CURLOPT_SSLKEY_BLOB(3) Library Functions Manual CURLOPT_SSLKEY_BLOB(3)
NAME
CURLOPT_SSLKEY_BLOB - private key for client cert from memory blob
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSLKEY_BLOB,
struct curl_blob *blob);
DESCRIPTION
Pass a pointer to a curl_blob structure, which contains information
(pointer and size) for a private key. Compatible with OpenSSL and Rustls.
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.
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, Rustls
and wolfSSL
EXAMPLE
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 result;
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_SSLCERT_BLOB, &blob);
curl_easy_setopt(curl, CURLOPT_SSLCERTTYPE, "PEM");
blob.data = 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");
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_SSLKEY(3), CURLOPT_SSLKEYTYPE(3)
libcurl 2026-10-18 CURLOPT_SSLKEY_BLOB(3)
curl 8.23.0 - Generated Mon Oct 19 15:53:39 CDT 2026