1 #include <openssl/ssl.h>
2
3 /*
4 * Demo 1: Client — Managed Connection — Blocking
5 * ==============================================
6 *
7 * This is an example of (part of) an application which uses libssl in a simple,
8 * synchronous, blocking fashion. The functions show all interactions with
9 * libssl the application makes, and would hypothetically be linked into a
10 * larger application.
11 */
12
13 /*
14 * The application is initializing and wants an SSL_CTX which it will use for
15 * some number of outgoing connections, which it creates in subsequent calls to
16 * new_conn. The application may also call this function multiple times to
17 * create multiple SSL_CTX.
18 */
create_ssl_ctx(void)19 SSL_CTX *create_ssl_ctx(void)
20 {
21 SSL_CTX *ctx;
22
23 #ifdef USE_QUIC
24 ctx = SSL_CTX_new(OSSL_QUIC_client_method());
25 #else
26 ctx = SSL_CTX_new(TLS_client_method());
27 #endif
28 if (ctx == NULL)
29 return NULL;
30
31 /* Enable trust chain verification. */
32 SSL_CTX_set_verify(ctx, SSL_VERIFY_PEER, NULL);
33
34 /* Load default root CA store. */
35 if (SSL_CTX_set_default_verify_paths(ctx) == 0) {
36 SSL_CTX_free(ctx);
37 return NULL;
38 }
39
40 return ctx;
41 }
42
43 /*
44 * The application wants to create a new outgoing connection using a given
45 * SSL_CTX.
46 *
47 * hostname is a string like "openssl.org:443" or "[::1]:443".
48 */
new_conn(SSL_CTX * ctx,const char * hostname)49 BIO *new_conn(SSL_CTX *ctx, const char *hostname)
50 {
51 BIO *out;
52 SSL *ssl = NULL;
53 const char *bare_hostname;
54 #ifdef USE_QUIC
55 static const unsigned char alpn[] = {5, 'd', 'u', 'm', 'm', 'y'};
56 #endif
57
58 out = BIO_new_ssl_connect(ctx);
59 if (out == NULL)
60 return NULL;
61
62 if (BIO_get_ssl(out, &ssl) == 0) {
63 BIO_free_all(out);
64 return NULL;
65 }
66
67 if (BIO_set_conn_hostname(out, hostname) == 0) {
68 BIO_free_all(out);
69 return NULL;
70 }
71
72 /* Returns the parsed hostname extracted from the hostname:port string. */
73 bare_hostname = BIO_get_conn_hostname(out);
74 if (bare_hostname == NULL) {
75 BIO_free_all(out);
76 return NULL;
77 }
78
79 /* Tell the SSL object the hostname to check certificates against. */
80 if (SSL_set1_host(ssl, bare_hostname) <= 0) {
81 BIO_free_all(out);
82 return NULL;
83 }
84
85 #ifdef USE_QUIC
86 /* Configure ALPN, which is required for QUIC. */
87 if (SSL_set_alpn_protos(ssl, alpn, sizeof(alpn))) {
88 /* Note: SSL_set_alpn_protos returns 1 for failure. */
89 BIO_free_all(out);
90 return NULL;
91 }
92 #endif
93
94 return out;
95 }
96
97 /*
98 * The application wants to send some block of data to the peer.
99 * This is a blocking call.
100 */
tx(BIO * bio,const void * buf,int buf_len)101 int tx(BIO *bio, const void *buf, int buf_len)
102 {
103 return BIO_write(bio, buf, buf_len);
104 }
105
106 /*
107 * The application wants to receive some block of data from
108 * the peer. This is a blocking call.
109 */
rx(BIO * bio,void * buf,int buf_len)110 int rx(BIO *bio, void *buf, int buf_len)
111 {
112 return BIO_read(bio, buf, buf_len);
113 }
114
115 /*
116 * The application wants to close the connection and free bookkeeping
117 * structures.
118 */
teardown(BIO * bio)119 void teardown(BIO *bio)
120 {
121 BIO_free_all(bio);
122 }
123
124 /*
125 * The application is shutting down and wants to free a previously
126 * created SSL_CTX.
127 */
teardown_ctx(SSL_CTX * ctx)128 void teardown_ctx(SSL_CTX *ctx)
129 {
130 SSL_CTX_free(ctx);
131 }
132
133 /*
134 * ============================================================================
135 * Example driver for the above code. This is just to demonstrate that the code
136 * works and is not intended to be representative of a real application.
137 */
main(int argc,char ** argv)138 int main(int argc, char **argv)
139 {
140 static char msg[384], host_port[300];
141 SSL_CTX *ctx = NULL;
142 BIO *b = NULL;
143 char buf[2048];
144 int l, mlen, res = 1;
145
146 if (argc < 3) {
147 fprintf(stderr, "usage: %s host port\n", argv[0]);
148 goto fail;
149 }
150
151 snprintf(host_port, sizeof(host_port), "%s:%s", argv[1], argv[2]);
152 mlen = snprintf(msg, sizeof(msg),
153 "GET / HTTP/1.0\r\nHost: %s\r\n\r\n", argv[1]);
154
155 ctx = create_ssl_ctx();
156 if (ctx == NULL) {
157 fprintf(stderr, "could not create context\n");
158 goto fail;
159 }
160
161 b = new_conn(ctx, host_port);
162 if (b == NULL) {
163 fprintf(stderr, "could not create connection\n");
164 goto fail;
165 }
166
167 l = tx(b, msg, mlen);
168 if (l < mlen) {
169 fprintf(stderr, "tx error\n");
170 goto fail;
171 }
172
173 for (;;) {
174 l = rx(b, buf, sizeof(buf));
175 if (l <= 0)
176 break;
177 fwrite(buf, 1, l, stdout);
178 }
179
180 res = 0;
181 fail:
182 if (b != NULL)
183 teardown(b);
184 if (ctx != NULL)
185 teardown_ctx(ctx);
186 return res;
187 }
188
