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| .TH CURLOPT_SSL_CTX_FUNCTION 3 "19 Jun 2014" "libcurl 7.37.0" "curl_easy_setopt options" |
| .SH NAME |
| CURLOPT_SSL_CTX_FUNCTION \- SSL context callback for OpenSSL or wolfSSL/CyaSSL |
| .SH SYNOPSIS |
| .nf |
| #include <curl/curl.h> |
| |
| CURLcode ssl_ctx_callback(CURL *curl, void *ssl_ctx, void *userptr); |
| |
| CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_FUNCTION, |
| ssl_ctx_callback); |
| .SH DESCRIPTION |
| This option only works for libcurl powered by OpenSSL or wolfSSL/CyaSSL. If |
| libcurl was built against another SSL library this functionality is absent. |
| |
| Pass a pointer to your callback function, which should match the prototype |
| shown above. |
| |
| 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 \fIssl_ctx\fP parameter is actually a pointer to the SSL |
| library's \fISSL_CTX\fP. 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 \fIuserptr\fP argument with the |
| \fICURLOPT_SSL_CTX_DATA(3)\fP option. |
| |
| 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. |
| |
| 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. |
| .SH DEFAULT |
| NULL |
| .SH PROTOCOLS |
| All TLS based protocols: HTTPS, FTPS, IMAPS, POP3S, SMTPS etc. |
| .SH EXAMPLE |
| .nf |
| /* OpenSSL specific */ |
| |
| #include <openssl/ssl.h> |
| #include <curl/curl.h> |
| #include <stdio.h> |
| |
| static CURLcode sslctx_function(CURL *curl, void *sslctx, void *parm) |
| { |
| X509_STORE *store; |
| X509 *cert=NULL; |
| BIO *bio; |
| char *mypem = /* example CA cert PEM - shortened */ |
| "-----BEGIN CERTIFICATE-----\n" |
| "MIIHPTCCBSWgAwIBAgIBADANBgkqhkiG9w0BAQQFADB5MRAwDgYDVQQKEwdSb290\n" |
| "IENBMR4wHAYDVQQLExVodHRwOi8vd3d3LmNhY2VydC5vcmcxIjAgBgNVBAMTGUNB\n" |
| "IENlcnQgU2lnbmluZyBBdXRob3JpdHkxITAfBgkqhkiG9w0BCQEWEnN1cHBvcnRA\n" |
| "Y2FjZXJ0Lm9yZzAeFw0wMzAzMzAxMjI5NDlaFw0zMzAzMjkxMjI5NDlaMHkxEDAO\n" |
| "GCSNe9FINSkYQKyTYOGWhlC0elnYjyELn8+CkcY7v2vcB5G5l1YjqrZslMZIBjzk\n" |
| "zk6q5PYvCdxTby78dOs6Y5nCpqyJvKeyRKANihDjbPIky/qbn3BHLt4Ui9SyIAmW\n" |
| "omTxJBzcoTWcFbLUvFUufQb1nA5V9FrWk9p2rSVzTMVD\n"\ |
| "-----END CERTIFICATE-----\n"; |
| /* get a BIO */ |
| bio=BIO_new_mem_buf(mypem, -1); |
| /* use it to read the PEM formatted certificate from memory into an X509 |
| * structure that SSL can use |
| */ |
| PEM_read_bio_X509(bio, &cert, 0, NULL); |
| if(cert == NULL) |
| printf("PEM_read_bio_X509 failed...\n"); |
| |
| /* get a pointer to the X509 certificate store (which may be empty!) */ |
| store=SSL_CTX_get_cert_store((SSL_CTX *)sslctx); |
| |
| /* add our certificate to this store */ |
| if(X509_STORE_add_cert(store, cert)==0) |
| printf("error adding certificate\n"); |
| |
| /* decrease reference counts */ |
| X509_free(cert); |
| BIO_free(bio); |
| |
| /* all set to go */ |
| return CURLE_OK; |
| } |
| |
| int main(void) |
| { |
| CURL * ch; |
| CURLcode rv; |
| |
| rv=curl_global_init(CURL_GLOBAL_ALL); |
| ch=curl_easy_init(); |
| rv=curl_easy_setopt(ch, CURLOPT_SSLCERTTYPE, "PEM"); |
| rv=curl_easy_setopt(ch, CURLOPT_SSL_VERIFYPEER, 1L); |
| rv=curl_easy_setopt(ch, CURLOPT_URL, "https://www.example.com/"); |
| |
| /* Retrieve page using cacerts' certificate -> will succeed |
| * load the certificate by installing a function doing the nescessary |
| * "modifications" to the SSL CONTEXT just before link init |
| */ |
| rv=curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function); |
| rv=curl_easy_perform(ch); |
| if(rv==CURLE_OK) |
| printf("*** transfer succeeded ***\n"); |
| else |
| printf("*** transfer failed ***\n"); |
| |
| curl_easy_cleanup(ch); |
| curl_global_cleanup(); |
| return rv; |
| } |
| .fi |
| .SH AVAILABILITY |
| Added in 7.11.0 for OpenSSL. Added in 7.42.0 for wolfSSL/CyaSSL. Other SSL |
| backends not supported. |
| .SH RETURN VALUE |
| Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. |
| .SH "SEE ALSO" |
| .BR CURLOPT_SSL_CTX_DATA "(3), " CURLOPT_SSL_VERIFYPEER "(3), " |