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 bool v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
  35 {
  36         uint32_t mask = ~0U;
  37
  38         if (netmask == 0) /* avoid 32-bit shift, which is undefined in C. */
  39                 return true;
  40         if (netmask < 32)
  41                 mask <<= (32 - netmask);
  42         return (htonl(addr_1) & mask) == (htonl(addr_2) & mask);
  43 }
  44
  45 /**
  46  * Find out whether the peer name of a given fd belongs to an acl.
  47  *
  48  * \param fd File descriptor.
  49  * \param acl The access control list.
  50  *
  51  * \return One if \a fd belongs to \a acl, zero otherwise.
  52  */
  53 static int acl_lookup(int fd, struct list_head *acl)
  54 {
  55         struct access_info *ai, *tmp;
  56         struct sockaddr_storage ss;
  57         socklen_t sslen = sizeof(ss);
  58         struct in_addr v4_addr;
  59
  60         if (getpeername(fd, (struct sockaddr *)&ss, &sslen) < 0) {
  61                 PARA_ERROR_LOG("Can not determine peer address: %s\n", strerror(errno));
  62                 goto no_match;
  63         }
  64         extract_v4_addr(&ss, &v4_addr);
  65         if (!v4_addr.s_addr)
  66                 goto no_match;
  67
  68         list_for_each_entry_safe(ai, tmp, acl, node)
  69                 if (v4_addr_match(v4_addr.s_addr, ai->addr.s_addr, ai->netmask))
  70                         return 1;
  71 no_match:
  72         return 0;
  73 }
  74
  75 /**
  76  * Add an entry to an access control list.
  77  *
  78  * \param acl The access control list.
  79  * \param addr The address to add.
  80  * \param netmask The netmask to use for this entry.
  81  */
  82 void acl_add_entry(struct list_head *acl, char *addr, int netmask)
  83 {
  84         struct access_info *ai = alloc(sizeof(struct access_info));
  85
  86         inet_pton(AF_INET, addr, &ai->addr);
  87         ai->netmask = netmask;
  88         PARA_INFO_LOG("adding %s/%u to access list\n", addr, ai->netmask);
  89         para_list_add(&ai->node, acl);
  90 }
  91
  92 /**
  93  * Delete an entry from an access control list.
  94  *
  95  * \param acl The access control list.
  96  * \param addr The address to delete.
  97  * \param netmask The netmask of the entry to be removed from the list.
  98  */
  99 static void acl_del_entry(struct list_head *acl, char *addr, unsigned netmask)
 100 {
 101         struct access_info *ai, *tmp;
 102         struct in_addr to_delete;
 103
 104         PARA_INFO_LOG("removing entries matching %s/%u\n", addr, netmask);
 105         inet_pton(AF_INET, addr, &to_delete);
 106
 107         list_for_each_entry_safe(ai, tmp, acl, node) {
 108                 if (v4_addr_match(to_delete.s_addr, ai->addr.s_addr,
 109                                         PARA_MIN(netmask, ai->netmask))) {
 110                         char dst[INET_ADDRSTRLEN + 1];
 111                         const char *p = inet_ntop(AF_INET, &ai->addr.s_addr,
 112                                 dst, sizeof(dst));
 113                         if (p)
 114                                 PARA_DEBUG_LOG("removing %s/%u\n", p,
 115                                         ai->netmask);
 116                         list_del(&ai->node);
 117                         free(ai);
 118                 }
 119         }
 120 }
 121
 122 /**
 123  * Compute a string containing the contents of an acl.
 124  *
 125  * \param acl The access control list.
 126  *
 127  * \return A string containing the contents of \a acl, or \p NULL
 128  * if \a acl is empty.
 129  */
 130 char *acl_get_contents(struct list_head *acl)
 131 {
 132         struct access_info *ai, *tmp_ai;
 133         char *ret = NULL;
 134
 135         list_for_each_entry_safe(ai, tmp_ai, acl, node) {
 136                 char *tmp = make_message("%s%s/%u ", ret? ret : "",
 137                         inet_ntoa(ai->addr), ai->netmask);
 138                 free(ret);
 139                 ret = tmp;
 140         }
 141         return ret;
 142 }
 143
 144 /**
 145  * Check whether the peer name of a given fd is allowed by an acl.
 146  *
 147  * \param fd File descriptor.
 148  * \param acl The access control list.
 149  * \param default_deny Whether \a acl is a whitelist.
 150  *
 151  * \return Positive if the peer of \a fd is permitted by \a acl, \p -E_ACL_PERM
 152  * otherwise.
 153  */
 154 int acl_check_access(int fd, struct list_head *acl, int default_deny)
 155 {
 156         int match = acl_lookup(fd, acl);
 157
 158         return (!match || default_deny) && (match || !default_deny)?
 159                 1 : -E_ACL_PERM;
 160 }
 161
 162 /**
 163  * Permit access for a range of IP addresses.
 164  *
 165  * \param addr The address to permit.
 166  * \param netmask The netmask of the entry to be permitted.
 167  * \param acl The access control list.
 168  * \param default_deny Whether \a acl is a whitelist.
 169  */
 170 void acl_allow(char *addr, int netmask,
 171                struct list_head *acl, int default_deny)
 172 {
 173         if (default_deny)
 174                 acl_add_entry(acl, addr, netmask);
 175         else
 176                 acl_del_entry(acl, addr, netmask);
 177 }
 178
 179 /**
 180  * Deny access for a range of IP addresses.
 181  *
 182  * \param addr The address to deny.
 183  * \param netmask The netmask of the entry to be denied.
 184  * \param acl The access control list.
 185  * \param default_deny Whether \a acl is a whitelist.
 186  */
 187 void acl_deny(char *addr, int netmask,
 188               struct list_head *acl, int default_deny)
 189 {
 190         acl_allow(addr, netmask, acl, !default_deny);
 191 }