Restrict password hash length.

Commit 6aa44060a3 removed pg_authid's TOAST table because the only
varlena column is rolpassword, which cannot be de-TOASTed during
authentication because we haven't selected a database yet and
cannot read pg_class.  Since that change, attempts to set password
hashes that require out-of-line storage will fail with a "row is
too big" error.  This error message might be confusing to users.

This commit places a limit on the length of password hashes so that
attempts to set long password hashes will fail with a more
user-friendly error.  The chosen limit of 512 bytes should be
sufficient to avoid "row is too big" errors independent of BLCKSZ,
but it should also be lenient enough for all reasonable use-cases
(or at least all the use-cases we could imagine).

Reviewed-by: Tom Lane, Jonathan Katz, Michael Paquier, Jacob Champion
Discussion: https://postgr.es/m/89e8649c-eb74-db25-7945-6d6b23992394%40gmail.com

2 files changed, 11 insertions, 0 deletions

diff --git a/src/test/regress/expected/password.out b/src/test/regress/expected/password.out
index 924d6e001d4..df3857460c2 100644
--- a/src/test/regress/expected/password.out
+++ b/src/test/regress/expected/password.out
@@ -127,6 +127,13 @@ SELECT rolname, rolpassword not like '%A6xHKoH/494E941doaPOYg==%' as is_rolpassw
  regress_passwd_sha_len2 | t
 (3 rows)
 
+-- Test that valid hashes that are too long are rejected
+CREATE ROLE regress_passwd10 PASSWORD 'SCRAM-SHA-256$000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004096:wNFxNSk1hAXBkgub8py3bg==$65zC6E+R0U7tiYTC9+Wtq4Thw6gUDj3eDCINij8TflU=:rC1I7tcVugrHEY2DT0iPjGyjM4aJxkMM9n8WBxtUtHU=';
+ERROR:  encrypted password is too long
+DETAIL:  Encrypted passwords must be no longer than 512 bytes.
+ALTER ROLE regress_passwd9 PASSWORD 'SCRAM-SHA-256$000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004096:wNFxNSk1hAXBkgub8py3bg==$65zC6E+R0U7tiYTC9+Wtq4Thw6gUDj3eDCINij8TflU=:rC1I7tcVugrHEY2DT0iPjGyjM4aJxkMM9n8WBxtUtHU=';
+ERROR:  encrypted password is too long
+DETAIL:  Encrypted passwords must be no longer than 512 bytes.
 DROP ROLE regress_passwd1;
 DROP ROLE regress_passwd2;
 DROP ROLE regress_passwd3;
diff --git a/src/test/regress/sql/password.sql b/src/test/regress/sql/password.sql
index bb82aa4aa24..e7a98045450 100644
--- a/src/test/regress/sql/password.sql
+++ b/src/test/regress/sql/password.sql
@@ -95,6 +95,10 @@ SELECT rolname, rolpassword not like '%A6xHKoH/494E941doaPOYg==%' as is_rolpassw
     WHERE rolname LIKE 'regress_passwd_sha_len%'
     ORDER BY rolname;
 
+-- Test that valid hashes that are too long are rejected
+CREATE ROLE regress_passwd10 PASSWORD 'SCRAM-SHA-256$000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004096:wNFxNSk1hAXBkgub8py3bg==$65zC6E+R0U7tiYTC9+Wtq4Thw6gUDj3eDCINij8TflU=:rC1I7tcVugrHEY2DT0iPjGyjM4aJxkMM9n8WBxtUtHU=';
+ALTER ROLE regress_passwd9 PASSWORD 'SCRAM-SHA-256$000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000000004096:wNFxNSk1hAXBkgub8py3bg==$65zC6E+R0U7tiYTC9+Wtq4Thw6gUDj3eDCINij8TflU=:rC1I7tcVugrHEY2DT0iPjGyjM4aJxkMM9n8WBxtUtHU=';
+
 DROP ROLE regress_passwd1;
 DROP ROLE regress_passwd2;
 DROP ROLE regress_passwd3;