router: Keep RSA onion public key in ASN.1 format

The OpenSSL "RSA" object is currently 408 bytes compares to the ASN.1 encoding
which is 140 for a 1024 RSA key.

We save 268 bytes per descriptor (routerinfo_t) *and* microdescriptor
(microdesc_t). Scaling this to 6000 relays, and considering client usually
only have microdescriptors, we save 1.608 MB of RAM which is considerable for
mobile client.

This commit makes it that we keep the RSA onion public key (used for TAP
handshake) in ASN.1 format instead of an OpenSSL RSA object.

Changes is done in both routerinfo_t and microdesc_t.

Closes #27246

Signed-off-by: David Goulet <dgoulet@torproject.org>

1 files changed, 1 insertions, 0 deletions

diff --git a/src/feature/nodelist/nodelist.h b/src/feature/nodelist/nodelist.h
index ed3a542971..cf7658cf9d 100644
--- a/src/feature/nodelist/nodelist.h
+++ b/src/feature/nodelist/nodelist.h
@@ -95,6 +95,7 @@ void node_get_pref_ipv6_dirport(const node_t *node, tor_addr_port_t *ap_out);
 int node_has_curve25519_onion_key(const node_t *node);
 const struct curve25519_public_key_t *node_get_curve25519_onion_key(
                                   const node_t *node);
+crypto_pk_t *node_get_rsa_onion_key(const node_t *node);
 
 MOCK_DECL(smartlist_t *, nodelist_get_list, (void));