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Make implementation of SASLprep compliant for ASCII characters

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This commit makes our implementation of SASLprep() compliant with RFC
3454 (Stringprep) and RFC 4013 (SASLprep).  Originally, as introduced in
60f11b87a2, the operation considered a password made of only ASCII
characters as valid, performing an optimization for this case to skip
the internal NFKC transformation.

However, the RFCs listed above use a different definition, with the
following characters being prohibited:
- 0x00~0x1F (0~31), control characters.
- 0x7F (127, DEL).

In its SCRAM protocol, Postgres has the idea to apply a password as-is
if SASLprep() is not a success, so this change is safe on
backward-compatibility grounds:
- A libpq client with the compliant SASLprep can connect to a server
with a non-compliant SASLprep.
- A libpq client with the non-compliant SASLprep can connect to a server
with a compliant SASLprep.

This commit removes the all-ASCII optimization used in pg_saslprep() and
applies SASLprep even if a password is made only of ASCII characters,
making the operation compatible with the RFC.  All the in-core callers
of pg_saslprep() do that:
- pg_be_scram_build_secret() in auth-scram.c, when generating a
SCRAM verifier for rolpassword in the backend.
- scram_init() in fe-auth-scram.c, when starting the SASL exchange.
- pg_fe_scram_build_secret() in fe-auth-scram.c, when generating a SCRAM
verifier for the frontend with libpq, to generate it for a ALTER/CREATE
ROLE command for example.

The test module test_saslprep shows the difference this change is
leading to.

Author: Michael Paquier <michael@paquier.xyz>
Reviewed-by: John Naylor <johncnaylorls@gmail.com>
Discussion: https://postgr.es/m/aaEJ-El2seZHeFcG@paquier.xyz
This commit is contained in:
Michael Paquier 2026-03-24 08:29:23 +09:00
parent 2e123e3c2b
commit 3d10ece612
3 changed files with 34 additions and 49 deletions
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12
src/common/saslprep.c
View file

@ -1061,18 +1061,6 @@ pg_saslprep(const char *input, char **output)
/* Ensure we return *output as NULL on failure */
*output = NULL;
/*
* Quick check if the input is pure ASCII. An ASCII string requires no
* further processing.
*/
if (pg_is_ascii(input))
{
*output = STRDUP(input);
if (!(*output))
goto oom;
return SASLPREP_SUCCESS;
}
/*
* Convert the input from UTF-8 to an array of Unicode codepoints.
*

66
src/test/modules/test_saslprep/expected/test_saslprep.out
View file

@ -19,38 +19,38 @@ SELECT
FROM generate_series(0,127) AS a;
dat | byt | saslprep
----------+------+-------------------
<NUL> | \x00 | ("\\x",SUCCESS)
<CTL_1> | \x01 | ("\\x01",SUCCESS)
<CTL_2> | \x02 | ("\\x02",SUCCESS)
<CTL_3> | \x03 | ("\\x03",SUCCESS)
<CTL_4> | \x04 | ("\\x04",SUCCESS)
<CTL_5> | \x05 | ("\\x05",SUCCESS)
<CTL_6> | \x06 | ("\\x06",SUCCESS)
<CTL_7> | \x07 | ("\\x07",SUCCESS)
<CTL_8> | \x08 | ("\\x08",SUCCESS)
<CTL_9> | \x09 | ("\\x09",SUCCESS)
<CTL_10> | \x0a | ("\\x0a",SUCCESS)
<CTL_11> | \x0b | ("\\x0b",SUCCESS)
<CTL_12> | \x0c | ("\\x0c",SUCCESS)
<CTL_13> | \x0d | ("\\x0d",SUCCESS)
<CTL_14> | \x0e | ("\\x0e",SUCCESS)
<CTL_15> | \x0f | ("\\x0f",SUCCESS)
<CTL_16> | \x10 | ("\\x10",SUCCESS)
<CTL_17> | \x11 | ("\\x11",SUCCESS)
<CTL_18> | \x12 | ("\\x12",SUCCESS)
<CTL_19> | \x13 | ("\\x13",SUCCESS)
<CTL_20> | \x14 | ("\\x14",SUCCESS)
<CTL_21> | \x15 | ("\\x15",SUCCESS)
<CTL_22> | \x16 | ("\\x16",SUCCESS)
<CTL_23> | \x17 | ("\\x17",SUCCESS)
<CTL_24> | \x18 | ("\\x18",SUCCESS)
<CTL_25> | \x19 | ("\\x19",SUCCESS)
<CTL_26> | \x1a | ("\\x1a",SUCCESS)
<CTL_27> | \x1b | ("\\x1b",SUCCESS)
<CTL_28> | \x1c | ("\\x1c",SUCCESS)
<CTL_29> | \x1d | ("\\x1d",SUCCESS)
<CTL_30> | \x1e | ("\\x1e",SUCCESS)
<CTL_31> | \x1f | ("\\x1f",SUCCESS)
<NUL> | \x00 | (,PROHIBITED)
<CTL_1> | \x01 | (,PROHIBITED)
<CTL_2> | \x02 | (,PROHIBITED)
<CTL_3> | \x03 | (,PROHIBITED)
<CTL_4> | \x04 | (,PROHIBITED)
<CTL_5> | \x05 | (,PROHIBITED)
<CTL_6> | \x06 | (,PROHIBITED)
<CTL_7> | \x07 | (,PROHIBITED)
<CTL_8> | \x08 | (,PROHIBITED)
<CTL_9> | \x09 | (,PROHIBITED)
<CTL_10> | \x0a | (,PROHIBITED)
<CTL_11> | \x0b | (,PROHIBITED)
<CTL_12> | \x0c | (,PROHIBITED)
<CTL_13> | \x0d | (,PROHIBITED)
<CTL_14> | \x0e | (,PROHIBITED)
<CTL_15> | \x0f | (,PROHIBITED)
<CTL_16> | \x10 | (,PROHIBITED)
<CTL_17> | \x11 | (,PROHIBITED)
<CTL_18> | \x12 | (,PROHIBITED)
<CTL_19> | \x13 | (,PROHIBITED)
<CTL_20> | \x14 | (,PROHIBITED)
<CTL_21> | \x15 | (,PROHIBITED)
<CTL_22> | \x16 | (,PROHIBITED)
<CTL_23> | \x17 | (,PROHIBITED)
<CTL_24> | \x18 | (,PROHIBITED)
<CTL_25> | \x19 | (,PROHIBITED)
<CTL_26> | \x1a | (,PROHIBITED)
<CTL_27> | \x1b | (,PROHIBITED)
<CTL_28> | \x1c | (,PROHIBITED)
<CTL_29> | \x1d | (,PROHIBITED)
<CTL_30> | \x1e | (,PROHIBITED)
<CTL_31> | \x1f | (,PROHIBITED)
| \x20 | ("\\x20",SUCCESS)
! | \x21 | ("\\x21",SUCCESS)
" | \x22 | ("\\x22",SUCCESS)
@ -146,7 +146,7 @@ SELECT
| | \x7c | ("\\x7c",SUCCESS)
} | \x7d | ("\\x7d",SUCCESS)
~ | \x7e | ("\\x7e",SUCCESS)
<DEL> | \x7f | ("\\x7f",SUCCESS)
<DEL> | \x7f | (,PROHIBITED)
(128 rows)
DROP EXTENSION test_saslprep;

5
src/test/modules/test_saslprep/t/001_saslprep_ranges.pl
View file

@ -25,15 +25,12 @@ $node->safe_psql('postgres', 'CREATE EXTENSION test_saslprep;');
# Among all the valid UTF-8 codepoint ranges, our implementation of
# SASLprep should never return an empty password if the operation is
# considered a success.
# The only exception is currently the nul character, prohibited in
# input of CREATE/ALTER ROLE.
my $result = $node->safe_psql(
'postgres', qq[SELECT * FROM test_saslprep_ranges()
WHERE status = 'SUCCESS' AND res IN (NULL, '')
]);
is($result, 'U+0000|SUCCESS|\x00|\x',
"valid codepoints returning an empty password");
is($result, '', "valid codepoints returning an empty password");
$node->stop;
done_testing();