## Examine and fix ezxml errors
re: Issue https://github.com/Unidata/netcdf-c/issues/2119
Multiple security issues were found in ezxml (see above Issue).
* CVE-2021-31598
* CVE-2021-31348 / CVE-2021-31347
* CVE-2021-31229
* CVE-2021-30485
* CVE-2021-26222
* CVE-2021-26221
* CVE-2021-26220
* CVE-2019-20202
* CVE-2019-20201
* CVE-2019-20200
* CVE-2019-20199
* CVE-2019-20198
* CVE-2019-20007
* CVE-2019-20006
* CVE-2019-20005
In addition, moved ezxml to libdispatch.
## Examine and fix selected oss-fuzz detected errors
Note that most of these errors are in the libsrc .m4 generated
code so fixing them is difficult. It would nice if we could tell
oss-fuzz to skip those files. They are old and crufty and
probably need a complete refactor.
Issue|Status
-----|------
35382|Fixed; old bug
35398|Closed by OSS-Fuzz
35442|Guarantee alloc > 0 or error; Old bug
35721|Assert failure; ok
35992|Fixed; old bug
36038|Fixed; old bug
36129|Unfixed; old bug
36229|Fixed by adding assert; old bug
37476|Unfixed; old bug
37824|Assert Failure; ok
38300|Closed by OSS-Fuzz
38537|Unfixed; old bug
38658|Unfixed; old bug
38699|Fixed maybe; old bug
38772|Nature of error is unclear, suspect that it results from using too large a type.
39248|Need more information
39394|Unfixed; old bug
On some versions of the HDF5 find_package call, it sets `HDF5_C_LIBRARIES` and `HDF5_HL_LIBRARIES`, but does not set the `HDF5_C_LIBRARY` or `HDF5_HL_LIBRARY` to anything. Control then falls out of the if block with these unset and it falls into the default setting at line 792. This does not include the path, so then when the later `CHECK_LIBRARY_EXISTS` calls are run, they do not have the full path to the library and will not link correctly. Since the link fails, the code defaults to thinking that none of the symbols are defined.
I don't think this change will have any affect since it only sets the symbols if they are unset.
Fixes an issue with strlen() reading outside the stack allocated buffer
by NC4_HDF5_inq_att, when reading a name whose length is NC_MAX_NAME.
Fixes https://bugs.chromium.org/p/oss-fuzz/issues/detail?id=39189 found
on GDAL
==1895951== Conditional jump or move depends on uninitialised value(s)
==1895951== at 0x483EF58: strlen (in /usr/lib/x86_64-linux-gnu/valgrind/vgpreload_memcheck-amd64-linux.so)
==1895951== by 0x48EF73E: ncindexlookup (ncindex.c:60)
==1895951== by 0x48E81DF: nc4_find_grp_att (nc4internal.c:587)
==1895951== by 0x48E5B39: nc4_get_att_ptrs (nc4attr.c:72)
==1895951== by 0x48F98A0: NC4_HDF5_inq_att (hdf5attr.c:818)
==1895951== by 0x48847F7: nc_inq_att (dattinq.c:91)
==1895951== by 0x10D693: pr_att (ncdump.c:767)
==1895951== by 0x110ADB: do_ncdump_rec (ncdump.c:1887)
==1895951== by 0x1112F1: do_ncdump (ncdump.c:2038)
==1895951== by 0x11248B: main (ncdump.c:2478)
==1895951==
==1895951== Use of uninitialised value of size 8
==1895951== at 0x48A24E4: crc64_little (dcrc64.c:173)
==1895951== by 0x48A27F4: NC_crc64 (dcrc64.c:229)
==1895951== by 0x4892D49: NC_hashmapkey (nchashmap.c:159)
==1895951== by 0x489314B: NC_hashmapget (nchashmap.c:263)
==1895951== by 0x48EF75F: ncindexlookup (ncindex.c:60)
==1895951== by 0x48E81DF: nc4_find_grp_att (nc4internal.c:587)
==1895951== by 0x48E5B39: nc4_get_att_ptrs (nc4attr.c:72)
==1895951== by 0x48F98A0: NC4_HDF5_inq_att (hdf5attr.c:818)
==1895951== by 0x48847F7: nc_inq_att (dattinq.c:91)
==1895951== by 0x10D693: pr_att (ncdump.c:767)
==1895951== by 0x110ADB: do_ncdump_rec (ncdump.c:1887)
==1895951== by 0x1112F1: do_ncdump (ncdump.c:2038)
==1895951==
Filter support has three goals:
1. Use the existing HDF5 filter implementations,
2. Allow filter metadata to be stored in the NumCodecs metadata format used by Zarr,
3. Allow filters to be used even when HDF5 is disabled
Detailed usage directions are define in docs/filters.md.
For now, the existing filter API is left in place. So filters
are defined using ''nc_def_var_filter'' using the HDF5 style
where the id and parameters are unsigned integers.
This is a big change since filters affect many parts of the code.
In the following, the terms "compressor" and "filter" and "codec" are generally
used synonomously.
### Filter-Related Changes:
* In order to support dynamic loading of shared filter libraries, a new library was added in the libncpoco directory; it helps to isolate dynamic loading across multiple platforms.
* Provide a json parsing library for use by plugins; this is created by merging libdispatch/ncjson.c with include/ncjson.h.
* Add a new _Codecs attribute to allow clients to see what codecs are being used; let ncdump -s print it out.
* Provide special headers to help support compilation of HDF5 filters when HDF5 is not enabled: netcdf_filter_hdf5_build.h and netcdf_filter_build.h.
* Add a number of new test to test the new nczarr filters.
* Let ncgen parse _Codecs attribute, although it is ignored.
### Plugin directory changes:
* Add support for the Blosc compressor; this is essential because it is the most common compressor used in Zarr datasets. This also necessitated adding a CMake FindBlosc.cmake file
* Add NCZarr support for the big-four filters provided by HDF5: shuffle, fletcher32, deflate (zlib), and szip
* Add a Codec defaulter (see docs/filters.md) for the big four filters.
* Make plugins work with windows by properly adding __declspec declaration.
### Misc. Non-Filter Changes
* Replace most uses of USE_NETCDF4 (deprecated) with USE_HDF5.
* Improve support for caching
* More fixes for path conversion code
* Fix misc. memory leaks
* Add new utility -- ncdump/ncpathcvt -- that does more or less the same thing as cygpath.
* Add a number of new test to test the non-filter fixes.
* Update the parsers
* Convert most instances of '#ifdef _MSC_VER' to '#ifdef _WIN32'
re: Issue https://github.com/Unidata/netcdf-c/issues/2096
The methods nc_set_var_chunk_cache_ints and nc_def_var_chunking_ints
are Fortran entry points for accessing the cache. They are not defined
if netcdf-c is built with --disable-hdf5.
Fix is to create dummy versions that do nothing and return NC_NOERR
when invoked. These dummy versions are defined when USE_HDF5 is false.
