[glibc/google/grte/v5-2.27/master] iconv: Accept redundant shift sequences in IBM1364 [BZ #26224]

[Stan Shebs <shebs@sourceware.org>]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=9babbdefdcda0df4a7772c0b7896e7c3f0d3e12a

commit 9babbdefdcda0df4a7772c0b7896e7c3f0d3e12a
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:
---
 iconvdata/ibm1364.c | 14 ++------------
 1 file changed, 2 insertions(+), 12 deletions(-)

diff --git a/iconvdata/ibm1364.c b/iconvdata/ibm1364.c
index b833273aa8..27900c4307 100644
--- a/iconvdata/ibm1364.c
+++ b/iconvdata/ibm1364.c
@@ -157,24 +157,14 @@ 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;							      \