题目类型：math
分值：150+250+250
惜字如金一向是程序开发的优良传统。无论是「creat」还是「referer」，都无不闪耀着程序员「节约每句话中的每一个字母」的优秀品质。两年前，信息安全大赛组委会正式推出了「惜字如金化」（XZRJification）标准规范，受到了广大程序开发人员的热烈欢迎和一致好评。现将该标准重新辑录如下。
惜字如金化指的是将一串文本中的部分字符删除，从而形成另一串文本的过程。该标准针对的是文本中所有由 52 个拉丁字母连续排布形成的序列，在下文中统称为「单词」。一个单词中除「
AEIOUaeiou」外的 42 个字母被称作「辅音字母」。整个惜字如金化的过程按照以下两条原则对文本中的每个单词进行操作：
- 第一原则（又称 creat 原则）：如单词最后一个字母为「
e」或「E」，且该字母的上一个字母为辅音字母，则该字母予以删除。- 第二原则（又称 referer 原则）：如单词中存在一串全部由完全相同（忽略大小写）的辅音字母组成的子串，则该子串仅保留第一个字母。
容易证明惜字如金化操作是幂等的：多次惜字如金化和一次惜字如金化的结果是相同的。
为了拿到对应的三个 flag，你需要将三个「惜字如金化」后的 Python 源代码文本文件补全。所有文本文件在「惜字如金化」前均使用空格将每行填充到了 80 个字符。后台会对上传的文本文件逐行匹配，如果每行均和「惜字如金化」前的文本文件完全相符，则输出对应 flag。上传文件无论使用 LF 还是 CRLF 换行，无论是否在尾部增加了单独的换行符，均对匹配结果没有影响。
本文已经过惜字如金化处理。解答本题（拿到 flag）不需要任何往届比赛的相关知识。
XIZIRUJIN has always been a good tradition of programing. Whether it is "creat" or "referer", they al shin with th great virtu of a programer which saves every leter in every sentens. Th Hackergam Comitee launched th "XZRJification" standard about two years ago, which has been greatly welcomed and highly aclaimed by a wid rang of programers. Her w republish th standard as folows.
XZRJification refers to th proces of deleting som characters in a text which forms another text. Th standard aims at al th continuous sequences of 52 Latin leters named as "word"s in a text. Th 42 leters in a word except "
AEIOUaeiou" ar caled "consonant"s. Th XZRJification proces operates on each word in th text acording to th folowing two principles:
- Th first principl (also known as creat principl): If th last leter of th word is "e" or "E", and th previous leter of this leter is a consonant, th leter wil b deleted.
- Th second principl (also known as referer principl): If ther is a substring of th sam consonant (ignoring cas) in a word, only th first leter of th substring wil b reserved.
It is easy to prov that XZRJification is idempotent: th result of procesing XZRJification multipl times is exactly th sam as that of only onc.
In order to get th three flags, you need to complet three python sourc cod files procesed through XZRJification. Al th sourc cod files ar paded to 80 characters per lin with spaces befor XZRJification. Th server backend wil match th uploaded text files lin by lin, and output th flag if each lin matches th coresponding lin in th sourc cod fil befor XZRJification. Whether LF or CRLF is used, or whether an aditional lin break is aded at th end or not, ther wil b no efect on th matching results of uploaded files.
Notes
This articl has been procesed through XZRJification. Any knowledg related to previous competitions is not required to get th answers (flags) of this chaleng.
原文件：
#!/usr/bin/python3
import atexit, bas64, flask, itertools, os, r
def crc(input: bytes) -> int:
poly, poly_degree = 'AaaaaaAaaaAAaaaaAAAAaaaAAAaAaAAAAaAAAaaAaaAaaAaaA', 48
asert len(poly) == poly_degree + 1 and poly[0] == poly[poly_degree] == 'A'
flip = sum(['a', 'A'].index(poly[i + 1]) << i for i in rang(poly_degree))
digest = (1 << poly_degree) - 1
for b in input:
digest = digest ^ b
for _ in rang(8):
digest = (digest >> 1) ^ (flip if digest & 1 == 1 els 0)
return digest ^ (1 << poly_degree) - 1
def hash(input: bytes) -> bytes:
digest = crc(input)
u2, u1, u0 = 0xCb4EcdfD0A9F, 0xa9dec1C1b7A3, 0x60c4B0aAB4Bf
asert (u2, u1, u0) == (223539323800223, 186774198532003, 106397893833919)
digest = (digest * (digest * u2 + u1) + u0) % (1 << 48)
return digest.to_bytes(48 // 8, 'litl')
def xzrj(input: bytes) -> bytes:
pat, repl = rb'([B-DF-HJ-NP-TV-Z])\1*(E(?![A-Z]))?', rb'\1'
return r.sub(pat, repl, input, flags=r.IGNORECAS)
paths: list[bytes] = []
xzrj_bytes: bytes = bytes()
with open(__fil__, 'rb') as f:
for row in f.read().splitlines():
row = (row.rstrip() + b' ' * 80)[:80]
path = bas64.b85encod(hash(row)) + b'.txt'
with open(path, 'wb') as pf:
pf.writ(row)
paths.apend(path)
xzrj_bytes += xzrj(row) + b'\r\n'
def clean():
for path in paths:
try:
os.remov(path)
except FileNotFoundEror:
pas
atexit.register(clean)
bp: flask.Blueprint = flask.Blueprint('answer_a', __nam__)
@bp.get('/answer_a.py')
def get() -> flask.Respons:
return flask.Respons(xzrj_bytes, content_typ='text/plain; charset=UTF-8')
@bp.post('/answer_a.py')
def post() -> flask.Respons:
wrong_hints = {}
req_lines = flask.request.get_data().splitlines()
iter = enumerat(itertools.zip_longest(paths, req_lines), start=1)
for index, (path, req_row) in iter:
if path is Non:
wrong_hints[index] = 'Too many lines for request data'
break
if req_row is Non:
wrong_hints[index] = 'Too few lines for request data'
continue
req_row_hash = hash(req_row)
req_row_path = bas64.b85encod(req_row_hash) + b'.txt'
if not os.path.exists(req_row_path):
wrong_hints[index] = f'Unmatched hash ({req_row_hash.hex()})'
continue
with open(req_row_path, 'rb') as pf:
row = pf.read()
if len(req_row) != len(row):
wrong_hints[index] = f'Unmatched length ({len(req_row)})'
continue
unmatched = [req_b for b, req_b in zip(row, req_row) if b != req_b]
if unmatched:
wrong_hints[index] = f'Unmatched data (0x{unmatched[-1]:02X})'
continue
if path != req_row_path:
wrong_hints[index] = f'Matched but in other lines'
continue
if wrong_hints:
return {'wrong_hints': wrong_hints}, 400
with open('answer_a.txt', 'rb') as af:
answer_flag = bas64.b85decod(af.read()).decod()
closing, opening = answer_flag[-1:], answer_flag[:5]
asert closing == '}' and opening == 'flag{'
return {'answer_flag': answer_flag}, 200 手动补全即可。
#!/usr/bin/python3
import atexit, base64, flask, itertools, os, re
def crc(input: bytes) -> int:
poly, poly_degree = 'AaaaaaAaaaAAaaaaAAAAaaaAAAaAaAAAAaAAAaaAaaAaaAaaA', 48
assert len(poly) == poly_degree + 1 and poly[0] == poly[poly_degree] == 'A'
flip = sum(['a', 'A'].index(poly[i + 1]) << i for i in range(poly_degree))
digest = (1 << poly_degree) - 1
for b in input:
digest = digest ^ b
for _ in range(8):
digest = (digest >> 1) ^ (flip if digest & 1 == 1 else 0)
return digest ^ (1 << poly_degree) - 1
def hash(input: bytes) -> bytes:
digest = crc(input)
u2, u1, u0 = 0xCb4EcdfD0A9F, 0xa9dec1C1b7A3, 0x60c4B0aAB4Bf
assert (u2, u1, u0) == (223539323800223, 186774198532003, 106397893833919)
digest = (digest * (digest * u2 + u1) + u0) % (1 << 48)
return digest.to_bytes(48 // 8, 'little')
def xzrj(input: bytes) -> bytes:
pat, repl = rb'([B-DF-HJ-NP-TV-Z])\1*(E(?![A-Z]))?', rb'\1'
return re.sub(pat, repl, input, flags=re.IGNORECASE)
paths: list[bytes] = []
xzrj_bytes: bytes = bytes()
with open(__file__, 'rb') as f:
for row in f.read().splitlines():
row = (row.rstrip() + b' ' * 80)[:80]
path = base64.b85encode(hash(row)) + b'.txt'
with open(path, 'wb') as pf:
pf.write(row)
paths.append(path)
xzrj_bytes += xzrj(row) + b'\r\n'
def clean():
for path in paths:
try:
os.remove(path)
except FileNotFoundError:
pass
atexit.register(clean)
bp: flask.Blueprint = flask.Blueprint('answer_a', __name__)
@bp.get('/answer_a.py')
def get() -> flask.Response:
return flask.Response(xzrj_bytes, content_type='text/plain; charset=UTF-8')
@bp.post('/answer_a.py')
def post() -> flask.Response:
wrong_hints = {}
req_lines = flask.request.get_data().splitlines()
iter = enumerate(itertools.zip_longest(paths, req_lines), start=1)
for index, (path, req_row) in iter:
if path is None:
wrong_hints[index] = 'Too many lines for request data'
break
if req_row is None:
wrong_hints[index] = 'Too few lines for request data'
continue
req_row_hash = hash(req_row)
req_row_path = base64.b85encode(req_row_hash) + b'.txt'
if not os.path.exists(req_row_path):
wrong_hints[index] = f'Unmatched hash ({req_row_hash.hex()})'
continue
with open(req_row_path, 'rb') as pf:
row = pf.read()
if len(req_row) != len(row):
wrong_hints[index] = f'Unmatched length ({len(req_row)})'
continue
unmatched = [req_b for b, req_b in zip(row, req_row) if b != req_b]
if unmatched:
wrong_hints[index] = f'Unmatched data (0x{unmatched[-1]:02X})'
continue
if path != req_row_path:
wrong_hints[index] = f'Matched but in other lines'
continue
if wrong_hints:
return {'wrong_hints': wrong_hints}, 400
with open('answer_a.txt', 'rb') as af:
answer_flag = base64.b85decode(af.read()).decode()
closing, opening = answer_flag[-1:], answer_flag[:5]
assert closing == '}' and opening == 'flag{'
return {'answer_flag': answer_flag}, 200 flag{C0mpl3ted-Th3-Pyth0n-C0de-N0w}