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ne_ssl_set_verify(3)

neon 0.30.2
30 September 2016

libneon27-dev

Header and static library files for libneon27

libneon27-gnutls-dev

Header and static library files for libneon27 (GnuTLS enabled)

neon-devel

Development libraries and C header files for the neon library

neon

HTTP and WebDAV client library with a C interface

libneon-devel

An HTTP and WebDAV Client Library

NAME

ne_ssl_set_verify - register an SSL certificate verification callback

SYNOPSIS


#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);

DESCRIPTION

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):
NE_SSL_NOTYETVALID
The certificate is not yet valid.
NE_SSL_EXPIRED
The certificate has expired.
NE_SSL_IDMISMATCH
The hostname used for the session does not match the hostname to which the certificate was issued.
NE_SSL_UNTRUSTED
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 \(lqsecure\(rq.
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).

EXAMPLES

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;

dump_cert(cert);
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); else 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 */ else return 0; /* trust the certificate anyway */ }
int main(...) { ne_session *sess = ne_session_create("https", "some.host.name", 443); ne_ssl_set_verify(sess, my_verify, "some.host.name"); ... }

SEE ALSO

ne_ssl_trust_cert, ne_ssl_readable_dname, ne_ssl_cert_subject

AUTHOR

Joe Orton <>
Author.

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