/*
	File:		MoreSecurity.h

	Contains:	Security utilities.

	Written by:	Quinn

	Copyright:	Copyright (c) 2002 by Apple Computer, Inc., All Rights Reserved.

	Disclaimer:	IMPORTANT:  This Apple software is supplied to you by Apple Computer, Inc.
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	Change History (most recent first):

$Log: MoreSecurity.h,v $
Revision 1.5  2003/01/20 07:58:32  eskimo1
Corrected some misspellings.

Revision 1.4  2002/12/12 17:47:57  eskimo1
There should only be one point 5 in the "how to use" comment.

Revision 1.3  2002/12/12 15:40:19  eskimo1
Eliminate MoreAuthCopyRightCFString because it makes no sense.  A helper tool should always have the right name hard-wired into it, and hardwiring a C string is even easier than hardwiring a CFString.

Revision 1.2  2002/11/25 16:42:29  eskimo1
Significant changes. Handle more edge cases better (for example, volumes with the "ignore permissions" flag turned on). Also brought MoreSecurity more into the CoreServices world.

Revision 1.1  2002/11/09 00:08:40  eskimo1
First checked in. A module containing security helpers.


*/

#pragma once

/////////////////////////////////////////////////////////////////

// MoreIsBetter Setup

#include "MoreSetup.h"

#if !TARGET_RT_MAC_MACHO
	#error MoreSecurity requires the use of Mach-O
#endif

// System prototypes

#include <Security/Security.h>
#include <CoreServices/CoreServices.h>

/////////////////////////////////////////////////////////////////

#ifdef __cplusplus
extern "C" {
#endif

/////////////////////////////////////////////////////////////////
#pragma mark ***** UID Management

// Basic utilities to manage your UIDs in setuid root programs.

// RUID = real user id      = ID of user who is running program
// EUID = effective user id = ID used to restrict privileged operations
// SUID = saved user id     = extra ID to allow setuid programs to switch in and out of privileged mode

extern int MoreSecPermanentlySetNonPrivilegedEUID(void);
    // Relinquish privileges by setting RUID, EUID, and SUID 
    // to the RUID.

extern int MoreSecTemporarilySetNonPrivilegedEUID(void);
    // Set the EUID to the RUID, which means that subsequent 
    // code runs with a non-zero EUID.  The process can 
    // still switch back to EUID when needed because the 
    // SUID is still 0.

extern int MoreSecSetPrivilegedEUID(void);
	// Set the EUID to 0.  This is only possible if either 
	// the EUID is already 0 or the SUID is 0.

// Typical Usage Patterns
// ----------------------
// #1 -- Do privileged operation and then drop privs
// 
//       DoPrivilegedStuff();
//       MoreSecPermanentlySetNonPrivilegedEUID();
//       DoNonPrivilegedStuff();
//
// #2 -- Switch in and out of privileged mode
//
//       MoreSecTemporarilySetNonPrivilegedEUID();
//       DoNonPrivilegedStuff();
//       MoreSecSetPrivilegedEUID();
//       DoPrivilegedStuff();
//       ... repeat as necessary ...
//       MoreSecPermanentlySetNonPrivilegedEUID();
//       DoNonPrivilegedStuff();
//

/////////////////////////////////////////////////////////////////
#pragma mark **** Environment Management

// This is a utility routine to destroy any environment that you might have 
// inherited from your parent.  It's most useful in a setuid root program, 
// which has to be careful that it doesn't rely on untrusted information 
// that it inherited.  Also useful for any privileged program which wants 
// to execute a non-privileged program and ensure that no privileged 
// information leaks to that program.

// The following is a set of bit masks used for the whatToDubya parameter 
// of the MoreSecDestroyInheritedEnvironment function.

enum {
    kMoreSecKeepNothingMask           = 0x0000,
    
    kMoreSecKeepArg0Mask              = 0x0001,
        // if set, don't reset argv[0] to the real 
        // executable path
    kMoreSecKeepEnvironmentMask       = 0x0002,
        // if set, don't clear environment
    kMoreSecKeepStandardFilesMask     = 0x0004,
        // if set, don't close stdin, stdout, stderr
    kMoreSecKeepOtherFilesMask        = 0x0008,
        // if set, don't close other file descriptors
    kMoreSecKeepSignalsMask           = 0x0010,
        // if set, don't reset signals to default
    kMoreSecKeepUmaskMask             = 0x0020,
        // if set, don't reset umask
    kMoreSecKeepNiceMask              = 0x0040,
        // if set, don't reset process nice values
    kMoreSecKeepResourceLimitsMask    = 0x0080,
        // if set, don't reset resource limits
    kMoreSecKeepCurrentDirMask        = 0x0100, 
        // if set, don't set CWD to "/"
    kMoreSecKeepTimersMask            = 0x0200, 
        // if set, don't reset all interval timers
        
    kMoreSecKeepEverythingMask        = 0x03FF
};

extern int MoreSecDestroyInheritedEnvironment(int whatToDubya, const char **argv);
    // This function eliminates most of the environmental 
    // factors that you have inherited from your parent 
    // process.  The function is intended for use by setuid 
    // root programs, who shouldn't trust any information 
    // supplied by a potentially malicious parent process.
    // 
    // The whatToDubya parameter is a bit mask that 
    // specifies what environmental factors to *keep*.  The 
    // most secure option is to pass kMoreSecKeepNothingMask 
    // (ie 0), which means you keep no environmental factors.
    //
    // The argv parameter allows the function to access argv 
    // without any special magic.  You can pass NULL if you 
    // whatToDubya has kMoreSecKeepArg0Mask set, which 
    // indicates that you don't want to reset argv[0].
    //
    // The function returns a errno-style error.  If it's 
    // non-zero you probably should err on the side of 
    // caution and refuse to start up.

/////////////////////////////////////////////////////////////////
#pragma mark **** Helper Tool Big Picture

// These utilities let you easily implement a setuid helper tool.
// This design is largely stolen from the DTS sample code "AuthSample", 
// with refinements to cover more cases and allow easy code reuse.
// 
// <http://developer.apple.com/samplecode/Sample_Code/Security/AuthSample.htm>
//
// To create a setuid root help tool, follow these simple instructions.
//
// 1. Define a request/response protocol based around CFDictionaries.
//    This is as simple as defining the set of keys in the request 
//    that describe the operation you want to do, and the set of 
//    keys in the response that hold the results of those operations 
//    (if any).
//
// 2. Create a helper tool whose "main" function looks like:
//
//  	int main(int argc, const char *argv[])
//  	{	
//  		int 				err;
//  		int 				result;
//  		AuthorizationRef 	auth;
//  		
//  		auth = MoreSecHelperToolCopyAuthRef();
//  	
//  		err = MoreSecDestroyInheritedEnvironment(kMoreSecKeepStandardFilesMask, argv);
//  		if (err == 0) {
//  			err = MoreUNIXIgnoreSIGPIPE();
//  		}
//  		if (err == 0) {
//  			err = MoreSecHelperToolMain(STDIN_FILENO, STDOUT_FILENO, auth, MyCommandProc, argc, argv);
//  		}
//  	
//  		return MoreSecErrorToHelperToolResult(err);
//  	}
// 
//    MyCommandProc is a callback that is executed when a request is 
//    passed to the tool.  It can do privileged operations, such as 
//    committing changes to System Configuration framework.  Its 
//    parameters are passed to it as a CFDictionary.  It can pass results 
//    back to the application by creating a response dictionary.
//
// 3. Put the tool in the "MacOS" folder inside your application package.
//    Decide on two tool names, one for the original template tool 
//    (for example, "HelperToolTemplate") and one for the working copy 
//    of the tool (for example, "HelperTool").
//
// 4. In your application, use MoreSecCopyHelperToolURLAndCheckBundled to find 
//    (or create) the working copy of your tool.  
// 
//		err = MoreSecCopyHelperToolURLAndCheckBundled(CFBundleGetMainBundle(), CFSTR("HelperToolTemplate"), 
//											  	 	  kApplicationSupportFolderType, CFSTR("My Application Name"), CFSTR("HelperTool"), 
//											  	 	  &tool);
//    
//    The working copy of the helper tool will exist within the user's 
//    Application Support folder.  See the description of 
//    MoreSecCopyHelperToolURLAndCheck[Bundled] for an explanation of this.
// 
// 5. Then use MoreSecExecuteRequestInHelperTool to execute the tool, passing it 
//    a request dictionary.  On success, you'll get back a response dictionary.  Use 
//    MoreSecGetErrorFromResponse to extract the error result from your tool's 
//    MyCommandProc routine.
//
// 6. For extra credit, use AuthorizationCopyRights to have your tool 
//    be self-limiting, as described in the Authorization Services docs.
//
//    <http://developer.apple.com/techpubs/macosx/CoreTechnologies/securityservices/authorizationservices/authservices.html>
// 
//              *              *              *              *
//
// This complex design is required for a number of reasons.
// 
//  o The technique of using a self-limiting setuid root helper tool is 
//    recommended by Apple's security team.
// 
//  o You need to use a working helper tool and a backup helper tool 
//    because of the problems in the Mac OS X Finder.  The problems 
//    are as follows:
//
//    - In Mac OS X 10.0.x, the Finder will silently not copy the  
//      setuid root attribute of a helper program within your bundle.
//
//    - In Mac OS X 10.1.x, the Finder will not copy the setuid root 
//      helper program within your bundle (and display a wacky error 
//      dialog).
//
//    - In Mac OS X 10.2.x, the Finder will refuse to copy an application 
//      that contains a setuid root helper tool.
//
//  o It's a general requirement that a Mac OS X application be 
//    self-contained, that is, it should be drag installable and not 
//    require the user to run an installer.
//
//  o It's a general requirement that a Mac OS X application be runnable 
//    from a read-only volume (like a CD-ROM).  Thus, you can't place 
//    the helper tool within the application bundle because copying it 
//    there would require the volume be writable.
//
//  o Users can choose to ignore privileges on a particular volume 
//    by checking a checkbox in the Finder Get Info window.  A setuid 
//    program on an volume that's ignoring privileges will not be 
//    effective (ie it won't run as EUID 0).
//
// By placing the setuid root helper tool within the Application Support 
// folder, this code allows you to copy the application bundle from 
// one disk to another without breaking it and without any weird error 
// dialogs.  In addition, you can copy the program to another machine 
// entirely, and the only thing the user has to do is to reenter their 
// admin password when they first run the application.  Finally, the 
// user's Application Support folder is typically inside their home 
// directory, which is typically on the system volume, and thus is 
// not ignoring privileges.

/////////////////////////////////////////////////////////////////
#pragma mark **** Helper Tool Implementation

// The following are special error codes used by the helper tool code. 
// These error codes can be mapped to the helper tool return status 
// (ie the result from main).  For example, kMoreSecResultParamErr maps 
// to a return status of 1, kMoreSecResultPrivilegesErr maps to 2, 
// and so on.

enum {
	kMoreSecResultBase			   = 5360,

	kMoreSecResultParamErr         = 5361,
	kMoreSecResultPrivilegesErr    = 5362,
	kMoreSecResultCanceledErr      = 5363, 
	kMoreSecResultInternalErrorErr = 5364,
	
	kMoreSecFirstResultErr = kMoreSecResultParamErr,
	kMoreSecLastResultErr  = kMoreSecResultInternalErrorErr
	
	// other errors defined below
};

extern int MoreSecErrorToHelperToolResult(int errNum);
	// A function to map an errno/OSStatus to a helper tool return 
	// status.  The MoreSec error codes are mapped as described 
	// above, and there is a minimal amount of mapping of other 
	// OSStatus values to those codes.
	
extern int MoreSecHelperToolResultToError(int toolResult);
	// This function maps a helper tool status to the corresponding 
	// errno/OSStatus value.

extern AuthorizationRef MoreSecHelperToolCopyAuthRef(void);
	// When started by AuthorizationExecuteWithPrivileges, a helper tool 
	// gets some important parameters via its environment.  However, 
	// a helper tool is *supposed* to blow away its environment 
	// (using MoreSecDestroyInheritedEnvironment) to minimise security 
	// risks.  This routine allows the tool to recover the parameters 
	// supplied by AuthorizationExecuteWithPrivileges before it 
	// calls MoreSecDestroyInheritedEnvironment to destroy the environment.
	// 
	// IMPORTANT: It's quite normal for this routine to return NULL.
	// You should just pass the result straight to MoreSecHelperToolMain.

typedef OSStatus (*MoreSecCommandProc)(AuthorizationRef auth, 
									   CFDictionaryRef request, CFDictionaryRef *response);
	// This is a callback type, called by MoreSecHelperToolMain to 
	// actually execute commands.
	// 
	// auth will not be NULL
	// request will not be NULL
	// response will not be NULL
	// *response will be NULL
	//
	// The EUID will be set to the RUID, while the SUID will be 0.
	// If you need to do a privileged operation, you should 
	// temporarily set the EUID to 0 via MoreSecSetPrivilegedEUID,
	// and set it back whenh you're done via MoreSecTemporarilySetNonPrivilegedEUID.
	//
	// If you don't need to return anything other than a function 
	// result to your client, you don't need to mess with response.
	// MoreSecHelperToolMain will create a dictionary containing 
	// your function result and pass that back to the client.
	// Even if you do return a dictionary in *response, 
	// MoreSecHelperToolMain will still put your function result into the 
	// kMoreSecErrorNumberKey key unless you've set up that key yourself.
	//
	// If you want to self-limit the capabilities of your helper tool, 
	// you might consider using AuthorizationCopyRights to make sure 
	// that the user has authorization to do specific operations.
	// 
	// If you do create a response, it must be it must be flattenable via 
	// the CFPropertyList APIs.

extern int MoreSecHelperToolMain(int fdIn, int fdOut, AuthorizationRef auth, 
								 MoreSecCommandProc commandProc, int argc, const char *argv[]);
	// This function is the helper tool half of MoreSecExecuteRequestInHelperTool.
	// It's designed to be called directly from your helper tool's "main" function, 
	// and to implement the entire tool, calling commandProc to handle the specific 
	// command.
	//
	// IMPORTANT: Contrary to the usual rules, this routine disposes of 
	// auth before returning.  This makes sense when you consider the 
	// standard "main" function, described above.
	//
	// fdIn  must be non-negative, typically you pass in STDIN_FILENO
	// fdOut must be non-negative, typically you pass in STDOUT_FILENO
	// auth may be NULL, typically you just pass in the result of MoreSecHelperToolCopyAuthRef
	// commandProc must not be NULL
	// argc must be 1 or 2, depending on whether the tool is running in self-repair mode, 
	// typically you just pass in the argc that was supplied to main
	// argv must not be NULL, typically you just pass in the value that was supplied to main

/////////////////////////////////////////////////////////////////
#pragma mark **** Calling Helper Tool

enum {
	kMoreSecIgnoringPrivsInFolderErr = 5370
};

extern OSStatus MoreSecIsFolderIgnoringPrivileges(const FSRef *folder, Boolean *ignoringPrivs);
	// Determines whether the specified folder is on a volume that's 
	// ignoring privileges (as per the "Ignore ownership on this volume" 
	// checkbox in the Finder's Get Info dialog).  There is a real API to 
	// do this but it's currently private. I've filed a request to get 
	// this made public [3061192].  Until that's done, I use a workaround 
	// that involves creating a temporary file within the folder and 
	// seeing if I can manipulate its permissions.  For this workaround to 
	// work the folder must be read/write accessible.
	//
	// folder must not be NULL; folder must reference a folder
	// ignoringPrivs must not be NULL;
	// on success, *ignoringPrivs is true if the volume on which the folder 
	// resides is ignoring privileges; on error, *ignoringPrivs is undefined

extern OSStatus MoreSecCopyHelperToolURLAndCheck(CFURLRef templateTool,
                                                 OSType folder, CFStringRef subFolderName, CFStringRef toolName,
                                                 CFURLRef *tool, Boolean *toolFound);
    // This routine returns a CFURL to your helper tool.  This CFURL typically 
	// points to a working copy of the tool inside the Application Support 
	// folder.  This routine confirms that the tool exists and is valid in that 
	// location.  If that check fails, it restores the tool from the template. 
	// Thus, the tool pointed to by the returned CFURL will be a valid copy of the 
	// template tool specified by templateTool.
	//
	// templateTool must not be NULL; the tool referenced by templateTool 
	// must exist; templateTool is a reference to your original helper tool; 
	// if your template tool is bundled within your application package, you might 
	// want to use the MoreSecCopyHelperToolURLAndCheckBundled wrapper routine 
	// (see below)
	//
	// folder is a Folder Manager folder selector; typically you pass kApplicationSupportFolderType
	//
	// subFolderName is the name of an optional sub-folder within the 
	// folder specified above; if this is not NULL, the returned URL 
	// points to within the named folder; if it is NULL, the URL points 
	// directly within the Folder Manager folder; if you don't want to 
	// pass NULL, you typically use the name of your application
	//
	// toolName is the name of the helper tool itself
	//
	// tool must not be NULL; *tool must be NULL; on success, *tool 
	// is a newly created CFURL that you must release; on error, *tool 
	// will be NULL
	//
	// On current systems, the returned URL will point to one of the 
	// following if the tool already exists.
	//
	//   ~/Library/Application Support/<subFolderName>/<toolName>
	//   /Library/Application Support/<subFolderName>/<toolName>
	//   /Network/Library/Application Support/<subFolderName>/<toolName>
	//   /System/Library/Application Support/<subFolderName>/<toolName>
	//
	// If the tool doesn't already exist, a copy will be made in:
	//
	//   ~/Library/Application Support/<subFolderName>/<toolName>
	//
	// and that URL will be return.d
	//
	// In all cases, you can treat <subFolderName> as the empty string 
	// if subFolderName is NULL.
	//
	// An error result of kMoreSecIgnoringPrivsInFolderErr means that 
	// the helper tool could not be created because the folder is 
	// on a volume that's ignoring privileges.
	//
	// IMPORTANT:
	// When create the helper tool from the template tool, this only copies the 
	// data fork of the tool.  If you the helper tool needs to access resources, 
	// you should either pass those resources in the request dictionary or 
	// pass it the URL of your bundle in the request dictionary.
	//
	// Note:
	// This does not verify any tool checksum or digital signature, 
	// for the reasons outlined in the comment "Notes on Code Signing"
	// (in "MoreSecurity.c").

extern OSStatus MoreSecCopyHelperToolURLAndCheckBundled(CFBundleRef inBundle, CFStringRef templateToolName, 
														OSType folder, CFStringRef subFolderName, CFStringRef toolName, 
														CFURLRef *tool, Boolean *toolFound);
	// Finds (or creates) a helper tool in a bundled application.  
	// inBundle and templateToolName describe the location of the template 
	// tool.  folder, subFolderName, and toolName describe the location of the 
	// working copy of the tool. 
	//
	// This routine is a simple composition of CFBundleCopyAuxiliaryExecutableURL and 
	// MoreSecCopyHelperToolURLAndCheck.
	//
	// inBundle must not be NULL; typically you just pass in CFBundleGetMainBundle()
	// 
	// templateToolName must not be NULL; the tool must exist within the executable 
	// folder of inBundle
	//
	// See MoreSecCopyHelperToolURLAndCheck for a full description of the folder, 
	// subFolderName, and toolName parameters.  Typically you pass 
	// kApplicationSupportFolderType for folder and your application name for 
	// subFolderName.
	//
	// tool must not be NULL; *tool must be NULL; on success, *tool will be 
	// a URL to the helper tool; on error, *tool will be NULL

extern OSStatus MoreSecExecuteRequestInHelperTool(CFURLRef helperTool, AuthorizationRef auth, 
											 	  CFDictionaryRef request, CFDictionaryRef *response);
	// Executes a privileged request in a helper tool.  helperTool is 
	// a reference to the helper tool to run.  You typically gets its value 
	// using MoreSecCopyHelperToolURLAndCheckBundled, although it's passed in as a 
	// parameter to allow flexibility.
	//
	// auth is your application's connection to Authorization Services. 
	// It's likely that you've used this connection to pre-authorization 
	// this operation, as described in the Authorization Services docs.
	//
	// <http://developer.apple.com/techpubs/macosx/CoreTechnologies/securityservices/authorizationservices/authservices.html>
	//
	// request specifies what you want the helper tool to do.  Its 
	// contents are not interpreted by MoreSecExecuteRequestInHelperTool, 
	// however, it must be flattenable via the CFPropertyList APIs.
	//
	// response is the reply from the helper tool.  It is not interpreted 
	// by MoreSecExecuteRequestInHelperTool other than to add a key
	// (kMoreSecErrorNumberKey) which contains the error from the 
	// helper tool's commandProc.
	//
	// helperTool must not be NULL
	// auth must not be NULL
	// request must not be NULL
	//  response must not be NULL
	// *response must be NULL

extern OSStatus MoreSecGetErrorFromResponse(CFDictionaryRef response);
	// this function returns the error stored in a helper tool 
	// response obtained via MoreSecExecuteRequestInHelperTool.
	//
	// response must not be NULL

#define kMoreSecErrorNumberKey CFSTR("com.apple.dts.MoreIsBetter.MoreSec.ErrorNumber")		// CFNumberRef, OSStatus
	// The dictionary key where the helper tool error is stored.
	
#ifdef __cplusplus
}
#endif