使用PyCrypto验证RSA签名遇运行时错误，怀疑签名或公钥输入格式有误

问题背景 #

尝试使用PyCrypto完成多组消息的RSA签名校验流程，运行时触发报错，初步怀疑问题出在签名、公钥的输入格式适配层面。

原始示例代码 #

from Crypto.PublicKey import RSA
from Crypto.Cipher import PKCS1_OAEP
from Crypto.Signature import PKCS1_v1_5
from Crypto.Hash import SHA512, SHA384, SHA256, SHA, MD5
from Crypto import Random
from base64 import b64encode, b64decode

hash = "SHA-256"

def verify(message, signature, pub_key):
    signer = PKCS1_v1_5.new(pub_key)
    if (hash == "SHA-512"):
        digest = SHA512.new()
    elif (hash == "SHA-384"):
        digest = SHA384.new()
    elif (hash == "SHA-256"):
        digest = SHA256.new()
    elif (hash == "SHA-1"):
        digest = SHA.new()
    else:
        digest = MD5.new()
    digest.update(message)
    return signer.verify(digest, signature)

verify = rsa.verify(content, b64decode(signature), RSA.importKey(b64decode(publicKey)))

测试输入值 #

content = "FID:XXX;feed:Funny;date:2021-02-01 12:24:26;UID:Ab27aNxbtkgmEd2nGGxsEpcYPO33;ratio:0.28465346534653463;title:Yawns are contagious;username:Jane;type:Image;url:https://i.imgur.com/vQA4D3o.gif;thumbnail:https://thumbor.forbes.com/thumbor/fit-in/416x416/filters%3Aformat%28jpg%29/https%3A%2F%2Fspecials-images.forbesimg.com%2Fimageserve%2F5f4977a36096df14bbef84d4%2F0x0.jpg%3Fbackground%3D000000%26cropX1%3D781%26cropX2%3D1650%26cropY1%3D314%26cropY2%3D1183;"

signature = "nH9ZeDqXCPFXYx8KQpBLR84SWw51FOz0bCEo7JBZAi+aKVOI7w9T+gJvSBX3oAioGiMTlqIorVjnIMcqdkcKQoDa1iNfIo9G2uVwMRAX8iCZMJKw9jBqboAn8uy8ia/wQwao9df5VZl1wxcOOlBuUnp5cvl90m510iol2T+JxFytn6bojscviSnAatconHXA3HrNy1kLk5zsGarGT9FasUu48YaEtp/ygxejhXiEeQn8fPx3mNtIQPe2IewH9zwC4yfGCwRaAf64Lp6VPktvT+ykM58dqvwxJU2GtD6GSD8Gj0wMP0TFqSZCotHCB7JWxGItY6vJU8tAbGOZRVOlGg=="

publicKey = "MIIBCgKCAQEAqgQkzNhzFmMoYzhtVF7eDPL/uc/i6hMv/0XhcM3A+Jwc+cBAnLMGcdkkUQC8EX9LJoi7CHJsTq5OfegJjhJH5W3UCBRwJZ9k5mP1wjtw00go7wLiH8beoD99ml2DgJMyLITfzgJxk6RJ+kyCB6sBnzTjVCTQFZg0JoEpsG0mqFuAepzHFUhMjEqfvxC3mzs7aUl5iDp2+QDrTVRWjlrYAO2GTYgig36i+tpH8/MD4MYEM4bgMIDp0RK/C5FXd+2XaKYDVqZoMNzrNwS7X24nFo+saodUsd++vQzqlvo0XfQBHRm7gIH+oHlG16y/uWsS9IZ/o6Qty5DOCISG8uAsJwIDAQAB"

报错堆栈信息 #

文件 "/workspace/main.py"，第52行，在add函数中
verifySignature(postID,uid,signature)

文件 "/workspace/main.py"，第28行，在verifySignature函数中
verify = rsa.verify(content, b64decode(signature), RSA.importKey(b64decode(publicKey)))

文件 "/layers/google.python.pip/pip/lib/python3.8/site-packages/rsa/pkcs1.py"，第356行，在verify方法中
message_hash = compute_hash(message, method_name)

文件 "/layers/google.python.pip/pip/lib/python3.8/site-packages/rsa/pkcs1.py"，第432行，在compute_hash方法中
assert hasattr(message, 'read') and hasattr(message.read, 'call')

问题根因 #

• 代码混用了两套独立的RSA实现逻辑：前面导入的全是pycryptodome（原PyCrypto）生态的模块，后续却直接调用未导入的第三方rsa库的verify接口，和初始导入的逻辑完全割裂。
• 第三方rsa库的verify接口存在强制输入约束：要求传入的原始消息是具备.read()方法的类文件对象，直接传入字符串会触发断言失败，这是当前报错的直接原因。
• 原有PyCrypto逻辑存在类型遗漏：PyCrypto的摘要更新接口要求传入字节类型数据，直接传入字符串会触发类型错误，需要对原始消息做UTF-8编码转换。
• 输入格式本身不存在兼容问题：提供的base64编码公钥是标准X.509格式，签名是标准PKCS#1 v1.5格式，解码后可直接被RSA接口识别，不需要额外格式转换。

修正后可运行代码 #

from Crypto.PublicKey import RSA
from Crypto.Signature import PKCS1_v1_5
from Crypto.Hash import SHA256
from base64 import b64decode

# 指定消息摘要算法
HASH_ALG = "SHA-256"

def pycrypto_rsa_verify(message: str, signature: bytes, pub_key_bytes: bytes) -> bool:
    public_key = RSA.import_key(pub_key_bytes)
    signer = PKCS1_v1_5.new(public_key)
    # 按指定算法初始化摘要对象
    digest = SHA256.new()
    # 字符串转字节后更新摘要内容
    digest.update(message.encode("utf-8"))
    # 签名校验无异常即返回通过，校验失败会抛出对应异常
    try:
        signer.verify(digest, signature)
        return True
    except (ValueError, TypeError):
        return False

# 传入测试值完成校验
content = "FID:XXX;feed:Funny;date:2021-02-01 12:24:26;UID:Ab27aNxbtkgmEd2nGGxsEpcYPO33;ratio:0.28465346534653463;title:Yawns are contagious;username:Jane;type:Image;url:https://i.imgur.com/vQA4D3o.gif;thumbnail:https://thumbor.forbes.com/thumbor/fit-in/416x416/filters%3Aformat%28jpg%29/https%3A%2F%2Fspecials-images.forbesimg.com%2Fimageserve%2F5f4977a36096df14bbef84d4%2F0x0.jpg%3Fbackground%3D000000%26cropX1%3D781%26cropX2%3D1650%26cropY1%3D314%26cropY2%3D1183;"
signature = "nH9ZeDqXCPFXYx8KQpBLR84SWw51FOz0bCEo7JBZAi+aKVOI7w9T+gJvSBX3oAioGiMTlqIorVjnIMcqdkcKQoDa1iNfIo9G2uVwMRAX8iCZMJKw9jBqboAn8uy8ia/wQwao9df5VZl1wxcOOlBuUnp5cvl90m510iol2T+JxFytn6bojscviSnAatconHXA3HrNy1kLk5zsGarGT9FasUu48YaEtp/ygxejhXiEeQn8fPx3mNtIQPe2IewH9zwC4yfGCwRaAf64Lp6VPktvT+ykM58dqvwxJU2GtD6GSD8Gj0wMP0TFqSZCotHCB7JWxGItY6vJU8tAbGOZRVOlGg=="
publicKey = "MIIBCgKCAQEAqgQkzNhzFmMoYzhtVF7eDPL/uc/i6hMv/0XhcM3A+Jwc+cBAnLMGcdkkUQC8EX9LJoi7CHJsTq5OfegJjhJH5W3UCBRwJZ9k5mP1wjtw00go7wLiH8beoD99ml2DgJMyLITfzgJxk6RJ+kyCB6sBnzTjVCTQFZg0JoEpsG0mqFuAepzHFUhMjEqfvxC3mzs7aUl5iDp2+QDrTVRWjlrYAO2GTYgig36i+tpH8/MD4MYEM4bgMIDp0RK/C5FXd+2XaKYDVqZoMNzrNwS7X24nFo+saodUsd++vQzqlvo0XfQBHRm7gIH+oHlG16y/uWsS9IZ/o6Qty5DOCISG8uAsJwIDAQAB"

verify_result = pycrypto_rsa_verify(
    message=content,
    signature=b64decode(signature),
    pub_key_bytes=b64decode(publicKey)
)

补充说明 #

如果坚持使用第三方rsa库做校验，需要导入io模块，把原始字符串包装成io.BytesIO类文件对象传入接口，才能通过断言检查。

内容的提问来源于stack exchange，提问作者Anters Bear