Private key passed as a blob (ssl::KeyBlob) not working

[b3rgschu3tz]

Description

With version 1.11.1 passing a private key as blob as described in the docs (https://docs.libcpr.org/advanced-usage.html) does not work. The following error is returned:
unable to set private key file: '(memory blob)' type PEM

Example/How to Reproduce

Like in the example:

cpr::SslOptions sslOpts = cpr::Ssl(ssl::CertFile{"cert.pem"}, ssl::KeyBlob{"-----BEGIN RSA PRIVATE KEY-----[...]"});
cpr::Response r = cpr::Get(cpr::Url{"https://www.httpbin.org/get"}, sslOpts);

Possible Fix

In the session.cpp file https://github.com/libcpr/cpr/blob/master/cpr/session.cpp#L471 the local string key_blob is assigned to the blob.data value.

...
else if (!options.key_blob.empty()) {
        std::string key_blob(options.key_blob);
        curl_blob blob{};
        // NOLINTNEXTLINE (readability-container-data-pointer)
        blob.data = &key_blob[0];
        blob.len = key_blob.length();
        curl_easy_setopt(curl_->handle, CURLOPT_SSLKEY_BLOB, &blob);
        if (!options.key_type.empty()) {
            curl_easy_setopt(curl_->handle, CURLOPT_SSLKEYTYPE, options.key_type.c_str());
        }
        if (!options.key_pass.empty()) {
            curl_easy_setopt(curl_->handle, CURLOPT_KEYPASSWD, options.key_pass.c_str());
        }
...

In the curl documentation it is stated:
If the blob is initialized with the flags member of struct curl_blob set to CURL_BLOB_COPY, the application does not have to keep the buffer around after setting this.
=> If it CURL_BLOB_COPY is not set the buffer has to be kept alive until the request is performed.
As far is I can understand key_blob will go out of scope and be destroyed after the if-branch, thus CURL_BLOB_COPY needs to be set.

When set, it works as expected.

Where did you get it from?

GitHub (branch e.g. master)

Additional Context/Your Environment

• OS: Debian
• Version: 1.11.1

[COM8]

@b3rgschu3tz thanks for reporting! Confirmed. This is a bug. Would you like to create a PR for fix this?

[b3rgschu3tz]

@b3rgschu3tz thanks for reporting! Confirmed. This is a bug. Would you like to create a PR for fix this?

Yes, I can do that. PR is here.