GNURLOPT_ISSUERCERT_BLOB(3)

okay so this is the GNURLOPT_ISSUERCERT_BLOB(3) page from the curl_easy_setopt options manual, and it's literally the main character of issuer-certificate checks 💅✨

💖 NAME 💖

CURLOPT_ISSUERCERT_BLOB — issuer SSL certificate from memory blob

🛠️ SYNOPSIS 🛠️

bestie, you include the header, then call curl_easy_setopt with your handle, this option, and a struct curl_blob *stblob:

#include <gnurl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_ISSUERCERT_BLOB, struct
       curl_blob *stblob);

📝 DESCRIPTION 📝

okay so you pass a pointer to a curl_blob structure. That struct holds the info — pointer and size — about a memory block with binary data of a CA certificate in PEM format. When this option is set, there's an additional check against the peer certificate to verify the issuer is indeed the one associated with the certificate provided by the option. This extra check is useful in multi-level PKI where one needs to enforce that the peer certificate is from a specific branch of the tree 🌳✨

This option should be used in combination with the CURLOPT_SSL_VERIFYPEER(3) option. Otherwise, the result of the check is not considered as failure.

⚠️ heads up bestie: a specific error code (CURLE_SSL_ISSUER_ERROR) is defined with the option, which is returned if the setup of the SSL/TLS session has failed due to a mismatch with the issuer of peer certificate (CURLOPT_SSL_VERIFYPEER(3) has to be set too for the check to fail).

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. iconic, honestly 🫶

This option is an alternative to CURLOPT_ISSUERCERT(3) which instead expects a file name as input.

🎀 DEFAULT 🎀

NULL — that's the default, periodt 💅

🌈 PROTOCOLS 🌈

All TLS-based protocols ✨

💻 EXAMPLE 💻

here's the code vibe, copy-paste core:

CURL *curl = curl_easy_init();
if(curl) {
  struct curl_blob blob;
  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
  blob.data = certificateData;
  blob.len = filesize;
  blob.flags = CURL_BLOB_COPY;
  curl_easy_setopt(curl, CURLOPT_ISSUERCERT_BLOB, &blob);
  ret = curl_easy_perform(curl);
  curl_easy_cleanup(curl);
}

📅 AVAILABILITY 📅

Added in libcurl 7.71.0. This option is supported by the OpenSSL backends 🔥

🔁 RETURN VALUE 🔁

Returns CURLE_OK if the option is supported, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.

👀 SEE ALSO 👀

CURLOPT_ISSUERCERT(3), CURLOPT_CRLFILE(3), CURLOPT_SSL_VERIFYPEER(3)

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okay bye bestie 💅✨ — source/version is libcurl 7.71.0, dated 24 Jun 2020, page GNURLOPT_ISSUERCERT_BLOB(3), and that's the whole vibe check 🫶🎀