[iconv] Fix CVE-2020-27618. Contributes to JB#54165
[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 email@example.com