pgsql: libq support for sslpassword connection param, DER format keys

libq support for sslpassword connection param,  DER format keys

This patch providies for support for password protected SSL client
keys in libpq, and for DER format keys, both encrypted and unencrypted.
There is a new connection parameter sslpassword, which is supplied to
the OpenSSL libraries via a callback function. The callback function can
also be set by an application by calling PQgetSSLKeyPassHook(). There is
also a function to retreive the connection setting, PQsslpassword().

Craig Ringer and Andrew Dunstan

Reviewed by: Greg Nancarrow

Discussion: https://postgr.es/m/f7ee88ed-95c4-95c1-d4bf-7b415363ab62@2ndQuadrant.com

Branch
------
master

Details
-------
https://git.postgresql.org/pg/commitdiff/4dc63552109f65cebbe168203bd62c5e4c753162

Modified Files
--------------
contrib/dblink/expected/dblink.out        |   2 +-
doc/src/sgml/libpq.sgml                   | 134 ++++++++++++++++++++++++++++++
doc/src/sgml/postgres-fdw.sgml            |   2 +-
src/interfaces/libpq/exports.txt          |   4 +
src/interfaces/libpq/fe-connect.c         |  14 ++++
src/interfaces/libpq/fe-secure-openssl.c  |  99 +++++++++++++++++++++-
src/interfaces/libpq/libpq-fe.h           |   9 ++
src/interfaces/libpq/libpq-int.h          |   2 +
src/test/ssl/Makefile                     |  22 ++++-
src/test/ssl/ssl/client-der.key           | Bin 0 -> 1191 bytes
src/test/ssl/ssl/client-encrypted-der.key | Bin 0 -> 1191 bytes
src/test/ssl/ssl/client-encrypted-pem.key |  30 +++++++
src/test/ssl/t/001_ssltests.pl            |  75 +++++++++++++++--
13 files changed, 376 insertions(+), 17 deletions(-)