CURLOPT_SSLCERT_BLOB - Man Page

SSL client certificate from memory blob

Synopsis

#include <curl/curl.h>

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

Description

Pass a pointer to a curl_blob structure, which contains (pointer and size) a client certificate. The format must be "P12" on 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.

Default

NULL

Protocols

This functionality affects  all TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. only

This option works only with the following TLS backends: OpenSSL, Schannel, mbedTLS and wolfSSL

Example

extern char *certificateData; /* point to data */
extern size_t filesize; /* size of data */

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    struct curl_blob stblob;
    stblob.data = certificateData;
    stblob.len = filesize;
    stblob.flags = CURL_BLOB_COPY;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    curl_easy_setopt(curl, CURLOPT_SSLCERT_BLOB, &stblob);
    curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "P12");
    curl_easy_setopt(curl, CURLOPT_KEYPASSWD, "s3cret");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

Availability

Added in curl 7.71.0

Return Value

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

See Also

CURLOPT_KEYPASSWD(3), CURLOPT_SSLCERTTYPE(3), CURLOPT_SSLKEY(3)

Referenced By

curl_easy_setopt(3), CURLOPT_PROXY_SSLCERT_BLOB(3), libcurl-symbols(3).

2026-09-08 libcurl