[glibc/release/2.27/master] iconv: Accept redundant shift sequences in IBM1364 [BZ #26224]

[glibc/release/2.27/master] iconv: Accept redundant shift sequences in IBM1364 [BZ #26224]

[Dmitry Levin]

https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d8ae6c00a945aadc971cf2c33d9fb0ed31ebb5df

commit d8ae6c00a945aadc971cf2c33d9fb0ed31ebb5df
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>
    (cherry picked from commit 9a99c682144bdbd40792ebf822fe9264e0376fb5)

Diff:
---
 NEWS                    |  6 ++++++
 iconv/tst-iconv_prog.sh | 16 ++++++++++------
 iconvdata/ibm1364.c     | 14 ++------------
 3 files changed, 18 insertions(+), 18 deletions(-)

diff --git a/NEWS b/NEWS
index cc36b41dba..95d69cd07e 100644
--- a/NEWS
+++ b/NEWS
@@ -92,6 +92,10 @@ Security related changes:
   corruption when they were passed a pseudo-zero argument.  Reported by Guido
   Vranken / ForAllSecure Mayhem.
 
+  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:
 
   [6889] 'PWD' mentioned but not specified
@@ -183,6 +187,8 @@ The following bugs are resolved with this release:
   [25423] Array overflow in backtrace on powerpc
   [25487] sinl() stack corruption from crafted input (CVE-2020-10029)
   [25620] libc: Signed comparison vulnerability in the ARMv7 memcpy() (CVE-2020-6096)
+  [26224] iconv hangs when converting some invalid inputs from several IBM
+    character sets (CVE-2020-27618)
   [26383] bind_textdomain_codeset doesn't accept //TRANSLIT anymore
 
 \f
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 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;							      \