acl.c

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