diff options
| -rw-r--r-- | include/libssh/session.h | 7 | ||||
| -rw-r--r-- | src/kex.c | 24 | ||||
| -rw-r--r-- | src/server.c | 2 |
3 files changed, 25 insertions, 8 deletions
diff --git a/include/libssh/session.h b/include/libssh/session.h index 86540bbf..5761fa2d 100644 --- a/include/libssh/session.h +++ b/include/libssh/session.h @@ -91,10 +91,11 @@ enum ssh_pending_call_e { #define SSH_OPT_FLAG_GSSAPI_AUTH 0x8 /* extensions flags */ +/* negotiation enabled */ +#define SSH_EXT_NEGOTIATION 0x01 /* server-sig-algs extension */ -#define SSH_EXT_SIG_RSA_SHA256 0x01 -#define SSH_EXT_SIG_RSA_SHA512 0x02 -#define SSH_EXT_ALL SSH_EXT_SIG_RSA_SHA256 | SSH_EXT_SIG_RSA_SHA512 +#define SSH_EXT_SIG_RSA_SHA256 0x02 +#define SSH_EXT_SIG_RSA_SHA512 0x04 /* members that are common to ssh_session and ssh_bind */ struct ssh_common_struct { @@ -541,13 +541,29 @@ SSH_PACKET_CALLBACK(ssh_packet_kexinit) ok = ssh_match_group(session->next_crypto->client_kex.methods[SSH_KEX], KEX_EXTENSION_CLIENT); if (ok) { + const char *hostkeys = NULL; + + /* The client supports extension negotiation */ + session->extensions |= SSH_EXT_NEGOTIATION; /* - * Enable all the supported extensions and when the time comes - * (after NEWKEYS) send them to the client. + * RFC 8332 Section 3.1: Use for Server Authentication + * Check what algorithms were provided in the SSH_HOSTKEYS list + * by the client and enable the respective extensions to provide + * correct signature in the next packet if RSA is negotiated */ + hostkeys = session->next_crypto->client_kex.methods[SSH_HOSTKEYS]; + ok = ssh_match_group(hostkeys, "rsa-sha2-512"); + if (ok) { + session->extensions |= SSH_EXT_SIG_RSA_SHA512; + } + ok = ssh_match_group(hostkeys, "rsa-sha2-256"); + if (ok) { + session->extensions |= SSH_EXT_SIG_RSA_SHA256; + } SSH_LOG(SSH_LOG_DEBUG, "The client supports extension " - "negotiation: enabling all extensions"); - session->extensions = SSH_EXT_ALL; + "negotiation. Enabled signature algorithms: %s%s", + session->extensions & SSH_EXT_SIG_RSA_SHA256 ? "SHA256" : "", + session->extensions & SSH_EXT_SIG_RSA_SHA512 ? " SHA512" : ""); } /* diff --git a/src/server.c b/src/server.c index c3e92ba6..a586964f 100644 --- a/src/server.c +++ b/src/server.c @@ -496,7 +496,7 @@ static void ssh_server_connection_callback(ssh_session session){ * our supported extensions now. This is the first message after * sending NEWKEYS message and after turning on crypto. */ - if (session->extensions && + if (session->extensions & SSH_EXT_NEGOTIATION && session->session_state != SSH_SESSION_STATE_AUTHENTICATED) { ssh_server_send_extensions(session); } |