---
name: "CURLOPT_PROXY_SSLKEY_BLOB"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/CURLOPT_PROXY_SSLKEY_BLOB"
---

# CURLOPT\_PROXY\_SSLKEY\_BLOB(3)

private key for proxy cert from memory blob

## NAME

CURLOPT\_PROXY\_SSLKEY\_BLOB - private key for proxy cert from memory blob

## SYNOPSIS

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

## DESCRIPTION

Pass a pointer to a curl\_blob structure that contains information (pointer and size) about the private key for connecting to the HTTPS proxy. Compatible with OpenSSL and Rustls. The format (like "PEM") must be specified with *[CURLOPT\_PROXY\_SSLKEYTYPE(3)](/CURLOPT_PROXY_SSLKEYTYPE/3.md)*.

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.

## 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 and Rustls

## EXAMPLE

```
extern char *certificateData; /* point to data */
extern size_t filesize; /* size of data */
extern char *privateKeyData; /* point to data */
extern size_t privateKeySize; /* size */
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/");
    curl_easy_setopt(curl, CURLOPT_PROXY, "https://proxy.example");
    blob.data = certificateData;
    blob.len = filesize;
    blob.flags = CURL_BLOB_COPY;
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLCERT_BLOB, &blob);
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLCERTTYPE, "PEM");
    blob.data = privateKeyData;
    blob.len = privateKeySize;
    curl_easy_setopt(curl, CURLOPT_PROXY_SSLKEY_BLOB, &blob);
    curl_easy_setopt(curl, CURLOPT_PROXY_KEYPASSWD, "s3cret");
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}
```

## AVAILABILITY

Added in curl 7.71.0

## RETURN VALUE

*[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* returns a CURLcode indicating success or error.

CURLE\_OK (0) means everything was OK, non-zero means an error occurred, see *[libcurl-errors(3)](/libcurl-errors/3.md)*.

## SEE ALSO

[**CURLOPT\_SSLKEY**(3)](/CURLOPT_SSLKEY/3.md), [**CURLOPT\_SSLKEYTYPE**(3)](/CURLOPT_SSLKEYTYPE/3.md), [**CURLOPT\_SSLKEY\_BLOB**(3)](/CURLOPT_SSLKEY_BLOB/3.md)