crypto/jitterentropy.c

   1 /*
   2  * Non-physical true random number generator based on timing jitter --
   3  * Jitter RNG standalone code.
   4  *
   5  * Copyright Stephan Mueller <smueller@chronox.de>, 2015 - 2019
   6  *
   7  * Design
   8  * ======
   9  *
  10  * See http://www.chronox.de/jent.html
  11  *
  12  * License
  13  * =======
  14  *
  15  * Redistribution and use in source and binary forms, with or without
  16  * modification, are permitted provided that the following conditions
  17  * are met:
  18  * 1. Redistributions of source code must retain the above copyright
  19  *    notice, and the entire permission notice in its entirety,
  20  *    including the disclaimer of warranties.
  21  * 2. Redistributions in binary form must reproduce the above copyright
  22  *    notice, this list of conditions and the following disclaimer in the
  23  *    documentation and/or other materials provided with the distribution.
  24  * 3. The name of the author may not be used to endorse or promote
  25  *    products derived from this software without specific prior
  26  *    written permission.
  27  *
  28  * ALTERNATIVELY, this product may be distributed under the terms of
  29  * the GNU General Public License, in which case the provisions of the GPL2 are
  30  * required INSTEAD OF the above restrictions.  (This clause is
  31  * necessary due to a potential bad interaction between the GPL and
  32  * the restrictions contained in a BSD-style copyright.)
  33  *
  34  * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED
  35  * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
  36  * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE, ALL OF
  37  * WHICH ARE HEREBY DISCLAIMED.  IN NO EVENT SHALL THE AUTHOR BE
  38  * LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
  39  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT
  40  * OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR
  41  * BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  42  * LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
  43  * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE
  44  * USE OF THIS SOFTWARE, EVEN IF NOT ADVISED OF THE POSSIBILITY OF SUCH
  45  * DAMAGE.
  46  */
  47
  48 /*
  49  * This Jitterentropy RNG is based on the jitterentropy library
  50  * version 2.1.2 provided at http://www.chronox.de/jent.html
  51  */
  52
  53 #ifdef __OPTIMIZE__
  54  #error "The CPU Jitter random number generator must not be compiled with optimizations. See documentation. Use the compiler switch -O0 for compiling jitterentropy.c."
  55 #endif
  56
  57 typedef unsigned long long      __u64;
  58 typedef long long               __s64;
  59 typedef unsigned int            __u32;
  60 #define NULL    ((void *) 0)
  61
  62 /* The entropy pool */
  63 struct rand_data {
  64         /* all data values that are vital to maintain the security
  65          * of the RNG are marked as SENSITIVE. A user must not
  66          * access that information while the RNG executes its loops to
  67          * calculate the next random value. */
  68         __u64 data;             /* SENSITIVE Actual random number */
  69         __u64 old_data;         /* SENSITIVE Previous random number */
  70         __u64 prev_time;        /* SENSITIVE Previous time stamp */
  71 #define DATA_SIZE_BITS ((sizeof(__u64)) * 8)
  72         __u64 last_delta;       /* SENSITIVE stuck test */
  73         __s64 last_delta2;      /* SENSITIVE stuck test */
  74         unsigned int osr;       /* Oversample rate */
  75 #define JENT_MEMORY_BLOCKS 64
  76 #define JENT_MEMORY_BLOCKSIZE 32
  77 #define JENT_MEMORY_ACCESSLOOPS 128
  78 #define JENT_MEMORY_SIZE (JENT_MEMORY_BLOCKS*JENT_MEMORY_BLOCKSIZE)
  79         unsigned char *mem;     /* Memory access location with size of
  80                                  * memblocks * memblocksize */
  81         unsigned int memlocation; /* Pointer to byte in *mem */
  82         unsigned int memblocks; /* Number of memory blocks in *mem */
  83         unsigned int memblocksize; /* Size of one memory block in bytes */
  84         unsigned int memaccessloops; /* Number of memory accesses per random
  85                                       * bit generation */
  86 };
  87
  88 /* Flags that can be used to initialize the RNG */
  89 #define JENT_DISABLE_MEMORY_ACCESS (1<<2) /* Disable memory access for more
  90                                            * entropy, saves MEMORY_SIZE RAM for
  91                                            * entropy collector */
  92
  93 /* -- error codes for init function -- */
  94 #define JENT_ENOTIME            1 /* Timer service not available */
  95 #define JENT_ECOARSETIME        2 /* Timer too coarse for RNG */
  96 #define JENT_ENOMONOTONIC       3 /* Timer is not monotonic increasing */
  97 #define JENT_EVARVAR            5 /* Timer does not produce variations of
  98                                    * variations (2nd derivation of time is
  99                                    * zero). */
 100 #define JENT_ESTUCK             8 /* Too many stuck results during init. */
 101
 102 /***************************************************************************
 103  * Helper functions
 104  ***************************************************************************/
 105
 106 void jent_get_nstime(__u64 *out);
 107 void *jent_zalloc(unsigned int len);
 108 void jent_zfree(void *ptr);
 109 int jent_fips_enabled(void);
 110 void jent_panic(char *s);
 111 void jent_memcpy(void *dest, const void *src, unsigned int n);
 112
 113 /**
 114  * Update of the loop count used for the next round of
 115  * an entropy collection.
 116  *
 117  * Input:
 118  * @ec entropy collector struct -- may be NULL
 119  * @bits is the number of low bits of the timer to consider
 120  * @min is the number of bits we shift the timer value to the right at
 121  *      the end to make sure we have a guaranteed minimum value
 122  *
 123  * @return Newly calculated loop counter
 124  */
 125 static __u64 jent_loop_shuffle(struct rand_data *ec,
 126                                unsigned int bits, unsigned int min)
 127 {
 128         __u64 time = 0;
 129         __u64 shuffle = 0;
 130         unsigned int i = 0;
 131         unsigned int mask = (1<<bits) - 1;
 132
 133         jent_get_nstime(&time);
 134         /*
 135          * Mix the current state of the random number into the shuffle
 136          * calculation to balance that shuffle a bit more.
 137          */
 138         if (ec)
 139                 time ^= ec->data;
 140         /*
 141          * We fold the time value as much as possible to ensure that as many
 142          * bits of the time stamp are included as possible.
 143          */
 144         for (i = 0; ((DATA_SIZE_BITS + bits - 1) / bits) > i; i++) {
 145                 shuffle ^= time & mask;
 146                 time = time >> bits;
 147         }
 148
 149         /*
 150          * We add a lower boundary value to ensure we have a minimum
 151          * RNG loop count.
 152          */
 153         return (shuffle + (1<<min));
 154 }
 155
 156 /***************************************************************************
 157  * Noise sources
 158  ***************************************************************************/
 159
 160 /**
 161  * CPU Jitter noise source -- this is the noise source based on the CPU
 162  *                            execution time jitter
 163  *
 164  * This function injects the individual bits of the time value into the
 165  * entropy pool using an LFSR.
 166  *
 167  * The code is deliberately inefficient with respect to the bit shifting
 168  * and shall stay that way. This function is the root cause why the code
 169  * shall be compiled without optimization. This function not only acts as
 170  * folding operation, but this function's execution is used to measure
 171  * the CPU execution time jitter. Any change to the loop in this function
 172  * implies that careful retesting must be done.
 173  *
 174  * Input:
 175  * @ec entropy collector struct -- may be NULL
 176  * @time time stamp to be injected
 177  * @loop_cnt if a value not equal to 0 is set, use the given value as number of
 178  *           loops to perform the folding
 179  *
 180  * Output:
 181  * updated ec->data
 182  *
 183  * @return Number of loops the folding operation is performed
 184  */
 185 static __u64 jent_lfsr_time(struct rand_data *ec, __u64 time, __u64 loop_cnt)
 186 {
 187         unsigned int i;
 188         __u64 j = 0;
 189         __u64 new = 0;
 190 #define MAX_FOLD_LOOP_BIT 4
 191 #define MIN_FOLD_LOOP_BIT 0
 192         __u64 fold_loop_cnt =
 193                 jent_loop_shuffle(ec, MAX_FOLD_LOOP_BIT, MIN_FOLD_LOOP_BIT);
 194
 195         /*
 196          * testing purposes -- allow test app to set the counter, not
 197          * needed during runtime
 198          */
 199         if (loop_cnt)
 200                 fold_loop_cnt = loop_cnt;
 201         for (j = 0; j < fold_loop_cnt; j++) {
 202                 new = ec->data;
 203                 for (i = 1; (DATA_SIZE_BITS) >= i; i++) {
 204                         __u64 tmp = time << (DATA_SIZE_BITS - i);
 205
 206                         tmp = tmp >> (DATA_SIZE_BITS - 1);
 207
 208                         /*
 209                         * Fibonacci LSFR with polynomial of
 210                         *  x^64 + x^61 + x^56 + x^31 + x^28 + x^23 + 1 which is
 211                         *  primitive according to
 212                         *   http://poincare.matf.bg.ac.rs/~ezivkovm/publications/primpol1.pdf
 213                         * (the shift values are the polynomial values minus one
 214                         * due to counting bits from 0 to 63). As the current
 215                         * position is always the LSB, the polynomial only needs
 216                         * to shift data in from the left without wrap.
 217                         */
 218                         tmp ^= ((new >> 63) & 1);
 219                         tmp ^= ((new >> 60) & 1);
 220                         tmp ^= ((new >> 55) & 1);
 221                         tmp ^= ((new >> 30) & 1);
 222                         tmp ^= ((new >> 27) & 1);
 223                         tmp ^= ((new >> 22) & 1);
 224                         new <<= 1;
 225                         new ^= tmp;
 226                 }
 227         }
 228         ec->data = new;
 229
 230         return fold_loop_cnt;
 231 }
 232
 233 /**
 234  * Memory Access noise source -- this is a noise source based on variations in
 235  *                               memory access times
 236  *
 237  * This function performs memory accesses which will add to the timing
 238  * variations due to an unknown amount of CPU wait states that need to be
 239  * added when accessing memory. The memory size should be larger than the L1
 240  * caches as outlined in the documentation and the associated testing.
 241  *
 242  * The L1 cache has a very high bandwidth, albeit its access rate is  usually
 243  * slower than accessing CPU registers. Therefore, L1 accesses only add minimal
 244  * variations as the CPU has hardly to wait. Starting with L2, significant
 245  * variations are added because L2 typically does not belong to the CPU any more
 246  * and therefore a wider range of CPU wait states is necessary for accesses.
 247  * L3 and real memory accesses have even a wider range of wait states. However,
 248  * to reliably access either L3 or memory, the ec->mem memory must be quite
 249  * large which is usually not desirable.
 250  *
 251  * Input:
 252  * @ec Reference to the entropy collector with the memory access data -- if
 253  *     the reference to the memory block to be accessed is NULL, this noise
 254  *     source is disabled
 255  * @loop_cnt if a value not equal to 0 is set, use the given value as number of
 256  *           loops to perform the folding
 257  *
 258  * @return Number of memory access operations
 259  */
 260 static unsigned int jent_memaccess(struct rand_data *ec, __u64 loop_cnt)
 261 {
 262         unsigned int wrap = 0;
 263         __u64 i = 0;
 264 #define MAX_ACC_LOOP_BIT 7
 265 #define MIN_ACC_LOOP_BIT 0
 266         __u64 acc_loop_cnt =
 267                 jent_loop_shuffle(ec, MAX_ACC_LOOP_BIT, MIN_ACC_LOOP_BIT);
 268
 269         if (NULL == ec || NULL == ec->mem)
 270                 return 0;
 271         wrap = ec->memblocksize * ec->memblocks;
 272
 273         /*
 274          * testing purposes -- allow test app to set the counter, not
 275          * needed during runtime
 276          */
 277         if (loop_cnt)
 278                 acc_loop_cnt = loop_cnt;
 279
 280         for (i = 0; i < (ec->memaccessloops + acc_loop_cnt); i++) {
 281                 unsigned char *tmpval = ec->mem + ec->memlocation;
 282                 /*
 283                  * memory access: just add 1 to one byte,
 284                  * wrap at 255 -- memory access implies read
 285                  * from and write to memory location
 286                  */
 287                 *tmpval = (*tmpval + 1) & 0xff;
 288                 /*
 289                  * Addition of memblocksize - 1 to pointer
 290                  * with wrap around logic to ensure that every
 291                  * memory location is hit evenly
 292                  */
 293                 ec->memlocation = ec->memlocation + ec->memblocksize - 1;
 294                 ec->memlocation = ec->memlocation % wrap;
 295         }
 296         return i;
 297 }
 298
 299 /***************************************************************************
 300  * Start of entropy processing logic
 301  ***************************************************************************/
 302
 303 /**
 304  * Stuck test by checking the:
 305  *      1st derivation of the jitter measurement (time delta)
 306  *      2nd derivation of the jitter measurement (delta of time deltas)
 307  *      3rd derivation of the jitter measurement (delta of delta of time deltas)
 308  *
 309  * All values must always be non-zero.
 310  *
 311  * Input:
 312  * @ec Reference to entropy collector
 313  * @current_delta Jitter time delta
 314  *
 315  * @return
 316  *      0 jitter measurement not stuck (good bit)
 317  *      1 jitter measurement stuck (reject bit)
 318  */
 319 static int jent_stuck(struct rand_data *ec, __u64 current_delta)
 320 {
 321         __s64 delta2 = ec->last_delta - current_delta;
 322         __s64 delta3 = delta2 - ec->last_delta2;
 323
 324         ec->last_delta = current_delta;
 325         ec->last_delta2 = delta2;
 326
 327         if (!current_delta || !delta2 || !delta3)
 328                 return 1;
 329
 330         return 0;
 331 }
 332
 333 /**
 334  * This is the heart of the entropy generation: calculate time deltas and
 335  * use the CPU jitter in the time deltas. The jitter is injected into the
 336  * entropy pool.
 337  *
 338  * WARNING: ensure that ->prev_time is primed before using the output
 339  *          of this function! This can be done by calling this function
 340  *          and not using its result.
 341  *
 342  * Input:
 343  * @entropy_collector Reference to entropy collector
 344  *
 345  * @return result of stuck test
 346  */
 347 static int jent_measure_jitter(struct rand_data *ec)
 348 {
 349         __u64 time = 0;
 350         __u64 current_delta = 0;
 351
 352         /* Invoke one noise source before time measurement to add variations */
 353         jent_memaccess(ec, 0);
 354
 355         /*
 356          * Get time stamp and calculate time delta to previous
 357          * invocation to measure the timing variations
 358          */
 359         jent_get_nstime(&time);
 360         current_delta = time - ec->prev_time;
 361         ec->prev_time = time;
 362
 363         /* Now call the next noise sources which also injects the data */
 364         jent_lfsr_time(ec, current_delta, 0);
 365
 366         /* Check whether we have a stuck measurement. */
 367         return jent_stuck(ec, current_delta);
 368 }
 369
 370 /**
 371  * Generator of one 64 bit random number
 372  * Function fills rand_data->data
 373  *
 374  * Input:
 375  * @ec Reference to entropy collector
 376  */
 377 static void jent_gen_entropy(struct rand_data *ec)
 378 {
 379         unsigned int k = 0;
 380
 381         /* priming of the ->prev_time value */
 382         jent_measure_jitter(ec);
 383
 384         while (1) {
 385                 /* If a stuck measurement is received, repeat measurement */
 386                 if (jent_measure_jitter(ec))
 387                         continue;
 388
 389                 /*
 390                  * We multiply the loop value with ->osr to obtain the
 391                  * oversampling rate requested by the caller
 392                  */
 393                 if (++k >= (DATA_SIZE_BITS * ec->osr))
 394                         break;
 395         }
 396 }
 397
 398 /**
 399  * The continuous test required by FIPS 140-2 -- the function automatically
 400  * primes the test if needed.
 401  *
 402  * Return:
 403  * 0 if FIPS test passed
 404  * < 0 if FIPS test failed
 405  */
 406 static void jent_fips_test(struct rand_data *ec)
 407 {
 408         if (!jent_fips_enabled())
 409                 return;
 410
 411         /* prime the FIPS test */
 412         if (!ec->old_data) {
 413                 ec->old_data = ec->data;
 414                 jent_gen_entropy(ec);
 415         }
 416
 417         if (ec->data == ec->old_data)
 418                 jent_panic("jitterentropy: Duplicate output detected\n");
 419
 420         ec->old_data = ec->data;
 421 }
 422
 423 /**
 424  * Entry function: Obtain entropy for the caller.
 425  *
 426  * This function invokes the entropy gathering logic as often to generate
 427  * as many bytes as requested by the caller. The entropy gathering logic
 428  * creates 64 bit per invocation.
 429  *
 430  * This function truncates the last 64 bit entropy value output to the exact
 431  * size specified by the caller.
 432  *
 433  * Input:
 434  * @ec Reference to entropy collector
 435  * @data pointer to buffer for storing random data -- buffer must already
 436  *       exist
 437  * @len size of the buffer, specifying also the requested number of random
 438  *      in bytes
 439  *
 440  * @return 0 when request is fulfilled or an error
 441  *
 442  * The following error codes can occur:
 443  *      -1      entropy_collector is NULL
 444  */
 445 int jent_read_entropy(struct rand_data *ec, unsigned char *data,
 446                       unsigned int len)
 447 {
 448         unsigned char *p = data;
 449
 450         if (!ec)
 451                 return -1;
 452
 453         while (0 < len) {
 454                 unsigned int tocopy;
 455
 456                 jent_gen_entropy(ec);
 457                 jent_fips_test(ec);
 458                 if ((DATA_SIZE_BITS / 8) < len)
 459                         tocopy = (DATA_SIZE_BITS / 8);
 460                 else
 461                         tocopy = len;
 462                 jent_memcpy(p, &ec->data, tocopy);
 463
 464                 len -= tocopy;
 465                 p += tocopy;
 466         }
 467
 468         return 0;
 469 }
 470
 471 /***************************************************************************
 472  * Initialization logic
 473  ***************************************************************************/
 474
 475 struct rand_data *jent_entropy_collector_alloc(unsigned int osr,
 476                                                unsigned int flags)
 477 {
 478         struct rand_data *entropy_collector;
 479
 480         entropy_collector = jent_zalloc(sizeof(struct rand_data));
 481         if (!entropy_collector)
 482                 return NULL;
 483
 484         if (!(flags & JENT_DISABLE_MEMORY_ACCESS)) {
 485                 /* Allocate memory for adding variations based on memory
 486                  * access
 487                  */
 488                 entropy_collector->mem = jent_zalloc(JENT_MEMORY_SIZE);
 489                 if (!entropy_collector->mem) {
 490                         jent_zfree(entropy_collector);
 491                         return NULL;
 492                 }
 493                 entropy_collector->memblocksize = JENT_MEMORY_BLOCKSIZE;
 494                 entropy_collector->memblocks = JENT_MEMORY_BLOCKS;
 495                 entropy_collector->memaccessloops = JENT_MEMORY_ACCESSLOOPS;
 496         }
 497
 498         /* verify and set the oversampling rate */
 499         if (0 == osr)
 500                 osr = 1; /* minimum sampling rate is 1 */
 501         entropy_collector->osr = osr;
 502
 503         /* fill the data pad with non-zero values */
 504         jent_gen_entropy(entropy_collector);
 505
 506         return entropy_collector;
 507 }
 508
 509 void jent_entropy_collector_free(struct rand_data *entropy_collector)
 510 {
 511         jent_zfree(entropy_collector->mem);
 512         entropy_collector->mem = NULL;
 513         jent_zfree(entropy_collector);
 514 }
 515
 516 int jent_entropy_init(void)
 517 {
 518         int i;
 519         __u64 delta_sum = 0;
 520         __u64 old_delta = 0;
 521         int time_backwards = 0;
 522         int count_mod = 0;
 523         int count_stuck = 0;
 524         struct rand_data ec = { 0 };
 525
 526         /* We could perform statistical tests here, but the problem is
 527          * that we only have a few loop counts to do testing. These
 528          * loop counts may show some slight skew and we produce
 529          * false positives.
 530          *
 531          * Moreover, only old systems show potentially problematic
 532          * jitter entropy that could potentially be caught here. But
 533          * the RNG is intended for hardware that is available or widely
 534          * used, but not old systems that are long out of favor. Thus,
 535          * no statistical tests.
 536          */
 537
 538         /*
 539          * We could add a check for system capabilities such as clock_getres or
 540          * check for CONFIG_X86_TSC, but it does not make much sense as the
 541          * following sanity checks verify that we have a high-resolution
 542          * timer.
 543          */
 544         /*
 545          * TESTLOOPCOUNT needs some loops to identify edge systems. 100 is
 546          * definitely too little.
 547          */
 548 #define TESTLOOPCOUNT 300
 549 #define CLEARCACHE 100
 550         for (i = 0; (TESTLOOPCOUNT + CLEARCACHE) > i; i++) {
 551                 __u64 time = 0;
 552                 __u64 time2 = 0;
 553                 __u64 delta = 0;
 554                 unsigned int lowdelta = 0;
 555                 int stuck;
 556
 557                 /* Invoke core entropy collection logic */
 558                 jent_get_nstime(&time);
 559                 ec.prev_time = time;
 560                 jent_lfsr_time(&ec, time, 0);
 561                 jent_get_nstime(&time2);
 562
 563                 /* test whether timer works */
 564                 if (!time || !time2)
 565                         return JENT_ENOTIME;
 566                 delta = time2 - time;
 567                 /*
 568                  * test whether timer is fine grained enough to provide
 569                  * delta even when called shortly after each other -- this
 570                  * implies that we also have a high resolution timer
 571                  */
 572                 if (!delta)
 573                         return JENT_ECOARSETIME;
 574
 575                 stuck = jent_stuck(&ec, delta);
 576
 577                 /*
 578                  * up to here we did not modify any variable that will be
 579                  * evaluated later, but we already performed some work. Thus we
 580                  * already have had an impact on the caches, branch prediction,
 581                  * etc. with the goal to clear it to get the worst case
 582                  * measurements.
 583                  */
 584                 if (CLEARCACHE > i)
 585                         continue;
 586
 587                 if (stuck)
 588                         count_stuck++;
 589
 590                 /* test whether we have an increasing timer */
 591                 if (!(time2 > time))
 592                         time_backwards++;
 593
 594                 /* use 32 bit value to ensure compilation on 32 bit arches */
 595                 lowdelta = time2 - time;
 596                 if (!(lowdelta % 100))
 597                         count_mod++;
 598
 599                 /*
 600                  * ensure that we have a varying delta timer which is necessary
 601                  * for the calculation of entropy -- perform this check
 602                  * only after the first loop is executed as we need to prime
 603                  * the old_data value
 604                  */
 605                 if (delta > old_delta)
 606                         delta_sum += (delta - old_delta);
 607                 else
 608                         delta_sum += (old_delta - delta);
 609                 old_delta = delta;
 610         }
 611
 612         /*
 613          * we allow up to three times the time running backwards.
 614          * CLOCK_REALTIME is affected by adjtime and NTP operations. Thus,
 615          * if such an operation just happens to interfere with our test, it
 616          * should not fail. The value of 3 should cover the NTP case being
 617          * performed during our test run.
 618          */
 619         if (3 < time_backwards)
 620                 return JENT_ENOMONOTONIC;
 621
 622         /*
 623          * Variations of deltas of time must on average be larger
 624          * than 1 to ensure the entropy estimation
 625          * implied with 1 is preserved
 626          */
 627         if ((delta_sum) <= 1)
 628                 return JENT_EVARVAR;
 629
 630         /*
 631          * Ensure that we have variations in the time stamp below 10 for at
 632          * least 10% of all checks -- on some platforms, the counter increments
 633          * in multiples of 100, but not always
 634          */
 635         if ((TESTLOOPCOUNT/10 * 9) < count_mod)
 636                 return JENT_ECOARSETIME;
 637
 638         /*
 639          * If we have more than 90% stuck results, then this Jitter RNG is
 640          * likely to not work well.
 641          */
 642         if ((TESTLOOPCOUNT/10 * 9) < count_stuck)
 643                 return JENT_ESTUCK;
 644
 645         return 0;
 646 }