Thread: pgsql: Disallow newlines in parameter values to be set in ALTER SYSTEM.

Disallow newlines in parameter values to be set in ALTER SYSTEM.

As noted by Julian Schauder in bug #14063, the configuration-file parser
doesn't support embedded newlines in string literals.  While there might
someday be a good reason to remove that restriction, there doesn't seem
to be one right now.  However, ALTER SYSTEM SET could accept strings
containing newlines, since many of the variable-specific value-checking
routines would just see a newline as whitespace.  This led to writing a
postgresql.auto.conf file that was broken and had to be removed manually.

Pending a reason to work harder, just throw an error if someone tries this.

In passing, fix several places in the ALTER SYSTEM logic that failed to
provide an errcode() for an ereport(), and thus would falsely log the
failure as an internal XX000 error.

Back-patch to 9.4 where ALTER SYSTEM was introduced.

Branch
------
REL9_5_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/f3d17491c49362b78da0c1a5b0691821dcc8c435

Modified Files
--------------
src/backend/utils/misc/guc.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)


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On Tue, Apr 5, 2016 at 1:05 AM, Tom Lane <tgl@sss.pgh.pa.us> wrote:

Disallow newlines in parameter values to be set in ALTER SYSTEM.

it's also fixed problem with setting parameter to ''. Before

alter system SET shared_preload_libraries = '';

produced wrong postgresql.auto.conf and the only way was to use RESET

alter system RESET shared_preload_libraries;

As noted by Julian Schauder in bug #14063, the configuration-file parser
doesn't support embedded newlines in string literals.  While there might
someday be a good reason to remove that restriction, there doesn't seem
to be one right now.  However, ALTER SYSTEM SET could accept strings
containing newlines, since many of the variable-specific value-checking
routines would just see a newline as whitespace.  This led to writing a
postgresql.auto.conf file that was broken and had to be removed manually.

Pending a reason to work harder, just throw an error if someone tries this.

In passing, fix several places in the ALTER SYSTEM logic that failed to
provide an errcode() for an ereport(), and thus would falsely log the
failure as an internal XX000 error.

Back-patch to 9.4 where ALTER SYSTEM was introduced.

Branch
------
REL9_5_STABLE

Details
-------
http://git.postgresql.org/pg/commitdiff/f3d17491c49362b78da0c1a5b0691821dcc8c435

Modified Files
--------------
src/backend/utils/misc/guc.c | 23 ++++++++++++++++++++---
1 file changed, 20 insertions(+), 3 deletions(-)


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