377 lines
12 KiB
C
377 lines
12 KiB
C
/*
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* Copyright 2023 The OpenSSL Project Authors. All Rights Reserved.
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*
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* Licensed under the Apache License 2.0 (the "License"). You may not use
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* this file except in compliance with the License. You can obtain a copy
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* in the file LICENSE in the source distribution or at
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* https://www.openssl.org/source/license.html
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*/
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/*
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* NB: Changes to this file should also be reflected in
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* doc/man7/ossl-guide-tls-client-non-block.pod
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*/
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#include <string.h>
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/* Include the appropriate header file for SOCK_STREAM */
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#ifdef _WIN32 /* Windows */
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# include <winsock2.h>
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#else /* Linux/Unix */
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# include <sys/socket.h>
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# include <sys/select.h>
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#endif
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#include <openssl/bio.h>
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#include <openssl/ssl.h>
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#include <openssl/err.h>
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/* Helper function to create a BIO connected to the server */
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static BIO *create_socket_bio(const char *hostname, const char *port, int family)
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{
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int sock = -1;
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BIO_ADDRINFO *res;
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const BIO_ADDRINFO *ai = NULL;
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BIO *bio;
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/*
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* Lookup IP address info for the server.
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*/
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if (!BIO_lookup_ex(hostname, port, BIO_LOOKUP_CLIENT, family, SOCK_STREAM, 0,
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&res))
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return NULL;
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/*
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* Loop through all the possible addresses for the server and find one
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* we can connect to.
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*/
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for (ai = res; ai != NULL; ai = BIO_ADDRINFO_next(ai)) {
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/*
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* Create a TCP socket. We could equally use non-OpenSSL calls such
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* as "socket" here for this and the subsequent connect and close
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* functions. But for portability reasons and also so that we get
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* errors on the OpenSSL stack in the event of a failure we use
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* OpenSSL's versions of these functions.
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*/
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sock = BIO_socket(BIO_ADDRINFO_family(ai), SOCK_STREAM, 0, 0);
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if (sock == -1)
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continue;
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/* Connect the socket to the server's address */
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if (!BIO_connect(sock, BIO_ADDRINFO_address(ai), BIO_SOCK_NODELAY)) {
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BIO_closesocket(sock);
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sock = -1;
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continue;
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}
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/* Set to nonblocking mode */
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if (!BIO_socket_nbio(sock, 1)) {
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sock = -1;
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continue;
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}
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/* We have a connected socket so break out of the loop */
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break;
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}
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/* Free the address information resources we allocated earlier */
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BIO_ADDRINFO_free(res);
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/* If sock is -1 then we've been unable to connect to the server */
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if (sock == -1)
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return NULL;
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/* Create a BIO to wrap the socket */
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bio = BIO_new(BIO_s_socket());
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if (bio == NULL) {
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BIO_closesocket(sock);
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return NULL;
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}
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/*
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* Associate the newly created BIO with the underlying socket. By
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* passing BIO_CLOSE here the socket will be automatically closed when
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* the BIO is freed. Alternatively you can use BIO_NOCLOSE, in which
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* case you must close the socket explicitly when it is no longer
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* needed.
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*/
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BIO_set_fd(bio, sock, BIO_CLOSE);
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return bio;
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}
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static void wait_for_activity(SSL *ssl, int write)
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{
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fd_set fds;
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int width, sock;
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/* Get hold of the underlying file descriptor for the socket */
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sock = SSL_get_fd(ssl);
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FD_ZERO(&fds);
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FD_SET(sock, &fds);
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width = sock + 1;
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/*
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* Wait until the socket is writeable or readable. We use select here
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* for the sake of simplicity and portability, but you could equally use
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* poll/epoll or similar functions
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*
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* NOTE: For the purposes of this demonstration code this effectively
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* makes this demo block until it has something more useful to do. In a
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* real application you probably want to go and do other work here (e.g.
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* update a GUI, or service other connections).
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*
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* Let's say for example that you want to update the progress counter on
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* a GUI every 100ms. One way to do that would be to add a 100ms timeout
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* in the last parameter to "select" below. Then, when select returns,
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* you check if it did so because of activity on the file descriptors or
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* because of the timeout. If it is due to the timeout then update the
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* GUI and then restart the "select".
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*/
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if (write)
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select(width, NULL, &fds, NULL, NULL);
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else
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select(width, &fds, NULL, NULL, NULL);
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}
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static int handle_io_failure(SSL *ssl, int res)
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{
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switch (SSL_get_error(ssl, res)) {
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case SSL_ERROR_WANT_READ:
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/* Temporary failure. Wait until we can read and try again */
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wait_for_activity(ssl, 0);
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return 1;
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case SSL_ERROR_WANT_WRITE:
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/* Temporary failure. Wait until we can write and try again */
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wait_for_activity(ssl, 1);
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return 1;
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case SSL_ERROR_ZERO_RETURN:
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/* EOF */
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return 0;
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case SSL_ERROR_SYSCALL:
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return -1;
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case SSL_ERROR_SSL:
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/*
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* If the failure is due to a verification error we can get more
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* information about it from SSL_get_verify_result().
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*/
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if (SSL_get_verify_result(ssl) != X509_V_OK)
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printf("Verify error: %s\n",
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X509_verify_cert_error_string(SSL_get_verify_result(ssl)));
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return -1;
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default:
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return -1;
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}
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}
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/*
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* Simple application to send a basic HTTP/1.0 request to a server and
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* print the response on the screen.
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*/
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int main(int argc, char *argv[])
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{
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SSL_CTX *ctx = NULL;
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SSL *ssl = NULL;
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BIO *bio = NULL;
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int res = EXIT_FAILURE;
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int ret;
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const char *request_start = "GET / HTTP/1.0\r\nConnection: close\r\nHost: ";
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const char *request_end = "\r\n\r\n";
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size_t written, readbytes;
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char buf[160];
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int eof = 0;
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char *hostname, *port;
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int argnext = 1;
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int ipv6 = 0;
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if (argc < 3) {
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printf("Usage: tls-client-non-block [-6] hostname port\n");
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goto end;
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}
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if (!strcmp(argv[argnext], "-6")) {
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if (argc < 4) {
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printf("Usage: tls-client-non-block [-6] hostname port\n");
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goto end;
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}
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ipv6 = 1;
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argnext++;
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}
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hostname = argv[argnext++];
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port = argv[argnext];
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/*
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* Create an SSL_CTX which we can use to create SSL objects from. We
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* want an SSL_CTX for creating clients so we use TLS_client_method()
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* here.
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*/
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ctx = SSL_CTX_new(TLS_client_method());
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if (ctx == NULL) {
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printf("Failed to create the SSL_CTX\n");
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goto end;
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}
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/*
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* Configure the client to abort the handshake if certificate
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* verification fails. Virtually all clients should do this unless you
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* really know what you are doing.
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*/
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SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
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/* Use the default trusted certificate store */
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if (!SSL_CTX_set_default_verify_paths(ctx)) {
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printf("Failed to set the default trusted certificate store\n");
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goto end;
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}
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/*
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* TLSv1.1 or earlier are deprecated by IETF and are generally to be
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* avoided if possible. We require a minimum TLS version of TLSv1.2.
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*/
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if (!SSL_CTX_set_min_proto_version(ctx, TLS1_2_VERSION)) {
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printf("Failed to set the minimum TLS protocol version\n");
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goto end;
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}
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/* Create an SSL object to represent the TLS connection */
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ssl = SSL_new(ctx);
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if (ssl == NULL) {
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printf("Failed to create the SSL object\n");
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goto end;
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}
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/*
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* Create the underlying transport socket/BIO and associate it with the
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* connection.
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*/
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bio = create_socket_bio(hostname, port, ipv6 ? AF_INET6 : AF_INET);
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if (bio == NULL) {
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printf("Failed to crete the BIO\n");
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goto end;
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}
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SSL_set_bio(ssl, bio, bio);
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/*
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* Tell the server during the handshake which hostname we are attempting
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* to connect to in case the server supports multiple hosts.
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*/
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if (!SSL_set_tlsext_host_name(ssl, hostname)) {
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printf("Failed to set the SNI hostname\n");
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goto end;
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}
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/*
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* Ensure we check during certificate verification that the server has
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* supplied a certificate for the hostname that we were expecting.
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* Virtually all clients should do this unless you really know what you
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* are doing.
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*/
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if (!SSL_set1_host(ssl, hostname)) {
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printf("Failed to set the certificate verification hostname");
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goto end;
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}
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/* Do the handshake with the server */
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while ((ret = SSL_connect(ssl)) != 1) {
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if (handle_io_failure(ssl, ret) == 1)
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continue; /* Retry */
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printf("Failed to connect to server\n");
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goto end; /* Cannot retry: error */
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}
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/* Write an HTTP GET request to the peer */
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while (!SSL_write_ex(ssl, request_start, strlen(request_start), &written)) {
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if (handle_io_failure(ssl, 0) == 1)
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continue; /* Retry */
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printf("Failed to write start of HTTP request\n");
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goto end; /* Cannot retry: error */
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}
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while (!SSL_write_ex(ssl, hostname, strlen(hostname), &written)) {
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if (handle_io_failure(ssl, 0) == 1)
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continue; /* Retry */
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printf("Failed to write hostname in HTTP request\n");
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goto end; /* Cannot retry: error */
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}
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while (!SSL_write_ex(ssl, request_end, strlen(request_end), &written)) {
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if (handle_io_failure(ssl, 0) == 1)
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continue; /* Retry */
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printf("Failed to write end of HTTP request\n");
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goto end; /* Cannot retry: error */
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}
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do {
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/*
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* Get up to sizeof(buf) bytes of the response. We keep reading until
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* the server closes the connection.
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*/
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while (!eof && !SSL_read_ex(ssl, buf, sizeof(buf), &readbytes)) {
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switch (handle_io_failure(ssl, 0)) {
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case 1:
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continue; /* Retry */
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case 0:
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eof = 1;
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continue;
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case -1:
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default:
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printf("Failed reading remaining data\n");
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goto end; /* Cannot retry: error */
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}
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}
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/*
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* OpenSSL does not guarantee that the returned data is a string or
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* that it is NUL terminated so we use fwrite() to write the exact
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* number of bytes that we read. The data could be non-printable or
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* have NUL characters in the middle of it. For this simple example
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* we're going to print it to stdout anyway.
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*/
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if (!eof)
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fwrite(buf, 1, readbytes, stdout);
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} while (!eof);
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/* In case the response didn't finish with a newline we add one now */
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printf("\n");
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/*
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* The peer already shutdown gracefully (we know this because of the
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* SSL_ERROR_ZERO_RETURN (i.e. EOF) above). We should do the same back.
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*/
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while ((ret = SSL_shutdown(ssl)) != 1) {
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if (ret < 0 && handle_io_failure(ssl, ret) == 1)
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continue; /* Retry */
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/*
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* ret == 0 is unexpected here because that means "we've sent a
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* close_notify and we're waiting for one back". But we already know
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* we got one from the peer because of the SSL_ERROR_ZERO_RETURN
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* (i.e. EOF) above.
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*/
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printf("Error shutting down\n");
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goto end; /* Cannot retry: error */
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}
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/* Success! */
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res = EXIT_SUCCESS;
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end:
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/*
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* If something bad happened then we will dump the contents of the
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* OpenSSL error stack to stderr. There might be some useful diagnostic
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* information there.
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*/
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if (res == EXIT_FAILURE)
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ERR_print_errors_fp(stderr);
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/*
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* Free the resources we allocated. We do not free the BIO object here
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* because ownership of it was immediately transferred to the SSL object
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* via SSL_set_bio(). The BIO will be freed when we free the SSL object.
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*/
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SSL_free(ssl);
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SSL_CTX_free(ctx);
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return res;
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}
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