From: Simon Ruderich Date: Fri, 11 Mar 2011 02:02:00 +0000 (+0100) Subject: src/connection.c: Use "invalid" certificate when the server certificate changes. X-Git-Tag: 0.1~15 X-Git-Url: https://ruderich.org/simon/gitweb/?a=commitdiff_plain;h=8bc073500cb894b9fd974b53801f7daa86e96d12;p=tlsproxy%2Ftlsproxy.git src/connection.c: Use "invalid" certificate when the server certificate changes. This special "invalid" certificate lets the client know there was a problem. --- diff --git a/src/connection.c b/src/connection.c index 1421afa..2732f30 100644 --- a/src/connection.c +++ b/src/connection.c @@ -48,7 +48,7 @@ static int initialize_tls_session_server(int peer_socket, static int read_http_request(FILE *client_fd, char *request, size_t length); static void send_bad_request(FILE *client_fd); static void send_forwarding_failure(FILE *client_fd); -static void tls_send_server_error(gnutls_session_t session); +static void tls_send_invalid_cert_message(gnutls_session_t session); #if 0 static void transfer_data(int client, int server); @@ -86,6 +86,9 @@ void handle_connection(int client_socket) { int client_session_init, server_session_init; /* gnutls_handshake() called? - used for goto out */ int client_session_started, server_session_started; + /* Validation failed? If yes we need to send the special "invalid" + * certificate. */ + int validation_failed; LOG(LOG_DEBUG, "new connection"); @@ -96,6 +99,7 @@ void handle_connection(int client_socket) { server_session_init = 0; client_session_started = 0; server_session_started = 0; + validation_failed = 0; client_fd = fdopen(client_socket, "a+"); if (NULL == client_fd) { @@ -175,36 +179,6 @@ void handle_connection(int client_socket) { LOG(LOG_DEBUG, "connection to server established"); - /* We've established a connection, tell the client. */ - fprintf(client_fd, "HTTP/1.0 200 Connection established\r\n"); - fprintf(client_fd, "\r\n"); - fflush(client_fd); - - /* Initialize TLS server credentials to talk to the client. */ - result = initialize_tls_session_client(client_socket, host, - &client_session, - &client_x509_cred); - if (0 != result) { - LOG(LOG_WARNING, "initialize_tls_session_client() failed"); - send_forwarding_failure(client_fd); - goto out; - } - client_session_init = 1; - - LOG(LOG_DEBUG, "starting client TLS handshake"); - - /* Try to establish TLS handshake between client and us. */ - result = gnutls_handshake(client_session); - if (GNUTLS_E_SUCCESS != result) { - LOG(LOG_WARNING, "client TLS handshake failed: %s", - gnutls_strerror(result)); - send_forwarding_failure(client_fd); - goto out; - } - client_session_started = 1; - - LOG(LOG_DEBUG, "client TLS handshake finished"); - result = initialize_tls_session_server(server_socket, &server_session, &server_x509_cred); /* Initialize TLS client credentials to talk to the server. */ @@ -227,14 +201,59 @@ void handle_connection(int client_socket) { } server_session_started = 1; - LOG(LOG_DEBUG, "server TLS handshake finished, transferring data"); + LOG(LOG_DEBUG, "server TLS handshake finished"); /* Make sure the server certificate is valid and known. */ if (0 != verify_tls_connection(server_session, host)) { LOG(LOG_ERROR, "server certificate validation failed!"); - tls_send_server_error(client_session); + /* We send the error message over our TLS connection to the client, + * but with an invalid certificate. */ + validation_failed = 1; + } + + /* Initialize TLS server credentials to talk to the client. */ + result = initialize_tls_session_client(client_socket, + /* use special host if the server + * certificate was invalid */ + (validation_failed) ? "invalid" + : host, + &client_session, + &client_x509_cred); + if (0 != result) { + LOG(LOG_WARNING, "initialize_tls_session_client() failed"); + send_forwarding_failure(client_fd); goto out; } + client_session_init = 1; + + /* We've established a connection, tell the client. */ + fprintf(client_fd, "HTTP/1.0 200 Connection established\r\n"); + fprintf(client_fd, "\r\n"); + fflush(client_fd); + + LOG(LOG_DEBUG, "starting client TLS handshake"); + + /* Try to establish TLS handshake between client and us. */ + result = gnutls_handshake(client_session); + if (GNUTLS_E_SUCCESS != result) { + LOG(LOG_WARNING, "client TLS handshake failed: %s", + gnutls_strerror(result)); + send_forwarding_failure(client_fd); + goto out; + } + client_session_started = 1; + + LOG(LOG_DEBUG, "client TLS handshake finished"); + + /* Tell the client that the verification failed. Shouldn't be necessary as + * the client should terminate the connection because he received the + * invalid certificate but better be sure. */ + if (validation_failed) { + tls_send_invalid_cert_message(client_session); + goto out; + } + + LOG(LOG_DEBUG, "transferring data"); /* Proxy data between client and server until one suite is done (EOF or * error). */ @@ -287,8 +306,13 @@ static int initialize_tls_session_client(int peer_socket, gnutls_session_t *session, gnutls_certificate_credentials_t *x509_cred) { int result; + int use_invalid_cert; char path[1024]; + /* The "invalid" hostname is special. If it's used we send an invalid + * certificate to let the client know something is wrong. */ + use_invalid_cert = 0 == strcmp(hostname, "invalid"); + /* Hostname too long. */ if (sizeof(path) - strlen(PROXY_SERVER_CERT_FORMAT) <= strlen(hostname)) { LOG(LOG_WARNING, @@ -315,9 +339,15 @@ gnutls_certificate_allocate_credentials(): %s", } /* Load proxy CA file, this CA "list" is send to the client. */ - result = gnutls_certificate_set_x509_trust_file(*x509_cred, - PROXY_CA_FILE, - GNUTLS_X509_FMT_PEM); + if (!use_invalid_cert) { + result = gnutls_certificate_set_x509_trust_file(*x509_cred, + PROXY_CA_FILE, + GNUTLS_X509_FMT_PEM); + /* If the invalid hostname was specified do nothing, we use a self-signed + * certificate in this case. */ + } else { + result = 1; + } if (0 >= result) { LOG(LOG_ERROR, "initialize_tls_session_client(): can't read CA file: '%s'", @@ -325,9 +355,18 @@ gnutls_certificate_allocate_credentials(): %s", return -1; } /* And certificate for this website and proxy's private key. */ - result = gnutls_certificate_set_x509_key_file(*x509_cred, - path, PROXY_KEY_FILE, - GNUTLS_X509_FMT_PEM); + if (!use_invalid_cert) { + result = gnutls_certificate_set_x509_key_file(*x509_cred, + path, PROXY_KEY_FILE, + GNUTLS_X509_FMT_PEM); + /* If the invalid hostname was specified load our special "invalid" + * certificate. */ + } else { + result = gnutls_certificate_set_x509_key_file(*x509_cred, + PROXY_INVALID_CERT_FILE, + PROXY_KEY_FILE, + GNUTLS_X509_FMT_PEM); + } if (GNUTLS_E_SUCCESS != result) { LOG(LOG_ERROR, "initialize_tls_session_client(): \ @@ -447,7 +486,7 @@ static void send_forwarding_failure(FILE *client_fd) { fprintf(client_fd, "HTTP/1.0 503 Forwarding failure\r\n"); fprintf(client_fd, "\r\n"); } -static void tls_send_server_error(gnutls_session_t session) { +static void tls_send_invalid_cert_message(gnutls_session_t session) { gnutls_record_send(session, "HTTP/1.0 500 Internal Server Error\r\n", 36); gnutls_record_send(session, "\r\n", 2); } diff --git a/src/tlsproxy.h b/src/tlsproxy.h index c151344..bcb9c2d 100644 --- a/src/tlsproxy.h +++ b/src/tlsproxy.h @@ -35,6 +35,9 @@ /* Paths to necessary TLS files: the CA and the server key. */ #define PROXY_CA_FILE "proxy-ca.pem" #define PROXY_KEY_FILE "proxy-key.pem" +/* Path to special "invalid" certificate send to the client when an error + * occurs. */ +#define PROXY_INVALID_CERT_FILE "proxy-invalid.pem" /* The server certificate for the given hostname is stored in * "./certificate-hostname-proxy.pem" - we use this for the connection to the * client. */