1 /* 2 * xt_time 3 * Copyright © CC Computer Consultants GmbH, 2007 4 * 5 * based on ipt_time by Fabrice MARIE <fabrice@netfilter.org> 6 * This is a module which is used for time matching 7 * It is using some modified code from dietlibc (localtime() function) 8 * that you can find at https://www.fefe.de/dietlibc/ 9 * This file is distributed under the terms of the GNU General Public 10 * License (GPL). Copies of the GPL can be obtained from gnu.org/gpl. 11 */ 12 13 #define pr_fmt(fmt) KBUILD_MODNAME ": " fmt 14 15 #include <linux/ktime.h> 16 #include <linux/module.h> 17 #include <linux/skbuff.h> 18 #include <linux/types.h> 19 #include <linux/netfilter/x_tables.h> 20 #include <linux/netfilter/xt_time.h> 21 22 struct xtm { 23 u_int8_t month; /* (1-12) */ 24 u_int8_t monthday; /* (1-31) */ 25 u_int8_t weekday; /* (1-7) */ 26 u_int8_t hour; /* (0-23) */ 27 u_int8_t minute; /* (0-59) */ 28 u_int8_t second; /* (0-59) */ 29 unsigned int dse; 30 }; 31 32 extern struct timezone sys_tz; /* ouch */ 33 34 static const u_int16_t days_since_year[] = { 35 0, 31, 59, 90, 120, 151, 181, 212, 243, 273, 304, 334, 36 }; 37 38 static const u_int16_t days_since_leapyear[] = { 39 0, 31, 60, 91, 121, 152, 182, 213, 244, 274, 305, 335, 40 }; 41 42 /* 43 * Since time progresses forward, it is best to organize this array in reverse, 44 * to minimize lookup time. 45 */ 46 enum { 47 DSE_FIRST = 2039, 48 SECONDS_PER_DAY = 86400, 49 }; 50 static const u_int16_t days_since_epoch[] = { 51 /* 2039 - 2030 */ 52 25202, 24837, 24472, 24106, 23741, 23376, 23011, 22645, 22280, 21915, 53 /* 2029 - 2020 */ 54 21550, 21184, 20819, 20454, 20089, 19723, 19358, 18993, 18628, 18262, 55 /* 2019 - 2010 */ 56 17897, 17532, 17167, 16801, 16436, 16071, 15706, 15340, 14975, 14610, 57 /* 2009 - 2000 */ 58 14245, 13879, 13514, 13149, 12784, 12418, 12053, 11688, 11323, 10957, 59 /* 1999 - 1990 */ 60 10592, 10227, 9862, 9496, 9131, 8766, 8401, 8035, 7670, 7305, 61 /* 1989 - 1980 */ 62 6940, 6574, 6209, 5844, 5479, 5113, 4748, 4383, 4018, 3652, 63 /* 1979 - 1970 */ 64 3287, 2922, 2557, 2191, 1826, 1461, 1096, 730, 365, 0, 65 }; 66 67 static inline bool is_leap(unsigned int y) 68 { 69 return y % 4 == 0 && (y % 100 != 0 || y % 400 == 0); 70 } 71 72 /* 73 * Each network packet has a (nano)seconds-since-the-epoch (SSTE) timestamp. 74 * Since we match against days and daytime, the SSTE value needs to be 75 * computed back into human-readable dates. 76 * 77 * This is done in three separate functions so that the most expensive 78 * calculations are done last, in case a "simple match" can be found earlier. 79 */ 80 static inline unsigned int localtime_1(struct xtm *r, time64_t time) 81 { 82 unsigned int v, w; 83 84 /* Each day has 86400s, so finding the hour/minute is actually easy. */ 85 div_u64_rem(time, SECONDS_PER_DAY, &v); 86 r->second = v % 60; 87 w = v / 60; 88 r->minute = w % 60; 89 r->hour = w / 60; 90 return v; 91 } 92 93 static inline void localtime_2(struct xtm *r, time64_t time) 94 { 95 /* 96 * Here comes the rest (weekday, monthday). First, divide the SSTE 97 * by seconds-per-day to get the number of _days_ since the epoch. 98 */ 99 r->dse = div_u64(time, SECONDS_PER_DAY); 100 101 /* 102 * 1970-01-01 (w=0) was a Thursday (4). 103 * -1 and +1 map Sunday properly onto 7. 104 */ 105 r->weekday = (4 + r->dse - 1) % 7 + 1; 106 } 107 108 static void localtime_3(struct xtm *r, time64_t time) 109 { 110 unsigned int year, i, w = r->dse; 111 112 /* 113 * In each year, a certain number of days-since-the-epoch have passed. 114 * Find the year that is closest to said days. 115 * 116 * Consider, for example, w=21612 (2029-03-04). Loop will abort on 117 * dse[i] <= w, which happens when dse[i] == 21550. This implies 118 * year == 2009. w will then be 62. 119 */ 120 for (i = 0, year = DSE_FIRST; days_since_epoch[i] > w; 121 ++i, --year) 122 /* just loop */; 123 124 w -= days_since_epoch[i]; 125 126 /* 127 * By now we have the current year, and the day of the year. 128 * r->yearday = w; 129 * 130 * On to finding the month (like above). In each month, a certain 131 * number of days-since-New Year have passed, and find the closest 132 * one. 133 * 134 * Consider w=62 (in a non-leap year). Loop will abort on 135 * dsy[i] < w, which happens when dsy[i] == 31+28 (i == 2). 136 * Concludes i == 2, i.e. 3rd month => March. 137 * 138 * (A different approach to use would be to subtract a monthlength 139 * from w repeatedly while counting.) 140 */ 141 if (is_leap(year)) { 142 /* use days_since_leapyear[] in a leap year */ 143 for (i = ARRAY_SIZE(days_since_leapyear) - 1; 144 i > 0 && days_since_leapyear[i] > w; --i) 145 /* just loop */; 146 r->monthday = w - days_since_leapyear[i] + 1; 147 } else { 148 for (i = ARRAY_SIZE(days_since_year) - 1; 149 i > 0 && days_since_year[i] > w; --i) 150 /* just loop */; 151 r->monthday = w - days_since_year[i] + 1; 152 } 153 154 r->month = i + 1; 155 } 156 157 static bool 158 time_mt(const struct sk_buff *skb, struct xt_action_param *par) 159 { 160 const struct xt_time_info *info = par->matchinfo; 161 unsigned int packet_time; 162 struct xtm current_time; 163 time64_t stamp; 164 165 /* 166 * We need real time here, but we can neither use skb->tstamp 167 * nor __net_timestamp(). 168 * 169 * skb->tstamp and skb->skb_mstamp_ns overlap, however, they 170 * use different clock types (real vs monotonic). 171 * 172 * Suppose you have two rules: 173 * 1. match before 13:00 174 * 2. match after 13:00 175 * 176 * If you match against processing time (ktime_get_real_seconds) it 177 * may happen that the same packet matches both rules if 178 * it arrived at the right moment before 13:00, so it would be 179 * better to check skb->tstamp and set it via __net_timestamp() 180 * if needed. This however breaks outgoing packets tx timestamp, 181 * and causes them to get delayed forever by fq packet scheduler. 182 */ 183 stamp = ktime_get_real_seconds(); 184 185 if (info->flags & XT_TIME_LOCAL_TZ) 186 /* Adjust for local timezone */ 187 stamp -= 60 * sys_tz.tz_minuteswest; 188 189 /* 190 * xt_time will match when _all_ of the following hold: 191 * - 'now' is in the global time range date_start..date_end 192 * - 'now' is in the monthday mask 193 * - 'now' is in the weekday mask 194 * - 'now' is in the daytime range time_start..time_end 195 * (and by default, libxt_time will set these so as to match) 196 * 197 * note: info->date_start/stop are unsigned 32-bit values that 198 * can hold values beyond y2038, but not after y2106. 199 */ 200 201 if (stamp < info->date_start || stamp > info->date_stop) 202 return false; 203 204 packet_time = localtime_1(¤t_time, stamp); 205 206 if (info->daytime_start < info->daytime_stop) { 207 if (packet_time < info->daytime_start || 208 packet_time > info->daytime_stop) 209 return false; 210 } else { 211 if (packet_time < info->daytime_start && 212 packet_time > info->daytime_stop) 213 return false; 214 215 /** if user asked to ignore 'next day', then e.g. 216 * '1 PM Wed, August 1st' should be treated 217 * like 'Tue 1 PM July 31st'. 218 * 219 * This also causes 220 * 'Monday, "23:00 to 01:00", to match for 2 hours, starting 221 * Monday 23:00 to Tuesday 01:00. 222 */ 223 if ((info->flags & XT_TIME_CONTIGUOUS) && 224 packet_time <= info->daytime_stop) 225 stamp -= SECONDS_PER_DAY; 226 } 227 228 localtime_2(¤t_time, stamp); 229 230 if (!(info->weekdays_match & (1 << current_time.weekday))) 231 return false; 232 233 /* Do not spend time computing monthday if all days match anyway */ 234 if (info->monthdays_match != XT_TIME_ALL_MONTHDAYS) { 235 localtime_3(¤t_time, stamp); 236 if (!(info->monthdays_match & (1 << current_time.monthday))) 237 return false; 238 } 239 240 return true; 241 } 242 243 static int time_mt_check(const struct xt_mtchk_param *par) 244 { 245 const struct xt_time_info *info = par->matchinfo; 246 247 if (info->daytime_start > XT_TIME_MAX_DAYTIME || 248 info->daytime_stop > XT_TIME_MAX_DAYTIME) { 249 pr_info_ratelimited("invalid argument - start or stop time greater than 23:59:59\n"); 250 return -EDOM; 251 } 252 253 if (info->flags & ~XT_TIME_ALL_FLAGS) { 254 pr_info_ratelimited("unknown flags 0x%x\n", 255 info->flags & ~XT_TIME_ALL_FLAGS); 256 return -EINVAL; 257 } 258 259 if ((info->flags & XT_TIME_CONTIGUOUS) && 260 info->daytime_start < info->daytime_stop) 261 return -EINVAL; 262 263 return 0; 264 } 265 266 static struct xt_match xt_time_mt_reg __read_mostly = { 267 .name = "time", 268 .family = NFPROTO_UNSPEC, 269 .match = time_mt, 270 .checkentry = time_mt_check, 271 .matchsize = sizeof(struct xt_time_info), 272 .me = THIS_MODULE, 273 }; 274 275 static int __init time_mt_init(void) 276 { 277 int minutes = sys_tz.tz_minuteswest; 278 279 if (minutes < 0) /* east of Greenwich */ 280 pr_info("kernel timezone is +%02d%02d\n", 281 -minutes / 60, -minutes % 60); 282 else /* west of Greenwich */ 283 pr_info("kernel timezone is -%02d%02d\n", 284 minutes / 60, minutes % 60); 285 286 return xt_register_match(&xt_time_mt_reg); 287 } 288 289 static void __exit time_mt_exit(void) 290 { 291 xt_unregister_match(&xt_time_mt_reg); 292 } 293 294 module_init(time_mt_init); 295 module_exit(time_mt_exit); 296 MODULE_AUTHOR("Jan Engelhardt <jengelh@medozas.de>"); 297 MODULE_DESCRIPTION("Xtables: time-based matching"); 298 MODULE_LICENSE("GPL"); 299 MODULE_ALIAS("ipt_time"); 300 MODULE_ALIAS("ip6t_time"); 301