首页
论坛
课程
招聘
ctf2018-第8题
2018-7-1 13:54 1018

ctf2018-第8题

2018-7-1 13:54
1018
进制转换36/62/64/256

struct buf {
    BYTE len0;
    BYTE len0_1; // len0_1 ==len0+4
    BYTE len1;
    BYTE len2;
    BYTE r0[len0+4];
    BYTE r1[len1];
    BYTE r2[len2];
};

.text:00401A19                 mov     al, [edx]
.text:00401A1B                 cmp     al, 1
.text:00401A1D                 jb      loc_4023E6
.text:00401A23                 cmp     al, 18h
.text:00401A25                 ja      loc_4023E6
.text:00401A2B                 mov     cl, [edx+1]
.text:00401A2E                 cmp     cl, 1
.text:00401A31                 mov     byte ptr [ebp+var_14], cl
.text:00401A34                 jb      loc_4023E6
.text:00401A3A                 cmp     cl, 18h
.text:00401A3D                 ja      loc_4023E6
.text:00401A43                 mov     bl, [edx+2]
.text:00401A46                 cmp     bl, 1
.text:00401A49                 jb      loc_4023E6
.text:00401A4F                 cmp     bl, 18h
.text:00401A52                 ja      loc_4023E6
.text:00401A58                 mov     cl, [edx+3]
.text:00401A5B                 cmp     cl, 1
.text:00401A5E                 jb      loc_4023E6
.text:00401A64                 cmp     cl, 18h
.text:00401A67                 ja      loc_4023E6
.text:00401A6D                 mov     esi, [ebp+var_14]
.text:00401A70                 and     eax, 0FFh
.text:00401A75                 and     esi, 0FFh
.text:00401A7B                 lea     edx, [eax+4]
.text:00401A7E                 cmp     edx, esi
.text:00401A80                 jnz     loc_4023E6
.text:00401A86                 and     ecx, 0FFh
.text:00401A8C                 and     ebx, 0FFh
.text:00401A92                 add     eax, ecx
.text:00401A94                 mov     ecx, [ebp+var_2C]
.text:00401A97                 mov     edx, [ecx+8]
.text:00401A9A                 lea     eax, [ebx+eax+8]
.text:00401A9E                 cmp     eax, edx
.text:00401AA0                 jnz     loc_4023E6

v1=g_bn1, v2=g_bn2
.text:00401D21                 push    offset aWelcomeToBbsPe ; "welcome to bbs.pediy.com."
.text:00401D26                 push    offset g_bn1
.text:00401D2B                 call    x_from_basen
.text:00401D30                 mov     edi, offset a0123456789abcd_0 ; 
.text:00401D35                 or      ecx, 0FFFFFFFFh
.text:00401D38                 xor     eax, eax
.text:00401D3A                 push    2Bh
.text:00401D3C                 repne scasb
.text:00401D3E                 not     ecx
.text:00401D40                 push    2Dh
.text:00401D42                 dec     ecx
.text:00401D43                 push    offset a0123456789abcd_0 ; 
.text:00401D48                 push    ecx
.text:00401D49                 mov     edi, offset aAuthorByLookhc ; "Author by Lookhc"
.text:00401D4E                 or      ecx, 0FFFFFFFFh
.text:00401D51                 repne scasb
.text:00401D53                 not     ecx
.text:00401D55                 dec     ecx
.text:00401D56                 push    ecx
.text:00401D57                 push    offset aAuthorByLookhc ; "Author by Lookhc"
.text:00401D5C                 push    offset g_bn2
.text:00401D61                 call    x_from_basen

校验r0[len0]
.text:00401DEB                 mov     edx, [ebp+var_38]
.text:00401DEE                 lea     eax, [ebp+var_44] ; must return 1
.text:00401DF1                 lea     ecx, [ebp+var_3C] ; must return 0
.text:00401DF4                 push    eax
.text:00401DF5                 push    ecx
.text:00401DF6                 mov     edi, edx
.text:00401DF8                 or      ecx, 0FFFFFFFFh
.text:00401DFB                 xor     eax, eax
.text:00401DFD                 mov     [ebp+var_3C], 64h
.text:00401E04                 mov     [ebp+var_44], 0
.text:00401E0B                 repne scasb
.text:00401E0D                 not     ecx
.text:00401E0F                 dec     ecx
.text:00401E10                 push    5
.text:00401E12                 push    ecx
.text:00401E13                 push    edx
.text:00401E14                 call    sub_4010A0      ; must return 1

校验buf的crc
.text:00401E29                 push    ecx
.text:00401E2A                 push    edx
.text:00401E2B                 push    offset loc_401ABF
.text:00401E30                 push    6780h
.text:00401E35                 push    13114F0Dh
.text:00401E3A                 push    1F6E1EA0h
.text:00401E3F                 call    sub_404A60      ; crc32(buf, 0) == 0
.text:00401E44                 add     esp, 1Ch
.text:00401E47                 mov     [ebp+lpMem], eax ; must be 0

这个循环会校验 r0^n == r1^n+r2^n (n: 3~9), 这个肯定不成立
.text:00401EF2                 cmp     eax, 0Ah
.text:00401EF5                 jge     loc_40210F
.text:00401EFB                 test    eax, eax
.text:00401EFD                 jnz     short loc_401F30
...
.text:004020FF                 call    bn_compare
.text:00402104                 test    eax, eax
.text:00402106                 jnz     loc_4022E9      ; always jmp

异常处理
.text:004022E9                 mov     eax, [ebp+var_3C] ; must be 0
.text:004022EC                 test    eax, eax
.text:004022EE                 jnz     short loc_402305
.text:004022F0                 lea     eax, [ebp+var_48]
.text:004022F3                 push    offset __TI1H   ; throw info for 'int'
.text:004022F8                 push    eax
.text:004022F9                 mov     [ebp+var_48], 1
.text:00402300                 call    __CxxThrowException@8 ; _CxxThrowException(x,x)

.text:00402367 ;   catch(...) // owned by 401EE8
.text:00402367                 mov     dword ptr [ebp-30h], 2
.text:0040236E                 mov     eax, offset loc_40211C
.text:00402373                 retn

.text:0040211C                 mov     eax, [ebp-30h]
.text:0040211F                 mov     [ebp+var_4], 0FFFFFFFFh
.text:00402126                 cmp     eax, 2
.text:00402129                 jnz     loc_402399

r1-r2=bn2
2*r1+4*r2=bn1
.text:00402189                 call    bn_add
...
.text:004021BB                 call    bn_compare

.text:004021CE                 push    4
.text:004021D0                 push    edx
.text:004021D1                 call    bn_int
...
.text:004021F5                 call    bn_mul
.text:004021FA                 lea     ecx, [ebp+var_1970]
.text:00402200                 push    2
.text:00402202                 push    ecx
.text:00402203                 call    bn_int
...
.text:00402226                 call    bn_mul
.text:0040222B                 mov     ecx, 84h
.text:00402230                 mov     esi, offset g_bn1
...
.text:0040225F                 call    bn_add
...
.text:0040228D                 call    bn_rebase

crc32_table = [
    0x00000000L, 0x77073096L, 0xee0e612cL, 0x990951baL, 0x076dc419L, 0x706af48fL, 0xe963a535L, 0x9e6495a3L,
    0x0edb8832L, 0x79dcb8a4L, 0xe0d5e91eL, 0x97d2d988L, 0x09b64c2bL, 0x7eb17cbdL, 0xe7b82d07L, 0x90bf1d91L,
    0x1db71064L, 0x6ab020f2L, 0xf3b97148L, 0x84be41deL, 0x1adad47dL, 0x6ddde4ebL, 0xf4d4b551L, 0x83d385c7L,
    0x136c9856L, 0x646ba8c0L, 0xfd62f97aL, 0x8a65c9ecL, 0x14015c4fL, 0x63066cd9L, 0xfa0f3d63L, 0x8d080df5L,
    0x3b6e20c8L, 0x4c69105eL, 0xd56041e4L, 0xa2677172L, 0x3c03e4d1L, 0x4b04d447L, 0xd20d85fdL, 0xa50ab56bL,
    0x35b5a8faL, 0x42b2986cL, 0xdbbbc9d6L, 0xacbcf940L, 0x32d86ce3L, 0x45df5c75L, 0xdcd60dcfL, 0xabd13d59L,
    0x26d930acL, 0x51de003aL, 0xc8d75180L, 0xbfd06116L, 0x21b4f4b5L, 0x56b3c423L, 0xcfba9599L, 0xb8bda50fL,
    0x2802b89eL, 0x5f058808L, 0xc60cd9b2L, 0xb10be924L, 0x2f6f7c87L, 0x58684c11L, 0xc1611dabL, 0xb6662d3dL,
    0x76dc4190L, 0x01db7106L, 0x98d220bcL, 0xefd5102aL, 0x71b18589L, 0x06b6b51fL, 0x9fbfe4a5L, 0xe8b8d433L,
    0x7807c9a2L, 0x0f00f934L, 0x9609a88eL, 0xe10e9818L, 0x7f6a0dbbL, 0x086d3d2dL, 0x91646c97L, 0xe6635c01L,
    0x6b6b51f4L, 0x1c6c6162L, 0x856530d8L, 0xf262004eL, 0x6c0695edL, 0x1b01a57bL, 0x8208f4c1L, 0xf50fc457L,
    0x65b0d9c6L, 0x12b7e950L, 0x8bbeb8eaL, 0xfcb9887cL, 0x62dd1ddfL, 0x15da2d49L, 0x8cd37cf3L, 0xfbd44c65L,
    0x4db26158L, 0x3ab551ceL, 0xa3bc0074L, 0xd4bb30e2L, 0x4adfa541L, 0x3dd895d7L, 0xa4d1c46dL, 0xd3d6f4fbL,
    0x4369e96aL, 0x346ed9fcL, 0xad678846L, 0xda60b8d0L, 0x44042d73L, 0x33031de5L, 0xaa0a4c5fL, 0xdd0d7cc9L,
    0x5005713cL, 0x270241aaL, 0xbe0b1010L, 0xc90c2086L, 0x5768b525L, 0x206f85b3L, 0xb966d409L, 0xce61e49fL,
    0x5edef90eL, 0x29d9c998L, 0xb0d09822L, 0xc7d7a8b4L, 0x59b33d17L, 0x2eb40d81L, 0xb7bd5c3bL, 0xc0ba6cadL,
    0xedb88320L, 0x9abfb3b6L, 0x03b6e20cL, 0x74b1d29aL, 0xead54739L, 0x9dd277afL, 0x04db2615L, 0x73dc1683L,
    0xe3630b12L, 0x94643b84L, 0x0d6d6a3eL, 0x7a6a5aa8L, 0xe40ecf0bL, 0x9309ff9dL, 0x0a00ae27L, 0x7d079eb1L,
    0xf00f9344L, 0x8708a3d2L, 0x1e01f268L, 0x6906c2feL, 0xf762575dL, 0x806567cbL, 0x196c3671L, 0x6e6b06e7L,
    0xfed41b76L, 0x89d32be0L, 0x10da7a5aL, 0x67dd4accL, 0xf9b9df6fL, 0x8ebeeff9L, 0x17b7be43L, 0x60b08ed5L,
    0xd6d6a3e8L, 0xa1d1937eL, 0x38d8c2c4L, 0x4fdff252L, 0xd1bb67f1L, 0xa6bc5767L, 0x3fb506ddL, 0x48b2364bL,
    0xd80d2bdaL, 0xaf0a1b4cL, 0x36034af6L, 0x41047a60L, 0xdf60efc3L, 0xa867df55L, 0x316e8eefL, 0x4669be79L,
    0xcb61b38cL, 0xbc66831aL, 0x256fd2a0L, 0x5268e236L, 0xcc0c7795L, 0xbb0b4703L, 0x220216b9L, 0x5505262fL,
    0xc5ba3bbeL, 0xb2bd0b28L, 0x2bb45a92L, 0x5cb36a04L, 0xc2d7ffa7L, 0xb5d0cf31L, 0x2cd99e8bL, 0x5bdeae1dL,
    0x9b64c2b0L, 0xec63f226L, 0x756aa39cL, 0x026d930aL, 0x9c0906a9L, 0xeb0e363fL, 0x72076785L, 0x05005713L,
    0x95bf4a82L, 0xe2b87a14L, 0x7bb12baeL, 0x0cb61b38L, 0x92d28e9bL, 0xe5d5be0dL, 0x7cdcefb7L, 0x0bdbdf21L,
    0x86d3d2d4L, 0xf1d4e242L, 0x68ddb3f8L, 0x1fda836eL, 0x81be16cdL, 0xf6b9265bL, 0x6fb077e1L, 0x18b74777L,
    0x88085ae6L, 0xff0f6a70L, 0x66063bcaL, 0x11010b5cL, 0x8f659effL, 0xf862ae69L, 0x616bffd3L, 0x166ccf45L,
    0xa00ae278L, 0xd70dd2eeL, 0x4e048354L, 0x3903b3c2L, 0xa7672661L, 0xd06016f7L, 0x4969474dL, 0x3e6e77dbL,
    0xaed16a4aL, 0xd9d65adcL, 0x40df0b66L, 0x37d83bf0L, 0xa9bcae53L, 0xdebb9ec5L, 0x47b2cf7fL, 0x30b5ffe9L,
    0xbdbdf21cL, 0xcabac28aL, 0x53b39330L, 0x24b4a3a6L, 0xbad03605L, 0xcdd70693L, 0x54de5729L, 0x23d967bfL,
    0xb3667a2eL, 0xc4614ab8L, 0x5d681b02L, 0x2a6f2b94L, 0xb40bbe37L, 0xc30c8ea1L, 0x5a05df1bL, 0x2d02ef8dL
]

crc32_table_highest_byte_map = [-1] * 256
for i in range(256):
    crc32_table_highest_byte_map[(crc32_table[i] >> 24) & 0xFF] = i


def array_to_int(k, base):
    v = 0
    n = 1
    for _ in k:
        v += n * _
        n *= base
    return v


def int_to_array(v, base):
    r = []
    while v != 0:
        r.append(v % base)
        v = v / base
    return r


def str_to_int(s, char_map):  # type:(str,str) -> int
    r = []
    for _ in s:
        r.append(char_map.find(_))
    return array_to_int(r, len(char_map))


def int_to_str(v, char_map):  # type:(int,str) -> str

    r = int_to_array(v, len(char_map))
    s = ''
    for _ in r:
        s = char_map[_] + s
    return s


def print_array(r):
    s = ''
    for _ in r:
        s += ('%x' % _).zfill(2) + ' '
    print s
    return


def print_int(v, base):
    r = int_to_array(v, base)
    print_array(r)
    return


def array_to_str(k):
    s = ''
    for _ in k:
        s += chr(_)
    return s


def str_to_array(s):
    k = []
    for _ in s:
        k.append(ord(s))
    return k


def crc32_update(k, crc):
    for b in k:
        crc = (crc >> 8) ^ crc32_table[b ^ (crc & 0xFF)]
    return crc


def get_crc32_update_init_value(k, crc):
    z = len(k) - 1
    while z >= 0:
        idx = crc32_table_highest_byte_map[(crc >> 24) & 0xFF]
        crc = ((crc32_table[idx] ^ crc) << 8) | (idx ^ k[z])
        z -= 1
    return crc


def crc32(k, crc_init=0):
    crc = crc_init
    crc = (~crc) & 0xFFFFFFFF
    crc = crc32_update(k, crc)
    crc = (~crc) & 0xFFFFFFFF
    return crc


def crc_RF(x):
    return crc32_table_highest_byte_map[x]


def crc_F(x):
    return (crc32_table[x] >> 24) & 0xFF


def crc_G(x):
    return (crc32_table[x] >> 16) & 0xFF


def crc_H(x):
    return (crc32_table[x] >> 8) & 0xFF


def crc_I(x):
    return (crc32_table[x] >> 0) & 0xFF


def crack_crc(s_head, s_tail, crc_init, crc_final):
    crc1 = (~crc_init) & 0xFFFFFFFF
    crc1 = crc32_update(s_head, crc1)
    crc2 = (~crc_final) & 0xFFFFFFFF
    crc2 = get_crc32_update_init_value(s_tail, crc2)

    # hxxps://bbs.pediy.com/thread-8699.htm
    W = (crc2 >> 24) & 0xFF
    X = (crc2 >> 16) & 0xFF
    Y = (crc2 >> 8) & 0xFF
    Z = (crc2 >> 0) & 0xFF

    A = (crc1 >> 24) & 0xFF
    B = (crc1 >> 16) & 0xFF
    C = (crc1 >> 8) & 0xFF
    D = (crc1 >> 0) & 0xFF

    p = crc_RF(W)
    o = crc_RF(X ^ crc_G(p))
    n = crc_RF(Y ^ crc_G(o) ^ crc_H(p))
    m = crc_RF(Z ^ crc_G(n) ^ crc_H(o) ^ crc_I(p))

    d = m ^ D
    c = n ^ C ^ crc_I(m)
    b = o ^ B ^ crc_H(m) ^ crc_I(n)
    a = p ^ A ^ crc_G(m) ^ crc_H(n) ^ crc_I(o)
    return [d, c, b, a]


def check_crc_table():
    print('xxstart')
    k3 = [0] * 256
    k2 = [0] * 256
    k1 = [0] * 256
    k0 = [0] * 256
    for _ in range(256):
        k3[(crc32_table[_] >> 24) & 0xFF] += 1
        k2[(crc32_table[_] >> 16) & 0xFF] += 1
        k1[(crc32_table[_] >> 8) & 0xFF] += 1
        k0[(crc32_table[_] >> 0) & 0xFF] += 1
    for _ in range(256):
        if k3[_] != 1:
            print('k3[%s]=%s' % (_, k3[_]))
        # if k2[_] != 1:
        #     print('k2[%s]=%s' % (_, k2[_]))
        # if k1[_] != 1:
        #     print('k1[%s]=%s' % (_, k1[_]))
        # if k0[_] != 1:
        #     print('k0[%s]=%s' % (_, k0[_]))
    print('xxend')
    return


def x_401080(v):
    if v == 0:
        return 0
    r = 1
    while (v & 1) == 0:
        v >>= 1
        r *= 2
        if v == 0:
            return 0
    return r


def x_4010A0(buf, bits):
    a1 = 0
    buf_len = (1 << bits) - 1
    v_cnt0 = buf_len
    v_cnt1 = 0
    v_cnt2 = 0

    _ = 0
    for _ in range(buf_len):
        c = buf[_]
        v_cnt0_v = x_401080(v_cnt0)
        v_cnt1_v = x_401080(v_cnt1)
        v_cnt2_v = x_401080(v_cnt2)
        _v_cnt0_v = v_cnt0_v if v_cnt0_v != 0 else 100
        _v_cnt1_v = v_cnt1_v if v_cnt1_v != 0 else 100
        _v_cnt2_v = v_cnt2_v if v_cnt2_v != 0 else 100
        if c == 0:
            if _v_cnt0_v >= _v_cnt1_v:
                break
            v_cnt0 -= v_cnt0_v
            v_cnt1 += v_cnt0_v
            a1 = v_cnt0_v
        elif c == 1:
            if _v_cnt0_v >= _v_cnt2_v:
                break
            v_cnt0 -= v_cnt0_v
            v_cnt2 += v_cnt0_v
            a1 = v_cnt0_v
        elif c == 2:
            if _v_cnt1_v >= _v_cnt0_v:
                break
            v_cnt0 += v_cnt1_v
            v_cnt1 -= v_cnt1_v
            a1 = v_cnt1_v
        elif c == 3:
            if _v_cnt1_v >= _v_cnt2_v:
                break
            v_cnt1 -= v_cnt1_v
            v_cnt2 += v_cnt1_v
            a1 = v_cnt1_v
        elif c == 4:
            if _v_cnt2_v >= _v_cnt0_v:
                break
            v_cnt0 += v_cnt2_v
            v_cnt2 -= v_cnt2_v
            a1 = v_cnt2_v
        elif c == 5:
            if _v_cnt2_v >= _v_cnt1_v:
                break
            v_cnt1 += v_cnt2_v
            v_cnt2 -= v_cnt2_v
            a1 = v_cnt2_v
    r = False
    a0 = v_cnt0
    if _ == (buf_len - 1) and a0 == 0 and a1 == 1:
        r = True
    return [r, a0, a1]


def x_crack_part1_raw(buf, offset, cond0, cond1, vct_max, strict=False):
    bits = 5
    # buf[(1 << bits) - 1] == 0
    i7_end = 6 if (offset != 0x18) else 1

    vct = []
    for i0 in range(6):
        for i1 in range(6):
            for i2 in range(6):
                for i3 in range(6):
                    for i4 in range(6):
                        for i5 in range(6):
                            for i6 in range(6):
                                for i7 in range(i7_end):
                                    buf[offset + 0] = i0
                                    buf[offset + 1] = i1
                                    buf[offset + 2] = i2
                                    buf[offset + 3] = i3
                                    buf[offset + 4] = i4
                                    buf[offset + 5] = i5
                                    buf[offset + 6] = i6
                                    buf[offset + 7] = i7
                                    r, a_0, a_1 = x_4010A0(buf, bits)
                                    if strict:
                                        ok = r
                                    else:
                                        ok = a_0 <= cond0 and (cond1 < 0 or a_1 <= cond1)
                                    if ok:
                                        v = [i0, i1, i2, i3, i4, i5, i6, i7]
                                        if strict:
                                            print('(%s): %s' % (len(vct), v))
                                        vct.append(v)
                                        if (vct_max > 0) and (len(vct) >= vct_max):
                                            return vct

    return vct


def x_crack_part1(count, use_cache=True):
    buf = [0] * 32

    print('crack_part1 0:8')
    offset = 0
    if use_cache:
        vct0 = [[0, 1, 3, 0, 4, 5, 0, 1], ]
    else:
        vct0 = x_crack_part1_raw(buf, offset, 0x10, -1, 1)
    print vct0
    for _ in range(8):
        buf[offset + _] = vct0[0][_]

    print('crack_part1 8:0x10')
    offset += 8
    if use_cache:
        vct1 = [[2, 1, 2, 4, 3, 0, 1, 3], ]
    else:
        vct1 = x_crack_part1_raw(buf, offset, 0x0F, -1, 1)
    print vct1
    for _ in range(8):
        buf[offset + _] = vct1[0][_]

    print('crack_part1 0x10:0x18')
    offset += 8
    if use_cache:
        vct2 = [[0, 2, 0, 2, 0, 2, 0, 4], ]
    else:
        vct2 = x_crack_part1_raw(buf, offset, 0, 1, 1)
    print vct2
    for _ in range(8):
        buf[offset + _] = vct2[0][_]

    print('crack_part1 0x18:0x20')
    offset += 8
    vct3 = x_crack_part1_raw(buf, offset, 0, 1, count, strict=True)

    r = []
    for a in range(len(vct3)):
        v = [_ for _ in buf]
        for b in range(8):
            v[offset + b] = vct3[a][b]
        # print_array(v)
        r.append(v)
    return r


def x_gen_sn(k):
    # char_map36 = 'abcdefghijklmnopqrstuvwxyz0123456789'
    char_map62 = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz'
    char_map64 = '0123456789ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz. '
    r0_0 = []
    for _ in range(0, len(k), 2):
        r0_0 = [k[_ + 1] * 6 + k[_], ] + r0_0
    v = array_to_int(r0_0, 36)
    # print_int(v, 36)
    # print int_to_str(v, char_map36)
    r0_0 = int_to_array(v, 256)

    r0_1 = [-1] * 4
    r0 = r0_0 + r0_1

    v1 = str_to_int('welcome to bbs.pediy.com.'[::-1], char_map64)
    v2 = str_to_int('Author by Lookhc'[::-1], char_map64)
    y = (v1 - v2 * 2) / 6
    x = y + v2
    r1 = int_to_array(x, 256)
    r2 = int_to_array(y, 256)

    k = [len(r0) - 4, len(r0), len(r1), len(r2)] + r0 + r1 + r2
    r0_1 = crack_crc(k[0:len(r0)], k[4 + len(r0):], 0, 0)
    r0 = r0_0 + r0_1
    k = [len(r0) - 4, len(r0), len(r1), len(r2)] + r0 + r1 + r2
    print int_to_str(array_to_int(k, 256), char_map62)
    return


def test():
    # count = 256
    count = 2
    ks = x_crack_part1(count, use_cache=True)
    for _ in range(len(ks)):
        x_gen_sn(ks[_])

    return


test()


看雪学院推出的专业资质证书《看雪安卓应用安全能力认证 v1.0》(中级和高级)!

收藏
点赞0
打赏
分享
最新回复 (0)
游客
登录 | 注册 方可回帖
返回