Miscellaneous GSS-API Sample Functions

To make the client and server programs work as shown, a number of other functions are required. These functions are used to display values. The functions are not otherwise needed. The functions in this category are as follows:

• send_token() – Transfers tokens and messages to a recipient

• recv_token() – Accepts tokens and messages from a sender

• display_status() – Shows the status returned by the last GSS-API function called

• write_all() – Writes a buffer to a file

• read_all() – Reads a file into a buffer

• display_ctx_flags() – Shows in a readable form information about the current context, such as whether confidentiality or mutual authentication is allowed

• print_token() – Prints out a token's value

The code for these functions is shown in the following example.

Example A-3 Code Listings for Miscellaneous GSS-API Functions

/*
 * Copyright 1994 by OpenVision Technologies, Inc.
 * 
 * Permission to use, copy, modify, distribute, and sell this software
 * and its documentation for any purpose is hereby granted without fee,
 * provided that the above copyright notice appears in all copies and
 * that both that copyright notice and this permission notice appear in
 * supporting documentation, and that the name of OpenVision not be used
 * in advertising or publicity pertaining to distribution of the software
 * without specific, written prior permission. OpenVision makes no
 * representations about the suitability of this software for any
 * purpose.  It is provided "as is" without express or implied warranty.
 * 
 * OPENVISION DISCLAIMS ALL WARRANTIES WITH REGARD TO THIS SOFTWARE,
 * INCLUDING ALL IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS, IN NO
 * EVENT SHALL OPENVISION BE LIABLE FOR ANY SPECIAL, INDIRECT OR
 * CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER RESULTING FROM LOSS OF
 * USE, DATA OR PROFITS, WHETHER IN AN ACTION OF CONTRACT, NEGLIGENCE OR
 * OTHER TORTIOUS ACTION, ARISING OUT OF OR IN CONNECTION WITH THE USE OR
 * PERFORMANCE OF THIS SOFTWARE.
 */

#if !defined(lint) && !defined(__CODECENTER__)
static char *rcsid = "$Header: /cvs/krbdev/krb5/src/appl/gss-sample/\
    gss-misc.c, v 1.15 1996/07/22 20:21:20 marc Exp $";
#endif

#include <stdio.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <errno.h>
#include <unistd.h>
#include <string.h>

#include <gssapi/gssapi.h>
#include <gssapi/gssapi_ext.h>
#include <gss-misc.h>

#include <stdlib.h>

FILE *display_file;

static void display_status_1
        (char *m, OM_uint32 code, int type);

static int write_all(int fildes, char *buf, unsigned int nbyte)
{
     int ret;
     char *ptr;

     for (ptr = buf; nbyte; ptr += ret, nbyte -= ret) {
          ret = write(fildes, ptr, nbyte);
          if (ret < 0) {
               if (errno == EINTR)
                    continue;
               return(ret);
          } else if (ret == 0) {
               return(ptr-buf);
          }
     }

     return(ptr-buf);
}

static int read_all(int fildes, char *buf, unsigned int nbyte)
{
     int ret;
     char *ptr;

     for (ptr = buf; nbyte; ptr += ret, nbyte -= ret) {
          ret = read(fildes, ptr, nbyte);
          if (ret < 0) {
               if (errno == EINTR)
                    continue;
               return(ret);
          } else if (ret == 0) {
               return(ptr-buf);
          }
     }

     return(ptr-buf);
}

/*
 * Function: send_token
 *
 * Purpose: Writes a token to a file descriptor.
 *
 * Arguments:
 *
 *      s               (r) an open file descriptor
 *      tok             (r) the token to write
 *
 * Returns: 0 on success, -1 on failure
 *
 * Effects:
 *
 * send_token writes the token length (as a network long) and then the
 * token data to the file descriptor s.  It returns 0 on success, and
 * -1 if an error occurs or if it could not write all the data.
 */
int send_token(s, tok)
     int s;
     gss_buffer_t tok;
{
     int len, ret;

     len = htonl(tok->length);

     ret = write_all(s, (char *) &len, 4);
     if (ret < 0) {
          perror("sending token length");
          return -1;
     } else if (ret != 4) {
         if (display_file)
             fprintf(display_file, 
                     "sending token length: %d of %d bytes written\n", 
                     ret, 4);
          return -1;
     }

     ret = write_all(s, tok->value, tok->length);
     if (ret < 0) {
          perror("sending token data");
          return -1;
     } else if (ret != tok->length) {
         if (display_file)
             fprintf(display_file, 
                     "sending token data: %d of %d bytes written\n", 
                     ret, tok->length);
         return -1;
     }
     
     return 0;
}

/*
 * Function: recv_token
 *
 * Purpose: Reads a token from a file descriptor.
 *
 * Arguments:
 *
 *      s               (r) an open file descriptor
 *      tok             (w) the read token
 *
 * Returns: 0 on success, -1 on failure
 *
 * Effects:
 * 
 * recv_token reads the token length (as a network long), allocates
 * memory to hold the data, and then reads the token data from the
 * file descriptor s.  It blocks to read the length and data, if
 * necessary.  On a successful return, the token should be freed with
 * gss_release_buffer.  It returns 0 on success, and -1 if an error
 * occurs or if it could not read all the data.
 */
int recv_token(s, tok)
     int s;
     gss_buffer_t tok;
{
     int ret;

     ret = read_all(s, (char *) &tok->length, 4);
     if (ret < 0) {
          perror("reading token length");
          return -1;
     } else if (ret != 4) {
         if (display_file)
             fprintf(display_file, 
                     "reading token length: %d of %d bytes read\n", 
                     ret, 4);
         return -1;
     }
          
     tok->length = ntohl(tok->length);
     tok->value = (char *) malloc(tok->length);
     if (tok->value == NULL) {
         if (display_file)
             fprintf(display_file, 
                     "Out of memory allocating token data\n");
          return -1;
     }

     ret = read_all(s, (char *) tok->value, tok->length);
     if (ret < 0) {
          perror("reading token data");
          free(tok->value);
          return -1;
     } else if (ret != tok->length) {
          fprintf(stderr, "sending token data: %d of %d bytes written\n", 
                  ret, tok->length);
          free(tok->value);
          return -1;
     }

     return 0;
}

static void display_status_1(m, code, type)
     char *m;
     OM_uint32 code;
     int type;
{
     OM_uint32 maj_stat, min_stat;
     gss_buffer_desc msg;
     OM_uint32 msg_ctx;
     
     msg_ctx = 0;
     while (1) {
          maj_stat = gss_display_status(&min_stat, code,
                                       type, GSS_C_NULL_OID,
                                       &msg_ctx, &msg);
          if (display_file)
              fprintf(display_file, "GSS-API error %s: %s\n", m,
                      (char *)msg.value); 
          (void) gss_release_buffer(&min_stat, &msg);
          
          if (!msg_ctx)
               break;
     }
}

/*
 * Function: display_status
 *
 * Purpose: displays GSS-API messages
 *
 * Arguments:
 *
 *      msg             a string to be displayed with the message
 *      maj_stat        the GSS-API major status code
 *      min_stat        the GSS-API minor status code
 *
 * Effects:
 *
 * The GSS-API messages associated with maj_stat and min_stat are
 * displayed on stderr, each preceded by "GSS-API error <msg>: " and
 * followed by a newline.
 */
void display_status(msg, maj_stat, min_stat)
     char *msg;
     OM_uint32 maj_stat;
     OM_uint32 min_stat;
{
     display_status_1(msg, maj_stat, GSS_C_GSS_CODE);
     display_status_1(msg, min_stat, GSS_C_MECH_CODE);
}

/*
 * Function: display_ctx_flags
 *
 * Purpose: displays the flags returned by context initiation in
 *          a human-readable form
 *
 * Arguments:
 *
 *      int             ret_flags
 *
 * Effects:
 *
 * Strings corresponding to the context flags are printed on
 * stdout, preceded by "context flag: " and followed by a newline
 */

void display_ctx_flags(flags)
     OM_uint32 flags;
{
     if (flags & GSS_C_DELEG_FLAG)
          fprintf(display_file, "context flag: GSS_C_DELEG_FLAG\n");
     if (flags & GSS_C_MUTUAL_FLAG)
          fprintf(display_file, "context flag: GSS_C_MUTUAL_FLAG\n");
     if (flags & GSS_C_REPLAY_FLAG)
          fprintf(display_file, "context flag: GSS_C_REPLAY_FLAG\n");
     if (flags & GSS_C_SEQUENCE_FLAG)
          fprintf(display_file, "context flag: GSS_C_SEQUENCE_FLAG\n");
     if (flags & GSS_C_CONF_FLAG )
          fprintf(display_file, "context flag: GSS_C_CONF_FLAG \n");
     if (flags & GSS_C_INTEG_FLAG )
          fprintf(display_file, "context flag: GSS_C_INTEG_FLAG \n");
}

void print_token(tok)
     gss_buffer_t tok;
{
    int i;
    unsigned char *p = tok->value;

    if (!display_file)
        return;
    for (i=0; i < tok->length; i++, p++) {
        fprintf(display_file, "%02x ", *p);
        if ((i % 16) == 15) {
            fprintf(display_file, "\n");
        }
    }
    fprintf(display_file, "\n");
    fflush(display_file);
}