1 #include <openssl/ssl.h>
2
3 /*
4 * Demo 3: Client — Client Creates FD — Blocking
5 * =============================================
6 *
7 * This is an example of (part of) an application which uses libssl in a simple,
8 * synchronous, blocking fashion. The client is responsible for creating the
9 * socket and passing it to libssl. The functions show all interactions with
10 * libssl the application makes, and would hypothetically be linked into a
11 * larger application.
12 */
13
14 /*
15 * The application is initializing and wants an SSL_CTX which it will use for
16 * some number of outgoing connections, which it creates in subsequent calls to
17 * new_conn. The application may also call this function multiple times to
18 * create multiple SSL_CTX.
19 */
create_ssl_ctx(void)20 SSL_CTX *create_ssl_ctx(void)
21 {
22 SSL_CTX *ctx;
23
24 #ifdef USE_QUIC
25 ctx = SSL_CTX_new(OSSL_QUIC_client_method());
26 #else
27 ctx = SSL_CTX_new(TLS_client_method());
28 #endif
29 if (ctx == NULL)
30 return NULL;
31
32 /* Enable trust chain verification. */
33 SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
34
35 /* Load default root CA store. */
36 if (SSL_CTX_set_default_verify_paths(ctx) == 0) {
37 SSL_CTX_free(ctx);
38 return NULL;
39 }
40
41 return ctx;
42 }
43
44 /*
45 * The application wants to create a new outgoing connection using a given
46 * SSL_CTX.
47 *
48 * hostname is a string like "openssl.org" used for certificate validation.
49 */
new_conn(SSL_CTX * ctx,int fd,const char * bare_hostname)50 SSL *new_conn(SSL_CTX *ctx, int fd, const char *bare_hostname)
51 {
52 SSL *ssl;
53 #ifdef USE_QUIC
54 static const unsigned char alpn[] = {5, 'd', 'u', 'm', 'm', 'y'};
55 #endif
56
57 ssl = SSL_new(ctx);
58 if (ssl == NULL)
59 return NULL;
60
61 SSL_set_connect_state(ssl); /* cannot fail */
62
63 if (SSL_set_fd(ssl, fd) <= 0) {
64 SSL_free(ssl);
65 return NULL;
66 }
67
68 if (SSL_set1_host(ssl, bare_hostname) <= 0) {
69 SSL_free(ssl);
70 return NULL;
71 }
72
73 if (SSL_set_tlsext_host_name(ssl, bare_hostname) <= 0) {
74 SSL_free(ssl);
75 return NULL;
76 }
77
78 #ifdef USE_QUIC
79 /* Configure ALPN, which is required for QUIC. */
80 if (SSL_set_alpn_protos(ssl, alpn, sizeof(alpn))) {
81 /* Note: SSL_set_alpn_protos returns 1 for failure. */
82 SSL_free(ssl);
83 return NULL;
84 }
85 #endif
86
87 return ssl;
88 }
89
90 /*
91 * The application wants to send some block of data to the peer.
92 * This is a blocking call.
93 */
tx(SSL * ssl,const void * buf,int buf_len)94 int tx(SSL *ssl, const void *buf, int buf_len)
95 {
96 return SSL_write(ssl, buf, buf_len);
97 }
98
99 /*
100 * The application wants to receive some block of data from
101 * the peer. This is a blocking call.
102 */
rx(SSL * ssl,void * buf,int buf_len)103 int rx(SSL *ssl, void *buf, int buf_len)
104 {
105 return SSL_read(ssl, buf, buf_len);
106 }
107
108 /*
109 * The application wants to close the connection and free bookkeeping
110 * structures.
111 */
teardown(SSL * ssl)112 void teardown(SSL *ssl)
113 {
114 SSL_free(ssl);
115 }
116
117 /*
118 * The application is shutting down and wants to free a previously
119 * created SSL_CTX.
120 */
teardown_ctx(SSL_CTX * ctx)121 void teardown_ctx(SSL_CTX *ctx)
122 {
123 SSL_CTX_free(ctx);
124 }
125
126 /*
127 * ============================================================================
128 * Example driver for the above code. This is just to demonstrate that the code
129 * works and is not intended to be representative of a real application.
130 */
131 #include <sys/types.h>
132 #include <sys/socket.h>
133 #include <sys/signal.h>
134 #include <netdb.h>
135 #include <unistd.h>
136
main(int argc,char ** argv)137 int main(int argc, char **argv)
138 {
139 int rc, fd = -1, l, mlen, res = 1;
140 static char msg[300];
141 struct addrinfo hints = {0}, *result = NULL;
142 SSL *ssl = NULL;
143 SSL_CTX *ctx = NULL;
144 char buf[2048];
145
146 if (argc < 3) {
147 fprintf(stderr, "usage: %s host port\n", argv[0]);
148 goto fail;
149 }
150
151 mlen = snprintf(msg, sizeof(msg),
152 "GET / HTTP/1.0\r\nHost: %s\r\n\r\n", argv[1]);
153
154 ctx = create_ssl_ctx();
155 if (ctx == NULL) {
156 fprintf(stderr, "cannot create context\n");
157 goto fail;
158 }
159
160 hints.ai_family = AF_INET;
161 hints.ai_socktype = SOCK_STREAM;
162 hints.ai_flags = AI_PASSIVE;
163 rc = getaddrinfo(argv[1], argv[2], &hints, &result);
164 if (rc < 0) {
165 fprintf(stderr, "cannot resolve\n");
166 goto fail;
167 }
168
169 signal(SIGPIPE, SIG_IGN);
170
171 #ifdef USE_QUIC
172 fd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP);
173 #else
174 fd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
175 #endif
176 if (fd < 0) {
177 fprintf(stderr, "cannot create socket\n");
178 goto fail;
179 }
180
181 rc = connect(fd, result->ai_addr, result->ai_addrlen);
182 if (rc < 0) {
183 fprintf(stderr, "cannot connect\n");
184 goto fail;
185 }
186
187 ssl = new_conn(ctx, fd, argv[1]);
188 if (ssl == NULL) {
189 fprintf(stderr, "cannot create connection\n");
190 goto fail;
191 }
192
193 l = tx(ssl, msg, mlen);
194 if (l < mlen) {
195 fprintf(stderr, "tx error\n");
196 goto fail;
197 }
198
199 for (;;) {
200 l = rx(ssl, buf, sizeof(buf));
201 if (l <= 0)
202 break;
203 fwrite(buf, 1, l, stdout);
204 }
205
206 res = 0;
207 fail:
208 if (ssl != NULL)
209 teardown(ssl);
210 if (ctx != NULL)
211 teardown_ctx(ctx);
212 if (fd >= 0)
213 close(fd);
214 if (result != NULL)
215 freeaddrinfo(result);
216 return res;
217 }
218
