Why Is My cURL Returning Zero-Length Content When Connecting to an HTTPS Site?

Troubleshooting HTTPS Connection Issues with cURL

You've encountered an issue where cURL is returning zero-length content when attempting to connect to a secure HTTPS site. Let's explore some potential solutions:

The problem may lie with the certificate verification process. cURL uses a bundled certificate file to validate remote HTTPS connections. However, this bundled file can become outdated, leading to authentication issues.

Solution:

1. Obtain the latest certificate file from the official cURL website: http://curl.haxx.se/ca/cacert.pem
2. Save the file to a convenient location on your site.
3. In your cURL request, include the following line:

curl_setopt ($curl_ch, CURLOPT_CAINFO, dirname(__FILE__)."/cacert.pem"); 

Alternative Solution:

1. In your php.ini file, add the following line:

curl.cainfo=/etc/ssl/certs/ca-certificates.crt

This will instruct PHP to use the system's certificate authority file.

Composer Package Solution:

For a more robust solution, consider using the certainty composer package: https://github.com/paragonie/certainty. It automates the certificate management process, ensuring your code is not vulnerable to certificate revocation or other issues.

It's essential to remember that disabling CURLOPT_VERIFYPEER and CURLOPT_VERIFYHOST leaves your code susceptible to man-in-the-middle attacks. Always verify HTTPS connections properly to maintain the integrity of your communication.

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