acl.c

   1 /*
   2  * Copyright (C) 2005-2009 Andre Noll <maan@systemlinux.org>
   3  *
   4  * Licensed under the GPL v2. For licencing details see COPYING.
   5  */
   6
   7 /** \file acl.c Access control lists for paraslash senders. */
   8
   9 #include "para.h"
  10 #include "error.h"
  11 #include "string.h"
  12 #include "list.h"
  13 #include "net.h"
  14
  15 /**
  16  * Describes one entry in the blacklist/whitelist of a paraslash sender.
  17  */
  18 struct access_info {
  19         /** The address to be black/whitelisted. */
  20         struct in_addr addr;
  21         /** The netmask for this entry. */
  22         unsigned netmask;
  23         /** The position of this entry in the acl. */
  24         struct list_head node;
  25 };
  26
  27 /**
  28  * Return true if addr_1 matches addr_2 in the first `netmask' bits.
  29  */
  30 static int v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
  31 {
  32         uint32_t mask = ~0U;
  33
  34         if (netmask < 32)
  35                 mask <<= (32 - netmask);
  36         return (htonl(addr_1) & mask) == (htonl(addr_2) & mask);
  37 }
  38
  39 /**
  40  * Find out whether the peer name of a given fd belongs to an acl.
  41  *
  42  * \param fd File descriptor.
  43  * \param acl The access control list.
  44  *
  45  * \return One if \a fd belongs to \a acl, zero otherwise.
  46  */
  47 static int acl_lookup(int fd, struct list_head *acl)
  48 {
  49         struct access_info *ai, *tmp;
  50         struct sockaddr_storage ss;
  51         socklen_t sslen = sizeof(ss);
  52         struct in_addr v4_addr;
  53
  54         if (getpeername(fd, (struct sockaddr *)&ss, &sslen) < 0) {
  55                 PARA_ERROR_LOG("Can not determine peer address: %s\n", strerror(errno));
  56                 goto no_match;
  57         }
  58         v4_addr = extract_v4_addr(&ss);
  59         if (!v4_addr.s_addr)
  60                 goto no_match;
  61
  62         list_for_each_entry_safe(ai, tmp, acl, node)
  63                 if (v4_addr_match(v4_addr.s_addr, ai->addr.s_addr, ai->netmask))
  64                         return 1;
  65 no_match:
  66         return 0;
  67 }
  68
  69 /**
  70  * Add an entry to an access control list.
  71  *
  72  * \param acl The access control list.
  73  * \param addr The address to add.
  74  * \param netmask The netmask to use for this entry.
  75  */
  76 static void acl_add_entry(struct list_head *acl, struct in_addr addr,
  77                 int netmask)
  78 {
  79         struct access_info *ai = para_malloc(sizeof(struct access_info));
  80         ai->addr = addr;
  81         ai->netmask = netmask;
  82         PARA_INFO_LOG("adding %s/%i to access list\n", inet_ntoa(ai->addr),
  83                 ai->netmask);
  84         para_list_add(&ai->node, acl);
  85 }
  86
  87 /**
  88  * Delete an entry from an access control list.
  89  *
  90  * \param acl The access control list.
  91  * \param addr The address to delete.
  92  * \param netmask The netmask of the entry to be removed from the list.
  93  */
  94 static void acl_del_entry(struct list_head *acl, struct in_addr addr,
  95                 int netmask)
  96 {
  97         struct access_info *ai, *tmp;
  98
  99         list_for_each_entry_safe(ai, tmp, acl, node) {
 100                 char *nad = para_strdup(inet_ntoa(ai->addr));
 101                 if (!strcmp(nad, inet_ntoa(addr)) &&
 102                                 ai->netmask == netmask) {
 103                         PARA_NOTICE_LOG("removing %s/%i from access list\n",
 104                                 nad, ai->netmask);
 105                         list_del(&ai->node);
 106                         free(ai);
 107                 }
 108                 free(nad);
 109         }
 110 }
 111
 112 /**
 113  * Compute a string containing the contents of an acl.
 114  *
 115  * \param acl The access control list.
 116  *
 117  * \return A string containing the contents of \a acl, or \p NULL
 118  * if \a acl is empty.
 119  */
 120 char *acl_get_contents(struct list_head *acl)
 121 {
 122         struct access_info *ai, *tmp_ai;
 123         char *ret = NULL;
 124
 125         list_for_each_entry_safe(ai, tmp_ai, acl, node) {
 126                 char *tmp = make_message("%s%s/%d ", ret? ret : "",
 127                         inet_ntoa(ai->addr), ai->netmask);
 128                 free(ret);
 129                 ret = tmp;
 130         }
 131         return ret;
 132 }
 133
 134 /**
 135  * Initialize an access control list.
 136  *
 137  * \param acl The list to initialize.
 138  * \param acl_info An array of strings of the form ip/netmask.
 139  * \param num The number of strings in \a acl_info.
 140  */
 141 void acl_init(struct list_head *acl, char * const *acl_info, int num)
 142 {
 143         int i;
 144
 145         INIT_LIST_HEAD(acl);
 146         for (i = 0; i < num; i++) {
 147                 char *arg = para_strdup(acl_info[i]);
 148                 char *p = strchr(arg, '/');
 149                 struct in_addr addr;
 150                 int netmask;
 151
 152                 if (!p)
 153                         goto err;
 154                 *p = '\0';
 155                 if (!inet_pton(AF_INET, arg, &addr))
 156                         goto err;
 157                 netmask = atoi(++p);
 158                 if (netmask < 0 || netmask > 32)
 159                         goto err;
 160                 acl_add_entry(acl, addr, netmask);
 161                 goto success;
 162 err:
 163                 PARA_CRIT_LOG("syntax error: %s\n", acl_info[i]);
 164 success:
 165                 free(arg);
 166                 continue;
 167         }
 168 }
 169
 170 /**
 171  * Check whether the peer name of a given fd is allowed by an acl.
 172  *
 173  * \param fd File descriptor.
 174  * \param acl The access control list.
 175  * \param default_deny Whether \a acl is a whitelist.
 176  *
 177  * \return Positive if the peer of \a fd is permitted by \a acl, \p -E_ACL_PERM
 178  * otherwise.
 179  */
 180 int acl_check_access(int fd, struct list_head *acl, int default_deny)
 181 {
 182         int match = acl_lookup(fd, acl);
 183
 184         return (!match || default_deny) && (match || !default_deny)?
 185                 1 : -E_ACL_PERM;
 186 }
 187
 188 /**
 189  * Permit access for a range of IP addresses.
 190  *
 191  * \param addr The address to permit.
 192  * \param netmask The netmask of the entry to be permitted.
 193  * \param acl The access control list.
 194  * \param default_deny Whether \a acl is a whitelist.
 195  */
 196 void acl_allow(struct in_addr addr, int netmask,
 197                 struct list_head *acl, int default_deny)
 198 {
 199         if (default_deny)
 200                 acl_add_entry(acl, addr, netmask);
 201         else
 202                 acl_del_entry(acl, addr, netmask);
 203 }
 204
 205 /**
 206  * Deny access for a range of IP addresses.
 207  *
 208  * \param addr The address to deny.
 209  * \param netmask The netmask of the entry to be denied.
 210  * \param acl The access control list.
 211  * \param default_deny Whether \a acl is a whitelist.
 212  */
 213 void acl_deny(struct in_addr addr, int netmask,
 214                 struct list_head *acl, int default_deny)
 215 {
 216         acl_allow(addr, netmask, acl, !default_deny);
 217 }