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 2c8fbca602dcb93bfdac92470a6050c28dd5f3c6..e05eb01764636103939d525cf36a4b786444d187 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 b985d63d77b671e2d1d6e155eafa39579722d567..4bdd5972ed4750c8c9abc115f63c51f1a01f6229 100644 (file)
--- a/src/backend/catalog/pg_proc.c
+++ b/src/backend/catalog/pg_proc.c
@@ -688,6 +688,9 @@ 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.
@@ -735,6 +738,9 @@ 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,
@@ -785,6 +791,9 @@ 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 26a3a52efc30f30bef5dab32d34107899c1a85d6..c1259f3381d2f17c515f3e5e1646d8444e484afe 100644 (file)
--- a/src/backend/commands/functioncmds.c
+++ b/src/backend/commands/functioncmds.c
@@ -960,7 +960,6 @@ 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 ebde468ffa35c4a7b907f0d5b10402fe2e4736de..a94fdc11fed611650372b59e4838c75bfdd5f815 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"
@@ -2409,3 +2410,86 @@ 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 e588bb15d2f95c42bbffbde0c0b780311aad28ae..4faf9bc7dea37bee9c28e20168063d1ef529660c 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 e19756b8eefeb0c85c5d1733deebded521584aa9..b00aedf6dd6f267aefca6cd38a8935c337c6b3b6 100644 (file)
--- a/src/pl/plperl/plperl.c
+++ b/src/pl/plperl/plperl.c
@@ -1395,6 +1395,9 @@ 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))

diff --git a/src/pl/plpgsql/src/pl_handler.c b/src/pl/plpgsql/src/pl_handler.c
index 12661d32cf4ae39970e2ca31d6567af9333d5c8d..d23b95be66a0257228cde34a5309b8dae3509870 100644 (file)
--- a/src/pl/plpgsql/src/pl_handler.c
+++ b/src/pl/plpgsql/src/pl_handler.c
@@ -217,6 +217,9 @@ 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))