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52 lines
1.7 KiB
Markdown
52 lines
1.7 KiB
Markdown
---
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title: "C18. Handle SSL Errors"
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order: 18
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status: "draft"
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---
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When an HTTPS request fails, `res.error()` returns values like `Error::SSLConnection` or `Error::SSLServerVerification`. Sometimes that's not enough to pinpoint the cause. That's where `Result::ssl_error()` and `Result::ssl_backend_error()` help.
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## Get the SSL error details
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```cpp
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httplib::Client cli("https://api.example.com");
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auto res = cli.Get("/");
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if (!res) {
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auto err = res.error();
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std::cerr << "error: " << httplib::to_string(err) << std::endl;
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if (err == httplib::Error::SSLConnection ||
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err == httplib::Error::SSLServerVerification) {
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std::cerr << "ssl_error: " << res.ssl_error() << std::endl;
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std::cerr << "ssl_backend_error: " << res.ssl_backend_error() << std::endl;
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}
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}
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```
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`ssl_error()` returns the error code from the SSL library (e.g., OpenSSL's `SSL_get_error()`). `ssl_backend_error()` gives you the backend's more detailed error value — for OpenSSL, that's `ERR_get_error()`.
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## Format OpenSSL errors as strings
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When you have a value from `ssl_backend_error()`, pass it to OpenSSL's `ERR_error_string()` to get a readable message.
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```cpp
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#include <openssl/err.h>
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if (res.ssl_backend_error() != 0) {
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char buf[256];
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ERR_error_string_n(res.ssl_backend_error(), buf, sizeof(buf));
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std::cerr << "openssl: " << buf << std::endl;
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}
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```
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## Common causes
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| Symptom | Usual suspect |
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| --- | --- |
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| `SSLServerVerification` | CA certificate path isn't configured, or the cert is self-signed |
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| `SSLServerHostnameVerification` | The cert's CN/SAN doesn't match the host |
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| `SSLConnection` | TLS version mismatch, no shared cipher suite |
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> To change certificate verification settings, see [T02. Control SSL certificate verification](../t02-cert-verification).
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