First Commit

Dockerfile

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+FROM python:3.10
+
+WORKDIR /app
+COPY _files /app
+
+RUN pip install -r requirements.txt --no-cache-dir
+
+CMD ["uvicorn", "app:app", "--host", "0.0.0.0", "--port", "80"]

_files/app.py

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+import os
+from fastapi import FastAPI
+from fastapi.responses import HTMLResponse
+
+app = FastAPI()
+
+def generate_substitution_cipher(flag):
+    substitution_rules = []
+    for i, char in enumerate(flag):
+        position = i + 1  # 1-based index
+        if char.isalpha():
+            if char.isupper():
+                substitution_rules.append(f"the {position}th flag is '{char}', upper.\n")
+            else:  # char is lowercase
+                substitution_rules.append(f"the {position}th flag is '{char}', lower.\n")
+        else:
+            substitution_rules.append(f"the {position}th flag is '{char}', character.\n")
+
+    substitution_dict = {
+        'a': 'x', 'b': 'y', 'c': 'z', 'd': 'a', 'e': 'b', 'f': 'c', 'g': 'd',
+        'h': 'e', 'i': 'f', 'j': 'g', 'k': 'h', 'l': 'i', 'm': 'j', 'n': 'k',
+        'o': 'l', 'p': 'm', 'q': 'n', 'r': 'o', 's': 'p', 't': 'q', 'u': 'r',
+        'v': 's', 'w': 't', 'x': 'u', 'y': 'v', 'z': 'w',
+        'A': 'X', 'B': 'Y', 'C': 'Z', 'D': 'A', 'E': 'B', 'F': 'C', 'G': 'D',
+        'H': 'E', 'I': 'F', 'J': 'G', 'K': 'H', 'L': 'I', 'M': 'J', 'N': 'K',
+        'O': 'L', 'P': 'M', 'Q': 'N', 'R': 'O', 'S': 'P', 'T': 'Q', 'U': 'R',
+        'V': 'S', 'W': 'T', 'X': 'U', 'Y': 'V', 'Z': 'W',
+        ' ': ' '  # 保持空格不变
+    }
+    
+    substitution_rules.append("The quick brown fox jumps a lazy dog.")
+    encrypted_rules = []
+    for rule in substitution_rules:
+        for char in rule:
+            if char in substitution_dict:
+                encrypted_rules.append(substitution_dict[char])
+            else:
+                encrypted_rules.append(char)
+
+    return ''.join(encrypted_rules)
+
+@app.get("/", response_class=HTMLResponse)
+async def read_root():
+    flag = os.getenv("GZCTF_FLAG", "Woodpecker{test-Flag_0}")
+    cipher_text = generate_substitution_cipher(flag)
+    return f"<h1>下面的密文有Flag哦（PS：单表替换）：</h1><p>{cipher_text}</p>"
+
+if __name__ == "__main__":
+    import uvicorn
+    uvicorn.run(app, host="0.0.0.0", port=8000)
+

_files/cli.py

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+import os
+
+def generate_substitution_cipher(flag):
+    substitution_rules = []
+    for i, char in enumerate(flag):
+        position = i + 1  # 1-based index
+        if char.isalpha():
+            if char.isupper():
+                substitution_rules.append(f"the {position}th flag is '{char}', upper.\n")
+            else:  # char is lowercase
+                substitution_rules.append(f"the {position}th flag is '{char}', lower.\n")
+        else:
+            # 对于非字母字符，记录其位置和类型
+            substitution_rules.append(f"the {position}th flag is '{char}', character.\n")
+
+    # 生成替换字典
+    substitution_dict = {
+        'a': 'x', 'b': 'y', 'c': 'z', 'd': 'a', 'e': 'b', 'f': 'c', 'g': 'd',
+        'h': 'e', 'i': 'f', 'j': 'g', 'k': 'h', 'l': 'i', 'm': 'j', 'n': 'k',
+        'o': 'l', 'p': 'm', 'q': 'n', 'r': 'o', 's': 'p', 't': 'q', 'u': 'r',
+        'v': 's', 'w': 't', 'x': 'u', 'y': 'v', 'z': 'w',
+        'A': 'X', 'B': 'Y', 'C': 'Z', 'D': 'A', 'E': 'B', 'F': 'C', 'G': 'D',
+        'H': 'E', 'I': 'F', 'J': 'G', 'K': 'H', 'L': 'I', 'M': 'J', 'N': 'K',
+        'O': 'L', 'P': 'M', 'Q': 'N', 'R': 'O', 'S': 'P', 'T': 'Q', 'U': 'R',
+        'V': 'S', 'W': 'T', 'X': 'U', 'Y': 'V', 'Z': 'W',
+        ' ': ' '  # 保持空格不变
+    }
+    
+    substitution_rules.append("The quick brown fox jumps a lazy dog.")
+    encrypted_rules = []
+    for rule in substitution_rules:
+        for char in rule:
+            if char in substitution_dict:
+                encrypted_rules.append(substitution_dict[char])
+            else:
+                encrypted_rules.append(char)
+    # 应用替换字典
+    return ''.join(encrypted_rules)
+
+# 示例Flag
+flag = os.getenv("GZCTF_FLAG", "Woodpecker{test-Flag_0}")
+cipher_text = generate_substitution_cipher(flag)
+print(cipher_text)
+

_files/requirements.txt

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+fastapi
+uvicorn