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Implement Apple's Diffie-Hellman based security type 30

apple-diffie-hellman
Andri Yngvason 2023-08-13 12:15:32 +00:00
parent 8ddca0a197
commit 3f20c261cd
3 changed files with 151 additions and 8 deletions
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8
include/common.h
View File

@ -43,6 +43,9 @@ enum nvnc_client_state {
VNC_CLIENT_STATE_WAITING_FOR_VENCRYPT_VERSION,
VNC_CLIENT_STATE_WAITING_FOR_VENCRYPT_SUBTYPE,
VNC_CLIENT_STATE_WAITING_FOR_VENCRYPT_PLAIN_AUTH,
#endif
#ifdef HAVE_CRYPTO
VNC_CLIENT_STATE_WAITING_FOR_APPLE_DH_RESPONSE,
#endif
VNC_CLIENT_STATE_WAITING_FOR_INIT,
VNC_CLIENT_STATE_READY,
@ -53,6 +56,7 @@ struct stream;
struct aml_handler;
struct aml_idle;
struct nvnc_display;
struct crypto_key;
struct nvnc_common {
void* userdata;
@ -93,6 +97,10 @@ struct nvnc_client {
struct encoder* encoder;
uint32_t cursor_seq;
int quality;
#ifdef HAVE_CRYPTO
struct crypto_key* apple_dh_secret;
#endif
};
LIST_HEAD(nvnc_client_list, nvnc_client);

14
include/rfb-proto.h
View File

@ -31,6 +31,7 @@ enum rfb_security_type {
RFB_SECURITY_TYPE_VNC_AUTH = 2,
RFB_SECURITY_TYPE_TIGHT = 16,
RFB_SECURITY_TYPE_VENCRYPT = 19,
RFB_SECURITY_TYPE_APPLE_DH = 30,
};
enum rfb_security_handshake_result {
@ -108,7 +109,7 @@ enum rfb_resize_status {
struct rfb_security_types_msg {
uint8_t n;
uint8_t types[1];
uint8_t types[0];
} RFB_PACKED;
struct rfb_error_reason {
@ -237,3 +238,14 @@ struct rfb_ntp_msg {
uint8_t padding[3];
uint32_t t0, t1, t2, t3;
} RFB_PACKED;
struct rfb_apple_dh_server_msg {
uint16_t generator;
uint16_t key_size;
uint8_t modulus_and_key[0];
} RFB_PACKED;
struct rfb_apple_dh_client_msg {
uint8_t encrypted_credentials[128];
uint8_t public_key[0];
} RFB_PACKED;

137
src/server.c
View File

@ -54,6 +54,10 @@
#include <gnutls/gnutls.h>
#endif
#ifdef HAVE_CRYPTO
#include "crypto.h"
#endif
#ifndef DRM_FORMAT_INVALID
#define DRM_FORMAT_INVALID 0
#endif
@ -63,6 +67,7 @@
#endif
#define DEFAULT_NAME "Neat VNC"
#define SECURITY_TYPES_MAX 3
#define EXPORT __attribute__((visibility("default")))
@ -196,6 +201,8 @@ static int handle_unsupported_version(struct nvnc_client* client)
static int on_version_message(struct nvnc_client* client)
{
struct nvnc* server = client->server;
if (client->buffer_len - client->buffer_index < 12)
return 0;
@ -206,17 +213,31 @@ static int on_version_message(struct nvnc_client* client)
if (strcmp(RFB_VERSION_MESSAGE, version_string) != 0)
return handle_unsupported_version(client);
struct rfb_security_types_msg security = { 0 };
security.n = 1;
security.types[0] = RFB_SECURITY_TYPE_NONE;
uint8_t buf[sizeof(struct rfb_security_types_msg) +
SECURITY_TYPES_MAX] = {};
struct rfb_security_types_msg* security =
(struct rfb_security_types_msg*)buf;
security->n = 0;
if (client->server->auth_fn) {
#ifdef ENABLE_TLS
if (client->server->auth_fn)
security.types[0] = RFB_SECURITY_TYPE_VENCRYPT;
if (server->tls_creds) {
security->types[security->n++] = RFB_SECURITY_TYPE_VENCRYPT;
}
#endif
stream_write(client->net_stream, &security, sizeof(security), NULL,
NULL);
#ifdef HAVE_CRYPTO
security->types[security->n++] = RFB_SECURITY_TYPE_APPLE_DH;
#endif
}
if (security->n == 0) {
security->n = 1;
security->types[0] = RFB_SECURITY_TYPE_NONE;
}
stream_write(client->net_stream, security, sizeof(*security) +
security->n, NULL, NULL);
client->state = VNC_CLIENT_STATE_WAITING_FOR_SECURITY;
return 12;
@ -368,6 +389,98 @@ static int on_vencrypt_plain_auth_message(struct nvnc_client* client)
}
#endif
#ifdef HAVE_CRYPTO
static int apple_dh_send_public_key(struct nvnc_client* client)
{
client->apple_dh_secret = crypto_keygen();
assert(client->apple_dh_secret);
struct crypto_key* pub =
crypto_derive_public_key(client->apple_dh_secret);
assert(pub);
uint8_t mod[256] = {};
int mod_len = crypto_key_p(pub, mod, sizeof(mod));
assert(mod_len == sizeof(mod));
uint8_t q[256] = {};
int q_len = crypto_key_q(pub, q, sizeof(q));
assert(q_len == sizeof(q));
struct rfb_apple_dh_server_msg msg = {
.generator = htons(crypto_key_g(client->apple_dh_secret)),
.key_size = htons(q_len),
};
stream_write(client->net_stream, &msg, sizeof(msg), NULL, NULL);
stream_write(client->net_stream, mod, mod_len, NULL, NULL);
stream_write(client->net_stream, q, q_len, NULL, NULL);
crypto_key_del(pub);
return 0;
}
static int on_apple_dh_response(struct nvnc_client* client)
{
struct nvnc* server = client->server;
struct rfb_apple_dh_client_msg* msg =
(void*)(client->msg_buffer + client->buffer_index);
uint8_t p[256];
int key_len = crypto_key_p(client->apple_dh_secret, p, sizeof(p));
assert(key_len == sizeof(p));
if (client->buffer_len - client->buffer_index < sizeof(*msg) + key_len)
return 0;
int g = crypto_key_g(client->apple_dh_secret);
struct crypto_key* remote_key = crypto_key_new(g, p, key_len,
msg->public_key, key_len);
assert(remote_key);
struct crypto_key* shared_secret =
crypto_derive_shared_secret(client->apple_dh_secret, remote_key);
assert(shared_secret);
uint8_t shared_buf[256];
crypto_key_q(shared_secret, shared_buf, sizeof(shared_buf));
crypto_key_del(shared_secret);
struct crypto_hash* hash_ctx = crypto_hash_new(CRYPTO_HASH_MD5);
crypto_hash_append(hash_ctx, shared_buf, sizeof(shared_buf));
uint8_t hash[16] = {};
crypto_hash_digest(hash_ctx, hash, sizeof(hash));
crypto_hash_del(hash_ctx);
struct crypto_cipher* cipher;
cipher = crypto_cipher_new(hash, CRYPTO_CIPHER_AES128_ECB);
assert(cipher);
char username[128] = {};
char* password = username + 64;
crypto_cipher_decrypt(cipher, (uint8_t*)username,
msg->encrypted_credentials, sizeof(username));
username[63] = '\0';
username[127] = '\0';
if (server->auth_fn(username, password, server->auth_ud)) {
nvnc_log(NVNC_LOG_INFO, "User \"%s\" authenticated", username);
security_handshake_ok(client);
client->state = VNC_CLIENT_STATE_WAITING_FOR_INIT;
} else {
nvnc_log(NVNC_LOG_INFO, "User \"%s\" rejected", username);
security_handshake_failed(client, "Invalid username or password");
crypto_cipher_del(cipher);
}
return sizeof(*msg) + key_len;
}
#endif // HAVE_CRYPTO
static int on_security_message(struct nvnc_client* client)
{
if (client->buffer_len - client->buffer_index < 1)
@ -385,6 +498,12 @@ static int on_security_message(struct nvnc_client* client)
vencrypt_send_version(client);
client->state = VNC_CLIENT_STATE_WAITING_FOR_VENCRYPT_VERSION;
break;
#endif
#ifdef HAVE_CRYPTO
case RFB_SECURITY_TYPE_APPLE_DH:
apple_dh_send_public_key(client);
client->state = VNC_CLIENT_STATE_WAITING_FOR_APPLE_DH_RESPONSE;
break;
#endif
default:
security_handshake_failed(client, "Unsupported security type");
@ -1165,6 +1284,10 @@ static int try_read_client_message(struct nvnc_client* client)
return on_vencrypt_subtype_message(client);
case VNC_CLIENT_STATE_WAITING_FOR_VENCRYPT_PLAIN_AUTH:
return on_vencrypt_plain_auth_message(client);
#endif
#ifdef HAVE_CRYPTO
case VNC_CLIENT_STATE_WAITING_FOR_APPLE_DH_RESPONSE:
return on_apple_dh_response(client);
#endif
case VNC_CLIENT_STATE_READY:
return on_client_message(client);