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Replace PostmasterRandom() with a stronger source, second attempt.
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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lines changed

‎configure

+109
Original file line numberDiff line numberDiff line change
@@ -739,6 +739,7 @@ GENHTML
739739
LCOV
740740
GCOV
741741
enable_debug
742+
enable_strong_random
742743
enable_rpath
743744
default_port
744745
WANTED_LANGUAGES
@@ -806,6 +807,7 @@ with_pgport
806807
enable_rpath
807808
enable_spinlocks
808809
enable_atomics
810+
enable_strong_random
809811
enable_debug
810812
enable_profiling
811813
enable_coverage
@@ -1478,6 +1480,7 @@ Optional Features:
14781480
executables
14791481
--disable-spinlocks do not use spinlocks
14801482
--disable-atomics do not use atomic operations
1483+
--disable-strong-random do not use a strong random number source
14811484
--enable-debug build with debugging symbols (-g)
14821485
--enable-profiling build with profiling enabled
14831486
--enable-coverage build with coverage testing instrumentation
@@ -3192,6 +3195,34 @@ fi
31923195

31933196

31943197

3198+
#
3199+
# Random number generation
3200+
#
3201+
3202+
3203+
# Check whether --enable-strong-random was given.
3204+
if test "${enable_strong_random+set}" = set; then :
3205+
enableval=$enable_strong_random;
3206+
case $enableval in
3207+
yes)
3208+
:
3209+
;;
3210+
no)
3211+
:
3212+
;;
3213+
*)
3214+
as_fn_error $? "no argument expected for --enable-strong-random option" "$LINENO" 5
3215+
;;
3216+
esac
3217+
3218+
else
3219+
enable_strong_random=yes
3220+
3221+
fi
3222+
3223+
3224+
3225+
31953226
#
31963227
# --enable-debug adds -g to compiler flags
31973228
#
@@ -14982,6 +15013,84 @@ $as_echo "#define USE_WIN32_SHARED_MEMORY 1" >>confdefs.h
1498215013
SHMEM_IMPLEMENTATION="src/backend/port/win32_shmem.c"
1498315014
fi
1498415015

15016+
# Select random number source
15017+
#
15018+
# You can override this logic by setting the appropriate USE_*RANDOM flag to 1
15019+
# in the template or configure command line.
15020+
15021+
# If not selected manually, try to select a source automatically.
15022+
if test "$enable_strong_random" = "yes" && test x"$USE_OPENSSL_RANDOM" = x"" && test x"$USE_WIN32_RANDOM" = x"" && test x"$USE_DEV_URANDOM" = x"" ; then
15023+
if test x"$with_openssl" = x"yes" ; then
15024+
USE_OPENSSL_RANDOM=1
15025+
elif test "$PORTNAME" = x"win32" ; then
15026+
USE_WIN32_RANDOM=1
15027+
else
15028+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking for /dev/urandom" >&5
15029+
$as_echo_n "checking for /dev/urandom... " >&6; }
15030+
if ${ac_cv_file__dev_urandom+:} false; then :
15031+
$as_echo_n "(cached) " >&6
15032+
else
15033+
test "$cross_compiling" = yes &&
15034+
as_fn_error $? "cannot check for file existence when cross compiling" "$LINENO" 5
15035+
if test -r "/dev/urandom"; then
15036+
ac_cv_file__dev_urandom=yes
15037+
else
15038+
ac_cv_file__dev_urandom=no
15039+
fi
15040+
fi
15041+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: $ac_cv_file__dev_urandom" >&5
15042+
$as_echo "$ac_cv_file__dev_urandom" >&6; }
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if test "x$ac_cv_file__dev_urandom" = xyes; then :
15044+
15045+
fi
15046+
15047+
15048+
if test x"$ac_cv_file__dev_urandom" = x"yes" ; then
15049+
USE_DEV_URANDOM=1
15050+
fi
15051+
fi
15052+
fi
15053+
15054+
{ $as_echo "$as_me:${as_lineno-$LINENO}: checking which random number source to use" >&5
15055+
$as_echo_n "checking which random number source to use... " >&6; }
15056+
if test "$enable_strong_random" = yes ; then
15057+
if test x"$USE_OPENSSL_RANDOM" = x"1" ; then
15058+
15059+
$as_echo "#define USE_OPENSSL_RANDOM 1" >>confdefs.h
15060+
15061+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: OpenSSL" >&5
15062+
$as_echo "OpenSSL" >&6; }
15063+
elif test x"$USE_WIN32_RANDOM" = x"1" ; then
15064+
15065+
$as_echo "#define USE_WIN32_RANDOM 1" >>confdefs.h
15066+
15067+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: Windows native" >&5
15068+
$as_echo "Windows native" >&6; }
15069+
elif test x"$USE_DEV_URANDOM" = x"1" ; then
15070+
15071+
$as_echo "#define USE_DEV_URANDOM 1" >>confdefs.h
15072+
15073+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: /dev/urandom" >&5
15074+
$as_echo "/dev/urandom" >&6; }
15075+
else
15076+
as_fn_error $? "
15077+
no source of strong random numbers was found
15078+
PostgreSQL can use OpenSSL or /dev/urandom as a source of random numbers,
15079+
for authentication protocols. You can use --disable-strong-random to use of a built-in
15080+
pseudo random number generator, but that may be insecure." "$LINENO" 5
15081+
fi
15082+
15083+
$as_echo "#define HAVE_STRONG_RANDOM 1" >>confdefs.h
15084+
15085+
else
15086+
{ $as_echo "$as_me:${as_lineno-$LINENO}: result: weak builtin PRNG" >&5
15087+
$as_echo "weak builtin PRNG" >&6; }
15088+
{ $as_echo "$as_me:${as_lineno-$LINENO}: WARNING:
15089+
*** Not using a strong random number source may be insecure." >&5
15090+
$as_echo "$as_me: WARNING:
15091+
*** Not using a strong random number source may be insecure." >&2;}
15092+
fi
15093+
1498515094
# If not set in template file, set bytes to use libc memset()
1498615095
if test x"$MEMSET_LOOP_LIMIT" = x"" ; then
1498715096
MEMSET_LOOP_LIMIT=1024

‎configure.in

+52
Original file line numberDiff line numberDiff line change
@@ -193,6 +193,13 @@ PGAC_ARG_BOOL(enable, spinlocks, yes,
193193
PGAC_ARG_BOOL(enable, atomics, yes,
194194
[do not use atomic operations])
195195

196+
#
197+
# Random number generation
198+
#
199+
PGAC_ARG_BOOL(enable, strong-random, yes,
200+
[do not use a strong random number source])
201+
AC_SUBST(enable_strong_random)
202+
196203
#
197204
# --enable-debug adds -g to compiler flags
198205
#
@@ -1965,6 +1972,51 @@ else
19651972
SHMEM_IMPLEMENTATION="src/backend/port/win32_shmem.c"
19661973
fi
19671974

1975+
# Select random number source
1976+
#
1977+
# You can override this logic by setting the appropriate USE_*RANDOM flag to 1
1978+
# in the template or configure command line.
1979+
1980+
# If not selected manually, try to select a source automatically.
1981+
if test "$enable_strong_random" = "yes" && test x"$USE_OPENSSL_RANDOM" = x"" && test x"$USE_WIN32_RANDOM" = x"" && test x"$USE_DEV_URANDOM" = x"" ; then
1982+
if test x"$with_openssl" = x"yes" ; then
1983+
USE_OPENSSL_RANDOM=1
1984+
elif test "$PORTNAME" = x"win32" ; then
1985+
USE_WIN32_RANDOM=1
1986+
else
1987+
AC_CHECK_FILE([/dev/urandom], [], [])
1988+
1989+
if test x"$ac_cv_file__dev_urandom" = x"yes" ; then
1990+
USE_DEV_URANDOM=1
1991+
fi
1992+
fi
1993+
fi
1994+
1995+
AC_MSG_CHECKING([which random number source to use])
1996+
if test "$enable_strong_random" = yes ; then
1997+
if test x"$USE_OPENSSL_RANDOM" = x"1" ; then
1998+
AC_DEFINE(USE_OPENSSL_RANDOM, 1, [Define to use OpenSSL for random number generation])
1999+
AC_MSG_RESULT([OpenSSL])
2000+
elif test x"$USE_WIN32_RANDOM" = x"1" ; then
2001+
AC_DEFINE(USE_WIN32_RANDOM, 1, [Define to use native Windows API for random number generation])
2002+
AC_MSG_RESULT([Windows native])
2003+
elif test x"$USE_DEV_URANDOM" = x"1" ; then
2004+
AC_DEFINE(USE_DEV_URANDOM, 1, [Define to use /dev/urandom for random number generation])
2005+
AC_MSG_RESULT([/dev/urandom])
2006+
else
2007+
AC_MSG_ERROR([
2008+
no source of strong random numbers was found
2009+
PostgreSQL can use OpenSSL or /dev/urandom as a source of random numbers,
2010+
for authentication protocols. You can use --disable-strong-random to use of a built-in
2011+
pseudo random number generator, but that may be insecure.])
2012+
fi
2013+
AC_DEFINE(HAVE_STRONG_RANDOM, 1, [Define to use have a strong random number source])
2014+
else
2015+
AC_MSG_RESULT([weak builtin PRNG])
2016+
AC_MSG_WARN([
2017+
*** Not using a strong random number source may be insecure.])
2018+
fi
2019+
19682020
# If not set in template file, set bytes to use libc memset()
19692021
if test x"$MEMSET_LOOP_LIMIT" = x"" ; then
19702022
MEMSET_LOOP_LIMIT=1024

‎contrib/pgcrypto/Makefile

+1-1
Original file line numberDiff line numberDiff line change
@@ -1,7 +1,7 @@
11
# contrib/pgcrypto/Makefile
22

33
INT_SRCS = md5.c sha1.c sha2.c internal.c internal-sha2.c blf.c rijndael.c \
4-
fortuna.c random.c pgp-mpi-internal.c imath.c
4+
pgp-mpi-internal.c imath.c
55
INT_TESTS = sha2
66

77
OSSL_SRCS = openssl.c pgp-mpi-openssl.c

‎contrib/pgcrypto/expected/pgp-compression_1.out

+42
Original file line numberDiff line numberDiff line change
@@ -0,0 +1,42 @@
1+
--
2+
-- PGP compression support
3+
--
4+
select pgp_sym_decrypt(dearmor('
5+
-----BEGIN PGP MESSAGE-----
6+
7+
ww0ECQMCsci6AdHnELlh0kQB4jFcVwHMJg0Bulop7m3Mi36s15TAhBo0AnzIrRFrdLVCkKohsS6+
8+
DMcmR53SXfLoDJOv/M8uKj3QSq7oWNIp95pxfA==
9+
=tbSn
10+
-----END PGP MESSAGE-----
11+
'), 'key', 'expect-compress-algo=1');
12+
pgp_sym_decrypt
13+
-----------------
14+
Secret message
15+
(1 row)
16+
17+
select pgp_sym_decrypt(
18+
pgp_sym_encrypt('Secret message', 'key', 'compress-algo=0'),
19+
'key', 'expect-compress-algo=0');
20+
ERROR: pg_random_bytes() is not supported by this build
21+
DETAIL: This functionality requires a source of strong random numbers
22+
HINT: You need to rebuild PostgreSQL using --enable-strong-random
23+
select pgp_sym_decrypt(
24+
pgp_sym_encrypt('Secret message', 'key', 'compress-algo=1'),
25+
'key', 'expect-compress-algo=1');
26+
ERROR: pg_random_bytes() is not supported by this build
27+
DETAIL: This functionality requires a source of strong random numbers
28+
HINT: You need to rebuild PostgreSQL using --enable-strong-random
29+
select pgp_sym_decrypt(
30+
pgp_sym_encrypt('Secret message', 'key', 'compress-algo=2'),
31+
'key', 'expect-compress-algo=2');
32+
ERROR: pg_random_bytes() is not supported by this build
33+
DETAIL: This functionality requires a source of strong random numbers
34+
HINT: You need to rebuild PostgreSQL using --enable-strong-random
35+
-- level=0 should turn compression off
36+
select pgp_sym_decrypt(
37+
pgp_sym_encrypt('Secret message', 'key',
38+
'compress-algo=2, compress-level=0'),
39+
'key', 'expect-compress-algo=0');
40+
ERROR: pg_random_bytes() is not supported by this build
41+
DETAIL: This functionality requires a source of strong random numbers
42+
HINT: You need to rebuild PostgreSQL using --enable-strong-random

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