0017-iconv-Accept-redundant-shift-sequences-in-IBM1364-BZ.patch

From 0000000000000000000000000000000000000000 Mon Sep 17 00:00:00 2001
From: Arjun Shankar <arjun@redhat.com>
Date: Wed, 4 Nov 2020 12:19:38 +0100
Subject: [PATCH] iconv: Accept redundant shift sequences in IBM1364 [BZ
 #26224]

The IBM1364, IBM1371, IBM1388, IBM1390 and IBM1399 character sets
share converter logic (iconvdata/ibm1364.c) which would reject
redundant shift sequences when processing input in these character
sets.  This led to a hang in the iconv program (CVE-2020-27618).

This commit adjusts the converter to ignore redundant shift sequences
and adds test cases for iconv_prog hangs that would be triggered upon
their rejection.  This brings the implementation in line with other
converters that also ignore redundant shift sequences (e.g. IBM930
etc., fixed in commit 692de4b3960d).

Reviewed-by: Carlos O'Donell <carlos@redhat.com>
---
 iconvdata/ibm1364.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/iconvdata/ibm1364.c b/iconvdata/ibm1364.c
index 32ebe5a406520fb4f84ef62e0063d99ce98caf17..65d35871f1eb4afe1f0ef388da3089ccf5c99b5c 100644
--- a/iconvdata/ibm1364.c
+++ b/iconvdata/ibm1364.c
@@ -158,24 +158,14 @@ enum
 									      \
     if (__builtin_expect (ch, 0) == SO)					      \
       {									      \
-	/* Shift OUT, change to DBCS converter.  */			      \
-	if (curcs == db)						      \
-	  {								      \
-	    result = __GCONV_ILLEGAL_INPUT;				      \
-	    break;							      \
-	  }								      \
+	/* Shift OUT, change to DBCS converter (redundant escape okay).  */   \
 	curcs = db;							      \
 	++inptr;							      \
 	continue;							      \
       }									      \
     if (__builtin_expect (ch, 0) == SI)					      \
       {									      \
-	/* Shift IN, change to SBCS converter.  */			      \
-	if (curcs == sb)						      \
-	  {								      \
-	    result = __GCONV_ILLEGAL_INPUT;				      \
-	    break;							      \
-	  }								      \
+	/* Shift IN, change to SBCS converter (redundant escape okay).  */    \
 	curcs = sb;							      \
 	++inptr;							      \
 	continue;							      \