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