Prevent privilege escalation in explicit calls to PL validators.

The primary role of PL validators is to be called implicitly during
CREATE FUNCTION, but they are also normal functions that a user can call
explicitly.  Add a permissions check to each validator to ensure that a
user cannot use explicit validator calls to achieve things he could not
otherwise achieve.  Back-patch to 8.4 (all supported versions).
Non-core procedural language extensions ought to make the same two-line
change to their own validators.

Andres Freund, reviewed by Tom Lane and Noah Misch.

Security: CVE-2014-0061

diff --git a/doc/src/sgml/plhandler.sgml b/doc/src/sgml/plhandler.sgml
index c9b804c0752180ec4ee658a007fe46f6e3ed2a72..59302517769f9b7f636084dfeafe224381c63404 100644 (file)
--- a/doc/src/sgml/plhandler.sgml
+++ b/doc/src/sgml/plhandler.sgml
@@ -179,7 +179,10 @@ CREATE LANGUAGE plsample
     or updated a function written in the procedural language.
     The passed-in OID is the OID of the function's <classname>pg_proc</>
     row.  The validator must fetch this row in the usual way, and do
-    whatever checking is appropriate.  Typical checks include verifying
+    whatever checking is appropriate.
+    First, call <function>CheckFunctionValidatorAccess()</> to diagnose
+    explicit calls to the validator that the user could not achieve through
+    <command>CREATE FUNCTION</>.  Typical checks then include verifying
     that the function's argument and result types are supported by the
     language, and that the function's body is syntactically correct
     in the language.  If the validator finds the function to be okay,

diff --git a/src/backend/catalog/pg_proc.c b/src/backend/catalog/pg_proc.c
index 9d5f1a6cbc2295b0f37f122df84b045939befcc9..5de7b338079649f3fd6327f62eb4dba80f596a02 100644 (file)
--- a/src/backend/catalog/pg_proc.c
+++ b/src/backend/catalog/pg_proc.c
@@ -694,6 +694,9 @@ fmgr_internal_validator(PG_FUNCTION_ARGS)
        Datum           tmp;
        char       *prosrc;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        /*
         * We do not honor check_function_bodies since it's unlikely the function
         * name will be found later if it isn't there now.
@@ -739,6 +742,9 @@ fmgr_c_validator(PG_FUNCTION_ARGS)
        char       *prosrc;
        char       *probin;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        /*
         * It'd be most consistent to skip the check if !check_function_bodies,
         * but the purpose of that switch is to be helpful for pg_dump loading,
@@ -790,6 +796,9 @@ fmgr_sql_validator(PG_FUNCTION_ARGS)
        bool            haspolyarg;
        int                     i;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcoid));
        if (!HeapTupleIsValid(tuple))
                elog(ERROR, "cache lookup failed for function %u", funcoid);

diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index 92abd44a600e4c8e034f6c9a9081309f61ef32f4..54b2054188e8803108148c7b0846cc7bb10ba387 100644 (file)
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -963,7 +963,6 @@ CreateFunction(CreateFunctionStmt *stmt, const char *queryString)
                                        prorows);
 }
 
-
 /*
  * RemoveFunction
  *             Deletes a function.

diff --git a/src/backend/utils/fmgr/fmgr.c b/src/backend/utils/fmgr/fmgr.c
index 5a0e92a4fc72b62d35ca9a5c59bfd38c0544a933..0a2d4ef956501c51905de2aa9e62d068b5194dc5 100644 (file)
--- a/src/backend/utils/fmgr/fmgr.c
+++ b/src/backend/utils/fmgr/fmgr.c
@@ -24,6 +24,7 @@
 #include "miscadmin.h"
 #include "nodes/nodeFuncs.h"
 #include "pgstat.h"
+#include "utils/acl.h"
 #include "utils/builtins.h"
 #include "utils/fmgrtab.h"
 #include "utils/guc.h"
@@ -2445,3 +2446,86 @@ get_call_expr_arg_stable(Node *expr, int argnum)
 
        return false;
 }
+
+/*-------------------------------------------------------------------------
+ *             Support routines for procedural language implementations
+ *-------------------------------------------------------------------------
+ */
+
+/*
+ * Verify that a validator is actually associated with the language of a
+ * particular function and that the user has access to both the language and
+ * the function.  All validators should call this before doing anything
+ * substantial.  Doing so ensures a user cannot achieve anything with explicit
+ * calls to validators that he could not achieve with CREATE FUNCTION or by
+ * simply calling an existing function.
+ *
+ * When this function returns false, callers should skip all validation work
+ * and call PG_RETURN_VOID().  This never happens at present; it is reserved
+ * for future expansion.
+ *
+ * In particular, checking that the validator corresponds to the function's
+ * language allows untrusted language validators to assume they process only
+ * superuser-chosen source code.  (Untrusted language call handlers, by
+ * definition, do assume that.)  A user lacking the USAGE language privilege
+ * would be unable to reach the validator through CREATE FUNCTION, so we check
+ * that to block explicit calls as well.  Checking the EXECUTE privilege on
+ * the function is often superfluous, because most users can clone the
+ * function to get an executable copy.  It is meaningful against users with no
+ * database TEMP right and no permanent schema CREATE right, thereby unable to
+ * create any function.  Also, if the function tracks persistent state by
+ * function OID or name, validating the original function might permit more
+ * mischief than creating and validating a clone thereof.
+ */
+bool
+CheckFunctionValidatorAccess(Oid validatorOid, Oid functionOid)
+{
+       HeapTuple       procTup;
+       HeapTuple       langTup;
+       Form_pg_proc procStruct;
+       Form_pg_language langStruct;
+       AclResult       aclresult;
+
+       /* Get the function's pg_proc entry */
+       procTup = SearchSysCache1(PROCOID, ObjectIdGetDatum(functionOid));
+       if (!HeapTupleIsValid(procTup))
+               elog(ERROR, "cache lookup failed for function %u", functionOid);
+       procStruct = (Form_pg_proc) GETSTRUCT(procTup);
+
+       /*
+        * Fetch pg_language entry to know if this is the correct validation
+        * function for that pg_proc entry.
+        */
+       langTup = SearchSysCache1(LANGOID, ObjectIdGetDatum(procStruct->prolang));
+       if (!HeapTupleIsValid(langTup))
+               elog(ERROR, "cache lookup failed for language %u", procStruct->prolang);
+       langStruct = (Form_pg_language) GETSTRUCT(langTup);
+
+       if (langStruct->lanvalidator != validatorOid)
+               ereport(ERROR,
+                               (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
+                                errmsg("language validation function %u called for language %u instead of %u",
+                                               validatorOid, procStruct->prolang,
+                                               langStruct->lanvalidator)));
+
+       /* first validate that we have permissions to use the language */
+       aclresult = pg_language_aclcheck(procStruct->prolang, GetUserId(),
+                                                                        ACL_USAGE);
+       if (aclresult != ACLCHECK_OK)
+               aclcheck_error(aclresult, ACL_KIND_LANGUAGE,
+                                          NameStr(langStruct->lanname));
+
+       /*
+        * Check whether we are allowed to execute the function itself. If we can
+        * execute it, there should be no possible side-effect of
+        * compiling/validation that execution can't have.
+        */
+       aclresult = pg_proc_aclcheck(functionOid, GetUserId(), ACL_EXECUTE);
+       if (aclresult != ACLCHECK_OK)
+               aclcheck_error(aclresult, ACL_KIND_PROC, NameStr(procStruct->proname));
+
+       ReleaseSysCache(procTup);
+       ReleaseSysCache(langTup);
+
+       return true;
+}

diff --git a/src/include/fmgr.h b/src/include/fmgr.h
index 4a412f8049c49fada4b1fa679bb8d454b213d410..84ef04de58b208ba092f761ec00b73c080d6bac3 100644 (file)
--- a/src/include/fmgr.h
+++ b/src/include/fmgr.h
@@ -624,6 +624,7 @@ extern Oid  get_fn_expr_argtype(FmgrInfo *flinfo, int argnum);
 extern Oid     get_call_expr_argtype(fmNodePtr expr, int argnum);
 extern bool get_fn_expr_arg_stable(FmgrInfo *flinfo, int argnum);
 extern bool get_call_expr_arg_stable(fmNodePtr expr, int argnum);
+extern bool CheckFunctionValidatorAccess(Oid validatorOid, Oid functionOid);
 
 /*
  * Routines in dfmgr.c

diff --git a/src/pl/plperl/plperl.c b/src/pl/plperl/plperl.c
index 896d748f6edaefb3a2373c65b8d7923af311ac02..7ea428e845ca60cbd2735214444573ce42a65408 100644 (file)
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1846,6 +1846,9 @@ plperl_validator(PG_FUNCTION_ARGS)
        bool            istrigger = false;
        int                     i;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        /* Get the new function's pg_proc entry */
        tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcoid));
        if (!HeapTupleIsValid(tuple))
@@ -1925,6 +1928,7 @@ PG_FUNCTION_INFO_V1(plperlu_validator);
 Datum
 plperlu_validator(PG_FUNCTION_ARGS)
 {
+       /* call plperl validator with our fcinfo so it gets our oid */
        return plperl_validator(fcinfo);
 }
 

diff --git a/src/pl/plpgsql/src/pl_handler.c b/src/pl/plpgsql/src/pl_handler.c
index e6e71432ff9ae72e43c402a4873446234dc7d7da..d5f696aaa8dfc8ca33992de5d0ba07597576653c 100644 (file)
--- a/src/pl/plpgsql/src/pl_handler.c
+++ b/src/pl/plpgsql/src/pl_handler.c
@@ -227,6 +227,9 @@ plpgsql_validator(PG_FUNCTION_ARGS)
        bool            istrigger = false;
        int                     i;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        /* Get the new function's pg_proc entry */
        tuple = SearchSysCache1(PROCOID, ObjectIdGetDatum(funcoid));
        if (!HeapTupleIsValid(tuple))

diff --git a/src/pl/plpython/plpython.c b/src/pl/plpython/plpython.c
index 57801cc252e409e9bd0d5027ac026ea087f71c7d..7610031af19eab1f2c0f07d7e36cfe8527151e7f 100644 (file)
--- a/src/pl/plpython/plpython.c
+++ b/src/pl/plpython/plpython.c
@@ -519,6 +519,9 @@ plpython_validator(PG_FUNCTION_ARGS)
        Form_pg_proc procStruct;
        bool            is_trigger;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        if (!check_function_bodies)
        {
                PG_RETURN_VOID();
@@ -5012,6 +5015,7 @@ PG_FUNCTION_INFO_V1(plpython2_validator);
 Datum
 plpython2_validator(PG_FUNCTION_ARGS)
 {
+       /* call plpython validator with our fcinfo so it gets our oid */
        return plpython_validator(fcinfo);
 }