CURLOPT_SSLCERT_BLOB - SSL client certificate from memory blob

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

Pass a pointer to a curl_blob structure, which contains (pointer and size) a client certificate. The format must be "P12" on Secure Transport or Schannel. The format must be "P12" or "PEM" on OpenSSL. The format must be "DER" or "PEM" on mbedTLS. The format must be specified with CURLOPT_SSLCERTTYPE(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_SSLCERT(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, Schannel, Secure Transport and mbedTLS

extern char *certificateData; /* point to data */
extern size_t filesize; /* size of data */
int main(void)
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    struct curl_blob stblob; = certificateData;
    stblob.len = filesize;
    stblob.flags = CURL_BLOB_COPY;
    curl_easy_setopt(curl, CURLOPT_URL, "");
    curl_easy_setopt(curl, CURLOPT_SSLCERT_BLOB, &stblob);
    curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "P12");
    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
    res = curl_easy_perform(curl);

Added in 7.71.0. This option is supported by the OpenSSL, Secure Transport, Schannel and mbedTLS (since 7.78.0) 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