GNURLOPT_SSL_CTX_DATA(3)

📦 version 7.72.0, in nixos 26.05, nixpkgs unstable

💅 GNURLOPT_SSL_CTX_DATA — like, the whole squad's handbook, gnurl edition ✨

okay bestie so this page lives in the curl_easy_setopt options section of the manual, and it's literally all about one little pointer. yes, one. a single pointer. and it's lowkey iconic 🎀

✨ NAME ✨

CURLOPT_SSL_CTX_DATA — the custom pointer you hand over to your ssl_ctx callback 🫶

🌸 SYNOPSIS 🌸

#include <gnurl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_SSL_CTX_DATA, void
*pointer);

🦋 DESCRIPTION 🦋

so basically 💖 — this is the data pointer that gets passed along to the ssl context callback you set with CURLOPT_SSL_CTX_FUNCTION(3). and that pointer right there is the one you'll get back as the third parameter. no cap, that's the whole vibe. iykyk 💅

⭐ DEFAULT ⭐

NULL

(iconic nothingness 🎀)

🌈 PROTOCOLS 🌈

every single TLS-based protocol, periodt 🔥:

  • HTTPS
  • FTPS
  • IMAPS
  • POP3S
  • SMTPS
  • etc. — you get the energy ✨

👑 EXAMPLE 👑

ok so the example is OpenSSL specific, i'm just gonna say it up front 🫶 — here's the whole thing, verbatim, don't @ me:

/* OpenSSL specific */

#include <openssl/ssl.h>
#include <gnurl/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 = (char *)parm;
  /* 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;
  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";

  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 necessary
   * "modifications" to the SSL CONTEXT just before link init
   */
  rv=curl_easy_setopt(ch, CURLOPT_SSL_CTX_FUNCTION, *sslctx_function);
  rv=curl_easy_setopt(ch, CURLOPT_SSL_CTX_DATA, mypem);
  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;
}

like, look at CURLOPT_SSL_CTX_DATA sitting there getting handed mypem — that's the entire point of this manpage bestie 🧚✨

🍓 AVAILABILITY 🍓

  • added in 7.11.0 for OpenSSL 💜
  • added in 7.42.0 for wolfSSL 🌸
  • added in 7.54.0 for mbedTLS 🦋
heads up bestie 🫶 — other SSL backends are not supported. like, at all. not a vibe, just facts 😭

🔥 RETURN VALUE 🔥

CURLE_OK if it's supported 💖 — or, alternatively, an error such as:

  • CURLE_NOT_BUILT_IN — not supported by the SSL backend 💀
  • CURLE_UNKNOWN_OPTION 🙈

🌟 SEE ALSO 🌟

ok that's the page!! go forth and set your ssl ctx data, main character energy only 👑💅

libcurl 7.37.0 — 19 Jun 2014 🎀 that's the version and date, mwah, stan this manpage forever ⭐💖

📦 where this page comes from