Wrapping and Sending a Message

Language:

The gss-client application needs to wrap, that is, encrypt the data before the data can be sent. The application goes through the following steps to wrap the message:

Determines the wrap size limit. This process ensures that the wrapped message can be accommodated by the protocol.
Obtains the source and destination names. Translates the names from object identifiers to strings.
Gets the list of mechanism names. Translates the names from object identifiers to strings.
Inserts the message into a buffer and wraps the message.
Sends the message to the server.

The following source code wraps a message.

Example 18 gss-client Example: call_server() – Wrap Message

/* Test gss_wrap_size_limit */
maj_stat = gss_wrap_size_limit(&min_stat, context, conf_req_flag, 
    GSS_C_QOP_DEFAULT, req_output_size, &max_input_size);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("wrap_size_limit call", maj_stat, min_stat);
} else
    fprintf (stderr, "gss_wrap_size_limit returned "
        "max input size = %d \n"
        "for req_output_size = %d with Integrity only\n",
         max_input_size, req_output_size, conf_req_flag);

conf_req_flag = 1;
maj_stat = gss_wrap_size_limit(&min_stat, context, conf_req_flag,
    GSS_C_QOP_DEFAULT, req_output_size, &max_input_size);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("wrap_size_limit call", maj_stat, min_stat);
} else
    fprintf (stderr, "gss_wrap_size_limit returned "
        " max input size = %d \n" "for req_output_size = %d with "
        "Integrity & Privacy \n", max_input_size, req_output_size );

maj_stat = gss_display_name(&min_stat, src_name, &sname, &name_type);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("displaying source name", maj_stat, min_stat);
    return -1;
}

maj_stat = gss_display_name(&min_stat, targ_name, &tname, 
    (gss_OID *) NULL);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("displaying target name", maj_stat, min_stat);
    return -1;
 }
fprintf(stderr, "\"%.*s\" to \"%.*s\", lifetime %u, flags %x, %s, %s\n",
    (int) sname.length, (char *) sname.value, (int) tname.length, 
    (char *) tname.value, lifetime, context_flags,
    (is_local) ? "locally initiated" : "remotely initiated",
    (is_open) ? "open" : "closed");

(void) gss_release_name(&min_stat, &src_name);
(void) gss_release_name(&min_stat, &targ_name);
(void) gss_release_buffer(&min_stat, &sname);
(void) gss_release_buffer(&min_stat, &tname);

maj_stat = gss_oid_to_str(&min_stat, name_type, &oid_name);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("converting oid->string", maj_stat, min_stat);
    return -1;
}
fprintf(stderr, "Name type of source name is %.*s.\n", (int) oid_name.length,
    (char *) oid_name.value);
(void) gss_release_buffer(&min_stat, &oid_name);

/* Now get the names supported by the mechanism */
maj_stat = gss_inquire_names_for_mech(&min_stat, mechanism, &mech_names);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("inquiring mech names", maj_stat, min_stat);
    return -1;
}

maj_stat = gss_oid_to_str(&min_stat, mechanism, &oid_name);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("converting oid->string", maj_stat, min_stat);
    return -1;
}
mechStr = (char *)__gss_oid_to_mech(mechanism);
fprintf(stderr, "Mechanism %.*s (%s) supports %d names\n", (int) oid_name.length, 
    (char *) oid_name.value, (mechStr == NULL ? "NULL" : mechStr),
    mech_names->count);
(void) gss_release_buffer(&min_stat, &oid_name);

for (i=0; i < mech_names->count; i++) {
    maj_stat = gss_oid_to_str(&min_stat, &mech_names->elements[i], &oid_name);
    if (maj_stat != GSS_S_COMPLETE) {
        display_status("converting oid->string", maj_stat, min_stat);
        return -1;
    }
    fprintf(stderr, "  %d: %.*s\n", i, (int) oid_name.length, (
    char *) oid_name.value);

    (void) gss_release_buffer(&min_stat, &oid_name);
    }
(void) gss_release_oid_set(&min_stat, &mech_names);

if (use_file) {
    read_file(msg, &in_buf);
} else {
    /* Wrap the message */
    in_buf.value = msg;
    in_buf.length = strlen(msg) + 1;
}

if (ret_flag & GSS_C_CONF_FLAG) {
    state = 1;
else
    state = 0;
}
maj_stat = gss_wrap(&min_stat, context, 1, GSS_C_QOP_DEFAULT, &in_buf, 
    &state, &out_buf);
if (maj_stat != GSS_S_COMPLETE) {
    display_status("wrapping message", maj_stat, min_stat);
    (void) close(s);
    (void) gss_delete_sec_context(&min_stat, &context, GSS_C_NO_BUFFER);
    return -1;
} else if (! state) {
    fprintf(stderr, "Warning!  Message not encrypted.\n");
}

/* Send to server */
if (send_token(s, &out_buf) < 0) {
    (void) close(s);
    (void) gss_delete_sec_context(&min_stat, &context, GSS_C_NO_BUFFER);
    return -1;
}
(void) gss_release_buffer(&min_stat, &out_buf);