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Michael Paquier 56c5a069e0 Fix buffer overrun in unicode string normalization with empty input
PostgreSQL 13 and newer versions are directly impacted by that through
the SQL function normalize(), which would cause a call of this function
to write one byte past its allocation if using in input an empty
string after recomposing the string with NFC and NFKC.  Older versions
(v10~v12) are not directly affected by this problem as the only code
path using normalization is SASLprep in SCRAM authentication that
forbids the case of an empty string, but let's make the code more robust
anyway there so as any out-of-core callers of this function are covered.

The solution chosen to fix this issue is simple, with the addition of a
fast-exit path if the decomposed string is found as empty.  This would
only happen for an empty string as at its lowest level a codepoint would
be decomposed as itself if it has no entry in the decomposition table or
if it has a decomposition size of 0.

Some tests are added to cover this issue in v13~.  Note that an empty
string has always been considered as normalized (grammar "IS NF[K]{C,D}
NORMALIZED", through the SQL function is_normalized()) for all the
operations allowed (NFC, NFD, NFKC and NFKD) since this feature has been
introduced as of 2991ac5.  This behavior is unchanged but some tests are
added in v13~ to check after that.

I have also checked "make normalization-check" in src/common/unicode/,
while on it (works in 13~, and breaks in older stable branches
independently of this commit).

The release notes should just mention this commit for v13~.

Reported-by: Matthijs van der Vleuten
Discussion: https://postgr.es/m/17277-0c527a373794e802@postgresql.org
Backpatch-through: 10
2021-11-11 15:02:01 +09:00
config jit: configure: Explicitly reference 'native' component. 2020-12-07 18:40:27 -08:00
contrib Don't try to read a multi-GB pg_stat_statements file in one call. 2021-10-31 19:13:48 -04:00
doc Doc: improve protocol spec for logical replication Type messages. 2021-11-10 13:12:58 -05:00
src Fix buffer overrun in unicode string normalization with empty input 2021-11-11 15:02:01 +09:00
.dir-locals.el Make Emacs perl-mode indent more like perltidy. 2019-01-13 11:32:36 -08:00
.gitattributes Remove contrib/tsearch2. 2017-02-13 11:06:11 -05:00
.gitignore Support for optimizing and emitting code in LLVM JIT provider. 2018-03-22 11:05:22 -07:00
aclocal.m4 Remove configure-time probe for DocBook DTD. 2020-11-30 15:24:13 -05:00
configure Clean up compilation warnings coming from PL/Perl with clang-12~ 2021-11-11 10:51:23 +09:00
configure.in Clean up compilation warnings coming from PL/Perl with clang-12~ 2021-11-11 10:51:23 +09:00
COPYRIGHT Update copyright for 2021 2021-01-02 13:06:24 -05:00
GNUmakefile.in Add new make targets world-bin and install-world-bin 2021-07-01 14:52:40 -04:00
HISTORY Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
Makefile Don't unset MAKEFLAGS in non-GNU Makefile. 2019-06-25 09:40:20 +12:00
README Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00
README.git Change documentation references to PG website to use https: not http: 2017-05-20 21:50:47 -04:00

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