etlegacy-libs/curl/docs/libcurl/opts/CURLOPT_SSL_CTX_FUNCTION.html
2016-09-16 06:35:46 +02:00

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<p class="level0"><a name="NAME"></a><h2 class="nroffsh">NAME</h2>
<p class="level0">CURLOPT_SSL_CTX_FUNCTION - SSL context callback for OpenSSL or wolfSSL/CyaSSL <a name="SYNOPSIS"></a><h2 class="nroffsh">SYNOPSIS</h2>
<p class="level0"><pre class="level0">
&#35;include &lt;curl/curl.h&gt;
&nbsp;
CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *userptr);
&nbsp;
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION,
&nbsp; ssl_ctx_callback);
</pre>
<a name="DESCRIPTION"></a><h2 class="nroffsh">DESCRIPTION</h2>
<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.
<p class="level0">Pass a pointer to your callback function, which should match the prototype shown above.
<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.
<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.
<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>
<p class="level0">NULL <a name="PROTOCOLS"></a><h2 class="nroffsh">PROTOCOLS</h2>
<p class="level0">All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. <a name="EXAMPLE"></a><h2 class="nroffsh">EXAMPLE</h2>
<p class="level0"><pre class="level0">
/* OpenSSL specific */
&nbsp;
&#35;include &lt;openssl/ssl.h&gt;
&#35;include &lt;curl/curl.h&gt;
&#35;include &lt;stdio.h&gt;
&nbsp;
static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm)
{
&nbsp; X509_STORE *store;
&nbsp; X509 *cert=NULL;
&nbsp; BIO *bio;
&nbsp; char *mypem = /* example CA cert PEM - shortened */
&nbsp; "-----BEGIN CERTIFICATE-----n"
&nbsp; "MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290n"
&nbsp; "IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNBn"
&nbsp; "IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRAn"
&nbsp; "Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAOn"
&nbsp; "GCSNe9FINSkYQKyTYOGWhlC0elnYjyELn8+CkcY7v2vcB5G5l1YjqrZslMZIBjzkn"
&nbsp; "zk6q5PYvCdxTby78dOs6Y5nCpqyJvKeyRKANihDjbPIky/qbn3BHLt4Ui9SyIAmWn"
&nbsp; "omTxJBzcoTWcFbLUvFUufQb1nA5V9FrWk9p2rSVzTMVDn"\
&nbsp; "-----END CERTIFICATE-----n";
&nbsp; /* get a BIO */
&nbsp; bio=BIO_new_mem_buf(mypem, -1);
&nbsp; /* use it to read the PEM formatted certificate from memory into an X509
&nbsp; * structure that SSL can use
&nbsp; */
&nbsp; PEM_read_bio_X509(bio, &cert, 0, NULL);
&nbsp; if(cert == NULL)
&nbsp; printf("PEM_read_bio_X509 failed...n");
&nbsp;
&nbsp; /* get a pointer to the X509 certificate store (which may be empty!) */
&nbsp; store=SSL_CTX_get_cert_store((SSL_CTX *)sslctx);
&nbsp;
&nbsp; /* add our certificate to this store */
&nbsp; if(X509_STORE_add_cert(store, cert)==0)
&nbsp; printf("error adding certificaten");
&nbsp;
&nbsp; /* decrease reference counts */
&nbsp; X509_free(cert);
&nbsp; BIO_free(bio);
&nbsp;
&nbsp; /* all set to go */
&nbsp; return CURLE_OK;
}
&nbsp;
int main(void)
{
&nbsp; CURL * ch;
&nbsp; CURLcode rv;
&nbsp;
&nbsp; rv=curl_global_init(CURL_GLOBAL_ALL);
&nbsp; ch=curl_easy_init();
&nbsp; rv=curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM");
&nbsp; rv=curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L);
&nbsp; rv=curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/");
&nbsp;
&nbsp; /* Retrieve page using cacerts' certificate -&gt; will succeed
&nbsp; * load the certificate by installing a function doing the nescessary
&nbsp; * "modifications" to the SSL CONTEXT just before link init
&nbsp; */
&nbsp; rv=curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
&nbsp; rv=curl_easy_perform(ch);
&nbsp; if(rv==CURLE_OK)
&nbsp; printf("*** transfer succeeded ***n");
&nbsp; else
&nbsp; printf("*** transfer failed ***n");
&nbsp;
&nbsp; curl_easy_cleanup(ch);
&nbsp; curl_global_cleanup();
&nbsp; return rv;
}
</pre>
<p class="level0"><a name="AVAILABILITY"></a><h2 class="nroffsh">AVAILABILITY</h2>
<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>
<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>
<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">
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