// SPDX-License-Identifier: MPL-2.0
//
// Do NOT modify or remove this copyright and license
//
// Copyright (c) 2024-2024 Seagate Technology LLC and/or its Affiliates, All Rights Reserved
//
// This software is subject to the terms of the Mozilla Public
// License, v. 2.0. If a copy of the MPL was not distributed with this
// file, You can obtain one at http://mozilla.org/MPL/2.0/.
//
// ******************************************************************************************
// 
// \file secure_file.h
// \brief Defines functions for working with a file securely according to cert-c recommendations.
//        System type unique functionality is available in systemtype_secure_file.c
//

#include "secure_file.h"
#include "common_types.h"
#include "type_conversion.h"
#include "memory_safety.h"
#include "io_utils.h"
#include "string_utils.h"

#include <stdarg.h>
#include <string.h>

#if defined (_WIN32)
    #include <direct.h> //getcwd
#else
    #include <unistd.h> //getcwd
#endif

eReturnValues replace_File_Name_In_Path(char fullPath[OPENSEA_PATH_MAX], char* newFileName)
{
    char* ptr = M_NULLPTR;
    size_t ptrLen = 0;
    size_t fullLength = 0;
    if (M_NULLPTR != (ptr = strrchr(fullPath, SYSTEM_PATH_SEPARATOR)))
    {
        ptr += 1;
    }
    else
    {
        return FAILURE;
    }
    ptrLen = safe_strlen(ptr);
    //now that we have a valid pointer, set all the remaining characters to null, then set the new file name in place.
    memset(ptr, 0, ptrLen);
    fullLength = (OPENSEA_PATH_MAX - safe_strlen(fullPath));
    snprintf(ptr, fullLength, "%s", newFileName);
    return SUCCESS;
}


void free_File_Attributes(fileAttributes** attributes)
{
    if (attributes != M_NULLPTR)
    {
        if (*attributes != M_NULLPTR)
        {
#if defined (_WIN32)
            if ((*attributes)->winSecurityDescriptor)
            {
                explicit_zeroes((*attributes)->winSecurityDescriptor, (*attributes)->securityDescriptorStringLength);
                safe_Free(C_CAST(void**, &(*attributes)->winSecurityDescriptor));
                (*attributes)->securityDescriptorStringLength = 0;
            }
#endif //_WIN32
            explicit_zeroes(*attributes, sizeof(fileAttributes));
            safe_Free(M_REINTERPRET_CAST(void**, attributes));
        }
    }
}

void free_Secure_File_Info(secureFileInfo** fileInfo)
{
    if (fileInfo != M_NULLPTR)
    {
        if (*fileInfo != M_NULLPTR)
        {
            if ((*fileInfo)->attributes != M_NULLPTR)
            {
                free_File_Attributes(&(*fileInfo)->attributes);
                (*fileInfo)->attributes = M_NULLPTR;
            }
            if ((*fileInfo)->uniqueID != M_NULLPTR)
            {
                explicit_zeroes((*fileInfo)->uniqueID, sizeof(fileUniqueIDInfo));
                safe_Free(C_CAST(void**, &(*fileInfo)->uniqueID));
            }
            explicit_zeroes(*fileInfo, sizeof(secureFileInfo));
        }
        safe_Free(C_CAST(void**, fileInfo));
    }
}

//The purpose of this function is to perform the security validation necessary to make sure this is a valid file
//on the system and minimize path traversal and validate permissions as much as reasonably possible.
//The goal is mitigation of https://cwe.mitre.org/data/definitions/22.html
//Will be using recommendations from https://wiki.sei.cmu.edu/confluence/pages/viewpage.action?pageId=87151932
//     as much as possible to accomplish this.-TJE
//expectedFileInfo can be M_NULLPTR for the first time opening a file.
// If reopening a file used earlier, it is recommended to provide this info so it can be validated as the same file
// It is recommended to not reopen files, but that may not always be possible. So this exists to help validate
// that a file has not changed in some unexpected way.-TJE
M_NODISCARD secureFileInfo* secure_Open_File(const char* filename, const char* mode, const fileExt* extList, fileAttributes* expectedFileInfo, fileUniqueIDInfo* uniqueIdInfo /*optional*/)
{
    secureFileInfo* fileInfo = C_CAST(secureFileInfo*, safe_calloc(1, sizeof(secureFileInfo)));
    if (fileInfo && filename && mode) /* Not checking extList and outInfo because it is optional */
    {
        bool creatingFile = false;
        bool exclusiveFlag = false;
        char* internalmode = M_CONST_CAST(char*, mode);//we will dup mode if we need to modify it later, so this cast is to get rid of a warning
        bool duplicatedModeForInternalUse = false;
        char* intFileName = M_NULLPTR;//allocated/dup'd later
        fileInfo->file = M_NULLPTR;
        if (strchr(internalmode, 'w') || strchr(internalmode, 'a'))
        {
            //file is being created and does not exist yet.
            //Get the canonical path to the directory that the file will be in
            creatingFile = true;
        }
        //C11 adds 'x' to mode so that on a write, this forces a failure
        //Since we may not always be in a system with C11 or support for wx/w+x, handle this manually.
        if (strchr(internalmode, 'w') && strchr(internalmode, 'x'))
        {
            exclusiveFlag = true;
#if !defined (USING_C11) && !(defined (_MSC_VER) && _MSC_VER < 1800) && !(defined (__GLIBC__) || defined (__GNU_LIBRARY__)) && !(defined (USING_MUSL_LIBC) && USING_MUSL_LIBC > 0)//Glibc supports x. VS2013+ support x
            //For systems that do not support 'x' need to adjust the mode manually so that we do not pass an invalid 'x' flag when it is not supported.
            //      While this can always be done regardless of standard/library, it is better to pass flags onwards when they are supported for additional verification by the library/system - TJE
            duplicatedModeForInternalUse = true;
            internalmode = strdup(mode);
            char* thex = strchr(internalmode, 'x');
            if (thex)
            {
                //remove it since it is not supported outside C11 and a few \libraries that use it as an extension
                if (safe_strlen(thex) > 1)
                {
                    size_t lenx = safe_strlen(thex);
                    memmove(thex, thex + 1, lenx - 1);
                    thex[lenx - 1] = '\0';
                }
                else
                {
                    thex[0] = '\0';
                }
            }
#endif //!C11 && !MSVC 2013+ && !GLIBC
        }
        else if (strchr(internalmode, 'x'))
        {
            //invalid mode. X is only allowed with W, W+
            fileInfo->error = SEC_FILE_INVALID_MODE;
            return fileInfo;
        }
        //Get canonical path here before doing anything else???
        if (creatingFile)
        {
            //setup path to the directory to make sure it exists since the file does not yet.
            //NOTE: If we only have the current file name, no relative path, etc, need to call a function to get the current working directory to
            //      use that as the path.
            if (strchr(filename, '/') //always check for forwards slash since Windows can accept this
#if defined (_WIN32)
                || strchr(filename, '\\')//only check for backslash on Windows since this is a common path seperator on Windows and is the "prefered" format
#endif//_WIN32
                )
            {
                //there is a path or relative path that can be used to setup for getting the canonical path
                char* lastsep = strrchr(filename, '/');
#if defined (_WIN32)
                //In Windows, we need to determine if the final seperator is a / or \.
                //So also check for \ and figure out which was the last one.
                //A user can pass a path with both and it can be accepted by Windows, which is why we validate both of these.
                char* lastwinsep = strrchr(filename, '\\');
                if (lastsep == M_NULLPTR || C_CAST(uintptr_t, lastwinsep) > C_CAST(uintptr_t, lastsep))
                {
                    //backslash was detected last, so change to this pointer instead for strndup
                    lastsep = lastwinsep;
                }
#endif//_WIN32
                intFileName = strndup(filename, C_CAST(uintptr_t, lastsep) - C_CAST(uintptr_t, filename));//path only. No file name
            }
            else
            {
                //no path, only the filename itself.
                //get the current working directory to use for the canonical file and path.
                //Will use getcwd to get this information.
                //NOTE: A common extension to getcwd is passing M_NULLPTR will have it allocate and return a buffer.
                //      This seems to exist on Linux, FreeBSD, Windows (_getcwd), openbsd, netbsd, and solaris...possibly more.
                //      While this is convenient, we are not using this to make sure behavior is as expected according to POSIX
                //NOTE: Windows can also use https://learn.microsoft.com/en-us/windows/win32/api/winbase/nf-winbase-getcurrentdirectory
                //need to allocate and call again
                char* workingdir = safe_malloc(OPENSEA_PATH_MAX);
                if (workingdir == M_NULLPTR)
                {
                    //return an error for invalid path
                    fileInfo->error = SEC_FILE_INVALID_PATH;
                    return fileInfo;
                }
                workingdir = getcwd(workingdir, OPENSEA_PATH_MAX);
                if (workingdir == M_NULLPTR)
                {
                    //return an error for invalid path
                    fileInfo->error = SEC_FILE_INVALID_PATH;
                    return fileInfo;
                }
                intFileName = workingdir;//we will free this later when we free intfilename
            }
        }
        else
        {
            //not creating a new file, so we will have what we need to get a full canonical path
            intFileName = strdup(filename);
        }
        if (intFileName == M_NULLPTR)
        {
            //return an error for invalid path
            fileInfo->error = SEC_FILE_INVALID_PATH;
            return fileInfo;
        }
        if (SUCCESS != get_Full_Path(intFileName, M_CONST_CAST(char*, fileInfo->fullpath)))
        {
            //unable to get the full path to this file.
            //This means something went wrong, and we need to return an error.
            fileInfo->error = SEC_FILE_INVALID_PATH;
            return fileInfo;
        }

        bool fileexists = false;
        if (!creatingFile || exclusiveFlag)
        {
            fileexists = os_File_Exists(intFileName);
            if (exclusiveFlag && fileexists)
            {
                fileInfo->error = SEC_FILE_FILE_ALREADY_EXISTS;
                if (duplicatedModeForInternalUse)
                {
                    safe_free(&internalmode);
                }
                safe_free(&intFileName);
                return fileInfo;
            }
            else if (!creatingFile && !fileexists)
            {
                fileInfo->error = SEC_FILE_INVALID_FILE;
                if (duplicatedModeForInternalUse)
                {
                    safe_free(&internalmode);
                }
                safe_free(&intFileName);
                return fileInfo;
            }
        }
        fileAttributes* beforeattrs = M_NULLPTR;
        if (creatingFile)
        {
            //append the filename to the end on fileInfo->fullpath
            //first add a trailing slash since one will not be present
            common_String_Concat(M_CONST_CAST(char*, fileInfo->fullpath), OPENSEA_PATH_MAX, SYSTEM_PATH_SEPARATOR_STR);
            if (strchr(filename, '/') //always check for forwards slash since Windows can accept this
#if defined (_WIN32)
                || strchr(filename, '\\')//only check for backslash on Windows since this is a common path seperator on Windows and is the "prefered" format
#endif//_WIN32
                )
            {
                //there is a path or relative path that we do not want to append to the canonical path
                char* lastsep = strrchr(filename, '/');
#if defined (_WIN32)
                //In Windows, we need to determine if the final seperator is a / or \.
                //So also check for \ and figure out which was the last one.
                //A user can pass a path with both and it can be accepted by Windows, which is why we validate both of these.
                char* lastwinsep = strrchr(filename, '\\');
                if (C_CAST(uintptr_t, lastwinsep) > C_CAST(uintptr_t, lastsep))
                {
                    //backslash was detected last, so change to this pointer instead for strndup
                    lastsep = lastwinsep;
                }
#endif//_WIN32
                common_String_Concat(M_CONST_CAST(char*, fileInfo->fullpath), OPENSEA_PATH_MAX, lastsep + 1);
            }
            else
            {
                common_String_Concat(M_CONST_CAST(char*, fileInfo->fullpath), OPENSEA_PATH_MAX, filename);
            }
        }
        else
        {
            //Validate the file extension if one was provided to check for since the full path will also resolve the extension.
            //        This check does not guarantee a file is correct since anyone can rename an extension, but it should help make sure the file
            //        being opened is closer to what is expected by the caller
            if (extList)
            {
                fileExt* currentExtension = M_CONST_CAST(fileExt*, extList);//we will increment this pointer as needed, so it cannot be const
                bool foundValidExtension = false;
                while (currentExtension && currentExtension->ext != M_NULLPTR)
                {
                    char* extension = strrchr(fileInfo->fullpath, '.');
                    if (extension && strcmp(extension, currentExtension->ext) == 0)
                    {
                        //valid extension
                        foundValidExtension = true;
                        break;
                    }
                    else if (extension && currentExtension->caseInsensitive && strcasecmp(extension, currentExtension->ext) == 0)
                    {
                        //valid extension with case insensitive comparison that was allowed
                        foundValidExtension = true;
                        break;
                    }
                    currentExtension += 1;
                }
                if (!foundValidExtension)
                {
                    safe_free(&intFileName);
                    if (duplicatedModeForInternalUse)
                    {
                        safe_free(&internalmode);
                    }
                    fileInfo->error = SEC_FILE_INVALID_FILE_EXTENSION;
                    return fileInfo;
                }
            }
            beforeattrs = os_Get_File_Attributes_By_Name(fileInfo->fullpath);
            //Do a first pass on file attribute comparison with the expected file attributes.
            //If no match, return an error
            //This may be done again later after opening the file since some things will not be available without opening the file handle.
            if (expectedFileInfo)
            {
                //check device ID and inode. These are unique on POSIX as a file ID. Windows is not far enough along to get this info yet.
                if ((expectedFileInfo->deviceID != beforeattrs->deviceID)
                    || (expectedFileInfo->inode != beforeattrs->inode)
                    || (expectedFileInfo->userID != beforeattrs->userID)
                    || (expectedFileInfo->groupID != beforeattrs->groupID)
                    )
                {
                    fileInfo->error = SEC_FILE_INVALID_FILE_ATTRIBTUES;
                    safe_free(&intFileName);
                    free_File_Attributes(&beforeattrs);
                    if (duplicatedModeForInternalUse)
                    {
                        safe_free(&internalmode);
                    }
                    return fileInfo;
                }
#if defined (_WIN32)
                //Validate Windows SIDs are equivalent
                //Convert the strings back to structures and use EqualSid and EqualAcl to do the comparisons.
                //There may be other formatting in the string that does not affect the permissions which is why the conversion is necessary.
                if (!exact_Compare_SIDS_And_DACL_Strings(beforeattrs->winSecurityDescriptor, expectedFileInfo->winSecurityDescriptor))
                {
                    fileInfo->error = SEC_FILE_INVALID_FILE_ATTRIBTUES;
                    safe_free(&intFileName);
                    if (duplicatedModeForInternalUse)
                    {
                        safe_free(&internalmode);
                    }
                    free_File_Attributes(&beforeattrs);
                    return fileInfo;
                }
#endif //_WIN32
            }
        }
        free_File_Attributes(&beforeattrs);

        //Canonical path will already have the proper system path separator in it. No need to search / in Windows
        fileInfo->filename = strrchr(fileInfo->fullpath, SYSTEM_PATH_SEPARATOR) + 1;//plus 1 to get past final seperator

        //Need to verify only the path. Passing the file in with it will cause it to fail since it is not a directory
        char* pathOnly = M_CONST_CAST(char*, fileInfo->fullpath);
        bool allocatedLocalPathOnly = false;
        char* lastsep = strrchr(fileInfo->fullpath, '/');
#if defined (_WIN32)
        //In Windows, we need to determine if the final seperator is a / or \.
        //So also check for \ and figure out which was the last one.
        //A user can pass a path with both and it can be accepted by Windows, which is why we validate both of these.
        char* lastwinsep = strrchr(fileInfo->fullpath, '\\');
        if (C_CAST(uintptr_t, lastwinsep) > C_CAST(uintptr_t, lastsep))
        {
            //backslash was detected last, so change to this pointer instead for strndup
            lastsep = lastwinsep;
        }
#endif//_WIN32
        pathOnly = strndup(fileInfo->fullpath, C_CAST(uintptr_t, lastsep) - C_CAST(uintptr_t, fileInfo->fullpath));//path only. No file name
        if (pathOnly)
        {
            allocatedLocalPathOnly = true;
        }
        else
        {
            pathOnly = M_CONST_CAST(char*, fileInfo->fullpath);
        }
#if defined (_DEBUG)
        printf("Checking directory security: %s\n", pathOnly);
#endif
        //Check for secure directory - This code must traverse the full path and validate permissions of the directories.
        if (os_Is_Directory_Secure(pathOnly))
        {
            fileInfo->file = M_NULLPTR;
#if defined (HAVE_C11_ANNEX_K) || defined (__STDC_SECURE_LIB__)
            errno_t fopenError = fopen_s(&fileInfo->file, fileInfo->fullpath, internalmode);
            if (fopenError == 0 && fileInfo->file != M_NULLPTR)
#else //fopen_s not available
            fileInfo->file = fopen(fileInfo->fullpath, internalmode);
            if (fileInfo->file != M_NULLPTR)
#endif //checking for MSFT secure functions or annex K of C11
            {
                //file is opened, check unique id if it was passed in to compare against
                fileInfo->uniqueID = os_Get_File_Unique_Identifying_Information(fileInfo->file);
                //compre to provided unique ID
                if (uniqueIdInfo)
                {
                    if (memcmp(uniqueIdInfo, fileInfo->uniqueID, sizeof(fileUniqueIDInfo)) != 0)
                    {
                        //This is not the same file as was meant to be opened. Close it and return an error.
                        fclose(fileInfo->file);
                        fileInfo->file = M_NULLPTR;
                        fileInfo->error = SEC_FILE_INVALID_FILE_UNIQUE_ID;
                        safe_free(&intFileName);
                        if (duplicatedModeForInternalUse)
                        {
                            safe_free(&internalmode);
                        }
                        if (pathOnly && allocatedLocalPathOnly)
                        {
                            safe_free(&pathOnly);
                        }
                        return fileInfo;
                    }
                }
                fileInfo->attributes = os_Get_File_Attributes_By_File(fileInfo->file);
                //compare to user provided attributes
                if (expectedFileInfo)
                {
                    //devid and inode already checked, but if user didn't provide unique id, it will not hurt to check again
                    if ((expectedFileInfo->deviceID != fileInfo->attributes->deviceID)
                        || (expectedFileInfo->inode != fileInfo->attributes->inode)
                        || (expectedFileInfo->userID != fileInfo->attributes->userID)
                        || (expectedFileInfo->groupID != fileInfo->attributes->groupID)
                        )
                    {
                        fclose(fileInfo->file);
                        fileInfo->file = M_NULLPTR;
                        fileInfo->error = SEC_FILE_INVALID_FILE_ATTRIBTUES;
                        safe_free(&intFileName);
                        if (duplicatedModeForInternalUse)
                        {
                            safe_free(&internalmode);
                        }
                        if (pathOnly && allocatedLocalPathOnly)
                        {
                            safe_free(&pathOnly);
                        }
                        return fileInfo;
                    }
#if defined (_WIN32)
                    //Validate Windows SIDs are equivalent
                    //Convert the strings back to structures and use EqualSid and EqualAcl to do the comparisons.
                    //There may be other formatting in the string that does not affect the permissions which is why the conversion is necessary.
                    if (!exact_Compare_SIDS_And_DACL_Strings(fileInfo->attributes->winSecurityDescriptor, expectedFileInfo->winSecurityDescriptor))
                    {
                        fclose(fileInfo->file);
                        fileInfo->file = M_NULLPTR;
                        fileInfo->error = SEC_FILE_INVALID_FILE_ATTRIBTUES;
                        safe_free(&intFileName);
                        if (duplicatedModeForInternalUse)
                        {
                            safe_free(&internalmode);
                        }
                        if (pathOnly && allocatedLocalPathOnly)
                        {
                            safe_free(&pathOnly);
                        }
                        return fileInfo;
                    }
#endif //_WIN32
                }

                fileInfo->isValid = true;

#if defined (USING_C11) && defined (to_sizet)
                fileInfo->fileSize = to_sizet(fileInfo->attributes->filesize);
#else
                fileInfo->fileSize = int64_to_sizet(fileInfo->attributes->filesize);
#endif
                fileInfo->fileno = fileno(fileInfo->file);
#if defined (_DEBUG)
                printf("Filesize set to %zu\n", fileInfo->fileSize);
#endif
            }
            else
            {
#if defined (HAVE_C11_ANNEX_K) || defined (__STDC_SECURE_LIB__)
                switch (fopenError)
#else
                switch (errno)
#endif
                {
                    //add other errno values to check for?
                    //https://pubs.opengroup.org/onlinepubs/9699919799/functions/fopen.html
                case EINVAL:
                default:
                    fileInfo->error = SEC_FILE_FAILURE;
                    break;
                }

            }
        }
        else
        {
            fileInfo->error = SEC_FILE_INSECURE_PATH;
            printf("Insecure path\n");
        }
        if (pathOnly && allocatedLocalPathOnly)
        {
            safe_free(&pathOnly);
        }
        if (duplicatedModeForInternalUse)
        {
            safe_free(&internalmode);
        }
        safe_free(&intFileName);
    }
    else if (fileInfo)
    {
        fileInfo->file = M_NULLPTR;
        fileInfo->error = SEC_FILE_FAILURE;
    }
    return fileInfo;
}

//We can add additional things to do before closing the file to validate things, flush, etc as needed to make this better.
M_NODISCARD eSecureFileError secure_Close_File(secureFileInfo* fileInfo)
{
    if (fileInfo)
    {
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file != M_NULLPTR)
        {
            int closeres = fclose(fileInfo->file);
            if (closeres == 0)
            {
                fileInfo->file = M_NULLPTR;
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else if (closeres == EOF)
            {
                fileInfo->error = SEC_FILE_FAILURE_CLOSING_FILE;
            }
            else
            {
                //unknown result, so call this an error.
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        else if (fileInfo->error != SEC_FILE_FAILURE_CLOSING_FILE)
        {
            //File was never opened, so return no error
            fileInfo->error = SEC_FILE_SUCCESS;
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD eSecureFileError secure_Read_File(secureFileInfo* M_RESTRICT fileInfo, void* M_RESTRICT buffer, size_t buffersize, size_t elementsize, size_t count, size_t* numberread/*optional*/)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            size_t readres = 0;
#if defined (__STDC_SECURE_LIB__)
            readres = fread_s(buffer, buffersize, elementsize, count, fileInfo->file);
#else
            if (buffer == M_NULLPTR)
            {
                fileInfo->error = SEC_FILE_INVALID_PARAMETER;
                return fileInfo->error;
            }
            else if (buffersize < (elementsize * count))
            {
                fileInfo->error = SEC_FILE_BUFFER_TOO_SMALL;
                return fileInfo->error;
            }
            readres = fread(buffer, elementsize, count, fileInfo->file);
#endif
            if (numberread)
            {
                *numberread = readres;
            }
            if (readres == 0)
            {
                if (elementsize == 0 || count == 0)
                {
                    fileInfo->error = SEC_FILE_SUCCESS;
                }
                else
                {
                    fileInfo->error = SEC_FILE_READ_WRITE_ERROR;
                }
            }
            else if (readres < count)
            {
                if (feof(fileInfo->file))
                {
                    //end of stream/file
                    fileInfo->error = SEC_FILE_END_OF_FILE_REACHED;
                }
                else if (ferror(fileInfo->file))
                {
                    fileInfo->error = SEC_FILE_READ_WRITE_ERROR;
                }
                else
                {
                    //some other kind of error???
                    fileInfo->error = SEC_FILE_READ_WRITE_ERROR;
                }
            }
            else if (readres == count)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else
            {
                //unknown result, so call this an error.
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD eSecureFileError secure_Write_File(secureFileInfo* M_RESTRICT fileInfo, void* M_RESTRICT buffer, size_t buffersize, size_t elementsize, size_t count, size_t* numberwritten/*optional*/)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            size_t writeres = 0;
            if (buffer == M_NULLPTR)
            {
                fileInfo->error = SEC_FILE_INVALID_PARAMETER;
                return fileInfo->error;
            }
            else if (buffersize < (elementsize * count))
            {
                fileInfo->error = SEC_FILE_BUFFER_TOO_SMALL;
                return fileInfo->error;
            }
            writeres = fwrite(buffer, elementsize, count, fileInfo->file);
            if (numberwritten)
            {
                *numberwritten = writeres;
            }
            if (writeres == 0)
            {
                if (elementsize == 0 || count == 0)
                {
                    fileInfo->error = SEC_FILE_SUCCESS;
                }
                else
                {
                    fileInfo->error = SEC_FILE_READ_WRITE_ERROR;
                }
            }
            else if (writeres < count)
            {
                if (ferror(fileInfo->file))
                {
                    fileInfo->error = SEC_FILE_WRITE_DISK_FULL;
                }
                else
                {
                    //some other kind of error???
                    fileInfo->error = SEC_FILE_READ_WRITE_ERROR;
                }
            }
            else if (writeres == count)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else
            {
                //unknown result, so call this an error.
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD eSecureFileError secure_Seek_File(secureFileInfo* fileInfo, offset_t offset, int initialPosition)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            int seekres = 0;
            //Windows has _fseeki64, which may be better to use instead for larger files or to be compatible with larger files.
            //Linux/posix have fseeko and ftello which use off_t which can be wider as well. (POSIX 2001)
#if defined (_WIN32)/*version check for this function?*/
            seekres = _fseeki64(fileInfo->file, offset, initialPosition);
#elif defined (POSIX_2001)
            seekres = fseeko(fileInfo->file, offset, initialPosition);
#else
            seekres = fseek(fileInfo->file, offset, initialPosition);
#endif
            if (seekres == 0)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else
            {
                fileInfo->error = SEC_FILE_SEEK_FAILURE;
            }
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD eSecureFileError secure_Rewind_File(secureFileInfo* fileInfo)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            fileInfo->error = secure_Seek_File(fileInfo, 0, SEEK_SET);
#if defined (__STDC_SECURE_LIB__)
            clearerr_s(fileInfo->file);
#else
            clearerr(fileInfo->file);//rewind clears errors and eof indicators, so call this to clear the errors in the stream.
#endif
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD offset_t secure_Tell_File(secureFileInfo* fileInfo)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            offset_t tellres = 0;
            //Windows has _fseeki64, which may be better to use instead for larger files or to be compatible with larger files.
            //Linux/posix have fseeko and ftello which use off_t which can be wider as well. (POSIX 2001)
            errno = 0;//ISO secure coding standard recommends this to ensure errno is interpretted correctly after this call
#if defined (_WIN32) /*version check for this function?*/
            tellres = _ftelli64(fileInfo->file);
#elif defined (POSIX_2001)
            tellres = ftello(fileInfo->file);
#else
            tellres = ftell(fileInfo->file);
#endif
            if (tellres >= 0)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else
            {
                fileInfo->error = SEC_FILE_SEEK_FAILURE;
            }
            return tellres;
        }
        return -1;
    }
    return -1;
}

eSecureFileError secure_Flush_File(secureFileInfo* fileInfo)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            int fflushres = fflush(fileInfo->file);
            if (fflushres == 0)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else if (fflushres == EOF && ferror(fileInfo->file))
            {
                fileInfo->error = SEC_FILE_FLUSH_FAILURE;
            }
            else /*not sure what to clasify this error as*/
            {
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD eSecureFileError secure_Remove_File(secureFileInfo* fileInfo)
{
    if (fileInfo)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_PATH;
        if (fileInfo->file && safe_strlen(fileInfo->fullpath) > 0)
        {
            //unlink the file is possible
#if defined (_WIN32)
            if (0 != _unlink(fileInfo->fullpath))
            {
                fileInfo->error = SEC_FILE_FAILURE;
            }
#elif defined (POSIX_2001) || defined (BSD4_3) || defined (__svr4__)
            if (0 != unlink(fileInfo->fullpath))
            {
                fileInfo->error = SEC_FILE_FAILURE;
            }
#else
            fileInfo->error = SEC_FILE_CANNOT_REMOVE_FILE_STILL_OPEN;
#endif
        }
        else if (safe_strlen(fileInfo->fullpath) > 0)
        {
            //remove the file
            if (0 != remove(fileInfo->fullpath))
            {
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

M_NODISCARD eSecureFileError secure_Delete_File_By_Name(const char* filename, eSecureFileDeleteNameAction deleteAction)
{
    if (filename)
    {
        //first get cannonical name
        DECLARE_ZERO_INIT_ARRAY(char, fullpath, 4096);
        if (SUCCESS != get_Full_Path(filename, C_CAST(char*, fullpath)))
        {
            //unable to get the full path to this file.
            //This means something went wrong, and we need to return an error.
            return SEC_FILE_INVALID_PATH;
        }
        char* lastsep = strrchr(fullpath, '/');
#if defined (_WIN32)
        //In Windows, we need to determine if the final seperator is a / or \.
        //So also check for \ and figure out which was the last one.
        //A user can pass a path with both and it can be accepted by Windows, which is why we validate both of these.
        char* lastwinsep = strrchr(fullpath, '\\');
        if (C_CAST(uintptr_t, lastwinsep) > C_CAST(uintptr_t, lastsep))
        {
            //backslash was detected last, so change to this pointer instead for strndup
            lastsep = lastwinsep;
        }
#endif//_WIN32
        //Check for secure directory - This code must traverse the full path and validate permissions of the directories.
        char* pathOnly = strndup(fullpath, C_CAST(uintptr_t, lastsep) - C_CAST(uintptr_t, fullpath));//path only. No file name
        if (!pathOnly)
        {
            pathOnly = C_CAST(char*, fullpath);
        }
        if (!os_Is_Directory_Secure(pathOnly))
        {
            safe_free(&pathOnly);
            return SEC_FILE_INSECURE_PATH;
        }
        safe_free(&pathOnly);
        //Check if the file is already open before attempting to remove it
        errno_t fileerror = 0;
        FILE* checkExist = M_NULLPTR;
#if defined (HAVE_C11_ANNEX_K) || defined (__STDC_SECURE_LIB__)
        fileerror = fopen_s(&checkExist, fullpath, "r");
#else
        errno = 0;
        checkExist = fopen(fullpath, "r");
        fileerror = errno;
#endif

        if (checkExist != M_NULLPTR && fileerror == 0)
        {
            fclose(checkExist);
            checkExist = M_NULLPTR;
            if (0 == remove(fullpath))
            {
                return SEC_FILE_SUCCESS;
            }
            else
            {
                return SEC_FILE_FAILURE;
            }
        }
        else if (os_File_Exists(fullpath))
        {
            switch (deleteAction)
            {
            case SEC_DELETE_NAME_FAIL_IF_OPEN:
                return SEC_FILE_CANNOT_REMOVE_FILE_STILL_OPEN;
            case SEC_DELETE_NAME_UNLINK_IF_OPEN:
                //File cannot be opened, so we must assume something else has it open, so unlink instead-TJE
#if defined (_WIN32)
                if (0 != _unlink(fullpath))
                {
                    return SEC_FILE_FAILURE;
                }
                return SEC_FILE_SUCCESS;
#elif defined (POSIX_2001) || defined (BSD4_3) || defined (__svr4__)
                if (0 != unlink(fullpath))
                {
                    return SEC_FILE_FAILURE;
                }
                return SEC_FILE_SUCCESS;
#else
                return SEC_FILE_CANNOT_REMOVE_FILE_STILL_OPEN;
#endif
            }
        }
        return SEC_FILE_FAILURE;
    }
    return SEC_FILE_INVALID_PATH;
}

eSecureFileError secure_GetPos_File(secureFileInfo* M_RESTRICT fileInfo, fpos_t* M_RESTRICT pos)
{
    if (fileInfo && pos)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            int getposres = fgetpos(fileInfo->file, pos);
            if (getposres == 0)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else
            {
                //TODO: inspect errno - ISO C security recommendation
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        return fileInfo->error;
    }
    else if (fileInfo)
    {
        //pos is invalid
        fileInfo->error = SEC_FILE_INVALID_PARAMETER;
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

eSecureFileError secure_SetPos_File(secureFileInfo* fileInfo, const fpos_t* pos)
{
    if (fileInfo && pos)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        fileInfo->error = SEC_FILE_INVALID_FILE;
        if (fileInfo->file)
        {
            int setposres = fsetpos(fileInfo->file, pos);
            if (setposres == 0)
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
            else
            {
                //TODO: inspect errno - ISO C security recommendation
                fileInfo->error = SEC_FILE_FAILURE;
            }
        }
        return fileInfo->error;
    }
    else if (fileInfo)
    {
        //pos is invalid
        fileInfo->error = SEC_FILE_INVALID_PARAMETER;
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

FUNC_ATTR_PRINTF(2, 0) eSecureFileError secure_vfprintf_File(secureFileInfo* M_RESTRICT fileInfo, const char* M_RESTRICT format, va_list args)
{
    if (fileInfo && fileInfo->file)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        if (format)
        {
            int vfprintfresult = 0;
#if defined (HAVE_C11_ANNEX_K) || defined (__STDC_SECURE_LIB__)
            vfprintfresult = vfprintf_s(fileInfo->file, format, args);
#else
            va_list verifyargs;
            va_copy(verifyargs, args);
            if (verify_Format_String_And_Args(format, args) > 0)
            {
                vfprintfresult = vfprintf(fileInfo->file, format, args);
            }
            else
            {
                vfprintfresult = -1;
            }
            va_end(verifyargs);
#endif
            if (vfprintfresult < 0 || ferror(fileInfo->file))
            {
                fileInfo->error = SEC_FILE_READ_WRITE_ERROR;
            }
            else
            {
                fileInfo->error = SEC_FILE_SUCCESS;
            }
        }
        else
        {
            //M_NULLPTR pointer for the format string
            fileInfo->error = SEC_FILE_INVALID_PARAMETER;
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}

FUNC_ATTR_PRINTF(2, 3) eSecureFileError secure_fprintf_File(secureFileInfo* M_RESTRICT fileInfo, const char* M_RESTRICT format, ...)
{
    if (fileInfo && fileInfo->file)
    {
        if (fileInfo->error == SEC_FILE_FAILURE_CLOSING_FILE)
        {
            return SEC_FILE_FAILURE_CLOSING_FILE;
        }
        if (format)
        {
            va_list args;
            va_start(args, format);
            eSecureFileError result = secure_vfprintf_File(fileInfo, format, args);
            va_end(args);
            return result;
        }
        else
        {
            //M_NULLPTR pointer for the format string
            fileInfo->error = SEC_FILE_INVALID_PARAMETER;
        }
        return fileInfo->error;
    }
    return SEC_FILE_INVALID_SECURE_FILE;
}
