/*

File: main.c

Abstract: Tool which demonstrates the use of FSCreateFileAndOpenForkUnicode to

create a file with restricted access from the outset but still allow the creating

process a read/write path to the new item's data fork.  This sample uses access control

lists to perform its task.  The target volume needs to have extended security enabled.

FSCreateFileAndOpenForkUnicode allows for the creation of a file with restricted access

on disk while still allowing for a read/write path for the creator.  In most cases it will

be more efficient in terms of system calls than FSCreateFileUnicode followed by FSOpenFork.

Version: <1.0>

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*/

#include <CoreServices/CoreServices.h>

#include <libgen.h>

#include <stdio.h>

#include <sys/acl.h>

#include <uuid/uuid.h>

#include <membership.h>

static OSStatus ConvertUTF8NameToHFSUniStr255(const char *inName, HFSUniStr255 *uniStr)

{

    OSStatus err = paramErr;

    CFStringRef tempString;

    tempString = CFStringCreateWithCString(kCFAllocatorDefault, inName, kCFStringEncodingUTF8);

    if (tempString)

    {

        err = FSGetHFSUniStrFromString(tempString, uniStr);

        CFRelease(tempString);

    }

    return err;

}

// return true if the volume supports extended security, false otherwise.

// If any errors are encountered return false.

static Boolean TargetVolumeSupportsExtendedSecurity(const FSRef *ref)

{

    Boolean         supportsExtendedSecurity = false;

    OSStatus        err;

    FSCatalogInfo   info;

    err = FSGetCatalogInfo(ref, kFSCatInfoVolume, &info, NULL, NULL, NULL);

    if (err == noErr)

    {   

        HParamBlockRec      paramBlock;

        GetVolParmsInfoBuffer   volParmsInfoBuffer;

        paramBlock.ioParam.ioNamePtr = NULL;

        paramBlock.ioParam.ioVRefNum = info.volume;

        paramBlock.ioParam.ioBuffer = (Ptr)&volParmsInfoBuffer;

        paramBlock.ioParam.ioReqCount = sizeof(GetVolParmsInfoBuffer);

        err = PBHGetVolParmsSync(&paramBlock);

        if ((err == noErr) && (volParmsInfoBuffer.vMVersion >= 3) && (volParmsInfoBuffer.vMExtendedAttributes & (1 << bSupportsExtendedFileSecurity)))

            supportsExtendedSecurity = true;

    }

    return supportsExtendedSecurity;

}

// create an ACL with a single ACE which allows the current user to read the object

static acl_t CreateReadOnlyForCurrentUserACL(void)

{

    acl_t   theACL = NULL;

    uuid_t  theUUID;

    int     result;

    result =  mbr_uid_to_uuid(geteuid(), theUUID);  // need the uuid for the ACE

    if (result == 0)

    {

        theACL = acl_init(1);   // create an empty ACL

        if (theACL)

        {

            Boolean freeACL = true;

            acl_entry_t newEntry;

            acl_permset_t newPermSet;

            result = acl_create_entry_np(&theACL, &newEntry, ACL_FIRST_ENTRY);

            if (result == 0)

            {   // allow

                result = acl_set_tag_type(newEntry, ACL_EXTENDED_ALLOW);

                if (result == 0)

                {   // the current user

                    result = acl_set_qualifier(newEntry, (const void *)theUUID);

                    if (result == 0)

                    {

                        result = acl_get_permset(newEntry, &newPermSet);

                        if (result == 0)

                        {   // to read data

                            result = acl_add_perm(newPermSet, ACL_READ_DATA);

                            if (result == 0)

                            {   

                                result = acl_set_permset(newEntry, newPermSet);

                                if (result == 0)

                                    freeACL = false;    // all set up and ready to go

                            }

                        }

                    }

                }

            }

            if (freeACL)

            {

                acl_free(theACL);

                theACL = NULL;

            }

        }

    }

    return theACL;

}

// This routine will create an FSFileSecurityRef which specifies a mode of 0 (no access) and

// an ACL with a single ACE which allows the current user to read the file.

static FSFileSecurityRef CreateReadOnlyACENoOtherAccess(void)

{

    FSFileSecurityRef   fileSecRef;

    // create a new FSFileSecurityRef

    fileSecRef = FSFileSecurityCreate(kCFAllocatorDefault);

    if (fileSecRef)

    {

        OSStatus err;

        Boolean releaseRef = true;  // set to false if we succeed at setting everything and have a valid ref to return

        err = FSFileSecuritySetMode(fileSecRef, 0);

        if (err == noErr)

        {

            acl_t theACL;

            theACL = CreateReadOnlyForCurrentUserACL();

            if (theACL)

            {

                if (FSFileSecuritySetAccessControlList(fileSecRef, theACL) == noErr)

                    releaseRef = false;

                acl_free(theACL);

            }

        }

        if (releaseRef)

        {

            CFRelease(fileSecRef);

            fileSecRef = NULL;

        }

    }

    return fileSecRef;

}

int main (int argc, const char * argv[]) {

    if (argc == 2)

    {

        char    *dirPath, *baseName;

        dirPath = dirname(argv[1]);

        if (dirPath != NULL)

        {

            FSRef   ref;

            OSStatus err;

            err = FSPathMakeRef((UInt8 *)dirPath, &ref, NULL);

            if (err == noErr)

            {

                HFSUniStr255 uniStr;

                baseName = basename(argv[1]);

                if (baseName != NULL)

                {

                    err = ConvertUTF8NameToHFSUniStr255(baseName, &uniStr);

                    if (err == noErr)

                    {

                        // check to see if target volume supports extended security - do not continue if it does not

                        if (TargetVolumeSupportsExtendedSecurity(&ref))

                        {

                            FSFileSecurityRef fileSecRef;

                            fileSecRef = CreateReadOnlyACENoOtherAccess();

                            if (fileSecRef)

                            {

                                SInt16              forkRefNum;

                                FSCatalogInfo       info;

                                FSPermissionInfo    *permInfo = (FSPermissionInfo *) info.permissions;

                                static const char   kWriteData[] = "0123456789";

                                permInfo->fileSec = fileSecRef;

                                // This will create a file on disk with the POSIX mode set to no access (000) and an ACL with a single ACE that allows the current user to read the file.

                                // The forkRefNum is an access path that allows read/write access to the file.  With these permissions in place even this process will not be able to 

                                // open the file for writing once it is closed.  Other processes running as this user (or any other non-super user) will not be able to open this file

                                // for writing since it was created from the outset with this user read only access.

                                err = FSCreateFileAndOpenForkUnicode(&ref, uniStr.length, uniStr.unicode, kFSCatInfoFSFileSecurityRef, &info, 0, NULL, fsRdWrPerm, &forkRefNum, NULL);

                                if (err == noErr)

                                {

                                    ByteCount actualCount;

                                    // new file created and data fork opened with read/write access

                                    err = FSWriteFork(forkRefNum, fsFromStart, 0, sizeof(kWriteData), kWriteData, &actualCount);

                                    if (err == noErr)

                                    {

                                        char    readBuffer[sizeof(kWriteData)];

                                        // read it back and make sure it is what we expected

                                        err = FSReadFork(forkRefNum, fsFromStart, 0, sizeof(kWriteData), readBuffer, &actualCount);

                                        if (err == noErr)

                                        {

                                            if (memcmp(kWriteData, readBuffer, sizeof(kWriteData)) != 0)

                                                printf("Data read was not what was expected: %s (expected %s)\n", readBuffer, kWriteData);

                                        }

                                        else

                                            printf("FSReadFork returned %ld\n", err);

                                    }

                                    (void) FSCloseFork(forkRefNum);

                                }

                                else

                                    printf("FSCreateFileAndOpenForkUnicode returned %ld\n", err);

                                CFRelease(fileSecRef);

                            }

                            else

                                printf("Could not create read only ACL\n");

                        }

                        else

                            printf("Target volume does not appear to support extended security\n");

                    }

                    else

                        printf("ConvertUTF8NameToHFSUniStr255 returned %ld for %s\n", err, baseName);

                }

                else

                    printf("Could not get basename for %s\n", argv[1]);

            }

            else

                printf("FSPathMakeRef returned %ld for %s [%ld]\n", err, argv[1]);

        }

        else

            printf("Could not get dirname for %s\n", argv[1]);

    }       

    else

        printf("usage: %s path\nThis tool will create a file at the location specified by path with mode 0 and an ACE which permits the owner to read the contents.\n", argv[0]);

    return 0;

}