ne_ssl_set_verify - Man Page

register an SSL certificate verification callback


#include <ne_session.h>

typedef int ne_ssl_verify_fn(void *userdata, int failures, const ne_ssl_certificate *cert);

void ne_ssl_set_verify(ne_session *session, ne_ssl_verify_fn verify_fn, void *userdata);


To enable manual SSL certificate verification, a callback can be registered using ne_ssl_set_verify. If such a callback is not registered, when a connection is established to an SSL server which does not present a certificate signed by a trusted CA (see ne_ssl_trust_cert), or if the certificate presented is invalid in some way, the connection will fail.

When the callback is invoked, the failures parameter gives a bitmask indicating in what way the automatic certificate verification failed. The value is equal to the bit-wise OR of one or more of the following constants (and is guaranteed to be non-zero):


The certificate is not yet valid.


The certificate has expired.


The hostname used for the session does not match the hostname to which the certificate was issued.


The Certificate Authority which signed the certificate is not trusted.

Note that if either of the NE_SSL_IDMISMATCH or NE_SSL_UNTRUSTED failures is given, the connection may have been intercepted by a third party, and must not be presumed to be “secure”.

The cert parameter passed to the callback represents the certificate which was presented by the server. If the server presented a chain of certificates, the chain can be accessed using ne_ssl_cert_signedby. The cert object given is not valid after the callback returns.

Return Value

The verification callback must return zero to indicate that the certificate should be trusted; and non-zero otherwise (in which case, the connection will fail).


The following code implements an example verification callback, using the dump_cert function from ne_ssl_cert_subject to display certification information. Notice that the hostname of the server used for the session is passed as the userdata parameter to the callback.

static int
my_verify(void *userdata, int failures, const ne_ssl_certificate *cert)
  const char *hostname = userdata;


  puts("Certificate verification failed - the connection may have been "
       "intercepted by a third party!");

  if (failures & NE_SSL_IDMISMATCH) { 
    const char *id = ne_ssl_cert_identity(cert);
    if (id) 
      printf("Server certificate was issued to '%s' not '%s'.\n",
             id, hostname);
      printf("The certificate was not issued for '%s'\n", hostname);

  if (failures & NE_SSL_UNTRUSTED)
    puts("The certificate is not signed by a trusted Certificate Authority.");

  /* ... check for validity failures ... */

  if (prompt_user())
    return 1; /* fail verification */
    return 0; /* trust the certificate anyway */

  ne_session *sess = ne_session_create("https", "", 443);
  ne_ssl_set_verify(sess, my_verify, "");

See Also

ne_ssl_trust_cert, ne_ssl_readable_dname, ne_ssl_cert_subject


Joe Orton



29 January 2024 neon 0.33.0 neon API reference