[glibc] iconv: Accept redundant shift sequences in IBM1364 [BZ #26224]

[glibc] iconv: Accept redundant shift sequences in IBM1364 [BZ #26224]

[Arjun Shankar]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9a99c682144bdbd40792ebf822fe9264e0376fb5

commit 9a99c682144bdbd40792ebf822fe9264e0376fb5
Author: Arjun Shankar <arjun@redhat.com>
Date:   Wed Nov 4 12:19:38 2020 +0100

    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>

Diff:
---
 NEWS                    |  4 +++-
 iconv/tst-iconv_prog.sh | 16 ++++++++++------
 iconvdata/ibm1364.c     | 14 ++------------
 3 files changed, 15 insertions(+), 19 deletions(-)

diff --git a/NEWS b/NEWS
index 4307c4b1b0..0335fb98e5 100644
--- a/NEWS
+++ b/NEWS
@@ -58,7 +58,9 @@ Changes to build and runtime requirements:
 
 Security related changes:
 
-  [Add security related changes here]
+  CVE-2020-27618: An infinite loop has been fixed in the iconv program when
+  invoked with input containing redundant shift sequences in the IBM1364,
+  IBM1371, IBM1388, IBM1390, or IBM1399 character sets.
 
 The following bugs are resolved with this release:
 
diff --git a/iconv/tst-iconv_prog.sh b/iconv/tst-iconv_prog.sh
index 8298136b7f..d8db7b335c 100644
--- a/iconv/tst-iconv_prog.sh
+++ b/iconv/tst-iconv_prog.sh
@@ -102,12 +102,16 @@ hangarray=(
 "\x00\x80;-c;IBM1161;UTF-8//TRANSLIT//IGNORE"
 "\x00\xdb;-c;IBM1162;UTF-8//TRANSLIT//IGNORE"
 "\x00\x70;-c;IBM12712;UTF-8//TRANSLIT//IGNORE"
-# These are known hangs that are yet to be fixed:
-# "\x00\x0f;-c;IBM1364;UTF-8"
-# "\x00\x0f;-c;IBM1371;UTF-8"
-# "\x00\x0f;-c;IBM1388;UTF-8"
-# "\x00\x0f;-c;IBM1390;UTF-8"
-# "\x00\x0f;-c;IBM1399;UTF-8"
+"\x00\x0f;-c;IBM1364;UTF-8"
+"\x0e\x0e;-c;IBM1364;UTF-8"
+"\x00\x0f;-c;IBM1371;UTF-8"
+"\x0e\x0e;-c;IBM1371;UTF-8"
+"\x00\x0f;-c;IBM1388;UTF-8"
+"\x0e\x0e;-c;IBM1388;UTF-8"
+"\x00\x0f;-c;IBM1390;UTF-8"
+"\x0e\x0e;-c;IBM1390;UTF-8"
+"\x00\x0f;-c;IBM1399;UTF-8"
+"\x0e\x0e;-c;IBM1399;UTF-8"
 "\x00\x53;-c;IBM16804;UTF-8//TRANSLIT//IGNORE"
 "\x00\x41;-c;IBM274;UTF-8//TRANSLIT//IGNORE"
 "\x00\x41;-c;IBM275;UTF-8//TRANSLIT//IGNORE"
diff --git a/iconvdata/ibm1364.c b/iconvdata/ibm1364.c
index 49e7267ab4..521f0825b7 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;							      \