1 files changed, 100 insertions, 0 deletions
diff --git a/doc/examples/ex-verify-ssh.c b/doc/examples/ex-verify-ssh.c
new file mode 100644
index 0000000..a2af8e5
--- /dev/null
+++ b/doc/examples/ex-verify-ssh.c
@@ -0,0 +1,100 @@
+/* This example code is placed in the public domain. */
+
+#ifdef HAVE_CONFIG_H
+#include <config.h>
+#endif
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <gnutls/gnutls.h>
+#include <gnutls/x509.h>
+#include <assert.h>
+#include "examples.h"
+
+#define CHECK(x) assert((x)>=0)
+
+/* This function will verify the peer's certificate, check
+ * if the hostname matches. In addition it will perform an
+ * SSH-style authentication, where ultimately trusted keys
+ * are only the keys that have been seen before.
+ */
+int _ssh_verify_certificate_callback(gnutls_session_t session)
+{
+        unsigned int status;
+        const gnutls_datum_t *cert_list;
+        unsigned int cert_list_size;
+        int ret, type;
+        gnutls_datum_t out;
+        const char *hostname;
+
+        /* read hostname */
+        hostname = gnutls_session_get_ptr(session);
+
+        /* This verification function uses the trusted CAs in the credentials
+         * structure. So you must have installed one or more CA certificates.
+         */
+        CHECK(gnutls_certificate_verify_peers3(session, hostname, &status));
+
+        type = gnutls_certificate_type_get(session);
+
+        CHECK(gnutls_certificate_verification_status_print(status,
+                                                           type, &out, 0));
+        printf("%s", out.data);
+
+        gnutls_free(out.data);
+
+        if (status != 0)        /* Certificate is not trusted */
+                return GNUTLS_E_CERTIFICATE_ERROR;
+
+        /* Do SSH verification */
+        cert_list = gnutls_certificate_get_peers(session, &cert_list_size);
+        if (cert_list == NULL) {
+                printf("No certificate was found!\n");
+                return GNUTLS_E_CERTIFICATE_ERROR;
+        }
+
+        /* service may be obtained alternatively using getservbyport() */
+        ret = gnutls_verify_stored_pubkey(NULL, NULL, hostname, "https",
+                                          type, &cert_list[0], 0);
+        if (ret == GNUTLS_E_NO_CERTIFICATE_FOUND) {
+                printf("Host %s is not known.", hostname);
+                if (status == 0)
+                        printf("Its certificate is valid for %s.\n",
+                               hostname);
+
+                /* the certificate must be printed and user must be asked on
+                 * whether it is trustworthy. --see gnutls_x509_crt_print() */
+
+                /* if not trusted */
+                return GNUTLS_E_CERTIFICATE_ERROR;
+        } else if (ret == GNUTLS_E_CERTIFICATE_KEY_MISMATCH) {
+                printf
+                    ("Warning: host %s is known but has another key associated.",
+                     hostname);
+                printf
+                    ("It might be that the server has multiple keys, or you are under attack\n");
+                if (status == 0)
+                        printf("Its certificate is valid for %s.\n",
+                               hostname);
+
+                /* the certificate must be printed and user must be asked on
+                 * whether it is trustworthy. --see gnutls_x509_crt_print() */
+
+                /* if not trusted */
+                return GNUTLS_E_CERTIFICATE_ERROR;
+        } else if (ret < 0) {
+                printf("gnutls_verify_stored_pubkey: %s\n",
+                       gnutls_strerror(ret));
+                return ret;
+        }
+
+        /* user trusts the key -> store it */
+        if (ret != 0) {
+                CHECK(gnutls_store_pubkey(NULL, NULL, hostname, "https",
+                                          type, &cert_list[0], 0, 0));
+        }
+
+        /* notify gnutls to continue handshake normally */
+        return 0;
+}