A
Advanced Topics in Oracle Label Security

This appendix covers topics of interest to advanced users of Oracle Label Security. It contains these sections:

• Analyzing the Relationships Between Labels
• OCI Interface for Setting Session Labels

Analyzing the Relationships Between Labels

This section describes relationships between labels. It contains these topics:

• Dominant and Dominated Labels
• Non-Comparable Labels
• Using Dominance Functions

Dominant and Dominated Labels

The relationship between two labels can be described in terms of dominance. A user's ability to access an object depends on whether the user's label dominates the label of the object. If a user's label does not dominate the object's label, the user is not allowed to access the object.

Label dominance is analyzed in terms of all its components: levels, compartments, and groups.

Table A-1 Dominance in the Comparison of Labels

Factor	Criteria for Dominance
Level	For label1 to dominate label2, the level of label1 must be greater than or equal to that of label2.
Compartment	For label1 to dominate label2, the compartments of label1 must contain all of the compartments of label2.
Group	For label1 to dominate label2, label1 must contain at least one of the groups of label2.

One label dominates another label if all of its components dominate the components of the other label. For example, the label HIGHLY_SENSITIVE:FINANCE,OPERATIONS dominates the label HIGHLY_SENSITIVE:FINANCE. Similarly, the label HIGHLY_SENSITIVE::WR_AP dominates the label HIGHLY_SENSITIVE::WR_AP, WR_AR.

Non-Comparable Labels

The relationship between two labels cannot always be defined by dominance. Two labels are non-comparable if neither label dominates the other. If any compartments differ between the two labels (as with HS:A and HS:B), then they are non-comparable. Similarly, the labels HS:A and S:B are non-comparable.

Using Dominance Functions

You can use dominance functions to specify ranges in queries. The following functions enable you to indicate dominance relationships between specified labels.

Table A-2 Functions to Determine Dominance

Function	Meaning
STRICTLY_DOMINATES	The value of label1 dominates that of label2, and is not equal to it.
DOMINATES	The value of label1 dominates, or is equal to, that of label2.
DOMINATED_BY	The value of label1 is dominated by that of label2.
STRICTLY_DOMINATED_BY	The value of label1 is dominated by that of label2, and is not equal to it.

Note that there are two types of dominance function. Whereas the SA_UTL dominance functions return BOOLEAN values, the standalone dominance functions return integers.

• DOMINATES Standalone Function
• STRICTLY_DOMINATES Standalone Function
• DOMINATED_BY Standalone Function
• STRICTLY_DOMINATED_BY Standalone Function
• SA_UTL.DOMINATES
• SA_UTL.STRICTLY_DOMINATES
• SA_UTL.DOMINATED_BY
• SA_UTL.STRICTLY_DOMINATED_BY

DOMINATES Standalone Function

The DOMINATES (DOM) function returns 1 (TRUE) if label1 dominates label2, or 0 (FALSE) if it does not.

Syntax:

FUNCTION DOMINATES (
  label1          IN NUMBER,
  label2          IN NUMBER) 
RETURN INTEGER; 

STRICTLY_DOMINATES Standalone Function

The STRICTLY_DOMINATES (SDOM) function returns 1 (TRUE) if label1 dominates label2 and is not equal to it.

Syntax:

FUNCTION STRICTLY_DOMINATES (
  label1          IN NUMBER,
  label2          IN NUMBER) 
RETURN INTEGER; 

DOMINATED_BY Standalone Function

The DOMINATED_BY (DOM_BY) function returns 1 (TRUE) if label1 is dominated by label2.

Syntax:

FUNCTION DOMINATED_BY (
  label1          IN NUMBER,
  label2          IN NUMBER
RETURN INTEGER;

STRICTLY_DOMINATED_BY Standalone Function

The STRICTLY_DOMINATED_BY (SDOM_BY) function returns 1 (TRUE) if label1 is dominated by label2 and is not equal to it.

Syntax:

FUNCTION STRICTLY_DOMINATED_BY (
  label1          IN NUMBER,
  label2          IN NUMBER) 
RETURN INTEGER; 

SA_UTL.DOMINATES

The SA_UTL.DOMINATES function returns TRUE if label1 dominates label2.

Syntax:

FUNCTION DOMINATES (
  label1          IN NUMBER,
  label2          IN NUMBER) 
RETURN BOOLEAN; 

SA_UTL.STRICTLY_DOMINATES

The SA_UTL.STRICTLY_DOMINATES function returns TRUE if label1 dominates label2 and is not equal to it.

Syntax:

FUNCTION STRICTLY_DOMINATES (
  label1          IN NUMBER,
  label2          IN NUMBER) 
RETURN BOOLEAN; 

SA_UTL.DOMINATED_BY

The SA_UTL.DOMINATED_BY function returns TRUE if label1 is dominated by label2.

Syntax:

FUNCTION DOMINATED_BY (
  label1          IN NUMBER,
  label2          IN NUMBER) 
RETURN BOOLEAN;

SA_UTL.STRICTLY_DOMINATED_BY

The SA_UTL.STRICTLY_DOMINATED_BY function returns TRUE if label1 is dominated by label2 and is not equal to it.

Syntax:

FUNCTION STRICTLY_DOMINATED_BY (
  label1          IN NUMBER,
  label2          IN NUMBER)
RETURN BOOLEAN;

OCI Interface for Setting Session Labels

When using OCI to connect, the policy's SYS_CONTEXT variables can be used to initialize the session label and the row label. The variables are set using the OCIAttrSet function to initialize "externally initialized" SYS_CONTEXT variables. These are available in Release 8.1.7 only when Oracle Label Security is installed.

Each policy has a SYS_CONTEXT named SA$policy_name_X. There are two variables that can be set: INITIAL_LABEL and INITIAL_ROW_LABEL.

When set to valid labels within the user's authorizations, the new values will be used instead of the default values stored for the user. This is the same mechanism used for remote connections

OCIAttrSet

Additional attributes are defined for OCIAttrSet to insert context. Use OCI_ATTR_APPCTX_SIZE to initialize the context array size with the desired number of context attributes:

OCIAttrSet(session, OCI_HTYPE_SESSION, 
                 (dvoid *)&size, (ub4)0, OCI_ATTR_APPCTX_SIZE, error_handle); 
 

Note that size is ub4 type.

OCIAttrGet

Then call OCIAttrGet with OCI_ATTR_APPCTX_LIST to get a handle on the application context list descriptor for the session:

(session, OCI_HTYPE_SESSION, 
               (dvoid *)&ctxl_desc, (ub4)0, OCI_ATTR_APPCTX_LIST, error_handle);

Note that ctxl_desc is (OCIParam *) type[

OCIParamGet

Then use the application context list descriptor to obtain an individual descriptor for the i-th application context:

OCIParamGet(ctxl_desc, OCI_DTYPE_PARAM, error_handle,(dvoid **)&ctx_desc, i);  

Note that ctx_desc is (OCIParam *) type.

OCIAttrSet

Set the appropriate values in the application context using the three new attributes OCI_ATTR_APPCTX_NAME, OCI_ATTR_APPCTX_ATTR, and OCI_ATTR_APPCTX_VALUE:

OCIAttrSet(ctx_desc, OCI_DTYPE_PARAM,
                 (dvoid *)ctx_name, sizeof(ctx_name), OCI_ATTR_APPCTX_NAME,
                 error_handle);  

OCIAttrSet(ctx_desc, OCI_DTYPE_PARAM,
                 (dvoid *)attr_name, sizeof(attr_name), OCI_ATTR_APPCTX_ATTR,
                 error_handle);  

OCIAttrSet(ctx_desc, OCI_DTYPE_PARAM,
                 (dvoid *)value, sizeof(value), OCI_ATTR_APPCTX_VALUE,
                 error_handle);  

Note that only character type is supported, because application context operations are based on VARCHAR2 type.

OCI Example

The following example shows how to use externalized SYS_CONTEXT with Oracle Label Security.

#ifdef RCSID
static char *RCSid =
   "$Header: ext_mls.c 09-may-00.10:07:08 jdoe Exp $ ";
#endif /* RCSID */

/* Copyright (c) Oracle Corporation 1999, 2000. All Rights Reserved. */

/*

   NAME
     ext_mls.c - <one-line expansion of the name>

   DESCRIPTION
     <short description of component this file declares/defines>

   PUBLIC FUNCTION(S)
     <list of external functions declared/defined - with one-line descriptions>

   PRIVATE FUNCTION(S)
     <list of static functions defined in .c file - with one-line descriptions>

   RETURNS
     <function return values, for .c file with single function>

   NOTES
     <other useful comments, qualifications, and so on>

   MODIFIED   (MM/DD/YY)
   jdoe      05/09/00 - cleanup
   jdoe      10/13/99 - standalone OCI program to test MLS SYS_CONTEXT
   jdoe      10/13/99 - Creation

*/
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <oci.h>

static OCIEnv *envhp;
static OCIError *errhp;

int main(/*_ int argc, char *argv[] _*/);

/* get and print error */
static void checkerr(/*_OCIError *errhp, sword status _*/);
/* print error */
static void printerr(char *call);
static sword status;

/* return the average of employees' salary */
static CONST text *const selectstmt = (text *)
     "select avg(sal) from sa_demo.emp";
 
int main(argc, argv)
int argc;
char *argv[];
{
  OCISession *authp = (OCISession *) 0;
  OCIServer *srvhp;
  OCISvcCtx *svchp;
  OCIDefine *defnp = (OCIDefine *) 0;
  dvoid *parmdp;
  ub4 ctxsize;
  OCIParam *ctxldesc;
  OCIParam *ctxedesc;
  OCIStmt *stmtp = (OCIStmt *) 0;
  ub4 avg_sal = 0;
  sword status;

  if (OCIInitialize((ub4) OCI_DEFAULT, (dvoid *) 0,
                    (dvoid * (*)(dvoid *, size_t)) 0,
                    (dvoid * (*)(dvoid *, dvoid *, size_t)) 0,
                    (void (*)(dvoid *, dvoid *)) 0))
    printerr("OCIInitialize");

  if (OCIEnvInit((OCIEnv **) &envhp, OCI_DEFAULT, (size_t) 0, (dvoid **) 0))
    printerr("OCIEnvInit");
  
  if (OCIHandleAlloc((dvoid *) envhp, (dvoid **) &errhp, OCI_HTYPE_ERROR,
                     (size_t) 0, (dvoid **) 0))
    printerr("OCIHandleAlloc:OCI_HTYPE_ERROR");

  if (OCIHandleAlloc((dvoid *) envhp, (dvoid **) &srvhp, OCI_HTYPE_SERVER,
                     (size_t) 0, (dvoid **) 0))
    printerr("OCIHandleAlloc:OCI_HTYPE_SERVER");

  if (OCIHandleAlloc((dvoid *) envhp, (dvoid **) &svchp, OCI_HTYPE_SVCCTX,
                     (size_t) 0, (dvoid **) 0))
    printerr("OCIHandleAlloc:OCI_HTYPE_SVCCTX");

  if (OCIServerAttach(srvhp, errhp, (text *) "", strlen(""), 0))
    printerr("OCIServerAttach");

  /* set attribute server context in the service context */
  if (OCIAttrSet((dvoid *) svchp, OCI_HTYPE_SVCCTX, (dvoid *) srvhp,
                 (ub4) 0, OCI_ATTR_SERVER, (OCIError *) errhp))
    printerr("OCIAttrSet:OCI_HTYPE_SVCCTX");

  if (OCIHandleAlloc((dvoid *) envhp, (dvoid **) &authp,
                     (ub4) OCI_HTYPE_SESSION, (size_t) 0, (dvoid **) 0))
    printerr("OCIHandleAlloc:OCI_HTYPE_SESSION");

  /* set application context to 1 */
  ctxsize = 1;

  /* set up app ctx buffer */
  if (OCIAttrSet((dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *) &ctxsize,
                 (ub4) 0, (ub4) OCI_ATTR_APPCTX_SIZE, errhp))
    printerr("OCIAttrSet:OCI_ATTR_APPCTX_SIZE");

  /* retrieve the list descriptor */
  if (OCIAttrGet((dvoid *) authp, (ub4) OCI_HTYPE_SESSION,
                 (dvoid *) &ctxldesc, 0, OCI_ATTR_APPCTX_LIST, errhp))
    printerr("OCIAttrGet:OCI_ATTR_APPCTX_LIST");

  if (status = OCIParamGet(ctxldesc, OCI_DTYPE_PARAM, errhp,
                           (dvoid **) &ctxedesc, 1))
    {
      if (status == OCI_NO_DATA)
        {
          printf("No Data found!\n");
          exit(1);
        }
    }

  /* set context namespace to SA$<pol_name>_X */
  if (OCIAttrSet((dvoid *) ctxedesc, (ub4) OCI_DTYPE_PARAM,
                 (dvoid *) "SA$HUMAN_RESOURCES_X",
                 (ub4) strlen((char *) "SA$HUMAN_RESOURCES_X"),
                 (ub4) OCI_ATTR_APPCTX_NAME, errhp))
    printerr("OCIAttrSet:OCI_ATTR_APPCTX_NAME:SA$HUMAN_RESOURCES_X");

  /* set context attribute to INITIAL_LABEL */
  if (OCIAttrSet((dvoid *) ctxedesc, (ub4) OCI_DTYPE_PARAM,
                 (dvoid *) "INITIAL_LABEL",
                 (ub4) strlen((char *) "INITIAL_LABEL"),
                 (ub4) OCI_ATTR_APPCTX_ATTR, errhp))
    printerr("OCIAttrSet:OCI_DTYPE_PARAM:INITIAL_LABEL");

  /* set context value to argv[3] - initial label */
  if (OCIAttrSet((dvoid *) ctxedesc, (ub4) OCI_DTYPE_PARAM,
                 (dvoid *) argv[3],
                 (ub4) strlen((char *) argv[3]),
                 (ub4) OCI_ATTR_APPCTX_VALUE, errhp))
    printerr("OCIAttrSet:argv[3]");

  /* username first command line argument */
  if (OCIAttrSet((dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *) argv[1],
                 (ub4) strlen((char *) argv[1]), (ub4) OCI_ATTR_USERNAME,
                 errhp))
    printerr("OCIAttrSet:username");

  /* password second command line argument */
  if (OCIAttrSet((dvoid *) authp, (ub4) OCI_HTYPE_SESSION, (dvoid *) argv[2],
                 (ub4) strlen((char *) argv[2]), (ub4) OCI_ATTR_PASSWORD,
                 errhp))
    printerr("OCIAttrSet:password");

  if (OCISessionBegin(svchp, errhp, authp, OCI_CRED_RDBMS, (ub4) OCI_DEFAULT))
    printerr("OCISessionBegin");

  if (OCIAttrSet((dvoid *) svchp, (ub4) OCI_HTYPE_SVCCTX, (dvoid *) authp,
                 (ub4) 0, (ub4) OCI_ATTR_SESSION, errhp))
    printerr("OCIAttrSet:OCI_ATTR_SESSION");

  if (OCIHandleAlloc((dvoid *) envhp, (dvoid **) &stmtp, OCI_HTYPE_STMT,
                     0, 0))
    printerr("OCIHandleAlloc:OCI_HTYPE_STMT");

  if (OCIStmtPrepare(stmtp, errhp, (CONST OraText *) selectstmt,
                     (ub4) strlen((const char *) selectstmt),
                     (ub4) OCI_NTV_SYNTAX, (ub4) OCI_DEFAULT))
    printerr("OCIStmtPrepare");

  if (OCIDefineByPos(stmtp, &defnp, errhp, (ub4) 1, (dvoid *) &avg_sal,
                     (sb4) sizeof(avg_sal), SQLT_INT, 0, 0, 0, OCI_DEFAULT))
    printerr("OCIDefineByPos");

  if (status = OCIStmtExecute(svchp, stmtp, errhp, 1, 0, NULL, NULL,
                              OCI_DEFAULT))
    {
      if (status == OCI_NO_DATA)
        {
          printf("No Data found!\n");
          exit(1);
        }
    }

  if (OCISessionEnd(svchp, errhp, authp, OCI_DEFAULT))
    printerr("OCISessionEnd");

  printf("average salary is: %d\n", avg_sal);
}

void checkerr(errhp, status)
     OCIError *errhp;
     sword status;
{
  text errbuf[512];
  sb4 errcode = 0;

  switch (status)
    {
    case OCI_ERROR:
      (void) OCIErrorGet((dvoid *) errhp, 1, NULL, &errcode, errbuf,
                         (ub4) sizeof(errbuf), OCI_HTYPE_ERROR);
      printf("Error - %.*s\n", 512, errbuf);
      break;
    default:
      break;
    }
}

void printerr(call)
     char *call;
{
  printf("Error: %s\n", call);
}
/* end of file ext_mls.c */