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[已解決] urllib.error.URLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed

Last Updated on 2021-09-26 by Clay

今天我想要透過 pytube 這個 Python 的第三方模組來下載影片時，發生了以下錯誤：

urllib.error.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:847)>

以前沒有碰過這樣的錯誤，看起來似乎也不像是 YouTube 更改了網頁版本的問題。上網一查，這才推測可能單純是 urllib 在我新電腦上的運作與之前的版本不同（？）。

簡單來說，這個問題似乎是驗證 SSL 憑證出錯的緣故，可能目標網站採用了自己簽署的憑證（看過此說法，但不太確定是否為真）。

發生錯誤範例程式

首先，看個簡單的報錯範例：

import urllib.request
r = urllib.request.urlopen('https://google.com')



Output:

Traceback (most recent call last):
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 1318, in do_open
    encode_chunked=req.has_header('Transfer-encoding'))
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1239, in request
    self._send_request(method, url, body, headers, encode_chunked)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1285, in _send_request
    self.endheaders(body, encode_chunked=encode_chunked)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1234, in endheaders
    self._send_output(message_body, encode_chunked=encode_chunked)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1026, in _send_output
    self.send(msg)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 964, in send
    self.connect()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/http/client.py", line 1400, in connect
    server_hostname=server_hostname)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 407, in wrap_socket
    _context=self, _session=session)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 817, in __init__
    self.do_handshake()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 1077, in do_handshake
    self._sslobj.do_handshake()
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/ssl.py", line 689, in do_handshake
    self._sslobj.do_handshake()
ssl.SSLError: [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:847)

During handling of the above exception, another exception occurred:

Traceback (most recent call last):
  File "<stdin>", line 1, in <module>
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 223, in urlopen
    return opener.open(url, data, timeout)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 526, in open
    response = self._open(req, data)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 544, in _open
    '_open', req)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 504, in _call_chain
    result = func(*args)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 1361, in https_open
    context=self._context, check_hostname=self._check_hostname)
  File "/Library/Frameworks/Python.framework/Versions/3.6/lib/python3.6/urllib/request.py", line 1320, in do_open
    raise URLError(err)
urllib.error.URLError: <urlopen error [SSL: CERTIFICATE_VERIFY_FAILED] certificate verify failed (_ssl.c:847)>

解決方法

然而，若是我們選擇不用認證此 SSL 憑證，則就可以讓 urllib 正常運作。

# coding: utf-8
import urllib.request
import ssl


def main():
    ssl._create_default_https_context = ssl._create_unverified_context
    r = urllib.request.urlopen('https://google.com')
    print(r.status)
    print(r)


if __name__ == '__main__':
    main()



Output:

200
<http.client.HTTPResponse object at 0x7fc1af051ef0>


除了這個方法外，如果只是要讓特定的連線不要驗證、其餘的連線都還是驗證 SSL 憑證的話，則可以這樣寫：

# coding: utf-8
import urllib.request
import ssl


def main():
    context = ssl._create_unverified_context()
    r = urllib.request.urlopen('https://google.com', context=context)
    print(r.status)
    print(r)


if __name__ == '__main__':
    main()



Output:

200
<http.client.HTTPResponse object at 0x7fc1af051ef0>

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