Add support for signing outgoing HTTP requests per RFC 9421 using
Ed25519 or HMAC-SHA256 algorithms.
New libcurl options:
- CURLOPT_HTTPSIG: signing algorithm ("ed25519" or "hmac-sha256")
- CURLOPT_HTTPSIG_KEY: path to hex-encoded key file
- CURLOPT_HTTPSIG_KEYID: key identifier for Signature-Input
- CURLOPT_HTTPSIG_HEADERS: space-separated components to sign
New CLI flags: --httpsig, --httpsig-key, --httpsig-keyid,
--httpsig-headers
The crypto layer follows the sha256.c multi-backend pattern with
implementations for OpenSSL (EVP_DigestSign) and wolfSSL
(wc_ed25519_sign_msg). HMAC-SHA256 uses the existing Curl_hmacit()
infrastructure which works on all backends.
Verified by test 5000 to 5021
Assisted-by: Daniel Stenberg
Signed-off-by: Sameeh Jubran <sameeh@wolfssl.com>
Closes#22386Closes#21239
