SSL_GET0_PEER_RPK(3ossl)

📦 version 15.1, in freebsd 15.1

💅 SSL_GET0_PEER_RPK(3ossl) 💅

Okay bestie, so this is the SSL_GET0_PEER_RPK(3ossl) page from the OpenSSL fam — it's the whole ✨raw public key✨ situation, aka RFC7250 support. Buckle up, it's actually so good.

🌸 NAME 🌸

SSL_add_expected_rpk, SSL_get_negotiated_client_cert_type, SSL_get_negotiated_server_cert_type, SSL_get0_peer_rpk, SSL_SESSION_get0_peer_rpk — literally all the raw public key (RFC7250) support you could ever need. No cap. 🔑

✨ SYNOPSIS ✨

#include <openssl/ssl.h>

int SSL_add_expected_rpk(SSL *s, EVP_PKEY *rpk);
int SSL_get_negotiated_client_cert_type(const SSL *s);
int SSL_get_negotiated_server_cert_type(const SSL *s);
EVP_PKEY *SSL_get0_peer_rpk(const SSL *s);
EVP_PKEY *SSL_SESSION_get0_peer_rpk(const SSL_SESSION *ss);

🦋 DESCRIPTION 🦋

Okay so here's the rundown, one function at a time:

  • SSL_add_expected_rpk() — adds a DANE TLSA record that matches the public key rpk to SSL s's DANE validation policy. It's giving "I expect to see this key, bestie." 🎀
  • SSL_get_negotiated_client_cert_type() — returns the connection's negotiated client certificate type. Slay. 💅
  • SSL_get_negotiated_server_cert_type() — returns the connection's negotiated server certificate type. Also slay. ✨
  • SSL_get0_peer_rpk() — returns the peer's raw public key from SSL s. Iconic.
  • SSL_SESSION_get0_peer_rpk() — returns the peer's raw public key from SSL_SESSION ss. Same energy, different object. 🫶

🧚 NOTES 🧚

So, when do raw public keys even happen? They're used in place of certificates when the option is negotiated. That's the whole vibe check. 💫

SSL_add_expected_rpk() can be called multiple times to configure multiple trusted keys — which is honestly so smart, because it makes key rotation possible. Picture this: a peer might show up offering an "old" key or a "new" key, and your endpoint has to be able to accept either one. Main character flexibility. 👑

When raw public keys are used, the certificate verify callback gets called, and you can use it to inspect the public key via X509_STORE_CTX_get0_rpk(3). Heads up though — raw public keys have no subject, no issuer, no validity dates, and no digital signature to verify. They're kinda bare-bones like that. 🙈 But they can be matched verbatim, or by their digest value, and that's done by specifying one or more TLSA records — see SSL_CTX_dane_enable(3).

Where does the raw public key actually come from? Typically it's taken from the certificate assigned to the connection (e.g. via SSL_use_certificate(3)). But — plot twist — if a certificate isn't configured, then the public key will be extracted from the assigned private key. 🍓

And now, the lore on SSL_add_expected_rpk(): it's a wrapper around SSL_dane_tlsa_add(3). When DANE is enabled via SSL_dane_enable(3), the configured TLSA records get used to validate the peer's public key or certificate. If DANE is not enabled, then no validation will occur. ⚠️ Not me warning you — that's literally in the docs, bestie. Be careful.

💀 RETURN VALUES 💀

  • SSL_add_expected_rpk() — returns 1 on success and 0 on failure. Classic. 🤷
  • SSL_get0_peer_rpk() and SSL_SESSION_get0_peer_rpk() — return the peer's raw public key as an EVP_PKEY, or NULL when the raw public key is not available. 😭
  • SSL_get_negotiated_client_cert_type() and SSL_get_negotiated_server_cert_type() — return one of these two values, periodt:
TLSEXT_cert_type_x509
TLSEXT_cert_type_rpk

🌈 SEE ALSO 🌈

Go read these next, iykyk — they're the whole friend group:

⭐ HISTORY ⭐

These functions were added in OpenSSL 3.2. So if you're on something older… bestie. Upgrade. 🔥

Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.

Okay that's the whole page, you ate that 💖 go forth and validate those raw public keys, you absolute queen 👑

Sign-off time, bestie: this gorgeous little page is from the OpenSSL 3.5.6 release, dated 2026-04-07 💜 Catch you in the next man page! 🦋✨

📦 where this page comes from