摸了一小会鱼。

glass

附件

重点是 libnative-lib.so。反汇编看一下操作也比较简单。没有完全做逆向，直接爆破了一下。需要三个三个爆破。

crack 
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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <stdint.h>
#include <signal.h>

int32_t clz(uint32_t i)
{
    int32_t ret = 0;
    uint32_t temp = ~i;

    while (temp & 0x80000000)
    {
        temp <<= 1;
        ret++;
    }
    return ret;
}

int32_t sub_11DC(int32_t i, int32_t len)
{
    char v2;     // r2
    uint32_t v3; // r1
    uint32_t v4; // r3
    uint32_t v5; // r2
    int32_t v6;  // zf
    if (len != 1)
    {
        if (len)
        {
            if (i <= len)
            {
                i = i == len;
            }
            else if ((len & (len - 1)) != 0)
            {
                v2 = clz((uint32_t)len) - clz((uint32_t)i);
                v3 = len << v2;
                v4 = 1 << v2;
                v5 = 0;
                while (1)
                {
                    if (i >= v3)
                    {
                        i -= v3;
                        v5 |= v4;
                    }
                    if (i >= v3 >> 1)
                    {
                        i -= v3 >> 1;
                        v5 |= v4 >> 1;
                    }
                    if (i >= v3 >> 2)
                    {
                        i -= v3 >> 2;
                        v5 |= v4 >> 2;
                    }
                    if (i >= v3 >> 3)
                    {
                        i -= v3 >> 3;
                        v5 |= v4 >> 3;
                    }
                    v6 = i == 0;
                    if (i)
                    {
                        v4 >>= 4;
                        v6 = v4 == 0;
                    }
                    if (v6)
                        break;
                    v3 >>= 4;
                }
                i = v5;
            }
            else
            {
                i >>= 31 - clz((uint32_t)len);
            }
        }
        else
        {
            i = raise(8);
        }
    }
    return i;
}

int32_t sub_126C(int32_t i, int32_t len)
{
    int32_t r1 = i, r2 = len;
    int32_t r0 = sub_11DC(i, len);

    int32_t r3 = r2 * r0;
    r1 = r1 - r3;

    return r1;
}

void subFFC(char *str1, char *str2, int32_t len)
{
    char v12[256];
    memset(v12, 0, 0x100);
    int32_t i;
    int32_t v7, v8;
    for (i = 0; i != 256; ++i)
    {
        str1[i] = i;
        v7 = sub_126C(i, len);
        v12[i] = str2[v7];
    }
    v8 = 0;
    int32_t v9 = 0;
    int32_t v10;
    while (v8 != 256)
    {
        v10 = (unsigned char)str1[v8];
        v9 = (v9 + v10 + (unsigned char)v12[v8]) % 256;
        str1[v8++] = str1[v9];
        str1[v9] = v10;
    }
}

void sub1088(char *str1, char *str2, int32_t len)
{
    int32_t v3, v4, v5;
    v3 = 0, v4 = 0;
    while (len)
    {
        --len;
        v4 = (v4 + 1) % 256;
        v5 = (unsigned char)str1[v4];
        v3 = (v3 + v5) % 256;
        str1[v4] = str1[v3];
        str1[v3] = v5;
        *str2++ ^= str1[(unsigned char)(v5 + str1[v4])];
    }
}

void sub_10D4(char *str1, int32_t len1, char *str2, int32_t len2)
{
    int32_t i; // r4
    char *v5;  // r6
    char v6;   // r5
    char v7;   // lr
    char v8;   // r12
    int32_t j; // lr
    int32_t k; // r6

    for (i = 0; i < len1; i += 3)
    {
        v5 = &str1[i];
        v6 = str1[i + 2];
        v7 = str1[i + 1];
        v8 = str1[i] ^ v6;
        str1[i] = v8;
        v5[2] = v6 ^ v7;
        v5[1] = v7 ^ v8;
    }
    for (j = 0; j < len1; j += len2)
    {
        for (k = 0; (len2 & ~(len2 >> 31)) != k && j + k < len1; ++k)
            str1[k] ^= str2[k];
        str1 += len2;
    }
}

void checkFlag(char *flag)
{
    char str_12345678[256];
    char empty_str[256];

    memset(empty_str, 0, 0x100);
    // qmemcpy(str_12345678, "12345678", sizeof(str_12345678));
    memcpy(str_12345678, "12345678", sizeof(str_12345678));
    int32_t len256 = strlen(str_12345678);
    subFFC(empty_str, str_12345678, len256);
    sub1088(empty_str, flag, 39);
    sub_10D4(flag, 39, str_12345678, len256);
}

char tocmp[] = {0xA3, 0x1A, 0xE3, 0x69, 0x2F, 0xBB, 0x1A, 0x84, 0x65, 0xC2, 0xAD, 0xAD, 0x9E, 0x96, 0x5, 0x2, 0x1F, 0x8E, 0x36, 0x4F, 0xE1, 0xEB, 0xAF, 0xF0, 0xEA, 0xC4, 0xA8, 0x2D, 0x42, 0xC7, 0x6E, 0x3F, 0xB0, 0xD3, 0xCC, 0x78, 0xF9, 0x98, 0x3F, 0x00};

int main()
{
    // char flag[40] = "CISCN{AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA}";
    char flag[40] = "CISCN{B6AAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA\0";

    char flag_cpy[40];
    int32_t i = 0;
    char j;
    int32_t k;
    int a, b, c;
    while (1)
    {
        printf("[+] %d\n", i);
        for (a = 0x2d; a < 0x7E; ++a)
        {
            for (b = 0x2d; b < 0x7E; ++b)
            {
                for (c = 0x2d; c < 0x7E; ++c)
                {
                    for (k = 0; k < 40; ++k)
                    {
                        printf("%x ", (unsigned char)flag_cpy[k]);
                    }
                    strcpy(flag_cpy, flag);
                    flag_cpy[i] = a;
                    flag_cpy[i + 1] = b;
                    flag_cpy[i + 2] = c;
                    checkFlag(flag_cpy);
                    if (flag_cpy[i] == tocmp[i] && flag_cpy[i + 1] == tocmp[i + 1] && flag_cpy[i + 2] == tocmp[i + 2])
                    {
                        for (k = 0; k < 40; ++k)
                        {
                            printf("%x ", (unsigned char)flag_cpy[k]);
                        }
                        putchar('\n');
                        printf("flag[%d]=%c\n", i, a);
                        printf("flag[%d]=%c\n", i + 1, b);
                        printf("flag[%d]=%c\n", i + 2, c);
                        flag[i] = a;
                        flag[i + 1] = b;
                        flag[i + 2] = c;
                        printf("%s\n", flag);
                        // exit(0);
                        goto label;
                    }
                }
            }
        }
    label:
        i += 3;
    }
    return 0;
}

但是分析一下的话很多函数都可以优化掉，例如 sub_126C 函数，就是将 12345678 均匀映射到 256 位的数组中。

TODO: 实现 angr 解题的脚本。

baby bc

附件

给了一个 baby.bc，file 一下发现是 LLVM 的 IR。

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$ file baby.bc
baby.bc: LLVM IR bitcode

用 clang 编译一下当成正常的逆向来做就行。

逆向时发现可以用符号执行直接找到输入。

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import angr
from angr.sim_options import MEMORY_FIND_STRICT_SIZE_LIMIT
from angr.storage.file import Flags
import claripy

def main():
    path_to_bin = './a.out'
    project = angr.Project(path_to_bin)

    st = project.factory.entry_state(add_options={angr.options.SYMBOLIC_WRITE_ADDRESSES})

    input_chars = [claripy.BVS('flag_{}'.format(i), 8) for i in range(25)]
    myinput = claripy.Concat(*input_chars)
    st.memory.store(0x6020C0, myinput)

    sm = project.factory.simulation_manager(st)
    print(sm.explore(find=0x401410))
    found_state = sm.found[0]
    print(found_state.solver.eval(found_state.memory.load(0x6020C0, 25), cast_to=bytes))

main()

即可出输入。

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$ python ppp.py
INFO    | 2021-05-15 20:01:30,308 | pyvex.lifting.libvex | unhandled opc_aux = 0x 6
first_opcode == 0xDF

INFO    | 2021-05-15 20:01:30,308 | pyvex.lifting.libvex | unhandled opc_aux = 0x 6
first_opcode == 0xDF

INFO    | 2021-05-15 20:01:30,309 | pyvex.lifting.libvex | unhandled opc_aux = 0x 6
first_opcode == 0xDF

<SimulationManager with 97 deadended, 1 found>
b'1425353142350212150442315'