner Koch <wk@gnupg.org>

Date:   Tue Nov 22 16:36:46 2022 +0100

    Fix an integer overflow in the CRL signature parser.

    * src/crl.c (parse_signature): N+N2 now checked for overflow.

    * src/ocsp.c (parse_response_extensions): Do not accept too large

    values.

    (parse_single_extensions): Ditto.

    --

    The second patch is an extra safegourd not related to the reported

    bug.

    GnuPG-bug-id: 6284

    Reported-by: Joseph Surin, elttam

diff --git a/src/crl.c b/src/crl.c

index 9f71c85..2e6ca29 100644

--- a/src/crl.c

+++ b/src/crl.c

@@ -1349,7 +1349,7 @@ parse_signature (ksba_crl_t crl)

          && !ti.is_constructed) )

     return gpg_error (GPG_ERR_INV_CRL_OBJ);

   n2 = ti.nhdr + ti.length;

-  if (n + n2 >= DIM(tmpbuf))

+  if (n + n2 >= DIM(tmpbuf) || (n + n2) < n)

     return gpg_error (GPG_ERR_TOO_LARGE);

   memcpy (tmpbuf+n, ti.buf, ti.nhdr);

   err = read_buffer (crl->reader, tmpbuf+n+ti.nhdr, ti.length);

diff --git a/src/ocsp.c b/src/ocsp.c

index d4cba04..657d15f 100644

--- a/src/ocsp.c

+++ b/src/ocsp.c

@@ -721,6 +721,12 @@ parse_response_extensions (ksba_ocsp_t ocsp,

           else

             ocsp->good_nonce = 1;

         }

+      if (ti.length > (1<<24))

+        {

+          /* Bail out on much too large objects.  */

+          err = gpg_error (GPG_ERR_BAD_BER);

+          goto leave;

+        }

       ex = xtrymalloc (sizeof *ex + strlen (oid) + ti.length);

       if (!ex)

         {

@@ -788,6 +794,12 @@ parse_single_extensions (struct ocsp_reqitem_s *ri,

       err = parse_octet_string (&data, &datalen, &ti);

       if (err)

         goto leave;

+      if (ti.length > (1<<24))

+        {

+          /* Bail out on much too large objects.  */

+          err = gpg_error (GPG_ERR_BAD_BER);

+          goto leave;

+        }

       ex = xtrymalloc (sizeof *ex + strlen (oid) + ti.length);

       if (!ex)

         {