1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN"
2 "http://www.w3.org/TR/html4/loose.dtd">
4 <title>CURLOPT_SSL_CTX_FUNCTION man page</title>
5 <meta name="generator" content="roffit">
6 <STYLE type="text/css">
12 P.level0, pre.level0 {
16 P.level1, pre.level1 {
20 P.level2, pre.level2 {
37 background-color: #e0e0e0;
43 font-family: monospace;
53 <p class="level0"><a name="NAME"></a><h2 class="nroffsh">NAME</h2>
54 <p class="level0">CURLOPT_SSL_CTX_FUNCTION - SSL context callback for OpenSSL or wolfSSL/CyaSSL <a name="SYNOPSIS"></a><h2 class="nroffsh">SYNOPSIS</h2>
55 <p class="level0"><pre class="level0">
56 #include <curl/curl.h>
58 CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *userptr);
60 CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION,
61 ssl_ctx_callback);
63 <a name="DESCRIPTION"></a><h2 class="nroffsh">DESCRIPTION</h2>
64 <p class="level0">This option only works for libcurl powered by OpenSSL or wolfSSL/CyaSSL. If libcurl was built against another SSL library this functionality is absent.
65 <p class="level0">Pass a pointer to your callback function, which should match the prototype shown above.
66 <p class="level0">This callback function gets called by libcurl just before the initialization of an SSL connection after having processed all other SSL related options to give a last chance to an application to modify the behaviour of the SSL initialization. The <span Class="emphasis">ssl_ctx</span> parameter is actually a pointer to the SSL library's <span Class="emphasis">SSL_CTX</span>. If an error is returned from the callback no attempt to establish a connection is made and the perform operation will return the callback's error code. Set the <span Class="emphasis">userptr</span> argument with the <a Class="emphasis" href="./CURLOPT_SSL_CTX_DATA.html">CURLOPT_SSL_CTX_DATA</a> option.
67 <p class="level0">This function will get called on all new connections made to a server, during the SSL negotiation. The SSL_CTX pointer will be a new one every time.
68 <p class="level0">To use this properly, a non-trivial amount of knowledge of your SSL library is necessary. For example, you can use this function to call library-specific callbacks to add additional validation code for certificates, and even to change the actual URI of a HTTPS request. <a name="DEFAULT"></a><h2 class="nroffsh">DEFAULT</h2>
69 <p class="level0">NULL <a name="PROTOCOLS"></a><h2 class="nroffsh">PROTOCOLS</h2>
70 <p class="level0">All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. <a name="EXAMPLE"></a><h2 class="nroffsh">EXAMPLE</h2>
71 <p class="level0"><pre class="level0">
72 /* OpenSSL specific */
74 #include <openssl/ssl.h>
75 #include <curl/curl.h>
76 #include <stdio.h>
78 static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
80 X509_STORE *store;
81 X509 *cert=NULL;
83 char *mypem = /* example CA cert PEM - shortened */
84 "-----BEGIN CERTIFICATE-----n"
85 "MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290n"
86 "IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBn"
87 "IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAn"
88 "Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAOn"
89 "GCSNe9FINSkYQKyTYOGWhlC0elnYjyELn8+CkcY7v2vcB5G5l1YjqrZslMZIBjzkn"
90 "zk6q5PYvCdxTby78dOs6Y5nCpqyJvKeyRKANihDjbPIky/qbn3BHLt4Ui9SyIAmWn"
91 "omTxJBzcoTWcFbLUvFUufQb1nA5V9FrWk9p2rSVzTMVDn"\
92 "-----END CERTIFICATE-----n";
93 /* get a BIO */
94 bio=BIO_new_mem_buf(mypem, -1);
95 /* use it to read the PEM formatted certificate from memory into an X509
96 * structure that SSL can use
98 PEM_read_bio_X509(bio, &cert, 0, NULL);
99 if(cert == NULL)
100 printf("PEM_read_bio_X509 failed...n");
102 /* get a pointer to the X509 certificate store (which may be empty!) */
103 store=SSL_CTX_get_cert_store((SSL_CTX *)sslctx);
105 /* add our certificate to this store */
106 if(X509_STORE_add_cert(store, cert)==0)
107 printf("error adding certificaten");
109 /* decrease reference counts */
110 X509_free(cert);
111 BIO_free(bio);
113 /* all set to go */
114 return CURLE_OK;
122 rv=curl_global_init(CURL_GLOBAL_ALL);
123 ch=curl_easy_init();
124 rv=curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM");
125 rv=curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L);
126 rv=curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/");
128 /* Retrieve page using cacerts' certificate -> will succeed
129 * load the certificate by installing a function doing the nescessary
130 * "modifications" to the SSL CONTEXT just before link init
132 rv=curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
133 rv=curl_easy_perform(ch);
134 if(rv==CURLE_OK)
135 printf("*** transfer succeeded ***n");
137 printf("*** transfer failed ***n");
139 curl_easy_cleanup(ch);
140 curl_global_cleanup();
145 <p class="level0"><a name="AVAILABILITY"></a><h2 class="nroffsh">AVAILABILITY</h2>
146 <p class="level0">Added in 7.11.0 for OpenSSL. Added in 7.42.0 for wolfSSL/CyaSSL. Other SSL backends not supported. <a name="RETURN"></a><h2 class="nroffsh">RETURN VALUE</h2>
147 <p class="level0">Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. <a name="SEE"></a><h2 class="nroffsh">SEE ALSO</h2>
148 <p class="level0"><a Class="manpage" href="./CURLOPT_SSL_CTX_DATA.html">CURLOPT_SSL_CTX_DATA</a>, <a Class="manpage" href="./CURLOPT_SSL_VERIFYPEER.html">CURLOPT_SSL_VERIFYPEER</a><p class="roffit">
149 This HTML page was made with <a href="http://daniel.haxx.se/projects/roffit/">roffit</a>.