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do_author.c

/* 
   Copyright (c) 1995-2000 by Cisco systems, Inc.

   Permission to use, copy, modify, and distribute modified and
   unmodified copies of this software for any purpose and without fee is
   hereby granted, provided that (a) this copyright and permission notice
   appear on all copies of the software and supporting documentation, (b)
   the name of Cisco Systems, Inc. not be used in advertising or
   publicity pertaining to distribution of the program without specific
   prior permission, and (c) notice be given in supporting documentation
   that use, modification, copying and distribution is by permission of
   Cisco Systems, Inc.

   Cisco Systems, Inc. makes no representations about the suitability
   of this software for any purpose.  THIS SOFTWARE IS PROVIDED ``AS
   IS'' AND WITHOUT ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING,
   WITHOUT LIMITATION, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND
   FITNESS FOR A PARTICULAR PURPOSE.
*/

#include "tac_plus.h"
#include "regexp.h"

static int get_nas_svc();
static int authorize_cmd();
static int authorize_exec();
static int authorize_svc();
static void post_authorization();
static int pre_authorization();

/* Return 0 is data->status is valid */
int
do_author(data)
struct author_data *data;
{
    char *username = data->id->username;
    int status;
    int svc;
    char *cmd, *protocol, *svcname;
    
    protocol = NULL;

    data->status = AUTHOR_STATUS_FAIL;    /* for safety */

    data->output_args = NULL;
    data->num_out_args = 0;

    /* If this user doesn't exist in our configs, do the default */

    if (!cfg_user_exists(username) && !cfg_user_exists(DEFAULT_USERNAME)) {
      
      if (cfg_no_user_permitted()) {
          if (debug & DEBUG_AUTHOR_FLAG)
            report(LOG_DEBUG, 
                   "user '%s' or '%s' not found, permitted by default", 
                   username, DEFAULT_USERNAME);

          data->status = AUTHOR_STATUS_PASS_ADD;
          data->output_args = NULL;
          data->num_out_args = 0;
          return (0);
      }

      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, 
               "user '%s' or '%s' not found, denied by default", 
               username, DEFAULT_USERNAME);
      data->status = AUTHOR_STATUS_FAIL;
      return (0);
    }

    if (!cfg_user_exists(username) && cfg_user_exists(DEFAULT_USERNAME)) {
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "Authorizing user '%s' instead of '%s'", 
               DEFAULT_USERNAME, username);
      }
      username = DEFAULT_USERNAME;
    }

    /* See if there's a program defined which will do authorization for us */
    if (pre_authorization(username, data)) 
      return(0);
    
    /* 
     * Decide what kind of authorization request this is. Currently
     * one of: exec, cmd, slip, arap, ppp or <string>
     * 
     * If it's a command typed to the exec, return its text in cmd.
     * 
     * If it's a ppp request, return the protocol name in protocol.
     */

    svc = get_nas_svc(data, &cmd, &protocol, &svcname);

    if (!svc) {
      /* if we can't identify the service in the request it's an error */
      data->status = AUTHOR_STATUS_ERROR;
      data->admin_msg =
        tac_strdup("No identifiable service/protocol in authorization request");
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "user %s %s", username, data->admin_msg);
      }
      return (0);
    }

    if (debug & DEBUG_AUTHOR_FLAG)
      report(LOG_DEBUG, "user '%s' found", username);

#ifdef MAXSESS
    /* Never permit if they're going over their session limit */
    switch (svc) {
    case N_svc_arap:
    case N_svc_ppp:
    case N_svc_slip:
    case N_svc_exec:
/*    case N_svc: */
      if (maxsess_check_count(username, data)) {
          return(0);
      }

    default:
      break;
    }
#endif /* MAXSESS */

    switch(svc) {
    default:
      report(LOG_ERR, "%s: Bad service type %d", session.peer, svc);
      data->status = AUTHOR_STATUS_FAIL;
      return(0);

    case N_svc_cmd:
      /* A command authorisation request */
      status = authorize_cmd(username, cmd, data);
      break;
 
    case N_svc_exec:
      if (authorize_exec(username, data)) 
          return(0);
      /* FALLTHRU */

    case N_svc_arap:
    case N_svc_ppp:
    case N_svc_slip:
      status = authorize_svc(username, svc, protocol, NULL, data);
      break;

    case N_svc:
      status = authorize_svc(username, svc, protocol, svcname, data);
      break;
    }

    post_authorization(username, data);
    return(status);    
}

/* If an before-authorization program has been specified, call it. 

   A return value of 1 means no further authorization is required
*/

static int
pre_authorization(username, data) 
char *username;
struct author_data *data;
{
    int status;
    char **out_args;
    int out_cnt, i;
    char *cmd;
    char error_str[255];
    int error_len = 255;

    out_cnt = 0;
    out_args = NULL;

    /* If a before-authorization program exists, call it to see how to
       proceed */

    cmd = cfg_get_pvalue(username, TAC_IS_USER, 
                   S_before, TAC_PLUS_RECURSE);
    if (!cmd) 
      return(0);

    if (debug & DEBUG_AUTHOR_FLAG)
      report(LOG_DEBUG, "Before authorization call: %s", cmd);

    status = call_pre_process(cmd, data, &out_args, &out_cnt, error_str,
                        error_len);

    switch (status) {
    default:
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "cmd %s returns %d (unrecognised value)", 
               cmd, status);

      data->status = AUTHOR_STATUS_ERROR;
      data->admin_msg = 
          tac_strdup("Illegal return status from pre-authorization command");
      data->msg = tac_strdup(error_str);
      data->num_out_args = 0;
      data->output_args = NULL;
      /* throw away out_args */
      for(i=0; i < out_cnt; i++) {
          free(out_args[i]);
      }
      if (out_args) {
          free(out_args);
      }
      return(1);

    case 0: /* Permit */
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "cmd %s returns 0 (unconditional permit)", cmd);

      data->status = AUTHOR_STATUS_PASS_ADD;
      data->num_out_args = 0;
      data->output_args = NULL;

      /* throw away out_args */
      for(i=0; i < out_cnt; i++) {
          free(out_args[i]);
      }
      if (out_args) {
          free(out_args);
      }
      return(1);
          
    case 1: /* Deny */
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "cmd %s returns %d (unconditional deny)", 
               cmd, status);

      data->status = AUTHOR_STATUS_FAIL;
      data->msg = tac_strdup(error_str);
      data->num_out_args = 0;
      data->output_args = NULL;

      /* throw away out_args */
      for(i=0; i < out_cnt; i++) {
          free(out_args[i]);
      }
      if (out_args) {
          free(out_args);
      }
      return(1);

    case 2: /* Use replacement AV pairs from program as final result */
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "cmd %s returns %d (permitted, args replaced)", 
               cmd, status);
          for(i=0; i < out_cnt; i++)
            report(LOG_DEBUG, "%s", out_args[i]); 
      }

      /* and install the new set of AV pairs as output */
      data->output_args = out_args;
      data->num_out_args = out_cnt;
      data->status = AUTHOR_STATUS_PASS_REPL;
      return(1); /* no more processing required */

    case 3: /* deny, but return attributes and server-msg to NAS */
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "cmd %s returns %d (deny, args replaced)", 
               cmd, status);
          for(i=0; i < out_cnt; i++)
            report(LOG_DEBUG, "%s", out_args[i]); 
      }

      /* and install the new set of AV pairs as output */
      data->output_args = out_args;
      data->num_out_args = out_cnt;
      data->msg = tac_strdup(error_str);
      data->status = AUTHOR_STATUS_FAIL;
      return(1); /* no more processing required */
    }
}

/* If an after-authorization program has been specified, call it. It
   can rewrite the output arguments in the authorization data, or
   change the authorization status by calling an external program.
*/

static void
post_authorization(username, data) 
    char *username;
    struct author_data *data;
{
    char **out_args;
    int out_cnt, i;
    int status;
    char *after = cfg_get_pvalue(username, TAC_IS_USER, 
                        S_after, TAC_PLUS_RECURSE);
    if (!after) 
      return;

    if (debug & DEBUG_AUTHOR_FLAG)
      report(LOG_DEBUG, "After authorization call: %s", after);

    status = call_post_process(after, data, &out_args, &out_cnt);

    if (status != 2) {
      /* throw away out_args */
      for(i=0; i < out_cnt; i++) {
          free(out_args[i]);
      }
      free(out_args);
    }

    switch (status) {
    default:
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, 
               "cmd %s returns %d (Error)", after, status);

      data->status = AUTHOR_STATUS_ERROR;
      return;

    case 0:                   /* Permit */
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "cmd %s returns 0 (no change)", after);
      return;
          
    case 1:                   /* Deny */
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "cmd %s returns %d (unconditional deny)", 
               after, status);

      data->status = AUTHOR_STATUS_FAIL;
      return;

    case 2:
      /* Use replacement AV pairs from program */
      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "cmd %s returns 2 (replace & continue)", 
               after);

      /* Free any existing AV output pairs */
      if (data->num_out_args) {
          for(i=0; i < data->num_out_args; i++) {
            free(data->output_args[i]);
          }
          free(data->output_args);
          data->output_args = NULL;
      }

      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "status is now AUTHOR_STATUS_PASS_REPL");
      }

      data->status = AUTHOR_STATUS_PASS_REPL;
      data->output_args = out_args;
      data->num_out_args = out_cnt;
      return;
    }
}


/* Return a pointer to the value part of an attr=value string */
static char *
value(s)
char *s;
{
    while (*s && *s != '=' && *s != '*')
      s++;
    if (*s)
      return (++s);
    return (NULL);
}

/* Reassemble the command arguments as typed by the user, out of the
   array of args we received. Return "" if there are no arguments */

static char *
assemble_args(data)
struct author_data *data;
{
    char *buf;
    int i;
    char *nas_arg, *v;
    int len;

    len = 0;
    for (i = 0; i < data->num_in_args; i++) {
      nas_arg = data->input_args[i];
      if (strncmp(nas_arg, "cmd-arg", strlen("cmd-arg"))==0)
          len += strlen(value(nas_arg)) + 1;
    }

    if (len <= 0) {
      return(tac_strdup(""));
    }

    buf = tac_malloc(len);
    buf[0] = '\0';

    for (i = 0; i < data->num_in_args; i++) {
      nas_arg = data->input_args[i];
      if (strncmp(nas_arg, "cmd-arg", strlen("cmd-arg")))
          continue;

      v = value(nas_arg);
      if (!v) {
          free(buf);
          return (NULL);
      }
      strcat(buf, v);
      if (i < (data->num_in_args - 1))
          strcat(buf, " ");
    }
    return (buf);
}


/* See if an exec is authorized. Either the user has explicitly
   authorized the exec, or she has authorized some commands (which
   implicitly authorizes an exec), or the default is permit.

   If she has explicitly authorized an exec, we need to process its
   attribute=value pairs. We indicate this by returning zero to the
   caller.

   Otherwise, we return 1, indicating no further processing is
   required for this request. */

static int
authorize_exec(user, data)
char *user;
struct author_data *data;
{
    NODE *svc;

    if (debug & DEBUG_AUTHOR_FLAG) 
      report(LOG_DEBUG, "exec authorization request for %s", user);

    /* Is an exec explicitly configured? If so, return 0 so we know to
       process its attributes */

    svc = cfg_get_svc_node(user, N_svc_exec, NULL, NULL, TAC_PLUS_RECURSE);
    if (svc) {
      if (debug & DEBUG_AUTHOR_FLAG) 
          report(LOG_DEBUG, "exec is explicitly permitted by line %d",
               svc->line);
      return (0);
    }

    /* No exec is configured. Are any commands configured? */
    svc = cfg_get_svc_node(user, N_svc_cmd, NULL, NULL, TAC_PLUS_RECURSE);
    if (svc) {
      if (debug & DEBUG_AUTHOR_FLAG) 
          report(LOG_DEBUG, "exec permitted because commands are configured");

      data->status = AUTHOR_STATUS_PASS_ADD;
      data->output_args = NULL;
      data->num_out_args = 0;
      return (1);
    }

    /* No exec or commands configured. What's the default? */
    if (cfg_user_svc_default_is_permit(user)) {

      if (debug & DEBUG_AUTHOR_FLAG) 
          report(LOG_DEBUG, "exec permitted by default");

      data->status = AUTHOR_STATUS_PASS_ADD;
      data->output_args = NULL;
      data->num_out_args = 0;
      return (1);
    }

    if (debug & DEBUG_AUTHOR_FLAG) 
      report(LOG_DEBUG, "exec denied by default");

    data->status = AUTHOR_STATUS_FAIL;
    data->num_out_args = 0;
    return(1);
}

/* Is an exec command authorized per our database(s)?  
   Return 0 if status is valid */

static int
authorize_cmd(user, cmd, data)
char *user, *cmd;
struct author_data *data;
{
    NODE *node;
    char *args;
    int match;

    args = assemble_args(data);

    if (!cmd) {
      data->status = AUTHOR_STATUS_ERROR;
      data->admin_msg = tac_strdup("No command found");
      report(LOG_ERR, "%s: %s %s", session.peer, cmd, data->admin_msg);
      data->num_out_args = 0;
      return (0);
    }

    node = cfg_get_cmd_node(user, cmd, TAC_PLUS_RECURSE);

    /* The command does not exist. Do the default */
    if (!node) {

      if (cfg_user_svc_default_is_permit(user)) {

          if (debug & DEBUG_AUTHOR_FLAG) 
            report(LOG_DEBUG, "cmd %s does not exist, permitted by default",
                   cmd);
          
          data->status = AUTHOR_STATUS_PASS_ADD;
          data->num_out_args = 0;
          if (args)
            free(args);
          return(0);
      }

      if (debug & DEBUG_AUTHOR_FLAG) 
          report(LOG_DEBUG, "cmd %s does not exist, denied by default",
               cmd);

      data->status = AUTHOR_STATUS_FAIL;
      data->num_out_args = 0;
      if (args)
          free(args);
      return(0);
    }

    /* The command exists. The default if nothing matches is DENY */
    data->status = AUTHOR_STATUS_FAIL;
    data->num_out_args = 0;

    for (node=node->value1; node && args; node = node->next) {
      match = regexec((regexp *) node->value1, args);

      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_INFO, "line %d compare %s %s '%s' & '%s' %smatch",
               node->line, cmd,
               node->type == N_permit ? "permit" : "deny",
               node->value, args, (match ? "" : "no "));
      }

      if (!match)
          continue;

      switch (node->type) {
      case N_permit:
          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, "%s %s permitted by line %d", 
                   cmd, args, node->line);
          }
          data->status = AUTHOR_STATUS_PASS_ADD;
          data->num_out_args = 0;
          break;
      case N_deny:
          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, "%s %s denied by line %d", 
                   cmd, args, node->line);
          }
          data->status = AUTHOR_STATUS_FAIL;
          data->num_out_args = 0;
          break;
      default:
          data->status = AUTHOR_STATUS_ERROR;
          data->admin_msg = tac_strdup("Server error illegal configuration node");
          report(LOG_ERR, "%s: %s %s %s", 
               session.peer, cmd, args, data->admin_msg);
          break;
      }
      if (args)
          free(args);
      args = NULL;
      return (0);
    }
    if (args)
      free(args);
    return (0);
}

static int
is_separator(ch)
char ch;
{
    return (ch == '=' || ch == '*');
}

/* check an attr=value pair for well-formedness */
static int
arg_ok(arg)
char *arg;
{
    char *p = arg;

    /* It must contain an attribute */
    if (!*p)
      return(0);

    for(p=arg; *p; p++) {
      if (is_separator(*p)) {
          if (p == arg) /* no attribute */
            return(0);
          return(1);
      }
    }
    /* no separator */
    return(0);
}


/* return 1 if attrs match, 0 otherwise */
static int
match_attrs(nas_arg, server_arg)
char *nas_arg, *server_arg;
{
    while (*nas_arg && *server_arg) {
      if (is_separator(*nas_arg) && is_separator(*server_arg)) {
          return (1);
      }
      if (*nas_arg != *server_arg)
          return (0);
      nas_arg++;
      server_arg++;
    }
    return (0);
}

/* return 1 if values match, 0 otherwise */
static int
match_values(nas_arg, server_arg)
char *nas_arg, *server_arg;
{
    while (*nas_arg && 
         *server_arg &&
         !is_separator(*nas_arg)) {
      nas_arg++;
      server_arg++;
    }

    if (!*nas_arg)
      return(0);

    /* skip separator */
    nas_arg++;
    if (*server_arg)
      server_arg++;
    
    /* compare values */
    return(STREQ(nas_arg, server_arg));
}

/* Return 1 if arg is mandatory, 0 otherwise */
static int
mandatory(arg)
char *arg;
{
    char *p = arg;

    while (*p && !is_separator(*p))
      p++;

    /* if we're not at the end, this must be the separator */
    if (*p && !is_separator(*p)) {
      report(LOG_ERR, "%s: Error on arg %s cannot find separator", 
             session.peer, arg);
      return (0);
    }
    return (*p == '=');
}

static int
optional(arg)
char *arg;
{
    return (!mandatory(arg));
}

/* PPP-LCP requests are a special case. If they are not explicitly
   configured, but there are other ppp services explicitly configured,
   we admit (return 0) any PPP-LCP request */

static int 
ppp_lcp_allowed(svc, protocol, user)
    int svc;
    char *user, *protocol;
{
    /* This is not a ppp/lcp request. Just Say No */
    if (!(svc == N_svc_ppp &&
        protocol &&
        STREQ(protocol, "lcp")))
      return(0);

    /* It is an LCP request. Are there PPP services configured */
    if (cfg_ppp_is_configured(user, TAC_PLUS_RECURSE)) {
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, 
               "ppp/lcp request permitted (ppp is configured for %s)",
               user);
      }
      return(1);
    }
    
    /* It is an LCP request but no PPP services are configured */
    if (debug & DEBUG_AUTHOR_FLAG) {
      report(LOG_DEBUG, "ppp/lcp request denied (ppp not configured for %s)",
             user);
    }
    return(0);
}

/* Return 0 means data->status is valid */
static int
authorize_svc(user, svc, protocol, svcname, data)
    char *user;
    int svc;
    char *svcname;
    struct author_data *data;
    char *protocol; /* valid only if svc == ppp */
{
    int max_args;
    char **out_args, **outp;
    char *nas_arg, *cfg_arg;
    int i, j;
    char **cfg_args;
    char **cfg_argp;
    int deny_by_default;
    NODE *node;

    int replaced = 0;
    int added = 0;
    int cfg_cnt;

    /* Does this service exist? */
    node = cfg_get_svc_node(user, svc, protocol, svcname, TAC_PLUS_RECURSE);

    if (!node) {
      /* Service not found. If the default is permit, or this is an
         PPP/LCP request and other ppp services are configured,
         we'll allow it. */

      if (cfg_user_svc_default_is_permit(user)) {

          if (debug & DEBUG_AUTHOR_FLAG)
            report(LOG_DEBUG, 
             "svc=%s protocol=%s svcname=%s not found, permitted by default", 
                   cfg_nodestring(svc), 
                   protocol ? protocol : "",
                   svcname ? svcname : "");

          data->status = AUTHOR_STATUS_PASS_ADD;
          data->num_out_args = 0;
          data->output_args = NULL;
          return(0);
      }

      if (ppp_lcp_allowed(svc, protocol, user)) {
          data->status = AUTHOR_STATUS_PASS_ADD;
          data->num_out_args = 0;
          data->output_args = NULL;
          return(0);
      }

      if (debug & DEBUG_AUTHOR_FLAG)
          report(LOG_DEBUG, "svc=%s protocol=%s not found, denied by default",
               cfg_nodestring(svc), protocol ? protocol : "");

      data->status = AUTHOR_STATUS_FAIL;
      data->num_out_args = 0;
      data->output_args = NULL;
      return(0);
    }
    
    /* Get server args configured in the config file. */
    cfg_args = cfg_get_svc_attrs(node, &deny_by_default);

    /* Check the nas args for well-formedness */
    for (i = 0; i < data->num_in_args; i++) {
      if (!arg_ok(data->input_args[i])) {
          char buf[MAX_INPUT_LINE_LEN+50];
          sprintf(buf, "Illegal arg %s from NAS", data->input_args[i]);
          data->status = AUTHOR_STATUS_ERROR;
          data->admin_msg = tac_strdup(buf);
          report(LOG_ERR, "%s: Error %s", session.peer, buf);

          /* free any server arguments */
          for(cfg_argp = cfg_args; cfg_args && *cfg_argp; cfg_argp++)
            free(*cfg_argp);
          free(cfg_args);
          return (0);
      }
    }

    /* How many configured AV pairs are there ? */
    for (cfg_cnt = 0; cfg_args && cfg_args[cfg_cnt];)
      cfg_cnt++;

    /* Allocate space for in + out args */
    max_args = cfg_cnt + data->num_in_args;
    out_args = (char **) tac_malloc((max_args + 1) * sizeof(char *));
    outp = out_args;
    data->num_out_args = 0;

    bzero(out_args, (max_args + 1) * sizeof(char *));

    for (i = 0; i < data->num_in_args; i++) {
      nas_arg = data->input_args[i];

      /* always pass these pairs through unchanged */
      if (match_attrs(nas_arg, "service=") ||
          match_attrs(nas_arg, "protocol=") ||
          match_attrs(nas_arg, "cmd=")) {

          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, "nas:%s (passed thru)", nas_arg);
          }
          *outp++ = tac_strdup(nas_arg);
          data->num_out_args++;
          continue;
      }

      /* NAS AV pair is mandatory */
      if (mandatory(nas_arg)) {

          /* a). look for an exact attribute,value match in the daemon's
             mandatory list. If found, add the AV pair to the output */

          for (j = 0; j < cfg_cnt; j++) {
            cfg_arg = cfg_args[j];
            if (optional(cfg_arg))
                continue;

            if (STREQ(nas_arg, cfg_arg)) {
                if (debug & DEBUG_AUTHOR_FLAG) {
                  report(LOG_DEBUG, "nas:%s, svr:%s -> add %s (a)",
                         nas_arg, cfg_arg, nas_arg);
                }
                *outp++ = tac_strdup(nas_arg);
                data->num_out_args++;
                goto next_nas_arg;
            }
          }

          /* b). If an exact match doesn't exist, look in the
             daemon's optional list for the first attribute
             match. If found, add the NAS AV pair to the output */

          for (j = 0; j < cfg_cnt; j++) {
            cfg_arg = cfg_args[j];
            if (mandatory(cfg_arg))
                continue;

            if (match_attrs(nas_arg, cfg_arg)) {
                if (debug & DEBUG_AUTHOR_FLAG) {
                  report(LOG_DEBUG, "nas:%s, svr:%s -> add %s (b)",
                         nas_arg, cfg_arg, nas_arg);
                }
                *outp++ = tac_strdup(nas_arg);
                data->num_out_args++;
                goto next_nas_arg;
            }
          }

          /* c). If no attribute match exists, deny the command if the
             default is to deny */

          if (deny_by_default) {
            data->status = AUTHOR_STATUS_FAIL;
            if (debug & DEBUG_AUTHOR_FLAG) {
                report(LOG_DEBUG, "nas:%s svr:absent, default=deny -> denied (c)",
                     nas_arg);
            }
            if (out_args) {
                for (i = 0; i < data->num_out_args; i++)
                  free(out_args[i]);
                free(out_args);
            }
            
            data->num_out_args = 0;
            data->output_args = NULL;
            
            /* free the server arguments */
            for(cfg_argp = cfg_args; *cfg_argp; cfg_argp++)
                free(*cfg_argp);
            free(cfg_args);
            return (0);
          }

          /* d). If the default is permit, add the NAS AV pair to
             the output */

          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, 
                   "nas:%s, svr:absent, default=permit -> add %s (d)",
                   nas_arg, nas_arg);
          }
          *outp++ = tac_strdup(nas_arg);
          data->num_out_args++;
          goto next_nas_arg;

      } else {

          /* NAS AV pair is Optional */

          /* e). look for an exact attribute,value match in the mandatory
             list. If found, add DAEMON's AV pair to output */

          for (j = 0; j < cfg_cnt; j++) {
            cfg_arg = cfg_args[j];
            if (optional(cfg_arg))
                continue;

            if (match_attrs(nas_arg, cfg_arg) &&
                match_values(nas_arg, cfg_arg)) {

                if (debug & DEBUG_AUTHOR_FLAG) {
                  report(LOG_DEBUG, "nas:%s svr:%s -> replace with %s (e)",
                         nas_arg, cfg_arg, cfg_arg);
                }
                *outp++ = tac_strdup(cfg_arg);
                data->num_out_args++;
                replaced++;
                goto next_nas_arg;
            }
          }

          /* f). If not found, look for the first attribute match in
             the mandatory list. If found, add DAEMONS's AV pair to
             output */
          
          for (j = 0; j < cfg_cnt; j++) {
            cfg_arg = cfg_args[j];
            if (optional(cfg_arg))
                continue;

            if (match_attrs(nas_arg, cfg_arg)) {
                if (debug & DEBUG_AUTHOR_FLAG) {
                  report(LOG_DEBUG, "nas:%s svr:%s -> replace with %s (f)",
                         nas_arg, cfg_arg, cfg_arg);
                }
                *outp++ = tac_strdup(cfg_arg);
                data->num_out_args++;
                replaced++;
                goto next_nas_arg;
            }
          }

          /* g). If no mandatory match exists, look for an exact
             attribute,value pair match among the daemon's optional AV
             pairs. If found add the DAEMON's matching AV pair to the
             output.
             */

          for (j = 0; j < cfg_cnt; j++) {
            cfg_arg = cfg_args[j];
            if (!optional(cfg_arg))
                continue;
            
            if (match_attrs(nas_arg, cfg_arg) && 
                match_values(nas_arg, cfg_arg)) {
                if (debug & DEBUG_AUTHOR_FLAG) {
                  report(LOG_DEBUG, "nas:%s svr:%s -> replace with %s (g)",
                         nas_arg, cfg_arg, cfg_arg);
                }
                *outp++ = tac_strdup(cfg_arg);
                data->num_out_args++;
                replaced++;
                goto next_nas_arg;
            }
          }

          /* h). If no exact match exists, locate the first
             attribute match among the daemon's optional AV
             pairs. If found add the DAEMON's matching AV pair to
             the output */

          for (j = 0; j < cfg_cnt; j++) {
            cfg_arg = cfg_args[j];
            if (!optional(cfg_arg))
                continue;
            
            if (match_attrs(nas_arg, cfg_arg)) {
                if (debug & DEBUG_AUTHOR_FLAG) {
                  report(LOG_DEBUG, "nas:%s svr:%s -> replace with %s (h)",
                         nas_arg, cfg_arg, cfg_arg);
                }
                *outp++ = tac_strdup(cfg_arg);
                data->num_out_args++;
                replaced++;
                goto next_nas_arg;
            }
          }


          /* i). If no match is found, delete the AV pair if default is
             deny */

          if (deny_by_default) {
            if (debug & DEBUG_AUTHOR_FLAG) {
                report(LOG_DEBUG, "nas:%s svr:absent/deny -> delete %s (i)",
                     nas_arg, nas_arg);
            }
            replaced++;
            goto next_nas_arg;
          }

          /* j). If the default is permit add the NAS AV pair to the output */

          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, "nas:%s svr:absent/permit -> add %s (j)",
                   nas_arg, nas_arg);
          }
          *outp++ = tac_strdup(nas_arg);
          data->num_out_args++;
          goto next_nas_arg;
      }
    next_nas_arg:;

    }

    
    /* k). After all AV pairs have been processed, for each mandatory
       DAEMON AV pair, if there is no attribute match already in the
       output list, add the AV pair (add only one AV pair for each
       mandatory attribute) */

    for (i = 0; i < cfg_cnt; i++) {
      cfg_arg = cfg_args[i];

      if (!mandatory(cfg_arg))
          continue;     

      for (j = 0; j < data->num_out_args; j++) {
          char *output_arg = out_args[j];

          if (match_attrs(cfg_arg, output_arg)) {
            goto next_cfg_arg;
          }
      }

      /* Attr is required by daemon but not present in
         output. Add it */

      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "nas:absent, server:%s -> add %s (k)",
               cfg_arg, cfg_arg);
      }
      added++;
      *outp++ = tac_strdup(cfg_arg);
      data->num_out_args++;

    next_cfg_arg:;
      
    }
       
    /* If we replaced or deleted some pairs we must return the entire
       list we've constructed */

    if (replaced) {
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "replaced %d args", replaced);
      }
      data->status = AUTHOR_STATUS_PASS_REPL;
      data->output_args = out_args;

      /* free the server arguments */
      for(cfg_argp = cfg_args; *cfg_argp; cfg_argp++)
          free(*cfg_argp);
      free(cfg_args);

      return (0);
    }

    /* We added something not on the original nas list, but didn't
       replace or delete anything. We should return only the
       additions */

    if (added) {

      if (debug & DEBUG_AUTHOR_FLAG) 
          report(LOG_DEBUG, "added %d args", added);

      /* throw away output args which are just copies of the input args */
      for (i = 0; i < data->num_in_args; i++) {
          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, "out_args[%d] = %s input copy discarded", 
                   i, out_args[i]);
          }
          free(out_args[i]);
          out_args[i] = NULL;
      }

      /* Now compact the new args added to the end of the array down
           to the beginning */

      j = 0;
      for (i = data->num_in_args; i < data->num_out_args; i++) {
          if (out_args[j]) /* we goofed */
            report(LOG_ERR, "%s: out_args[%d] should be NULL", 
                   session.peer, j);
          if (!out_args[i]) /* we goofed */
            report(LOG_ERR, "%s: out_args[%d] should not be NULL",
                   session.peer, i);

          if (debug & DEBUG_AUTHOR_FLAG) {
            report(LOG_DEBUG, "out_args[%d] = %s compacted to out_args[%d]", 
                   i, out_args[i], j);
          }
          out_args[j++] = out_args[i];
          out_args[i] = NULL;
      }
      data->num_out_args = j;
      if (debug & DEBUG_AUTHOR_FLAG) {
          report(LOG_DEBUG, "%d output args", data->num_out_args);
      }

      /* should/could do a realloc here but it won't matter */
      data->status = AUTHOR_STATUS_PASS_ADD;
      data->output_args = out_args;

      /* free the server arguments */
      for(cfg_argp = cfg_args; *cfg_argp; cfg_argp++)
          free(*cfg_argp);
      free(cfg_args);

      return (0);
    }

    /* no additions or replacements. Input and output are
       identical. Don't need to return anything */

    if (debug & DEBUG_AUTHOR_FLAG) {
      report(LOG_DEBUG, "added %d", added);
    }
    data->status = AUTHOR_STATUS_PASS_ADD;
    if (out_args) {
      for (i = 0; i < data->num_out_args; i++) {
          free(out_args[i]);
      }
      free(out_args);
    }

    /* Final sanity check */
    if (data->num_out_args != data->num_in_args) {
      data->status = AUTHOR_STATUS_ERROR;
      data->admin_msg = tac_strdup("Bad output arg cnt from do_author");
      report(LOG_ERR, "%s: Error %s", session.peer, data->admin_msg);

      /* free the server arguments */
      for(cfg_argp = cfg_args; *cfg_argp; cfg_argp++)
          free(*cfg_argp);
      free(cfg_args);

      return (0);
    }

    data->num_out_args = 0;
    data->output_args = NULL;

    /* free the server arguments */
    for(cfg_argp = cfg_args; *cfg_argp; cfg_argp++)
      free(*cfg_argp);
    free(cfg_args);

    return (0);
}

/* Return an integer indicating which kind of service is being
   requested. 

   Conveniently this integer is one of our node types. If the service
   is a command authorisation request, also return the command name in
   cmdname. 

   If this service is a ppp request, return the protocol name in
   protocol.

   If this service is not one of the standard, known ones, return its
   name in svcname.
*/

static int
get_nas_svc(data, cmdname, protocol, svcname)
struct author_data *data;
char **cmdname, **protocol, **svcname;
{
    int i;
    char *nas_arg;
    
    *cmdname = NULL;
    *protocol = NULL;
    *svcname = NULL;

    for (i = 0; i < data->num_in_args; i++) {
      nas_arg = data->input_args[i];

      if (STREQ(nas_arg, "service=shell")) {
          for (i = 0; i < data->num_in_args; i++) {
            nas_arg = data->input_args[i];
            if (strncmp(nas_arg, "cmd", strlen("cmd")) == 0) {
                /* A cmd=<nothing> means we are authorising exec startup */
                if ((int)strlen(nas_arg) <= 4)
                  return (N_svc_exec);

                /* A non-null command means we are authorising a command */
                *cmdname = nas_arg + strlen("cmd") + 1;
                return (N_svc_cmd);
            }
          }
          return(0);
      }

      if (STREQ(nas_arg, "service=slip")) {
          return (N_svc_slip);
      }
      if (STREQ(nas_arg, "service=arap")) {
          return (N_svc_arap);
      }
      if (STREQ(nas_arg, "service=ppp")) {
          for (i = 0; i < data->num_in_args; i++) {
            nas_arg = data->input_args[i];
            if (strncmp(nas_arg, "protocol", strlen("protocol")) == 0) {
                *protocol = nas_arg + strlen("protocol") + 1;
                return(N_svc_ppp);
            }
          }
      }

      if (strncmp(nas_arg, "service=", strlen("service=")) ==0 ) {
          *svcname = nas_arg + strlen("service=");
          return(N_svc);
      }
    }
    return (0);
}

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