From nasm to masm

[Yoshi]

when i use nasm.exe in cmd and choose the filepath to my asm file it will generate a new file. Just like this in cmd; nasm.exe mynasmsource.asm. this will geneate a new file.

 

now i want do the same with masm32. i got the same source but this time written in masm, now i need that new file like what nasm.exe generated.

how?

Edited September 5, 2013 by Yoshi

[mrexodia]

convert INTEL to NASM syntax...

C++ code (not tested too much, but should work for basic ASM instructions):

static bool issegment(const char* str){    if(!strncasecmp(str, "gs", 2))        return true;    if(!strncasecmp(str, "fs", 2))        return true;    if(!strncasecmp(str, "es", 2))        return true;    if(!strncasecmp(str, "ds", 2))        return true;    if(!strncasecmp(str, "cs", 2))        return true;    if(!strncasecmp(str, "ss", 2))        return true;    return false;}static const char* Intel2Nasm(const char* intel){    char temp[256]="";    static char nasm[256]="";    memset(nasm, 0, sizeof(nasm));    memset(temp, 0, sizeof(temp));    int len=strlen(intel);    for(int i=0,j=0; i<len; i++) //fix basic differences and problems    {        if(!strncasecmp(intel+i, "ptr", 3)) //remote "ptr"        {            i+=2;            if(intel[i+1]==' ')                i++;            continue;        }        else if(!strncasecmp(intel+i, "  ", 2)) //remove double spaces            continue;        else if(intel[i]=='\t') //tab=space        {            j+=sprintf(temp+j, " ");            continue;        }        j+=sprintf(temp+j, "%c", intel[i]);    }    len=strlen(temp);    for(int i=0,j=0; i<len; i++)    {        if(temp[i]==' ' and temp[i+1]==',')            continue;        else if(temp[i]==',' and temp[i+1]==' ')        {            j+=sprintf(nasm+j, ",");            i++;            continue;        }        else if(issegment(temp+i) and temp[i+2]==' ')        {            j+=sprintf(nasm+j, "%c%c", temp[i], temp[i+1]);            i+=2;            continue;        }        else if(temp[i]==':' and temp[i+1]==' ')        {            j+=sprintf(nasm+j, ":");            i++;            continue;        }        j+=sprintf(nasm+j, "%c", temp[i]);    }    len=strlen(nasm);    for(int i=0,j=0; i<len; i++)    {        if(issegment(nasm+i) and nasm[i+2]==':' and nasm[i+3]=='[')        {            j+=sprintf(temp+j, "[%c%c:", nasm[i], nasm[i+1]);            i+=3;            continue;        }        j+=sprintf(temp+j, "%c", nasm[i]);    }    strcpy(nasm, temp);    return nasm;}

intel2nasm.zip

Edited September 5, 2013 by Mr. eXoDia

[ragdog]

I think you mean make a Exe from a source?

 

ml /c /coff /Cp "xyz.Asm"
link /SUBSYSTEM:WINDOWS /RELEASE /VERSION:4.0 /OUT:"xyz.exe" "xyz.obj" 

[Yoshi]

thank both of you but that is not really what i want to do.

 

let me explain.

 

i found a crypter.

in this package there is nasm/nasm.exe. and a stub.asm.

 

when i use nasm.exe in cmd and choose the filepath to the stub.asm, it will generate a new stub file. this new stub file will be used in the crypter.

 

now i got my own written stub in masm which is called stub2.asm.so how do i convert my own stub to a new file and use it in the crypter?

Edited September 5, 2013 by Yoshi

[mrexodia]

I knew you meant this, you need to manually convert the syntax. MASM uses invoke for example, nasm doesnt have this. Notice that default interpretion mode in NASM is DEC, so you should prefix your values with 'h'

The converter provided converts stuff like "mov byte ptr fs:[X]" to "mov byte [fs:X]" automatically. You could use the code I provided to parse a file and convert the basic syntax first.

Greetings

[Yoshi]

okidoki mister exodia high thank for you and ragdog

[Yoshi]

okidoki mister exodia high thank for you and ragdog

[ragdog]

Ahh convert the source to Masm

 

Is not really difficult

 

A other good option is Load the compiled exe in Ida or Olly and you see the Masm syntax