acl.c

   1 /*
   2  * Copyright (C) 2005-2008 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 /**
  29  * Return true if addr_1 matches addr_2 in the first `netmask' bits.
  30  */
  31 static int v4_addr_match(uint32_t addr_1, uint32_t addr_2, uint8_t netmask)
  32 {
  33         uint32_t mask = ~0U;
  34
  35         if (netmask < 32)
  36                 mask <<= (32 - netmask);
  37         return (htonl(addr_1) & mask) == (htonl(addr_2) & mask);
  38 }
  39
  40 /**
  41  * Find out whether the peer name of a given fd belongs to an acl.
  42  *
  43  * \param fd File descriptor.
  44  * \param acl The access control list.
  45  *
  46  * \return One if \a fd belongs to \a acl, zero otherwise.
  47  */
  48 static int acl_lookup(int fd, struct list_head *acl)
  49 {
  50         struct access_info *ai, *tmp;
  51         struct sockaddr_storage ss;
  52         socklen_t sslen = sizeof(ss);
  53         struct in_addr v4_addr;
  54
  55         if (getpeername(fd, (struct sockaddr *)&ss, &sslen) < 0) {
  56                 PARA_ERROR_LOG("Can not determine peer address: %s\n", strerror(errno));
  57                 goto no_match;
  58         }
  59         v4_addr = extract_v4_addr(&ss);
  60         if (!v4_addr.s_addr)
  61                 goto no_match;
  62
  63         list_for_each_entry_safe(ai, tmp, acl, node)
  64                 if (v4_addr_match(v4_addr.s_addr, ai->addr.s_addr, ai->netmask))
  65                         return 1;
  66 no_match:
  67         return 0;
  68 }
  69
  70 /**
  71  * Add an entry to an access control list.
  72  *
  73  * \param acl The access control list.
  74  * \param addr The address to add.
  75  * \param netmask The netmask to use for this entry.
  76  */
  77 static void acl_add_entry(struct list_head *acl, struct in_addr addr,
  78                 int netmask)
  79 {
  80         struct access_info *ai = para_malloc(sizeof(struct access_info));
  81         ai->addr = addr;
  82         ai->netmask = netmask;
  83         PARA_INFO_LOG("adding %s/%i to access list\n", inet_ntoa(ai->addr),
  84                 ai->netmask);
  85         para_list_add(&ai->node, acl);
  86 }
  87
  88
  89 /**
  90  * Delete an entry from an access control list.
  91  *
  92  * \param acl The access control list.
  93  * \param addr The address to delete.
  94  * \param netmask The netmask of the entry to be removed from the list.
  95  */
  96 static void acl_del_entry(struct list_head *acl, struct in_addr addr,
  97                 int netmask)
  98 {
  99         struct access_info *ai, *tmp;
 100
 101         list_for_each_entry_safe(ai, tmp, acl, node) {
 102                 char *nad = para_strdup(inet_ntoa(ai->addr));
 103                 if (!strcmp(nad, inet_ntoa(addr)) &&
 104                                 ai->netmask == netmask) {
 105                         PARA_NOTICE_LOG("removing %s/%i from access list\n",
 106                                 nad, ai->netmask);
 107                         list_del(&ai->node);
 108                         free(ai);
 109                 }
 110                 free(nad);
 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         int i;
 146
 147         INIT_LIST_HEAD(acl);
 148         for (i = 0; i < num; i++) {
 149                 char *arg = para_strdup(acl_info[i]);
 150                 char *p = strchr(arg, '/');
 151                 struct in_addr addr;
 152                 int netmask;
 153
 154                 if (!p)
 155                         goto err;
 156                 *p = '\0';
 157                 if (!inet_pton(AF_INET, arg, &addr))
 158                         goto err;
 159                 netmask = atoi(++p);
 160                 if (netmask < 0 || netmask > 32)
 161                         goto err;
 162                 acl_add_entry(acl, addr, netmask);
 163                 goto success;
 164 err:
 165                 PARA_CRIT_LOG("syntax error: %s\n", acl_info[i]);
 166 success:
 167                 free(arg);
 168                 continue;
 169         }
 170 }
 171
 172
 173 /**
 174  * Check whether the peer name of a given fd is allowed by an acl.
 175  *
 176  * \param fd File descriptor.
 177  * \param acl The access control list.
 178  * \param default_deny Whether \a acl is a whitelist.
 179  *
 180  * \return Positive if the peer of \a fd is permitted by \a acl, \p -E_ACL_PERM
 181  * otherwise.
 182  */
 183 int acl_check_access(int fd, struct list_head *acl, int default_deny)
 184 {
 185         int match = acl_lookup(fd, acl);
 186
 187         return (!match || default_deny) && (match || !default_deny)?
 188                 1 : -E_ACL_PERM;
 189 }
 190
 191 /**
 192  * Permit access for a range of IP addresses.
 193  *
 194  * \param addr The address to permit.
 195  * \param netmask The netmask of the entry to be permitted.
 196  * \param acl The access control list.
 197  * \param default_deny Whether \a acl is a whitelist.
 198  */
 199 void acl_allow(struct in_addr addr, int netmask,
 200                 struct list_head *acl, int default_deny)
 201 {
 202         if (default_deny)
 203                 acl_add_entry(acl, addr, netmask);
 204         else
 205                 acl_del_entry(acl, addr, netmask);
 206 }
 207
 208 /**
 209  * Deny access for a range of IP addresses.
 210  *
 211  * \param addr The address to permit.
 212  * \param netmask The netmask of the entry to be permitted.
 213  * \param acl The access control list.
 214  * \param default_deny Whether \a acl is a whitelist.
 215  */
 216 void acl_deny(struct in_addr addr, int netmask,
 217                 struct list_head *acl, int default_deny)
 218 {
 219         acl_allow(addr, netmask, acl, !default_deny);
 220 }