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Some authentication methods allowed it, others did not. In the client-side, libpq does not even try to authenticate with an empty password, which makes using empty passwords hazardous: an administrator might think that an account with an empty password cannot be used to log in, because psql doesn't allow it, and not realize that a different client would in fact allow it. To clear that confusion and to be be consistent, disallow empty passwords in all authentication methods. All the authentication methods that used plaintext authentication over the wire, except for BSD authentication, already checked that the password received from the user was not empty. To avoid forgetting it in the future again, move the check to the recv_password_packet function. That only forbids using an empty password with plaintext authentication, however. MD5 and SCRAM need a different fix: * In stable branches, check that the MD5 hash stored for the user does not not correspond to an empty string. This adds some overhead to MD5 authentication, because the server needs to compute an extra MD5 hash, but it is not noticeable in practice. * In HEAD, modify CREATE and ALTER ROLE to clear the password if an empty string, or a password hash that corresponds to an empty string, is specified. The user-visible behavior is the same as in the stable branches, the user cannot log in, but it seems better to stop the empty password from entering the system in the first place. Secondly, it is fairly expensive to check that a SCRAM hash doesn't correspond to an empty string, because computing a SCRAM hash is much more expensive than an MD5 hash by design, so better avoid doing that on every authentication. We could clear the password on CREATE/ALTER ROLE also in stable branches, but we would still need to check at authentication time, because even if we prevent empty passwords from being stored in pg_authid, there might be existing ones there already. Reported by Jeroen van der Ham, Ben de Graaff and Jelte Fennema. Security: CVE-2017-7546
79 lines
3.2 KiB
SQL
79 lines
3.2 KiB
SQL
--
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-- Tests for password verifiers
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--
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-- Tests for GUC password_encryption
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SET password_encryption = 'novalue'; -- error
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SET password_encryption = true; -- ok
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SET password_encryption = 'md5'; -- ok
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SET password_encryption = 'scram-sha-256'; -- ok
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-- consistency of password entries
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SET password_encryption = 'md5';
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CREATE ROLE regress_passwd1 PASSWORD 'role_pwd1';
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SET password_encryption = 'on';
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CREATE ROLE regress_passwd2 PASSWORD 'role_pwd2';
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SET password_encryption = 'scram-sha-256';
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CREATE ROLE regress_passwd3 PASSWORD 'role_pwd3';
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CREATE ROLE regress_passwd4 PASSWORD NULL;
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-- check list of created entries
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--
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-- The scram verifier will look something like:
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-- SCRAM-SHA-256$4096:E4HxLGtnRzsYwg==$6YtlR4t69SguDiwFvbVgVZtuz6gpJQQqUMZ7IQJK5yI=:ps75jrHeYU4lXCcXI4O8oIdJ3eO8o2jirjruw9phBTo=
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--
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-- Since the salt is random, the exact value stored will be different on every test
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-- run. Use a regular expression to mask the changing parts.
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SELECT rolname, regexp_replace(rolpassword, '(SCRAM-SHA-256)\$(\d+):([a-zA-Z0-9+/=]+)\$([a-zA-Z0-9+=/]+):([a-zA-Z0-9+/=]+)', '\1$\2:<salt>$<storedkey>:<serverkey>') as rolpassword_masked
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FROM pg_authid
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WHERE rolname LIKE 'regress_passwd%'
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ORDER BY rolname, rolpassword;
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-- Rename a role
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ALTER ROLE regress_passwd2 RENAME TO regress_passwd2_new;
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-- md5 entry should have been removed
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SELECT rolname, rolpassword
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FROM pg_authid
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WHERE rolname LIKE 'regress_passwd2_new'
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ORDER BY rolname, rolpassword;
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ALTER ROLE regress_passwd2_new RENAME TO regress_passwd2;
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-- Change passwords with ALTER USER. With plaintext or already-encrypted
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-- passwords.
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SET password_encryption = 'md5';
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-- encrypt with MD5
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ALTER ROLE regress_passwd2 PASSWORD 'foo';
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-- already encrypted, use as they are
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ALTER ROLE regress_passwd1 PASSWORD 'md5cd3578025fe2c3d7ed1b9a9b26238b70';
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ALTER ROLE regress_passwd3 PASSWORD 'SCRAM-SHA-256$4096:VLK4RMaQLCvNtQ==$6YtlR4t69SguDiwFvbVgVZtuz6gpJQQqUMZ7IQJK5yI=:ps75jrHeYU4lXCcXI4O8oIdJ3eO8o2jirjruw9phBTo=';
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SET password_encryption = 'scram-sha-256';
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-- create SCRAM verifier
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ALTER ROLE regress_passwd4 PASSWORD 'foo';
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-- already encrypted with MD5, use as it is
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CREATE ROLE regress_passwd5 PASSWORD 'md5e73a4b11df52a6068f8b39f90be36023';
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SELECT rolname, regexp_replace(rolpassword, '(SCRAM-SHA-256)\$(\d+):([a-zA-Z0-9+/=]+)\$([a-zA-Z0-9+=/]+):([a-zA-Z0-9+/=]+)', '\1$\2:<salt>$<storedkey>:<serverkey>') as rolpassword_masked
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FROM pg_authid
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WHERE rolname LIKE 'regress_passwd%'
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ORDER BY rolname, rolpassword;
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-- An empty password is not allowed, in any form
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CREATE ROLE regress_passwd_empty PASSWORD '';
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ALTER ROLE regress_passwd_empty PASSWORD 'md585939a5ce845f1a1b620742e3c659e0a';
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ALTER ROLE regress_passwd_empty PASSWORD 'SCRAM-SHA-256$4096:hpFyHTUsSWcR7O9P$LgZFIt6Oqdo27ZFKbZ2nV+vtnYM995pDh9ca6WSi120=:qVV5NeluNfUPkwm7Vqat25RjSPLkGeoZBQs6wVv+um4=';
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SELECT rolpassword FROM pg_authid WHERE rolname='regress_passwd_empty';
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DROP ROLE regress_passwd1;
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DROP ROLE regress_passwd2;
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DROP ROLE regress_passwd3;
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DROP ROLE regress_passwd4;
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DROP ROLE regress_passwd5;
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DROP ROLE regress_passwd_empty;
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-- all entries should have been removed
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SELECT rolname, rolpassword
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FROM pg_authid
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WHERE rolname LIKE 'regress_passwd%'
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ORDER BY rolname, rolpassword;
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