Make contrib modules' installation scripts more secure.

Hostile objects located within the installation-time search_path could
capture references in an extension's installation or upgrade script.
If the extension is being installed with superuser privileges, this
opens the door to privilege escalation.  While such hazards have existed
all along, their urgency increases with the v13 "trusted extensions"
feature, because that lets a non-superuser control the installation path
for a superuser-privileged script.  Therefore, make a number of changes
to make such situations more secure:

* Tweak the construction of the installation-time search_path to ensure
that references to objects in pg_catalog can't be subverted; and
explicitly add pg_temp to the end of the path to prevent attacks using
temporary objects.

* Disable check_function_bodies within installation/upgrade scripts,
so that any security gaps in SQL-language or PL-language function bodies
cannot create a risk of unwanted installation-time code execution.

* Adjust lookup of type input/receive functions and join estimator
functions to complain if there are multiple candidate functions.  This
prevents capture of references to functions whose signature is not the
first one checked; and it's arguably more user-friendly anyway.

* Modify various contrib upgrade scripts to ensure that catalog
modification queries are executed with secure search paths.  (These
are in-place modifications with no extension version changes, since
it is the update process itself that is at issue, not the end result.)

Extensions that depend on other extensions cannot be made fully secure
by these methods alone; therefore, revert the "trusted" marking that
commit eb67623c applied to earthdistance and hstore_plperl, pending
some better solution to that set of issues.

Also add documentation around these issues, to help extension authors
write secure installation scripts.

Patch by me, following an observation by Andres Freund; thanks
to Noah Misch for review.

Security: CVE-2020-14350

contrib/btree_gist/btree_gist--1.1--1.2.sql

@@ -8,56 +8,72 @@
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
 
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
+
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
 ('gbt_oid_distance(internal,oid,int2,oid)', '{internal,oid,int2,oid,internal}'),
 ('gbt_oid_union(bytea,internal)', '{internal,internal}'),
-('gbt_oid_same(internal,internal,internal)', '{gbtreekey8,gbtreekey8,internal}'),
+('gbt_oid_same(internal,internal,internal)', '{SCH.gbtreekey8,SCH.gbtreekey8,internal}'),
 ('gbt_int2_distance(internal,int2,int2,oid)', '{internal,int2,int2,oid,internal}'),
 ('gbt_int2_union(bytea,internal)', '{internal,internal}'),
-('gbt_int2_same(internal,internal,internal)', '{gbtreekey4,gbtreekey4,internal}'),
+('gbt_int2_same(internal,internal,internal)', '{SCH.gbtreekey4,SCH.gbtreekey4,internal}'),
 ('gbt_int4_distance(internal,int4,int2,oid)', '{internal,int4,int2,oid,internal}'),
 ('gbt_int4_union(bytea,internal)', '{internal,internal}'),
-('gbt_int4_same(internal,internal,internal)', '{gbtreekey8,gbtreekey8,internal}'),
+('gbt_int4_same(internal,internal,internal)', '{SCH.gbtreekey8,SCH.gbtreekey8,internal}'),
 ('gbt_int8_distance(internal,int8,int2,oid)', '{internal,int8,int2,oid,internal}'),
 ('gbt_int8_union(bytea,internal)', '{internal,internal}'),
-('gbt_int8_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}'),
+('gbt_int8_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}'),
 ('gbt_float4_distance(internal,float4,int2,oid)', '{internal,float4,int2,oid,internal}'),
 ('gbt_float4_union(bytea,internal)', '{internal,internal}'),
-('gbt_float4_same(internal,internal,internal)', '{gbtreekey8,gbtreekey8,internal}'),
+('gbt_float4_same(internal,internal,internal)', '{SCH.gbtreekey8,SCH.gbtreekey8,internal}'),
 ('gbt_float8_distance(internal,float8,int2,oid)', '{internal,float8,int2,oid,internal}'),
 ('gbt_float8_union(bytea,internal)', '{internal,internal}'),
-('gbt_float8_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}'),
+('gbt_float8_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}'),
 ('gbt_ts_distance(internal,timestamp,int2,oid)', '{internal,timestamp,int2,oid,internal}'),
 ('gbt_tstz_distance(internal,timestamptz,int2,oid)', '{internal,timestamptz,int2,oid,internal}'),
 ('gbt_ts_union(bytea,internal)', '{internal,internal}'),
-('gbt_ts_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}'),
+('gbt_ts_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}'),
 ('gbt_time_distance(internal,time,int2,oid)', '{internal,time,int2,oid,internal}'),
 ('gbt_time_union(bytea,internal)', '{internal,internal}'),
-('gbt_time_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}'),
+('gbt_time_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}'),
 ('gbt_date_distance(internal,date,int2,oid)', '{internal,date,int2,oid,internal}'),
 ('gbt_date_union(bytea,internal)', '{internal,internal}'),
-('gbt_date_same(internal,internal,internal)', '{gbtreekey8,gbtreekey8,internal}'),
+('gbt_date_same(internal,internal,internal)', '{SCH.gbtreekey8,SCH.gbtreekey8,internal}'),
 ('gbt_intv_distance(internal,interval,int2,oid)', '{internal,interval,int2,oid,internal}'),
 ('gbt_intv_union(bytea,internal)', '{internal,internal}'),
-('gbt_intv_same(internal,internal,internal)', '{gbtreekey32,gbtreekey32,internal}'),
+('gbt_intv_same(internal,internal,internal)', '{SCH.gbtreekey32,SCH.gbtreekey32,internal}'),
 ('gbt_cash_distance(internal,money,int2,oid)', '{internal,money,int2,oid,internal}'),
 ('gbt_cash_union(bytea,internal)', '{internal,internal}'),
-('gbt_cash_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}'),
+('gbt_cash_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}'),
 ('gbt_macad_union(bytea,internal)', '{internal,internal}'),
-('gbt_macad_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}'),
+('gbt_macad_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}'),
 ('gbt_text_union(bytea,internal)', '{internal,internal}'),
-('gbt_text_same(internal,internal,internal)', '{gbtreekey_var,gbtreekey_var,internal}'),
+('gbt_text_same(internal,internal,internal)', '{SCH.gbtreekey_var,SCH.gbtreekey_var,internal}'),
 ('gbt_bytea_union(bytea,internal)', '{internal,internal}'),
-('gbt_bytea_same(internal,internal,internal)', '{gbtreekey_var,gbtreekey_var,internal}'),
+('gbt_bytea_same(internal,internal,internal)', '{SCH.gbtreekey_var,SCH.gbtreekey_var,internal}'),
 ('gbt_numeric_union(bytea,internal)', '{internal,internal}'),
-('gbt_numeric_same(internal,internal,internal)', '{gbtreekey_var,gbtreekey_var,internal}'),
+('gbt_numeric_same(internal,internal,internal)', '{SCH.gbtreekey_var,SCH.gbtreekey_var,internal}'),
 ('gbt_bit_union(bytea,internal)', '{internal,internal}'),
-('gbt_bit_same(internal,internal,internal)', '{gbtreekey_var,gbtreekey_var,internal}'),
+('gbt_bit_same(internal,internal,internal)', '{SCH.gbtreekey_var,SCH.gbtreekey_var,internal}'),
 ('gbt_inet_union(bytea,internal)', '{internal,internal}'),
-('gbt_inet_same(internal,internal,internal)', '{gbtreekey16,gbtreekey16,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+('gbt_inet_same(internal,internal,internal)', '{SCH.gbtreekey16,SCH.gbtreekey16,internal}')
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;

contrib/citext/citext--1.1--1.2.sql

@@ -41,14 +41,28 @@ ALTER FUNCTION replace(citext, citext, citext) PARALLEL SAFE;
 ALTER FUNCTION split_part(citext, citext, int) PARALLEL SAFE;
 ALTER FUNCTION translate(citext, citext, text) PARALLEL SAFE;
 
+-- We have to update aggregates the hard way for lack of ALTER support
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
+
 UPDATE pg_proc SET proparallel = 's'
-WHERE oid = 'min(citext)'::pg_catalog.regprocedure;
+WHERE oid = (my_schema || '.min(' || my_schema || '.citext)')::pg_catalog.regprocedure;
 
 UPDATE pg_proc SET proparallel = 's'
-WHERE oid = 'max(citext)'::pg_catalog.regprocedure;
+WHERE oid = (my_schema || '.max(' || my_schema || '.citext)')::pg_catalog.regprocedure;
+
+UPDATE pg_aggregate SET aggcombinefn = (my_schema || '.citext_smaller')::regproc
+WHERE aggfnoid = (my_schema || '.max(' || my_schema || '.citext)')::pg_catalog.regprocedure;
 
-UPDATE pg_aggregate SET aggcombinefn = 'citext_smaller'
-WHERE aggfnoid = 'max(citext)'::pg_catalog.regprocedure;
+UPDATE pg_aggregate SET aggcombinefn = (my_schema || '.citext_larger')::regproc
+WHERE aggfnoid = (my_schema || '.max(' || my_schema || '.citext)')::pg_catalog.regprocedure;
 
-UPDATE pg_aggregate SET aggcombinefn = 'citext_larger'
-WHERE aggfnoid = 'max(citext)'::pg_catalog.regprocedure;
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;

contrib/citext/citext--1.2--1.3.sql

@@ -3,5 +3,19 @@
 -- complain if script is sourced in psql, rather than via ALTER EXTENSION
 \echo Use "ALTER EXTENSION citext UPDATE TO '1.3'" to load this file. \quit
 
-UPDATE pg_aggregate SET aggcombinefn = 'citext_smaller'
-WHERE aggfnoid = 'min(citext)'::pg_catalog.regprocedure;
+-- We have to update aggregates the hard way for lack of ALTER support
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
+
+UPDATE pg_aggregate SET aggcombinefn = (my_schema || '.citext_smaller')::regproc
+WHERE aggfnoid = (my_schema || '.min(' || my_schema || '.citext)')::pg_catalog.regprocedure;
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;

contrib/cube/cube--1.1--1.2.sql

@@ -7,16 +7,31 @@
 -- We use to_regprocedure() so that query doesn't fail if run against 9.6beta1 definitions,
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
-('g_cube_consistent(internal,cube,int4,oid,internal)', '{internal,cube,int2,oid,internal}'),
-('g_cube_distance(internal,cube,smallint,oid)', '{internal,cube,smallint,oid,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
+('g_cube_consistent(internal,SCH.cube,int4,oid,internal)', '{internal,SCH.cube,int2,oid,internal}'),
+('g_cube_distance(internal,SCH.cube,smallint,oid)', '{internal,SCH.cube,smallint,oid,internal}')
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
 
 ALTER FUNCTION cube_in(cstring) PARALLEL SAFE;
 ALTER FUNCTION cube(float8[], float8[]) PARALLEL SAFE;

contrib/cube/cube--1.3--1.4.sql

@@ -12,6 +12,15 @@
 -- bound into a particular opclass.  There's no SQL command for that,
 -- so fake it with a manual update on pg_depend.
 --
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
+
 UPDATE pg_catalog.pg_depend
 SET deptype = 'a'
 WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
@@ -20,14 +29,10 @@ WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
      FROM pg_catalog.pg_depend
      WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
        AND refclassid = 'pg_catalog.pg_proc'::pg_catalog.regclass
-       AND (refobjid = 'g_cube_compress(pg_catalog.internal)'::pg_catalog.regprocedure))
+       AND (refobjid = (my_schema || '.g_cube_compress(pg_catalog.internal)')::pg_catalog.regprocedure))
   AND refclassid = 'pg_catalog.pg_opclass'::pg_catalog.regclass
   AND deptype = 'i';
 
-ALTER OPERATOR FAMILY gist_cube_ops USING gist drop function 3 (cube);
-ALTER EXTENSION cube DROP function g_cube_compress(pg_catalog.internal);
-DROP FUNCTION g_cube_compress(pg_catalog.internal);
-
 UPDATE pg_catalog.pg_depend
 SET deptype = 'a'
 WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
@@ -36,10 +41,18 @@ WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
      FROM pg_catalog.pg_depend
      WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
        AND refclassid = 'pg_catalog.pg_proc'::pg_catalog.regclass
-       AND (refobjid = 'g_cube_decompress(pg_catalog.internal)'::pg_catalog.regprocedure))
+       AND (refobjid = (my_schema || '.g_cube_decompress(pg_catalog.internal)')::pg_catalog.regprocedure))
   AND refclassid = 'pg_catalog.pg_opclass'::pg_catalog.regclass
   AND deptype = 'i';
 
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
+
+ALTER OPERATOR FAMILY gist_cube_ops USING gist drop function 3 (cube);
+ALTER EXTENSION cube DROP function g_cube_compress(pg_catalog.internal);
+DROP FUNCTION g_cube_compress(pg_catalog.internal);
+
 ALTER OPERATOR FAMILY gist_cube_ops USING gist drop function 4 (cube);
 ALTER EXTENSION cube DROP function g_cube_decompress(pg_catalog.internal);
 DROP FUNCTION g_cube_decompress(pg_catalog.internal);

contrib/earthdistance/earthdistance--1.1.sql

@@ -31,7 +31,7 @@ CREATE DOMAIN earth AS cube
   CONSTRAINT not_point check(cube_is_point(value))
   CONSTRAINT not_3d check(cube_dim(value) <= 3)
   CONSTRAINT on_surface check(abs(cube_distance(value, '(0)'::cube) /
-  earth() - 1) < '10e-7'::float8);
+  earth() - '1'::float8) < '10e-7'::float8);
 
 CREATE FUNCTION sec_to_gc(float8)
 RETURNS float8

contrib/earthdistance/earthdistance.control

@@ -3,5 +3,4 @@ comment = 'calculate great-circle distances on the surface of the Earth'
 default_version = '1.1'
 module_pathname = '$libdir/earthdistance'
 relocatable = true
-trusted = true
 requires = 'cube'

contrib/hstore/hstore--1.1--1.2.sql

@@ -9,10 +9,13 @@
 -- dependent on the extension.
 
 DO LANGUAGE plpgsql
-
 $$
-
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
 BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
    PERFORM 1
    FROM pg_proc p
@@ -27,6 +30,7 @@ BEGIN
 
    IF NOT FOUND
    THEN
+        PERFORM pg_catalog.set_config('search_path', old_path, true);
 
         CREATE FUNCTION hstore_to_json(hstore)
         RETURNS json
@@ -43,6 +47,7 @@ BEGIN
 
    END IF;
 
+PERFORM pg_catalog.set_config('search_path', old_path, true);
 END;
 
 $$;

contrib/hstore/hstore--1.3--1.4.sql

@@ -7,23 +7,38 @@
 -- We use to_regprocedure() so that query doesn't fail if run against 9.6beta1 definitions,
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
-('ghstore_same(internal,internal,internal)', '{ghstore,ghstore,internal}'),
-('ghstore_consistent(internal,internal,int4,oid,internal)', '{internal,hstore,int2,oid,internal}'),
-('gin_extract_hstore(internal,internal)', '{hstore,internal}'),
-('gin_extract_hstore_query(internal,internal,int2,internal,internal)', '{hstore,internal,int2,internal,internal}'),
-('gin_consistent_hstore(internal,int2,internal,int4,internal,internal)', '{internal,int2,hstore,int4,internal,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
+('ghstore_same(internal,internal,internal)', '{SCH.ghstore,SCH.ghstore,internal}'),
+('ghstore_consistent(internal,internal,int4,oid,internal)', '{internal,SCH.hstore,int2,oid,internal}'),
+('gin_extract_hstore(internal,internal)', '{SCH.hstore,internal}'),
+('gin_extract_hstore_query(internal,internal,int2,internal,internal)', '{SCH.hstore,internal,int2,internal,internal}'),
+('gin_consistent_hstore(internal,int2,internal,int4,internal,internal)', '{internal,int2,SCH.hstore,int4,internal,internal}')
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
 
 UPDATE pg_catalog.pg_proc SET
-  prorettype = 'ghstore'::pg_catalog.regtype
-WHERE oid = pg_catalog.to_regprocedure('ghstore_union(internal,internal)');
+  prorettype = (my_schema || '.ghstore')::pg_catalog.regtype
+WHERE oid = pg_catalog.to_regprocedure((my_schema || '.ghstore_union(internal,internal)'));
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
 
 ALTER FUNCTION hstore_in(cstring) PARALLEL SAFE;
 ALTER FUNCTION hstore_out(hstore) PARALLEL SAFE;

contrib/hstore_plperl/hstore_plperl.control

@@ -3,5 +3,4 @@ comment = 'transform between hstore and plperl'
 default_version = '1.0'
 module_pathname = '$libdir/hstore_plperl'
 relocatable = true
-trusted = true
 requires = 'hstore,plperl'

contrib/intagg/intagg--1.0--1.1.sql

@@ -6,6 +6,18 @@
 ALTER FUNCTION int_agg_state(internal, int4) PARALLEL SAFE;
 ALTER FUNCTION int_agg_final_array(internal) PARALLEL SAFE;
 ALTER FUNCTION int_array_enum(int4[]) PARALLEL SAFE;
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_proc SET proparallel = 's'
-WHERE oid = 'int_array_aggregate(int4)'::pg_catalog.regprocedure;
+WHERE oid = (my_schema || '.int_array_aggregate(int4)')::pg_catalog.regprocedure;
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;

contrib/intarray/intarray--1.1--1.2.sql

@@ -7,23 +7,38 @@
 -- We use to_regprocedure() so that query doesn't fail if run against 9.6beta1 definitions,
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
 ('g_int_consistent(internal,_int4,int4,oid,internal)', '{internal,_int4,int2,oid,internal}'),
 ('g_intbig_consistent(internal,internal,int4,oid,internal)', '{internal,_int4,int2,oid,internal}'),
-('g_intbig_same(internal,internal,internal)', '{intbig_gkey,intbig_gkey,internal}'),
+('g_intbig_same(internal,internal,internal)', '{SCH.intbig_gkey,SCH.intbig_gkey,internal}'),
 ('ginint4_queryextract(internal,internal,int2,internal,internal,internal,internal)', '{_int4,internal,int2,internal,internal,internal,internal}'),
 ('ginint4_consistent(internal,int2,internal,int4,internal,internal,internal,internal)', '{internal,int2,_int4,int4,internal,internal,internal,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
 
 UPDATE pg_catalog.pg_proc SET
-  prorettype = 'intbig_gkey'::pg_catalog.regtype
-WHERE oid = pg_catalog.to_regprocedure('g_intbig_union(internal,internal)');
+  prorettype = (my_schema || '.intbig_gkey')::pg_catalog.regtype
+WHERE oid = pg_catalog.to_regprocedure(my_schema || '.g_intbig_union(internal,internal)');
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
 
 ALTER FUNCTION bqarr_in(cstring) PARALLEL SAFE;
 ALTER FUNCTION bqarr_out(query_int) PARALLEL SAFE;

contrib/ltree/ltree--1.0--1.1.sql

@@ -7,26 +7,41 @@
 -- We use to_regprocedure() so that query doesn't fail if run against 9.6beta1 definitions,
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
-('ltree_consistent(internal,internal,int2,oid,internal)', '{internal,ltree,int2,oid,internal}'),
-('ltree_same(internal,internal,internal)', '{ltree_gist,ltree_gist,internal}'),
-('_ltree_consistent(internal,internal,int2,oid,internal)', '{internal,_ltree,int2,oid,internal}'),
-('_ltree_same(internal,internal,internal)', '{ltree_gist,ltree_gist,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
+('ltree_consistent(internal,internal,int2,oid,internal)', '{internal,SCH.ltree,int2,oid,internal}'),
+('ltree_same(internal,internal,internal)', '{SCH.ltree_gist,SCH.ltree_gist,internal}'),
+('_ltree_consistent(internal,internal,int2,oid,internal)', '{internal,SCH._ltree,int2,oid,internal}'),
+('_ltree_same(internal,internal,internal)', '{SCH.ltree_gist,SCH.ltree_gist,internal}')
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
 
 UPDATE pg_catalog.pg_proc SET
-  prorettype = 'ltree_gist'::pg_catalog.regtype
-WHERE oid = pg_catalog.to_regprocedure('ltree_union(internal,internal)');
+  prorettype = (my_schema || '.ltree_gist')::pg_catalog.regtype
+WHERE oid = pg_catalog.to_regprocedure(my_schema || '.ltree_union(internal,internal)');
 
 UPDATE pg_catalog.pg_proc SET
-  prorettype = 'ltree_gist'::pg_catalog.regtype
-WHERE oid = pg_catalog.to_regprocedure('_ltree_union(internal,internal)');
+  prorettype = (my_schema || '.ltree_gist')::pg_catalog.regtype
+WHERE oid = pg_catalog.to_regprocedure(my_schema || '._ltree_union(internal,internal)');
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
 
 ALTER FUNCTION ltree_in(cstring) PARALLEL SAFE;
 ALTER FUNCTION ltree_out(ltree) PARALLEL SAFE;

contrib/pg_trgm/pg_trgm--1.2--1.3.sql

@@ -7,21 +7,36 @@
 -- We use to_regprocedure() so that query doesn't fail if run against 9.6beta1 definitions,
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
 ('gtrgm_consistent(internal,text,int4,oid,internal)', '{internal,text,int2,oid,internal}'),
 ('gtrgm_distance(internal,text,int4,oid)', '{internal,text,int2,oid,internal}'),
 ('gtrgm_union(bytea,internal)', '{internal,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
 
 UPDATE pg_catalog.pg_proc SET
-  prorettype = 'gtrgm'::pg_catalog.regtype
-WHERE oid = pg_catalog.to_regprocedure('gtrgm_union(internal,internal)');
+  prorettype = (my_schema || '.gtrgm')::pg_catalog.regtype
+WHERE oid = pg_catalog.to_regprocedure(my_schema || '.gtrgm_union(internal,internal)');
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
 
 ALTER FUNCTION set_limit(float4) PARALLEL UNSAFE;
 ALTER FUNCTION show_limit() PARALLEL SAFE;

contrib/seg/seg--1.0--1.1.sql

@@ -7,15 +7,30 @@
 -- We use to_regprocedure() so that query doesn't fail if run against 9.6beta1 definitions,
 -- wherein the signatures have been updated already.  In that case to_regprocedure() will
 -- return NULL and no updates will happen.
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
 
 UPDATE pg_catalog.pg_proc SET
   proargtypes = pg_catalog.array_to_string(newtypes::pg_catalog.oid[], ' ')::pg_catalog.oidvector,
   pronargs = pg_catalog.array_length(newtypes, 1)
 FROM (VALUES
-(NULL::pg_catalog.text, NULL::pg_catalog.regtype[]), -- establish column types
-('gseg_consistent(internal,seg,int4,oid,internal)', '{internal,seg,int2,oid,internal}')
-) AS update_data (oldproc, newtypes)
-WHERE oid = pg_catalog.to_regprocedure(oldproc);
+(NULL::pg_catalog.text, NULL::pg_catalog.text[]), -- establish column types
+('gseg_consistent(internal,SCH.seg,int4,oid,internal)', '{internal,SCH.seg,int2,oid,internal}')
+) AS update_data (oldproc, newtypestext),
+LATERAL (
+  SELECT array_agg(replace(typ, 'SCH', my_schema)::regtype) as newtypes FROM unnest(newtypestext) typ
+) ls
+WHERE oid = to_regprocedure(my_schema || '.' || replace(oldproc, 'SCH', my_schema));
+
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
 
 ALTER FUNCTION seg_in(cstring) PARALLEL SAFE;
 ALTER FUNCTION seg_out(seg) PARALLEL SAFE;

contrib/seg/seg--1.2--1.3.sql

@@ -12,6 +12,15 @@
 -- bound into a particular opclass.  There's no SQL command for that,
 -- so fake it with a manual update on pg_depend.
 --
+DO LANGUAGE plpgsql
+$$
+DECLARE
+  my_schema pg_catalog.text := pg_catalog.quote_ident(pg_catalog.current_schema());
+  old_path pg_catalog.text := pg_catalog.current_setting('search_path');
+BEGIN
+-- for safety, transiently set search_path to just pg_catalog+pg_temp
+PERFORM pg_catalog.set_config('search_path', 'pg_catalog, pg_temp', true);
+
 UPDATE pg_catalog.pg_depend
 SET deptype = 'a'
 WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
@@ -20,14 +29,10 @@ WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
      FROM pg_catalog.pg_depend
      WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
        AND refclassid = 'pg_catalog.pg_proc'::pg_catalog.regclass
-       AND (refobjid = 'gseg_compress(pg_catalog.internal)'::pg_catalog.regprocedure))
+       AND (refobjid = (my_schema || '.gseg_compress(internal)')::pg_catalog.regprocedure))
   AND refclassid = 'pg_catalog.pg_opclass'::pg_catalog.regclass
   AND deptype = 'i';
 
-ALTER OPERATOR FAMILY gist_seg_ops USING gist drop function 3 (seg);
-ALTER EXTENSION seg DROP function gseg_compress(pg_catalog.internal);
-DROP function gseg_compress(pg_catalog.internal);
-
 UPDATE pg_catalog.pg_depend
 SET deptype = 'a'
 WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
@@ -36,10 +41,18 @@ WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
      FROM pg_catalog.pg_depend
      WHERE classid = 'pg_catalog.pg_amproc'::pg_catalog.regclass
        AND refclassid = 'pg_catalog.pg_proc'::pg_catalog.regclass
-       AND (refobjid = 'gseg_decompress(pg_catalog.internal)'::pg_catalog.regprocedure))
+       AND (refobjid = (my_schema || '.gseg_decompress(internal)')::pg_catalog.regprocedure))
   AND refclassid = 'pg_catalog.pg_opclass'::pg_catalog.regclass
   AND deptype = 'i';
 
+PERFORM pg_catalog.set_config('search_path', old_path, true);
+END
+$$;
+
+ALTER OPERATOR FAMILY gist_seg_ops USING gist drop function 3 (seg);
+ALTER EXTENSION seg DROP function gseg_compress(pg_catalog.internal);
+DROP function gseg_compress(pg_catalog.internal);
+
 ALTER OPERATOR FAMILY gist_seg_ops USING gist drop function 4 (seg);
 ALTER EXTENSION seg DROP function gseg_decompress(pg_catalog.internal);
 DROP function gseg_decompress(pg_catalog.internal);

doc/src/sgml/earthdistance.sgml

@@ -10,9 +10,8 @@
  <para>
   The <filename>earthdistance</filename> module provides two different approaches to
   calculating great circle distances on the surface of the Earth. The one
-  described first depends on the <filename>cube</filename> module (which
-  <emphasis>must</emphasis> be installed before <filename>earthdistance</filename> can be
-  installed). The second one is based on the built-in <type>point</type> data type,
+  described first depends on the <filename>cube</filename> module.
+  The second one is based on the built-in <type>point</type> data type,
   using longitude and latitude for the coordinates.
  </para>
 
@@ -24,11 +23,27 @@
  </para>
 
  <para>
-  This module is considered <quote>trusted</quote>, that is, it can be
-  installed by non-superusers who have <literal>CREATE</literal> privilege
-  on the current database.
+  The <filename>cube</filename> module must be installed
+  before <filename>earthdistance</filename> can be installed
+  (although you can use the <literal>CASCADE</literal> option
+  of <command>CREATE EXTENSION</command> to install both in one command).
  </para>
 
+ <caution>
+  <para>
+   It is strongly recommended that <filename>earthdistance</filename>
+   and <filename>cube</filename> be installed in the same schema, and that
+   that schema be one for which CREATE privilege has not been and will not
+   be granted to any untrusted users.
+   Otherwise there are installation-time security hazards
+   if <filename>earthdistance</filename>'s schema contains objects defined
+   by a hostile user.
+   Furthermore, when using <filename>earthdistance</filename>'s functions
+   after installation, the entire search path should contain only trusted
+   schemas.
+  </para>
+ </caution>
+
  <sect2>
   <title>Cube-Based Earth Distances</title>
 

doc/src/sgml/hstore.sgml

@@ -918,10 +918,14 @@ ALTER TABLE tablename ALTER hstorecol TYPE hstore USING hstorecol || '';
    Python dictionaries.
   </para>
 
-  <para>
-   Of these additional extensions, <literal>hstore_plperl</literal> is
-   considered trusted; the rest are not.
-  </para>
+  <caution>
+   <para>
+    It is strongly recommended that the transform extensions be installed in
+    the same schema as <filename>hstore</filename>.  Otherwise there are
+    installation-time security hazards if a transform extension's schema
+    contains objects defined by a hostile user.
+   </para>
+  </caution>
  </sect2>
 
  <sect2>

doc/src/sgml/ltree.sgml

@@ -835,6 +835,15 @@ ltreetest=> SELECT ins_label(path,2,'Space') FROM test WHERE path <@ 'Top.
    creating a function, <type>ltree</type> values are mapped to Python lists.
    (The reverse is currently not supported, however.)
   </para>
+
+  <caution>
+   <para>
+    It is strongly recommended that the transform extensions be installed in
+    the same schema as <filename>ltree</filename>.  Otherwise there are
+    installation-time security hazards if a transform extension's schema
+    contains objects defined by a hostile user.
+   </para>
+  </caution>
  </sect2>
 
  <sect2>

doc/src/sgml/ref/create_extension.sgml

@@ -177,6 +177,33 @@ CREATE EXTENSION [ IF NOT EXISTS ] <replaceable class="parameter">extension_name
    system views.
   </para>
 
+  <caution>
+   <para>
+    Installing an extension as superuser requires trusting that the
+    extension's author wrote the extension installation script in a secure
+    fashion.  It is not terribly difficult for a malicious user to create
+    trojan-horse objects that will compromise later execution of a
+    carelessly-written extension script, allowing that user to acquire
+    superuser privileges.  However, trojan-horse objects are only hazardous
+    if they are in the <varname>search_path</varname> during script
+    execution, meaning that they are in the extension's installation target
+    schema or in the schema of some extension it depends on.  Therefore, a
+    good rule of thumb when dealing with extensions whose scripts have not
+    been carefully vetted is to install them only into schemas for which
+    CREATE privilege has not been and will not be granted to any untrusted
+    users.  Likewise for any extensions they depend on.
+   </para>
+
+   <para>
+    The extensions supplied with <productname>PostgreSQL</productname> are
+    believed to be secure against installation-time attacks of this sort,
+    except for a few that depend on other extensions.  As stated in the
+    documentation for those extensions, they should be installed into secure
+    schemas, or installed into the same schemas as the extensions they
+    depend on, or both.
+   </para>
+  </caution>
+
   <para>
    For information about writing new extensions, see
    <xref linkend="extend-extensions"/>.
@@ -188,10 +215,16 @@ CREATE EXTENSION [ IF NOT EXISTS ] <replaceable class="parameter">extension_name
 
   <para>
    Install the <link linkend="hstore">hstore</link> extension into the
-   current database:
+   current database, placing its objects in schema <literal>addons</literal>:
+<programlisting>
+CREATE EXTENSION hstore SCHEMA addons;
+</programlisting>
+   Another way to accomplish the same thing:
 <programlisting>
+SET search_path = addons;
 CREATE EXTENSION hstore;
-</programlisting></para>
+</programlisting>
+  </para>
  </refsect1>
 
  <refsect1>

src/backend/commands/extension.c

@@ -908,9 +908,21 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 								 GUC_ACTION_SAVE, true, 0, false);
 
 	/*
-	 * Set up the search path to contain the target schema, then the schemas
-	 * of any prerequisite extensions, and nothing else.  In particular this
-	 * makes the target schema be the default creation target namespace.
+	 * Similarly disable check_function_bodies, to ensure that SQL functions
+	 * won't be parsed during creation.
+	 */
+	if (check_function_bodies)
+		(void) set_config_option("check_function_bodies", "off",
+								 PGC_USERSET, PGC_S_SESSION,
+								 GUC_ACTION_SAVE, true, 0, false);
+
+	/*
+	 * Set up the search path to have the target schema first, making it be
+	 * the default creation target namespace.  Then add the schemas of any
+	 * prerequisite extensions, unless they are in pg_catalog which would be
+	 * searched anyway.  (Listing pg_catalog explicitly in a non-first
+	 * position would be bad for security.)  Finally add pg_temp to ensure
+	 * that temp objects can't take precedence over others.
 	 *
 	 * Note: it might look tempting to use PushOverrideSearchPath for this,
 	 * but we cannot do that.  We have to actually set the search_path GUC in
@@ -924,9 +936,10 @@ execute_extension_script(Oid extensionOid, ExtensionControlFile *control,
 		Oid			reqschema = lfirst_oid(lc);
 		char	   *reqname = get_namespace_name(reqschema);
 
-		if (reqname)
+		if (reqname && strcmp(reqname, "pg_catalog") != 0)
 			appendStringInfo(&pathbuf, ", %s", quote_identifier(reqname));
 	}
+	appendStringInfoString(&pathbuf, ", pg_temp");
 
 	(void) set_config_option("search_path", pathbuf.data,
 							 PGC_USERSET, PGC_S_SESSION,

src/backend/commands/operatorcmds.c

@@ -297,6 +297,7 @@ ValidateJoinEstimator(List *joinName)
 {
 	Oid			typeId[5];
 	Oid			joinOid;
+	Oid			joinOid2;
 	AclResult	aclresult;
 
 	typeId[0] = INTERNALOID;	/* PlannerInfo */
@@ -307,15 +308,26 @@ ValidateJoinEstimator(List *joinName)
 
 	/*
 	 * As of Postgres 8.4, the preferred signature for join estimators has 5
-	 * arguments, but we still allow the old 4-argument form. Try the
-	 * preferred form first.
+	 * arguments, but we still allow the old 4-argument form.  Whine about
+	 * ambiguity if both forms exist.
 	 */
 	joinOid = LookupFuncName(joinName, 5, typeId, true);
-	if (!OidIsValid(joinOid))
-		joinOid = LookupFuncName(joinName, 4, typeId, true);
-	/* If not found, reference the 5-argument signature in error msg */
-	if (!OidIsValid(joinOid))
-		joinOid = LookupFuncName(joinName, 5, typeId, false);
+	joinOid2 = LookupFuncName(joinName, 4, typeId, true);
+	if (OidIsValid(joinOid))
+	{
+		if (OidIsValid(joinOid2))
+			ereport(ERROR,
+					(errcode(ERRCODE_AMBIGUOUS_FUNCTION),
+					 errmsg("join estimator function %s has multiple matches",
+							NameListToString(joinName))));
+	}
+	else
+	{
+		joinOid = joinOid2;
+		/* If not found, reference the 5-argument signature in error msg */
+		if (!OidIsValid(joinOid))
+			joinOid = LookupFuncName(joinName, 5, typeId, false);
+	}
 
 	/* estimators must return float8 */
 	if (get_func_rettype(joinOid) != FLOAT8OID)

src/backend/commands/typecmds.c

@@ -1627,21 +1627,31 @@ findTypeInputFunction(List *procname, Oid typeOid)
 {
 	Oid			argList[3];
 	Oid			procOid;
+	Oid			procOid2;
 
 	/*
 	 * Input functions can take a single argument of type CSTRING, or three
-	 * arguments (string, typioparam OID, typmod).  They must return the
-	 * target type.
+	 * arguments (string, typioparam OID, typmod).  Whine about ambiguity if
+	 * both forms exist.
 	 */
 	argList[0] = CSTRINGOID;
+	argList[1] = OIDOID;
+	argList[2] = INT4OID;
 
 	procOid = LookupFuncName(procname, 1, argList, true);
-	if (!OidIsValid(procOid))
+	procOid2 = LookupFuncName(procname, 3, argList, true);
+	if (OidIsValid(procOid))
 	{
-		argList[1] = OIDOID;
-		argList[2] = INT4OID;
-
-		procOid = LookupFuncName(procname, 3, argList, true);
+		if (OidIsValid(procOid2))
+			ereport(ERROR,
+					(errcode(ERRCODE_AMBIGUOUS_FUNCTION),
+					 errmsg("type input function %s has multiple matches",
+							NameListToString(procname))));
+	}
+	else
+	{
+		procOid = procOid2;
+		/* If not found, reference the 1-argument signature in error msg */
 		if (!OidIsValid(procOid))
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_FUNCTION),
@@ -1649,6 +1659,7 @@ findTypeInputFunction(List *procname, Oid typeOid)
 							func_signature_string(procname, 1, NIL, argList))));
 	}
 
+	/* Input functions must return the target type. */
 	if (get_func_rettype(procOid) != typeOid)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),
@@ -1714,21 +1725,31 @@ findTypeReceiveFunction(List *procname, Oid typeOid)
 {
 	Oid			argList[3];
 	Oid			procOid;
+	Oid			procOid2;
 
 	/*
 	 * Receive functions can take a single argument of type INTERNAL, or three
-	 * arguments (internal, typioparam OID, typmod).  They must return the
-	 * target type.
+	 * arguments (internal, typioparam OID, typmod).  Whine about ambiguity if
+	 * both forms exist.
 	 */
 	argList[0] = INTERNALOID;
+	argList[1] = OIDOID;
+	argList[2] = INT4OID;
 
 	procOid = LookupFuncName(procname, 1, argList, true);
-	if (!OidIsValid(procOid))
+	procOid2 = LookupFuncName(procname, 3, argList, true);
+	if (OidIsValid(procOid))
 	{
-		argList[1] = OIDOID;
-		argList[2] = INT4OID;
-
-		procOid = LookupFuncName(procname, 3, argList, true);
+		if (OidIsValid(procOid2))
+			ereport(ERROR,
+					(errcode(ERRCODE_AMBIGUOUS_FUNCTION),
+					 errmsg("type receive function %s has multiple matches",
+							NameListToString(procname))));
+	}
+	else
+	{
+		procOid = procOid2;
+		/* If not found, reference the 1-argument signature in error msg */
 		if (!OidIsValid(procOid))
 			ereport(ERROR,
 					(errcode(ERRCODE_UNDEFINED_FUNCTION),
@@ -1736,6 +1757,7 @@ findTypeReceiveFunction(List *procname, Oid typeOid)
 							func_signature_string(procname, 1, NIL, argList))));
 	}
 
+	/* Receive functions must return the target type. */
 	if (get_func_rettype(procOid) != typeOid)
 		ereport(ERROR,
 				(errcode(ERRCODE_INVALID_OBJECT_DEFINITION),