some small fixes

CTFs/2014-CSAW-CTF/reverse-engineering/eggshells-100/eggshells-master/nasm.py

@@ -0,0 +1,133 @@
+import utils
+import os
+import subprocess
+import tempfile
+import sys
+import re
+
+subprocess.STARTF_USESHOWWINDOW = 1 # Hiding console windows in subprocess calls
+
+if sys.platform.startswith('linux') or sys.platform.startswith('darwin'):
+    NASM = '/usr/bin/nasm'
+    NDISASM = '/usr/bin/ndisasm'
+
+elif sys.platform.startswith('win32'):
+    NASM = 'nasm/nasm.exe'
+    NDISASM = 'nasm/ndisasm.exe'
+
+if not os.path.exists(NASM):
+    raise EnvironmentError('nasm not found')
+if not os.path.exists(NDISASM):
+    raise EnvironmentError('ndisasm not found')
+
+hex_regex = re.compile(r'0x\w*')
+
+def delete_file(filename):
+    """
+    Deletes file from the disk if it exists
+    """
+    if os.path.exists(filename):
+        os.unlink(filename)
+
+
+def assemble(asm, mode="elf"):
+    '''
+    Assemble using nasm, return raw hex bytes.
+    '''
+    temp = tempfile.NamedTemporaryFile(delete=False)
+
+    linkme = tempfile.NamedTemporaryFile(delete=False)
+    dir = tempfile.gettempdir()
+    try:
+        temp.write(asm)
+        temp.close()
+        linkme.close()
+
+        startupinfo = subprocess.STARTUPINFO()
+        startupinfo.dwFlags = subprocess.STARTF_USESHOWWINDOW
+        
+        link = subprocess.check_output([NASM, '-f ' + mode, temp.name, '-o ' + dir + '/link.o'], startupinfo=startupinfo)
+        out = subprocess.check_output([NASM, temp.name, '-o ' + temp.name + '.elf'], startupinfo=startupinfo)
+
+        asm = open(temp.name + '.elf', 'rb')
+        asm = asm.read()
+        delete_file(temp.name + '.elf')
+        delete_file(linkme.name)
+        delete_file(dir + '/link.o')
+        delete_file(temp.name)
+        return asm
+    except:
+        delete_file(temp.name + '.elf')
+        delete_file(linkme.name)
+        delete_file(dir + '/link.o')
+        delete_file(temp.name)
+        return "assembly failed"
+
+
+def disassemble(elf, mode=32):
+    '''
+    Disassemble using ndisasm. Return the output.
+    '''
+    temp = tempfile.NamedTemporaryFile(delete=False)
+    try:
+        temp.write(elf)
+        temp.close()
+
+        startupinfo = subprocess.STARTUPINFO()
+        startupinfo.dwFlags = subprocess.STARTF_USESHOWWINDOW
+
+        asm = subprocess.check_output([NDISASM, '-a', '-b ' + str(mode), temp.name], startupinfo=startupinfo)
+        delete_file(temp.name)
+
+    except:
+        delete_file(temp.name)
+        return 'disassembly failed'
+
+        #return asm
+        
+    disasm = asm.split('\n')
+    disasm = [" ".join(x.split()).split(' ', 2) for x in disasm ]
+
+    # Join line continuations together and mark them for removal
+    marked = []
+    for x in range(len(disasm)):
+        if len(disasm[x]) == 1:
+            disasm[x-1][1] += disasm[x][0][1:]
+            marked.append(x)
+    for x in marked[::-1]:
+        disasm.pop(x)        
+
+    # Join the disassembly back together for output
+    # Also provide string and decimal representations of hex values
+    disassembly = ''
+    for line in disasm:
+        hexvals = hex_regex.findall(line[2])
+        if len(hexvals) > 0 and ('push' in line[2] or 'mov' in line[2]):
+            line = list(line) # Why you give me tuple Distorm?
+            if len(hexvals[0][2:]) > 2:
+                line[2] = line[2] + '\t; ' + hexvals[0][2:].decode('hex')
+            else:
+                line[2] = line[2] + '\t; ' + str(int(hexvals[0], 16))
+
+        disassembly += "0x%08s (%02x) %-20s %s" % (line[0], len(line[1])//2, line[1], line[2]) + "\n"
+    return disassembly
+
+
+if __name__ == '__main__':
+    print disassemble('\x48\x31\xc0\x50\x48\xbf\x2f\x62\x69\x6e\x2f\x2f\x73\x68\x57\xb0\x3b\x48\x89\xe7\x48\x31\xf6\x48\x31\xd2\x0f\x05', 64)
+
+    asm = '''
+    BITS 32
+    main:
+            ; execve("/bin/sh", 0, 0)
+            xor eax, eax
+            push eax
+            push 0x68732f2f         ; "//sh" -> stack
+            push 0x6e69622f         ; "/bin" -> stack
+            mov ebx, esp                ; arg1 = "/bin//sh\0"
+            mov ecx, eax                ; arg2 = 0
+            mov edx, eax                ; arg3 = 0
+            mov al, 11
+            int 0x80
+    '''
+    print repr(assemble(asm, "elf"))