acl.c

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