CURLOPT_SSLKEY_BLOB - private key for client cert from memory blob

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLKEY_BLOB,
                          struct curl_blob *blob);

Pass a pointer to a curl_blob structure, which contains information (pointer and size) for a private key. Compatible with OpenSSL. The format (like "PEM") must be specified with CURLOPT_SSLKEYTYPE(3).

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.

This option is an alternative to CURLOPT_SSLKEY(3) which instead expects a filename as input.


All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc.

This option works only with the following TLS backends: OpenSSL

extern char *certificateData; /* point to cert */
extern size_t filesize; /* size of cert */
extern char *privateKeyData; /* point to key */
extern size_t privateKeySize; /* size of key */
int main(void)
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    struct curl_blob blob;
    curl_easy_setopt(curl, CURLOPT_URL, ""); = certificateData;
    blob.len = filesize;
    blob.flags = CURL_BLOB_COPY;
    curl_easy_setopt(curl, CURLOPT_SSLCERT_BLOB, &blob);
    curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "PEM"); = privateKeyData;
    blob.len = privateKeySize;
    curl_easy_setopt(curl, CURLOPT_SSLKEY_BLOB, &blob);
    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
    curl_easy_setopt(curl, CURLOPT_SSLKEYTYPE, "PEM");
    res = curl_easy_perform(curl);

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

Returns CURLE_OK if TLS enabled, CURLE_UNKNOWN_OPTION if not, or CURLE_OUT_OF_MEMORY if there was insufficient heap space.


2024-05-22 libcurl