&#ローカル発行者の証明書を取得できません&# エラーの解決

When working with SSL/TLS certificates, encountering the "Unable to get local issuer certificate" error can be frustrating, especially when it interrupts secure communication between a client and a server. Whether you're trying to make an HTTPS request, configure a web server, or access a secure website, this error can disrupt the process. In this guide, we’ll explore the causes, common scenarios, and step-by-step solutions to resolve this issue.
What Does the 'Unable to Get Local Issuer Certificate' Error Mean?
The "Unable to get local issuer certificate" error usually occurs when a system is unable to verify the SSL certificate chain due to a missing or untrusted root or intermediate certificate. SSL certificates rely on a chain of trust, which is a hierarchical structure of certificates that begins with a root certificate issued by a trusted certificate authority (CA). If any link in this chain is missing or improperly configured, the system can’t establish a secure connection, resulting in this error.
Common Scenarios Where the Error Occurs
This error can arise in various environments and situations. Let’s look at some of the most common scenarios:
Development Environments (e.g., cURL, Node.js, Python)
In development environments, developers often use tools like cURL, Node.js, or Python to make HTTPS requests. When the system lacks the necessary root certificates, these requests can fail, showing the "Unable to get local issuer certificate" error. This typically happens if the development environment is isolated or doesn’t have access to the system’s CA certificates.
Web Browsers
Web browsers may display this error when trying to access a website that has an improperly configured SSL certificate chain. This could be because the site is missing intermediate certificates or is using an expired root certificate. The browser blocks access as a security measure, warning the user of an untrusted connection.
Server Configurations (e.g., Apache, Nginx)
In production environments, web servers like Apache and Nginx may trigger this error if they aren’t configured with the correct certificate chain. Misconfigured or missing intermediate certificates are a common cause when deploying SSL certificates on web servers.
Root Causes of the Error
Understanding the root causes of this error is crucial for resolving it. Here are some typical reasons why you might see this error:

1. Missing Root or Intermediate Certificates: The server is unable to provide a full certificate chain, leading the client to distrust the connection.
2. Misconfigured Certificate Chain: The certificate chain is incorrectly ordered or incomplete.
3. Expired or Untrusted Certificates: The root certificate may have expired or been revoked, causing the certificate chain to break.
4. Outdated CA Certificates: The local system’s CA certificates may be outdated or missing trusted root certificates. How SSL Certificate Chains Work To better understand how this error occurs, it’s important to know how SSL certificate chains function. A certificate chain starts with a root certificate issued by a trusted certificate authority. This root certificate is used to verify intermediate certificates, which in turn verify the server’s certificate. If any certificate in this chain is missing or untrusted, the client will be unable to verify the server’s certificate, resulting in the "Unable to get local issuer certificate" error. Ensuring that the full chain is properly configured is key to preventing this issue. Troubleshooting Steps for Resolving the Error Now that we understand what causes this error, let’s look at how to resolve it. Here are some steps you can follow:
5. Verify the Certificate Chain One of the first things you should do is verify the SSL certificate chain. You can use tools like OpenSSL to inspect the chain and see if any certificates are missing or misconfigured. For example, using the following command can help you check the certificate chain: bash Copy code openssl s_client -connect yourdomain.com:443 -showcerts This command will display the server’s certificate and the intermediate certificates it provides. If the chain is incomplete, you will know which certificate is missing.
6. Update Trusted Root Certificates If the error occurs because the client is missing a trusted root certificate, updating your system’s trusted root certificates may solve the problem. On Linux, for example, you can update the CA certificates with the following command: bash Copy code sudo update-ca-certificates This command ensures that your system has the latest set of trusted root certificates, helping resolve the issue.
7. Configure Certificate Bundles Correctly When configuring SSL on servers like Apache or Nginx, it’s essential to concatenate the server certificate with the intermediate and root certificates into a certificate bundle. If the bundle is incomplete or out of order, clients won’t be able to verify the certificate chain, resulting in the error. Make sure to configure the certificate chain correctly when setting up your web server. Platform-Specific Fixes Different platforms and tools require specific solutions to fix the "Unable to get local issuer certificate" error. Below are fixes for common development environments:
8. cURL In cURL, this error can often be resolved by specifying the correct CA bundle using the --cacert flag. You can download the latest CA certificates and use them as follows: bash Copy code curl --cacert /path/to/cacert.pem https://yourdomain.com Alternatively, you can update the CA certificates on your system, which cURL will use by default.
9. Node.js For Node.js, you may need to update the NODE_EXTRA_CA_CERTS environment variable to include the path to your CA certificates. You can do this with the following command: bash Copy code export NODE_EXTRA_CA_CERTS="/path/to/cacert.pem" This will allow Node.js to use the specified CA bundle when making HTTPS requests.
10. Python リクエスト Python では、必要な CA 証明書が見つからない場合、一般的なリクエスト ライブラリがこのエラーを引き起こす可能性があります。信頼されたルート証明書の最新リストを含む certifi パッケージをインストールすると、通常は問題が解決します。 バッシュ コードをコピーする pip インストール証明書 verify パラメーターを使用して、コード内で CA バンドルを直接指定することもできます。 パイソン コードをコピーする インポートリクエスト request.get('https://yourdomain.com', verify='/path/to/cacert.pem') 「ローカル発行者の証明書を取得できません」エラーの防止 今後このエラーが発生しないようにするには、信頼されたルート証明書を使用してシステムを定期的に更新する必要があります。導入時に SSL 証明書の検証を自動化し、証明書チェーンを検査するツールを使用すると、本番環境に影響を与える前に潜在的な問題を特定するのに役立ちます。さらに、必要なすべての中間証明書を使用して証明書チェーンが適切に構成されていることを常に確認してください。 結論 「ローカル発行者の証明書を取得できません」エラーにより安全な接続が中断される可能性がありますが、SSL 証明書チェーンの根本的な問題を理解し、対象を絞った修正を適用することで、この問題を効果的に解決できます。 cURL や Node.js などの開発ツールを使用している場合でも、運用サーバーを構成している場合でも、このガイドで概説されているトラブルシューティング手順に従うと、根本原因を特定して修正するのに役立ちます。システムの CA 証明書を最新の状態に保ち、展開中に SSL 構成を検証することで、今後このエラーが発生するのを防ぐことができます。

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