TLA  Line data    Source code

       1                 : /*-------------------------------------------------------------------------
       2                 :  *
       3                 :  * usercontext.c
       4                 :  *    Convenience functions for running code as a different database user.
       5                 :  *
       6                 :  * Portions Copyright (c) 1996-2023, PostgreSQL Global Development Group
       7                 :  * Portions Copyright (c) 1994, Regents of the University of California
       8                 :  *
       9                 :  *
      10                 :  * IDENTIFICATION
      11                 :  *    src/backend/utils/init/usercontext.c
      12                 :  *
      13                 :  *-------------------------------------------------------------------------
      14                 :  */
      15                 : #include "postgres.h"
      16                 : 
      17                 : #include "miscadmin.h"
      18                 : #include "utils/acl.h"
      19                 : #include "utils/guc.h"
      20                 : #include "utils/usercontext.h"
      21                 : 
      22                 : /*
      23                 :  * Temporarily switch to a new user ID.
      24                 :  *
      25                 :  * If the current user doesn't have permission to SET ROLE to the new user,
      26                 :  * an ERROR occurs.
      27                 :  *
      28                 :  * If the new user doesn't have permission to SET ROLE to the current user,
      29                 :  * SECURITY_RESTRICTED_OPERATION is imposed and a new GUC nest level is
      30                 :  * created so that any settings changes can be rolled back.
      31                 :  */
      32                 : void
      33 GNC      147872 : SwitchToUntrustedUser(Oid userid, UserContext *context)
      34                 : {
      35                 :     /* Get the current user ID and security context. */
      36          147872 :     GetUserIdAndSecContext(&context->save_userid,
      37                 :                            &context->save_sec_context);
      38                 : 
      39                 :     /* Check that we have sufficient privileges to assume the target role. */
      40          147872 :     if (!member_can_set_role(context->save_userid, userid))
      41               2 :         ereport(ERROR,
      42                 :                 (errcode(ERRCODE_INSUFFICIENT_PRIVILEGE),
      43                 :                  errmsg("role \"%s\" cannot SET ROLE to \"%s\"",
      44                 :                         GetUserNameFromId(context->save_userid, false),
      45                 :                         GetUserNameFromId(userid, false))));
      46                 : 
      47                 :     /*
      48                 :      * Try to prevent the user to which we're switching from assuming the
      49                 :      * privileges of the current user, unless they can SET ROLE to that user
      50                 :      * anyway.
      51                 :      */
      52          147870 :     if (member_can_set_role(userid, context->save_userid))
      53                 :     {
      54                 :         /*
      55                 :          * Each user can SET ROLE to the other, so there's no point in
      56                 :          * imposing any security restrictions. Just let the user do whatever
      57                 :          * they want.
      58                 :          */
      59          147844 :         SetUserIdAndSecContext(userid, context->save_sec_context);
      60          147844 :         context->save_nestlevel = -1;
      61                 :     }
      62                 :     else
      63                 :     {
      64              26 :         int sec_context = context->save_sec_context;
      65                 : 
      66                 :         /*
      67                 :          * This user can SET ROLE to the target user, but not the other way
      68                 :          * around, so protect ourselves against the target user by setting
      69                 :          * SECURITY_RESTRICTED_OPERATION to prevent certain changes to the
      70                 :          * session state. Also set up a new GUC nest level, so that we can roll
      71                 :          * back any GUC changes that may be made by code running as the target
      72                 :          * user, inasmuch as they could be malicious.
      73                 :          */
      74              26 :         sec_context |= SECURITY_RESTRICTED_OPERATION;
      75              26 :         SetUserIdAndSecContext(userid, sec_context);
      76              26 :         context->save_nestlevel = NewGUCNestLevel();
      77                 :     }
      78          147870 : }
      79                 : 
      80                 : /*
      81                 :  * Switch back to the original user ID.
      82                 :  *
      83                 :  * If we created a new GUC nest level, also roll back any changes that were
      84                 :  * made within it.
      85                 :  */
      86                 : void
      87          147855 : RestoreUserContext(UserContext *context)
      88                 : {
      89          147855 :     if (context->save_nestlevel != -1)
      90              20 :         AtEOXact_GUC(false, context->save_nestlevel);
      91          147855 :     SetUserIdAndSecContext(context->save_userid, context->save_sec_context);
      92          147855 : }