curl/docs/libcurl/opts/CURLOPT_SSH_HOSTKEYFUNCTION.md
Daniel Stenberg eefcc1bda4
docs: introduce "curldown" for libcurl man page format
curldown is this new file format for libcurl man pages. It is markdown
inspired with differences:

- Each file has a set of leading headers with meta-data
- Supports a small subset of markdown
- Uses .md file extensions for editors/IDE/GitHub to treat them nicely
- Generates man pages very similar to the previous ones
- Generates man pages that still convert nicely to HTML on the website
- Detects and highlights mentions of curl symbols automatically (when
  their man page section is specified)

tools:

- cd2nroff: converts from curldown to nroff man page
- nroff2cd: convert an (old) nroff man page to curldown
- cdall: convert many nroff pages to curldown versions
- cd2cd: verifies and updates a curldown to latest curldown

This setup generates .3 versions of all the curldown versions at build time.

CI:

Since the documentation is now technically markdown in the eyes of many
things, the CI runs many more tests and checks on this documentation,
including proselint, link checkers and tests that make sure we capitalize the
first letter after a period...

Closes #12730
2024-01-23 00:29:02 +01:00

99 lines
2.2 KiB
Markdown

---
c: Copyright (C) Daniel Stenberg, <daniel.se>, et al.
SPDX-License-Identifier: curl
Title: CURLOPT_SSH_HOSTKEYFUNCTION
Section: 3
Source: libcurl
See-also:
- CURLOPT_SSH_HOSTKEYDATA (3)
- CURLOPT_SSH_KNOWNHOSTS (3)
---
# NAME
CURLOPT_SSH_HOSTKEYFUNCTION - callback to check host key
# SYNOPSIS
~~~c
#include <curl/curl.h>
int keycallback(void *clientp,
int keytype,
const char *key,
size_t keylen);
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSH_HOSTKEYFUNCTION,
keycallback);
~~~
# DESCRIPTION
Pass a pointer to your callback function, which should match the prototype
shown above. It overrides CURLOPT_SSH_KNOWNHOSTS(3).
This callback gets called when the verification of the SSH host key is needed.
**key** is **keylen** bytes long and is the key to check. **keytype**
says what type it is, from the **CURLKHTYPE_*** series in the
**curl_khtype** enum.
**clientp** is a custom pointer set with CURLOPT_SSH_HOSTKEYDATA(3).
The callback MUST return one of the following return codes to tell libcurl how
to act:
## CURLKHMATCH_OK
The host key is accepted, the connection should continue.
## CURLKHMATCH_MISMATCH
the host key is rejected, the connection is canceled.
# DEFAULT
NULL
# PROTOCOLS
SCP and SFTP
# EXAMPLE
~~~c
struct mine {
void *custom;
};
int hostkeycb(void *clientp, /* passed with CURLOPT_SSH_HOSTKEYDATA */
int keytype, /* CURLKHTYPE */
const char *key, /* host key to check */
size_t keylen) /* length of the key */
{
/* 'clientp' points to the callback_data struct */
/* investigate the situation and return the correct value */
return CURLKHMATCH_OK;
}
int main(void)
{
struct mine callback_data;
CURL *curl = curl_easy_init();
if(curl) {
curl_easy_setopt(curl, CURLOPT_URL, "sftp://example.com/thisfile.txt");
curl_easy_setopt(curl, CURLOPT_SSH_HOSTKEYFUNCTION, hostkeycb);
curl_easy_setopt(curl, CURLOPT_SSH_HOSTKEYDATA, &callback_data);
curl_easy_perform(curl);
}
}
~~~
# AVAILABILITY
Added in 7.84.0 , work only with libssh2 backend.
# RETURN VALUE
Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not.