<feed xmlns='http://www.w3.org/2005/Atom'>
<title>delta/postgresql.git/contrib/pgcrypto/Makefile, branch master</title>
<subtitle>git.postgresql.org: git/postgresql.git
</subtitle>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/'/>
<entry>
<title>pgcrypto: Remove non-OpenSSL support</title>
<updated>2021-11-05T13:06:59+00:00</updated>
<author>
<name>Peter Eisentraut</name>
<email>peter@eisentraut.org</email>
</author>
<published>2021-11-05T12:59:42+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=db7d1a7b0530e8cbd045744e1c75b0e63fb6916f'/>
<id>db7d1a7b0530e8cbd045744e1c75b0e63fb6916f</id>
<content type='text'>
pgcrypto had internal implementations of some encryption algorithms,
as an alternative to calling out to OpenSSL.  These were rarely used,
since most production installations are built with OpenSSL.  Moreover,
maintaining parallel code paths makes the code more complex and
difficult to maintain.

This patch removes these internal implementations.  Now, pgcrypto is
only built if OpenSSL support is configured.

Reviewed-by: Daniel Gustafsson &lt;daniel@yesql.se&gt;
Discussion: https://www.postgresql.org/message-id/flat/0b42f1df-8cba-6a30-77d7-acc241cc88c1%40enterprisedb.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
pgcrypto had internal implementations of some encryption algorithms,
as an alternative to calling out to OpenSSL.  These were rarely used,
since most production installations are built with OpenSSL.  Moreover,
maintaining parallel code paths makes the code more complex and
difficult to maintain.

This patch removes these internal implementations.  Now, pgcrypto is
only built if OpenSSL support is configured.

Reviewed-by: Daniel Gustafsson &lt;daniel@yesql.se&gt;
Discussion: https://www.postgresql.org/message-id/flat/0b42f1df-8cba-6a30-77d7-acc241cc88c1%40enterprisedb.com
</pre>
</div>
</content>
</entry>
<entry>
<title>Introduce --with-ssl={openssl} as a configure option</title>
<updated>2021-02-01T10:19:44+00:00</updated>
<author>
<name>Michael Paquier</name>
<email>michael@paquier.xyz</email>
</author>
<published>2021-02-01T10:19:44+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=fe61df7f82aa6e0879476146dbe1da9c89b4946b'/>
<id>fe61df7f82aa6e0879476146dbe1da9c89b4946b</id>
<content type='text'>
This is a replacement for the existing --with-openssl, extending the
logic to make easier the addition of new SSL libraries.  The grammar is
chosen to be similar to --with-uuid, where multiple values can be
chosen, with "openssl" as the only supported value for now.

The original switch, --with-openssl, is kept for compatibility.

Author: Daniel Gustafsson, Michael Paquier
Reviewed-by: Jacob Champion
Discussion: https://postgr.es/m/FAB21FC8-0F62-434F-AA78-6BD9336D630A@yesql.se
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This is a replacement for the existing --with-openssl, extending the
logic to make easier the addition of new SSL libraries.  The grammar is
chosen to be similar to --with-uuid, where multiple values can be
chosen, with "openssl" as the only supported value for now.

The original switch, --with-openssl, is kept for compatibility.

Author: Daniel Gustafsson, Michael Paquier
Reviewed-by: Jacob Champion
Discussion: https://postgr.es/m/FAB21FC8-0F62-434F-AA78-6BD9336D630A@yesql.se
</pre>
</div>
</content>
</entry>
<entry>
<title>Introduce SHA1 implementations in the cryptohash infrastructure</title>
<updated>2021-01-23T02:33:04+00:00</updated>
<author>
<name>Michael Paquier</name>
<email>michael@paquier.xyz</email>
</author>
<published>2021-01-23T02:33:04+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=a8ed6bb8f4cf259b95c1bff5da09a8f4c79dca46'/>
<id>a8ed6bb8f4cf259b95c1bff5da09a8f4c79dca46</id>
<content type='text'>
With this commit, SHA1 goes through the implementation provided by
OpenSSL via EVP when building the backend with it, and uses as fallback
implementation KAME which was located in pgcrypto and already shaped for
an integration with a set of init, update and final routines.
Structures and routines have been renamed to make things consistent with
the fallback implementations of MD5 and SHA2.

uuid-ossp has used for ages a shortcut with pgcrypto to fetch a copy of
SHA1 if needed.  This was built depending on the build options within
./configure, so this cleans up some code and removes the build
dependency between pgcrypto and uuid-ossp.

Note that this will help with the refactoring of HMAC, as pgcrypto
offers the option to use MD5, SHA1 or SHA2, so only the second option
was missing to make that possible.

Author: Michael Paquier
Reviewed-by: Heikki Linnakangas
Discussion: https://postgr.es/m/X9HXKTgrvJvYO7Oh@paquier.xyz
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
With this commit, SHA1 goes through the implementation provided by
OpenSSL via EVP when building the backend with it, and uses as fallback
implementation KAME which was located in pgcrypto and already shaped for
an integration with a set of init, update and final routines.
Structures and routines have been renamed to make things consistent with
the fallback implementations of MD5 and SHA2.

uuid-ossp has used for ages a shortcut with pgcrypto to fetch a copy of
SHA1 if needed.  This was built depending on the build options within
./configure, so this cleans up some code and removes the build
dependency between pgcrypto and uuid-ossp.

Note that this will help with the refactoring of HMAC, as pgcrypto
offers the option to use MD5, SHA1 or SHA2, so only the second option
was missing to make that possible.

Author: Michael Paquier
Reviewed-by: Heikki Linnakangas
Discussion: https://postgr.es/m/X9HXKTgrvJvYO7Oh@paquier.xyz
</pre>
</div>
</content>
</entry>
<entry>
<title>Refactor MD5 implementations according to new cryptohash infrastructure</title>
<updated>2020-12-10T02:59:10+00:00</updated>
<author>
<name>Michael Paquier</name>
<email>michael@paquier.xyz</email>
</author>
<published>2020-12-10T02:59:10+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=b67b57a966af0c4a9547ac6fff334d3c256d9c2a'/>
<id>b67b57a966af0c4a9547ac6fff334d3c256d9c2a</id>
<content type='text'>
This commit heavily reorganizes the MD5 implementations that exist in
the tree in various aspects.

First, MD5 is added to the list of options available in cryptohash.c and
cryptohash_openssl.c.  This means that if building with OpenSSL, EVP is
used for MD5 instead of the fallback implementation that Postgres had
for ages.  With the recent refactoring work for cryptohash functions,
this change is straight-forward.  If not building with OpenSSL, a
fallback implementation internal to src/common/ is used.

Second, this reduces the number of MD5 implementations present in the
tree from two to one, by moving the KAME implementation from pgcrypto to
src/common/, and by removing the implementation that existed in
src/common/.  KAME was already structured with an init/update/final set
of routines by pgcrypto (see original pgcrypto/md5.h) for compatibility
with OpenSSL, so moving it to src/common/ has proved to be a
straight-forward move, requiring no actual manipulation of the internals
of each routine.  Some benchmarking has not shown any performance gap
between both implementations.

Similarly to the fallback implementation used for SHA2, the fallback
implementation of MD5 is moved to src/common/md5.c with an internal
header called md5_int.h for the init, update and final routines.  This
gets then consumed by cryptohash.c.

The original routines used for MD5-hashed passwords are moved to a
separate file called md5_common.c, also in src/common/, aimed at being
shared between all MD5 implementations as utility routines to keep
compatibility with any code relying on them.

Like the SHA2 changes, this commit had its round of tests on both Linux
and Windows, across all versions of OpenSSL supported on HEAD, with and
even without OpenSSL.

Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20201106073434.GA4961@paquier.xyz
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This commit heavily reorganizes the MD5 implementations that exist in
the tree in various aspects.

First, MD5 is added to the list of options available in cryptohash.c and
cryptohash_openssl.c.  This means that if building with OpenSSL, EVP is
used for MD5 instead of the fallback implementation that Postgres had
for ages.  With the recent refactoring work for cryptohash functions,
this change is straight-forward.  If not building with OpenSSL, a
fallback implementation internal to src/common/ is used.

Second, this reduces the number of MD5 implementations present in the
tree from two to one, by moving the KAME implementation from pgcrypto to
src/common/, and by removing the implementation that existed in
src/common/.  KAME was already structured with an init/update/final set
of routines by pgcrypto (see original pgcrypto/md5.h) for compatibility
with OpenSSL, so moving it to src/common/ has proved to be a
straight-forward move, requiring no actual manipulation of the internals
of each routine.  Some benchmarking has not shown any performance gap
between both implementations.

Similarly to the fallback implementation used for SHA2, the fallback
implementation of MD5 is moved to src/common/md5.c with an internal
header called md5_int.h for the init, update and final routines.  This
gets then consumed by cryptohash.c.

The original routines used for MD5-hashed passwords are moved to a
separate file called md5_common.c, also in src/common/, aimed at being
shared between all MD5 implementations as utility routines to keep
compatibility with any code relying on them.

Like the SHA2 changes, this commit had its round of tests on both Linux
and Windows, across all versions of OpenSSL supported on HEAD, with and
even without OpenSSL.

Author: Michael Paquier
Reviewed-by: Daniel Gustafsson
Discussion: https://postgr.es/m/20201106073434.GA4961@paquier.xyz
</pre>
</div>
</content>
</entry>
<entry>
<title>Remove support for upgrading extensions from "unpackaged" state.</title>
<updated>2020-02-19T21:59:14+00:00</updated>
<author>
<name>Tom Lane</name>
<email>tgl@sss.pgh.pa.us</email>
</author>
<published>2020-02-19T21:59:14+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=70a7732007bc4689f4c7a44e738eb2d892dac1e3'/>
<id>70a7732007bc4689f4c7a44e738eb2d892dac1e3</id>
<content type='text'>
Andres Freund pointed out that allowing non-superusers to run
"CREATE EXTENSION ... FROM unpackaged" has security risks, since
the unpackaged-to-1.0 scripts don't try to verify that the existing
objects they're modifying are what they expect.  Just attaching such
objects to an extension doesn't seem too dangerous, but some of them
do more than that.

We could have resolved this, perhaps, by still requiring superuser
privilege to use the FROM option.  However, it's fair to ask just what
we're accomplishing by continuing to lug the unpackaged-to-1.0 scripts
forward.  None of them have received any real testing since 9.1 days,
so they may not even work anymore (even assuming that one could still
load the previous "loose" object definitions into a v13 database).
And an installation that's trying to go from pre-9.1 to v13 or later
in one jump is going to have worse compatibility problems than whether
there's a trivial way to convert their contrib modules into extension
style.

Hence, let's just drop both those scripts and the core-code support
for "CREATE EXTENSION ... FROM".

Discussion: https://postgr.es/m/20200213233015.r6rnubcvl4egdh5r@alap3.anarazel.de
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Andres Freund pointed out that allowing non-superusers to run
"CREATE EXTENSION ... FROM unpackaged" has security risks, since
the unpackaged-to-1.0 scripts don't try to verify that the existing
objects they're modifying are what they expect.  Just attaching such
objects to an extension doesn't seem too dangerous, but some of them
do more than that.

We could have resolved this, perhaps, by still requiring superuser
privilege to use the FROM option.  However, it's fair to ask just what
we're accomplishing by continuing to lug the unpackaged-to-1.0 scripts
forward.  None of them have received any real testing since 9.1 days,
so they may not even work anymore (even assuming that one could still
load the previous "loose" object definitions into a v13 database).
And an installation that's trying to go from pre-9.1 to v13 or later
in one jump is going to have worse compatibility problems than whether
there's a trivial way to convert their contrib modules into extension
style.

Hence, let's just drop both those scripts and the core-code support
for "CREATE EXTENSION ... FROM".

Discussion: https://postgr.es/m/20200213233015.r6rnubcvl4egdh5r@alap3.anarazel.de
</pre>
</div>
</content>
</entry>
<entry>
<title>Split all OBJS style lines in makefiles into one-line-per-entry style.</title>
<updated>2019-11-05T22:41:07+00:00</updated>
<author>
<name>Andres Freund</name>
<email>andres@anarazel.de</email>
</author>
<published>2019-11-05T22:41:07+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=01368e5d9da77099b38aac527b01b85cc7869b25'/>
<id>01368e5d9da77099b38aac527b01b85cc7869b25</id>
<content type='text'>
When maintaining or merging patches, one of the most common sources
for conflicts are the list of objects in makefiles. Especially when
the split across lines has been changed on both sides, which is
somewhat common due to attempting to stay below 80 columns, those
conflicts are unnecessarily laborious to resolve.

By splitting, and alphabetically sorting, OBJS style lines into one
object per line, conflicts should be less frequent, and easier to
resolve when they still occur.

Author: Andres Freund
Discussion: https://postgr.es/m/20191029200901.vww4idgcxv74cwes@alap3.anarazel.de
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When maintaining or merging patches, one of the most common sources
for conflicts are the list of objects in makefiles. Especially when
the split across lines has been changed on both sides, which is
somewhat common due to attempting to stay below 80 columns, those
conflicts are unnecessarily laborious to resolve.

By splitting, and alphabetically sorting, OBJS style lines into one
object per line, conflicts should be less frequent, and easier to
resolve when they still occur.

Author: Andres Freund
Discussion: https://postgr.es/m/20191029200901.vww4idgcxv74cwes@alap3.anarazel.de
</pre>
</div>
</content>
</entry>
<entry>
<title>Import changes from IMath versions (1.3, 1.29].</title>
<updated>2019-02-16T21:12:28+00:00</updated>
<author>
<name>Noah Misch</name>
<email>noah@leadboat.com</email>
</author>
<published>2019-02-16T21:12:28+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=48e24ba6b7fd3bfd156b51e8d768fd48df0d288b'/>
<id>48e24ba6b7fd3bfd156b51e8d768fd48df0d288b</id>
<content type='text'>
Upstream fixed bugs over the years, but none are confirmed to have
affected pgcrypto.  We're better off naively tracking upstream than
reactively maintaining a twelve-year-old snapshot of upstream.  Add a
header comment describing the synchronization procedure.  Discard use of
INVERT_COMPARE_RESULT(); the domain of the comparisons in question is
{-1,0,1}, controlled entirely by code in imath.c.

Andrew Gierth reviewed the Makefile change.  Tom Lane reviewed the
synchronization procedure description.

Discussion: https://postgr.es/m/20190203035704.GA6226@rfd.leadboat.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Upstream fixed bugs over the years, but none are confirmed to have
affected pgcrypto.  We're better off naively tracking upstream than
reactively maintaining a twelve-year-old snapshot of upstream.  Add a
header comment describing the synchronization procedure.  Discard use of
INVERT_COMPARE_RESULT(); the domain of the comparisons in question is
{-1,0,1}, controlled entirely by code in imath.c.

Andrew Gierth reviewed the Makefile change.  Tom Lane reviewed the
synchronization procedure description.

Discussion: https://postgr.es/m/20190203035704.GA6226@rfd.leadboat.com
</pre>
</div>
</content>
</entry>
<entry>
<title>Support SCRAM-SHA-256 authentication (RFC 5802 and 7677).</title>
<updated>2017-03-07T12:25:40+00:00</updated>
<author>
<name>Heikki Linnakangas</name>
<email>heikki.linnakangas@iki.fi</email>
</author>
<published>2017-03-07T12:25:40+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=818fd4a67d610991757b610755e3065fb99d80a5'/>
<id>818fd4a67d610991757b610755e3065fb99d80a5</id>
<content type='text'>
This introduces a new generic SASL authentication method, similar to the
GSS and SSPI methods. The server first tells the client which SASL
authentication mechanism to use, and then the mechanism-specific SASL
messages are exchanged in AuthenticationSASLcontinue and PasswordMessage
messages. Only SCRAM-SHA-256 is supported at the moment, but this allows
adding more SASL mechanisms in the future, without changing the overall
protocol.

Support for channel binding, aka SCRAM-SHA-256-PLUS is left for later.

The SASLPrep algorithm, for pre-processing the password, is not yet
implemented. That could cause trouble, if you use a password with
non-ASCII characters, and a client library that does implement SASLprep.
That will hopefully be added later.

Authorization identities, as specified in the SCRAM-SHA-256 specification,
are ignored. SET SESSION AUTHORIZATION provides more or less the same
functionality, anyway.

If a user doesn't exist, perform a "mock" authentication, by constructing
an authentic-looking challenge on the fly. The challenge is derived from
a new system-wide random value, "mock authentication nonce", which is
created at initdb, and stored in the control file. We go through these
motions, in order to not give away the information on whether the user
exists, to unauthenticated users.

Bumps PG_CONTROL_VERSION, because of the new field in control file.

Patch by Michael Paquier and Heikki Linnakangas, reviewed at different
stages by Robert Haas, Stephen Frost, David Steele, Aleksander Alekseev,
and many others.

Discussion: https://www.postgresql.org/message-id/CAB7nPqRbR3GmFYdedCAhzukfKrgBLTLtMvENOmPrVWREsZkF8g%40mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAB7nPqSMXU35g%3DW9X74HVeQp0uvgJxvYOuA4A-A3M%2B0wfEBv-w%40mail.gmail.com
Discussion: https://www.postgresql.org/message-id/55192AFE.6080106@iki.fi
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This introduces a new generic SASL authentication method, similar to the
GSS and SSPI methods. The server first tells the client which SASL
authentication mechanism to use, and then the mechanism-specific SASL
messages are exchanged in AuthenticationSASLcontinue and PasswordMessage
messages. Only SCRAM-SHA-256 is supported at the moment, but this allows
adding more SASL mechanisms in the future, without changing the overall
protocol.

Support for channel binding, aka SCRAM-SHA-256-PLUS is left for later.

The SASLPrep algorithm, for pre-processing the password, is not yet
implemented. That could cause trouble, if you use a password with
non-ASCII characters, and a client library that does implement SASLprep.
That will hopefully be added later.

Authorization identities, as specified in the SCRAM-SHA-256 specification,
are ignored. SET SESSION AUTHORIZATION provides more or less the same
functionality, anyway.

If a user doesn't exist, perform a "mock" authentication, by constructing
an authentic-looking challenge on the fly. The challenge is derived from
a new system-wide random value, "mock authentication nonce", which is
created at initdb, and stored in the control file. We go through these
motions, in order to not give away the information on whether the user
exists, to unauthenticated users.

Bumps PG_CONTROL_VERSION, because of the new field in control file.

Patch by Michael Paquier and Heikki Linnakangas, reviewed at different
stages by Robert Haas, Stephen Frost, David Steele, Aleksander Alekseev,
and many others.

Discussion: https://www.postgresql.org/message-id/CAB7nPqRbR3GmFYdedCAhzukfKrgBLTLtMvENOmPrVWREsZkF8g%40mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAB7nPqSMXU35g%3DW9X74HVeQp0uvgJxvYOuA4A-A3M%2B0wfEBv-w%40mail.gmail.com
Discussion: https://www.postgresql.org/message-id/55192AFE.6080106@iki.fi
</pre>
</div>
</content>
</entry>
<entry>
<title>Refactor SHA2 functions and move them to src/common/.</title>
<updated>2017-03-07T12:23:49+00:00</updated>
<author>
<name>Heikki Linnakangas</name>
<email>heikki.linnakangas@iki.fi</email>
</author>
<published>2017-03-07T12:23:49+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=273c458a2b3a0fb73968020ea5e9e35eb6928967'/>
<id>273c458a2b3a0fb73968020ea5e9e35eb6928967</id>
<content type='text'>
This way both frontend and backends can use them. The functions are taken
from pgcrypto, which now fetches the source files it needs from
src/common/.

A new interface is designed for the SHA2 functions, which allow linking
to either OpenSSL or the in-core stuff taken from KAME as needed.

Michael Paquier, reviewed by Robert Haas.

Discussion: https://www.postgresql.org/message-id/CAB7nPqTGKuTM5jiZriHrNaQeVqp5e_iT3X4BFLWY_HyHxLvySQ%40mail.gmail.com
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This way both frontend and backends can use them. The functions are taken
from pgcrypto, which now fetches the source files it needs from
src/common/.

A new interface is designed for the SHA2 functions, which allow linking
to either OpenSSL or the in-core stuff taken from KAME as needed.

Michael Paquier, reviewed by Robert Haas.

Discussion: https://www.postgresql.org/message-id/CAB7nPqTGKuTM5jiZriHrNaQeVqp5e_iT3X4BFLWY_HyHxLvySQ%40mail.gmail.com
</pre>
</div>
</content>
</entry>
<entry>
<title>Replace PostmasterRandom() with a stronger source, second attempt.</title>
<updated>2016-12-05T11:42:59+00:00</updated>
<author>
<name>Heikki Linnakangas</name>
<email>heikki.linnakangas@iki.fi</email>
</author>
<published>2016-12-05T11:42:59+00:00</published>
<link rel='alternate' type='text/html' href='http://trove.baserock.org/cgit/delta/postgresql.git/commit/?id=fe0a0b5993dfe24e4b3bcf52fa64ff41a444b8f1'/>
<id>fe0a0b5993dfe24e4b3bcf52fa64ff41a444b8f1</id>
<content type='text'>
This adds a new routine, pg_strong_random() for generating random bytes,
for use in both frontend and backend. At the moment, it's only used in
the backend, but the upcoming SCRAM authentication patches need strong
random numbers in libpq as well.

pg_strong_random() is based on, and replaces, the existing implementation
in pgcrypto. It can acquire strong random numbers from a number of sources,
depending on what's available:

- OpenSSL RAND_bytes(), if built with OpenSSL
- On Windows, the native cryptographic functions are used
- /dev/urandom

Unlike the current pgcrypto function, the source is chosen by configure.
That makes it easier to test different implementations, and ensures that
we don't accidentally fall back to a less secure implementation, if the
primary source fails. All of those methods are quite reliable, it would be
pretty surprising for them to fail, so we'd rather find out by failing
hard.

If no strong random source is available, we fall back to using erand48(),
seeded from current timestamp, like PostmasterRandom() was. That isn't
cryptographically secure, but allows us to still work on platforms that
don't have any of the above stronger sources. Because it's not very secure,
the built-in implementation is only used if explicitly requested with
--disable-strong-random.

This replaces the more complicated Fortuna algorithm we used to have in
pgcrypto, which is unfortunate, but all modern platforms have /dev/urandom,
so it doesn't seem worth the maintenance effort to keep that. pgcrypto
functions that require strong random numbers will be disabled with
--disable-strong-random.

Original patch by Magnus Hagander, tons of further work by Michael Paquier
and me.

Discussion: https://www.postgresql.org/message-id/CAB7nPqRy3krN8quR9XujMVVHYtXJ0_60nqgVc6oUk8ygyVkZsA@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAB7nPqRWkNYRRPJA7-cF+LfroYV10pvjdz6GNvxk-Eee9FypKA@mail.gmail.com
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This adds a new routine, pg_strong_random() for generating random bytes,
for use in both frontend and backend. At the moment, it's only used in
the backend, but the upcoming SCRAM authentication patches need strong
random numbers in libpq as well.

pg_strong_random() is based on, and replaces, the existing implementation
in pgcrypto. It can acquire strong random numbers from a number of sources,
depending on what's available:

- OpenSSL RAND_bytes(), if built with OpenSSL
- On Windows, the native cryptographic functions are used
- /dev/urandom

Unlike the current pgcrypto function, the source is chosen by configure.
That makes it easier to test different implementations, and ensures that
we don't accidentally fall back to a less secure implementation, if the
primary source fails. All of those methods are quite reliable, it would be
pretty surprising for them to fail, so we'd rather find out by failing
hard.

If no strong random source is available, we fall back to using erand48(),
seeded from current timestamp, like PostmasterRandom() was. That isn't
cryptographically secure, but allows us to still work on platforms that
don't have any of the above stronger sources. Because it's not very secure,
the built-in implementation is only used if explicitly requested with
--disable-strong-random.

This replaces the more complicated Fortuna algorithm we used to have in
pgcrypto, which is unfortunate, but all modern platforms have /dev/urandom,
so it doesn't seem worth the maintenance effort to keep that. pgcrypto
functions that require strong random numbers will be disabled with
--disable-strong-random.

Original patch by Magnus Hagander, tons of further work by Michael Paquier
and me.

Discussion: https://www.postgresql.org/message-id/CAB7nPqRy3krN8quR9XujMVVHYtXJ0_60nqgVc6oUk8ygyVkZsA@mail.gmail.com
Discussion: https://www.postgresql.org/message-id/CAB7nPqRWkNYRRPJA7-cF+LfroYV10pvjdz6GNvxk-Eee9FypKA@mail.gmail.com
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