使用Python oracledb连接Oracle Cloud数据库时遭遇SSL握手失败问题求助

Let’s walk through the most likely causes and fixes for your SSL handshake error when connecting to Oracle Autonomous Database (ADB) with python-oracledb:

1. The Most Likely Culprit: Using the Wrong Connection String #

Since you’ve set Mutual TLS (mTLS) Authentication to "Not Required" in your ADB’s Network settings, you need to use a TLS-only connection string—not the mTLS one you copied initially.

mTLS connection strings include the ssl_server_cert_dn parameter, which expects a client certificate for authentication. Since you disabled mTLS, this parameter causes the SSL handshake to fail.

Fix Steps: #

• Go back to your ADB’s DB Connection > Connection Strings page
• Switch to the TLS tab (not the mTLS tab)
• Copy the connection string from this tab. It should look similar to this:

  (description= (retry_count=20)(retry_delay=3)(address=(protocol=tcps)(port=1522)(host=adb.uk-london-1.oraclecloud.com))(connect_data=(service_name=abc123xyzredacted.adb.oraclecloud.com))(security=(ssl_server_dn_match=yes)))
  

• Update your PYTHON_CONNECTSTRING environment variable with this new string.

2. Verify Python's SSL Library Compatibility #

The SSLV3_ALERT_HANDSHAKE_FAILURE error can also occur if your Python environment uses an outdated SSL library that doesn’t support TLS 1.2 or higher (Oracle Cloud requires TLS 1.2+ for ADB connections).

Check Your SSL Version: #

Run this quick script to confirm your setup:

import ssl
print("OpenSSL Version:", ssl.OPENSSL_VERSION)

• If your OpenSSL version is older than 1.0.2, you’ll need to upgrade your Python installation or the underlying OpenSSL library.
• For Python 3.9+, you should already have a compatible version, but double-check to rule this out.

3. ADMIN Account & Permissions: You're Good to Go #

Your ADMIN account has full administrative privileges by default, so you don’t need to create a separate user for this connection test. The error you’re seeing is at the network/SSL layer, not a permission issue.

4. Quick Sanity Checks #

• Confirm your public IP address is correctly added to the ADB’s Access Control List (ACL). If you’re using a VPN or proxy, your outgoing IP might differ from what you added—double-check with a tool like curl ifconfig.me to get your current public IP.
• Ensure your PYTHON_USERNAME, PYTHON_PASSWORD, and PYTHON_CONNECTSTRING environment variables are set correctly (no typos, extra spaces, or missing quotes).

Test the Fix #

To rule out environment variable issues, try hardcoding the correct credentials and connection string temporarily (just for testing):

import oracledb

un = "ADMIN"
pw = "your_database_password"
cs = "(description= (retry_count=20)(retry_delay=3)(address=(protocol=tcps)(port=1522)(host=adb.uk-london-1.oraclecloud.com))(connect_data=(service_name=abc123xyzredacted.adb.oraclecloud.com))(security=(ssl_server_dn_match=yes)))"

with oracledb.connect(user=un, password=pw, dsn=cs) as connection:
    with connection.cursor() as cursor:
        sql = """select sysdate from dual"""
        for r in cursor.execute(sql):
            print(r)

If this works, you can safely switch back to using environment variables for production.

内容的提问来源于stack exchange，提问作者powlo