CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256(3) Library Functions Manual
NAME
CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256 - SHA256 hash of SSH server public
key
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256,
char *sha256);
DESCRIPTION
Pass a char pointer pointing to a string containing a Base64-encoded
SHA256 hash of the remote host's public key. The transfer fails if the
given hash does not match the hash the remote host provides.
The application does not have to keep the string around after setting
this option.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.
This option is used to verify a new connection only. The SHA256 hash
check is performed when libcurl establishes a new SSH connection; once
that connection has been successfully verified, it is deemed vetted and
may be reused without performing the SHA256 (or any other host key)
verification again, even if you subsequently change SSH
verification-related options. When this SHA256-based verification is
enabled for a new connection, libcurl does not additionally consult
CURLOPT_SSH_KNOWNHOSTS(3) or SSH host key callbacks (including
CURLOPT_SSH_HOST_PUBLIC_KEY_MD5(3)) for that connection, so you should
not expect multiple host verification methods to be applied to the same
new connection.
DEFAULT
NULL
PROTOCOLS
This functionality affects scp and sftp
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
CURLcode result;
curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/file");
curl_easy_setopt(curl, CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256,
"NDVkMTQxMGQ1ODdmMjQ3MjczYjAyOTY5MmRkMjVmNDQ=");
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
}
}
NOTES
Requires the libssh2 backend.
AVAILABILITY
Added in curl 7.80.0
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_SSH_AUTH_TYPES(3), CURLOPT_SSH_HOST_PUBLIC_KEY_MD5(3),
CURLOPT_SSH_PUBLIC_KEYFILE(3)
libcurl 2026-06-09
CURLOPT_SSH_HOST_PUBLIC_KEY_SHA256(3)
curl 8.20.0 - Generated Wed Jun 10 08:07:28 CDT 2026