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/src/backend/catalog/pg_proc.c b/src/backend/catalog/pg_proc.c
index 45d224ef409e5dd299d257f81d7a44c712b608d9..e2e11163e9058548670dbd0856c6f6ff0b89e17c 100644 (file)
--- a/src/backend/catalog/pg_proc.c
+++ b/src/backend/catalog/pg_proc.c
@@ -623,6 +623,9 @@ 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.
@@ -672,6 +675,9 @@ 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,
@@ -724,6 +730,9 @@ fmgr_sql_validator(PG_FUNCTION_ARGS)
        bool            haspolyarg;
        int                     i;
 
+       if (!CheckFunctionValidatorAccess(fcinfo->flinfo->fn_oid, funcoid))
+               PG_RETURN_VOID();
+
        tuple = SearchSysCache(PROCOID,
                                                   ObjectIdGetDatum(funcoid),
                                                   0, 0, 0);

diff --git a/src/backend/commands/functioncmds.c b/src/backend/commands/functioncmds.c
index 2151fd94f09d0e4a270c8654028881c2c1515c1d..db22a288885688d708902776d152c047293362f3 100644 (file)
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -929,7 +929,6 @@ 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 00711a6f86c73369161272a9b9c14c731aaaaa3f..bcfbf5ac373bd9eb7d91283deabaae7b4e5d8d7f 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"
@@ -2428,3 +2429,87 @@ 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 = SearchSysCache(PROCOID, ObjectIdGetDatum(functionOid), 0, 0, 0);
+       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 = SearchSysCache(LANGOID, ObjectIdGetDatum(procStruct->prolang),
+                                                        0, 0, 0);
+       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 cf309cdbd63ece89303d350016e37c5b816a9a68..83dba75f30dc41f8b17005f73a9de3ad2ba1312d 100644 (file)
--- a/src/include/fmgr.h
+++ b/src/include/fmgr.h
@@ -518,6 +518,7 @@ 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 01c95ff6b14e1f4b8ef295d5e4d41e844ffe5b89..b65ea31a86cabaf5c1c8d8cc0ba831a7ba7cc4a7 100644 (file)
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1094,6 +1094,9 @@ 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 = SearchSysCache(PROCOID,
                                                   ObjectIdGetDatum(funcoid),

diff --git a/src/pl/plpgsql/src/pl_handler.c b/src/pl/plpgsql/src/pl_handler.c
index 3b362e78e763ba72040f20bec1798ba12ffc5250..9e07a2dc6a58ad19635198de8f188f1c0ccfdc19 100644 (file)
--- a/src/pl/plpgsql/src/pl_handler.c
+++ b/src/pl/plpgsql/src/pl_handler.c
@@ -136,6 +136,9 @@ 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 = SearchSysCache(PROCOID,
                                                   ObjectIdGetDatum(funcoid),