/* * random.c -- A strong random number generator * * Version 1.04, last modified 26-Apr-98 * * Copyright Theodore Ts'o, 1994, 1995, 1996, 1997, 1998. All rights * reserved. * * Redistribution and use in source and binary forms, with or without * modification, are permitted provided that the following conditions * are met: * 1. Redistributions of source code must retain the above copyright * notice, and the entire permission notice in its entirety, * including the disclaimer of warranties. * 2. Redistributions in binary form must reproduce the above copyright * notice, this list of conditions and the following disclaimer in the * documentation and/or other materials provided with the distribution. * 3. The name of the author may not be used to endorse or promote * products derived from this software without specific prior * written permission. * * ALTERNATIVELY, this product may be distributed under the terms of * the GNU Public License, in which case the provisions of the GPL are * required INSTEAD OF the above restrictions. (This clause is * necessary due to a potential bad interaction between the GPL and * the restrictions contained in a BSD-style copyright.) * * THIS SOFTWARE IS PROVIDED ``AS IS'' AND ANY EXPRESS OR IMPLIED * WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE * DISCLAIMED. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, * INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES * (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR * SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, * STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED * OF THE POSSIBILITY OF SUCH DAMAGE. */ /* * (now, with legal B.S. out of the way.....) * * This routine gathers environmental noise from device drivers, etc., * and returns good random numbers, suitable for cryptographic use. * Besides the obvious cryptographic uses, these numbers are also good * for seeding TCP sequence numbers, and other places where it is * desirable to have numbers which are not only random, but hard to * predict by an attacker. * * Theory of operation * =================== * * Computers are very predictable devices. Hence it is extremely hard * to produce truly random numbers on a computer --- as opposed to * pseudo-random numbers, which can easily generated by using a * algorithm. Unfortunately, it is very easy for attackers to guess * the sequence of pseudo-random number generators, and for some * applications this is not acceptable. So instead, we must try to * gather "environmental noise" from the computer's environment, which * must be hard for outside attackers to observe, and use that to * generate random numbers. In a Unix environment, this is best done * from inside the kernel. * * Sources of randomness from the environment include inter-keyboard * timings, inter-interrupt timings from some interrupts, and other * events which are both (a) non-deterministic and (b) hard for an * outside observer to measure. Randomness from these sources are * added to an "entropy pool", which is mixed using a CRC-like function. * This is not cryptographically strong, but it is adequate assuming * the randomness is not chosen maliciously, and it is fast enough that * the overhead of doing it on every interrupt is very reasonable. * As random bytes are mixed into the entropy pool, the routines keep * an *estimate* of how many bits of randomness have been stored into * the random number generator's internal state. * * When random bytes are desired, they are obtained by taking the SHA * hash of the contents of the "entropy pool". The SHA hash avoids * exposing the internal state of the entropy pool. It is believed to * be computationally infeasible to derive any useful information * about the input of SHA from its output. Even if it is possible to * analyze SHA in some clever way, as long as the amount of data * returned from the generator is less than the inherent entropy in * the pool, the output data is totally unpredictable. For this * reason, the routine decreases its internal estimate of how many * bits of "true randomness" are contained in the entropy pool as it * outputs random numbers. * * If this estimate goes to zero, the routine can still generate * random numbers; however, an attacker may (at least in theory) be * able to infer the future output of the generator from prior * outputs. This requires successful cryptanalysis of SHA, which is * not believed to be feasible, but there is a remote possibility. * Nonetheless, these numbers should be useful for the vast majority * of purposes. * * Exported interfaces ---- output * =============================== * * There are three exported interfaces; the first is one designed to * be used from within the kernel: * * void get_random_bytes(void *buf, int nbytes); * * This interface will return the requested number of random bytes, * and place it in the requested buffer. * * The two other interfaces are two character devices /dev/random and * /dev/urandom. /dev/random is suitable for use when very high * quality randomness is desired (for example, for key generation or * one-time pads), as it will only return a maximum of the number of * bits of randomness (as estimated by the random number generator) * contained in the entropy pool. * * The /dev/urandom device does not have this limit, and will return * as many bytes as are requested. As more and more random bytes are * requested without giving time for the entropy pool to recharge, * this will result in random numbers that are merely cryptographically * strong. For many applications, however, this is acceptable. * * Exported interfaces ---- input * ============================== * * The current exported interfaces for gathering environmental noise * from the devices are: * * void add_keyboard_randomness(unsigned char scancode); * void add_mouse_randomness(__u32 mouse_data); * void add_interrupt_randomness(int irq); * void add_blkdev_randomness(int irq); * * add_keyboard_randomness() uses the inter-keypress timing, as well as the * scancode as random inputs into the "entropy pool". * * add_mouse_randomness() uses the mouse interrupt timing, as well as * the reported position of the mouse from the hardware. * * add_interrupt_randomness() uses the inter-interrupt timing as random * inputs to the entropy pool. Note that not all interrupts are good * sources of randomness! For example, the timer interrupts is not a * good choice, because the periodicity of the interrupts is to * regular, and hence predictable to an attacker. Disk interrupts are * a better measure, since the timing of the disk interrupts are more * unpredictable. * * add_blkdev_randomness() times the finishing time of block requests. * * All of these routines try to estimate how many bits of randomness a * particular randomness source. They do this by keeping track of the * first and second order deltas of the event timings. * * Ensuring unpredictability at system startup * ============================================ * * When any operating system starts up, it will go through a sequence * of actions that are fairly predictable by an adversary, especially * if the start-up does not involve interaction with a human operator. * This reduces the actual number of bits of unpredictability in the * entropy pool below the value in entropy_count. In order to * counteract this effect, it helps to carry information in the * entropy pool across shut-downs and start-ups. To do this, put the * following lines an appropriate script which is run during the boot * sequence: * * echo "Initializing random number generator..." * random_seed=/var/run/random-seed * # Carry a random seed from start-up to start-up * # Load and then save 512 bytes, which is the size of the entropy pool * if [ -f $random_seed ]; then * cat $random_seed >/dev/urandom * fi * dd if=/dev/urandom of=$random_seed count=1 * chmod 600 $random_seed * * and the following lines in an appropriate script which is run as * the system is shutdown: * * # Carry a random seed from shut-down to start-up * # Save 512 bytes, which is the size of the entropy pool * echo "Saving random seed..." * random_seed=/var/run/random-seed * dd if=/dev/urandom of=$random_seed count=1 * chmod 600 $random_seed * * For example, on most modern systems using the System V init * scripts, such code fragments would be found in * /etc/rc.d/init.d/random. On older Linux systems, the correct script * location might be in /etc/rcb.d/rc.local or /etc/rc.d/rc.0. * * Effectively, these commands cause the contents of the entropy pool * to be saved at shut-down time and reloaded into the entropy pool at * start-up. (The 'dd' in the addition to the bootup script is to * make sure that /etc/random-seed is different for every start-up, * even if the system crashes without executing rc.0.) Even with * complete knowledge of the start-up activities, predicting the state * of the entropy pool requires knowledge of the previous history of * the system. * * Configuring the /dev/random driver under Linux * ============================================== * * The /dev/random driver under Linux uses minor numbers 8 and 9 of * the /dev/mem major number (#1). So if your system does not have * /dev/random and /dev/urandom created already, they can be created * by using the commands: * * mknod /dev/random c 1 8 * mknod /dev/urandom c 1 9 * * Acknowledgements: * ================= * * Ideas for constructing this random number generator were derived * from Pretty Good Privacy's random number generator, and from private * discussions with Phil Karn. Colin Plumb provided a faster random * number generator, which speed up the mixing function of the entropy * pool, taken from PGPfone. Dale Worley has also contributed many * useful ideas and suggestions to improve this driver. * * Any flaws in the design are solely my responsibility, and should * not be attributed to the Phil, Colin, or any of authors of PGP. * * The code for SHA transform was taken from Peter Gutmann's * implementation, which has been placed in the public domain. * The code for MD5 transform was taken from Colin Plumb's * implementation, which has been placed in the public domain. The * MD5 cryptographic checksum was devised by Ronald Rivest, and is * documented in RFC 1321, "The MD5 Message Digest Algorithm". * * Further background information on this topic may be obtained from * RFC 1750, "Randomness Recommendations for Security", by Donald * Eastlake, Steve Crocker, and Jeff Schiller. */ #include #include #include #include #include #include #include #include #include #include #include #include #include #include /* * Configuration information */ #undef RANDOM_BENCHMARK #undef BENCHMARK_NOINT #define ROTATE_PARANOIA #define POOLWORDS 128 /* Power of 2 - note that this is 32-bit words */ #define POOLBITS (POOLWORDS*32) /* * The pool is stirred with a primitive polynomial of degree POOLWORDS * over GF(2). The taps for various sizes are defined below. They are * chosen to be evenly spaced (minimum RMS distance from evenly spaced; * the numbers in the comments are a scaled squared error sum) except * for the last tap, which is 1 to get the twisting happening as fast * as possible. */ #if POOLWORDS == 2048 /* 115 x^2048+x^1638+x^1231+x^819+x^411+x^1+1 */ #define TAP1 1638 #define TAP2 1231 #define TAP3 819 #define TAP4 411 #define TAP5 1 #elif POOLWORDS == 1024 /* 290 x^1024+x^817+x^615+x^412+x^204+x^1+1 */ /* Alt: 115 x^1024+x^819+x^616+x^410+x^207+x^2+1 */ #define TAP1 817 #define TAP2 615 #define TAP3 412 #define TAP4 204 #define TAP5 1 #elif POOLWORDS == 512 /* 225 x^512+x^411+x^308+x^208+x^104+x+1 */ /* Alt: 95 x^512+x^409+x^307+x^206+x^102+x^2+1 * 95 x^512+x^409+x^309+x^205+x^103+x^2+1 */ #define TAP1 411 #define TAP2 308 #define TAP3 208 #define TAP4 104 #define TAP5 1 #elif POOLWORDS == 256 /* 125 x^256+x^205+x^155+x^101+x^52+x+1 */ #define TAP1 205 #define TAP2 155 #define TAP3 101 #define TAP4 52 #define TAP5 1 #elif POOLWORDS == 128 /* 105 x^128+x^103+x^76+x^51+x^25+x+1 */ /* Alt: 70 x^128+x^103+x^78+x^51+x^27+x^2+1 */ #define TAP1 103 #define TAP2 76 #define TAP3 51 #define TAP4 25 #define TAP5 1 #elif POOLWORDS == 64 /* 15 x^64+x^52+x^39+x^26+x^14+x+1 */ #define TAP1 52 #define TAP2 39 #define TAP3 26 #define TAP4 14 #define TAP5 1 #elif POOLWORDS == 32 /* 15 x^32+x^26+x^20+x^14+x^7+x^1+1 */ #define TAP1 26 #define TAP2 20 #define TAP3 14 #define TAP4 7 #define TAP5 1 #elif POOLWORDS & (POOLWORDS-1) #error POOLWORDS must be a power of 2 #else #error No primitive polynomial available for chosen POOLWORDS #endif /* * For the purposes of better mixing, we use the CRC-32 polynomial as * well to make a twisted Generalized Feedback Shift Reigster * * (See M. Matsumoto & Y. Kurita, 1992. Twisted GFSR generators. ACM * Transactions on Modeling and Computer Simulation 2(3):179-194. * Also see M. Matsumoto & Y. Kurita, 1994. Twisted GFSR generators * II. ACM Transactions on Mdeling and Computer Simulation 4:254-266) * * Thanks to Colin Plumb for suggesting this. * We have not analyzed the resultant polynomial to prove it primitive; * in fact it almost certainly isn't. Nonetheless, the irreducible factors * of a random large-degree polynomial over GF(2) are more than large enough * that periodicity is not a concern. * * The input hash is much less sensitive than the output hash. All that * we want of it is that it be a good non-cryptographic hash; i.e. it * not produce collisions when fed "random" data of the sort we expect * to see. As long as the pool state differs for different inputs, we * have preserved the input entropy and done a good job. The fact that an * intelligent attacker can construct inputs that will produce controlled * alterations to the pool's state is not important because we don't * consider such inputs to contribute any randomness. * The only property we need with respect to them is * that the attacker can't increase his/her knowledge of the pool's state. * Since all additions are reversible (knowing the final state and the * input, you can reconstruct the initial state), if an attacker has * any uncertainty about the initial state, he/she can only shuffle that * uncertainty about, but never cause any collisions (which would * decrease the uncertainty). * * The chosen system lets the state of the pool be (essentially) the input * modulo the generator polymnomial. Now, for random primitive polynomials, * this is a universal class of hash functions, meaning that the chance * of a collision is limited by the attacker's knowledge of the generator * polynomail, so if it is chosen at random, an attacker can never force * a collision. Here, we use a fixed polynomial, but we *can* assume that * ###--> it is unknown to the processes generating the input entropy. <-### * Because of this important property, this is a good, collision-resistant * hash; hash collisions will occur no more often than chance. */ /* * The minimum number of bits to release a "wait on input". Should * probably always be 8, since a /dev/random read can return a single * byte. */ #define WAIT_INPUT_BITS 8 /* * The limit number of bits under which to release a "wait on * output". Should probably always be the same as WAIT_INPUT_BITS, so * that an output wait releases when and only when a wait on input * would block. */ #define WAIT_OUTPUT_BITS WAIT_INPUT_BITS /* There is actually only one of these, globally. */ struct random_bucket { unsigned add_ptr; unsigned entropy_count; #ifdef ROTATE_PARANOIA int input_rotate; #endif __u32 pool[POOLWORDS]; }; #ifdef RANDOM_BENCHMARK /* For benchmarking only */ struct random_benchmark { unsigned long long start_time; int times; /* # of samples */ unsigned long min; unsigned long max; unsigned long accum; /* accumulator for average */ const char *descr; int unit; unsigned long flags; }; #define BENCHMARK_INTERVAL 500 static void initialize_benchmark(struct random_benchmark *bench, const char *descr, int unit); static void begin_benchmark(struct random_benchmark *bench); static void end_benchmark(struct random_benchmark *bench); struct random_benchmark timer_benchmark; #endif /* There is one of these per entropy source */ struct timer_rand_state { __u32 last_time; __s32 last_delta,last_delta2; int dont_count_entropy:1; }; static struct random_bucket random_state; static struct timer_rand_state keyboard_timer_state; static struct timer_rand_state mouse_timer_state; static struct timer_rand_state extract_timer_state; static struct timer_rand_state *irq_timer_state[NR_IRQS]; static struct timer_rand_state *blkdev_timer_state[MAX_BLKDEV]; static struct wait_queue *random_read_wait; static struct wait_queue *random_write_wait; static ssize_t random_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos); static ssize_t random_read_unlimited(struct file * file, char * buf, size_t nbytes, loff_t *ppos); static unsigned int random_poll(struct file *file, poll_table * wait); static ssize_t random_write(struct file * file, const char * buffer, size_t count, loff_t *ppos); static int random_ioctl(struct inode * inode, struct file * file, unsigned int cmd, unsigned long arg); static inline void fast_add_entropy_words(struct random_bucket *r, __u32 x, __u32 y); static void add_entropy_words(struct random_bucket *r, __u32 x, __u32 y); #ifndef MIN #define MIN(a,b) (((a) < (b)) ? (a) : (b)) #endif /* * Unfortunately, while the GCC optimizer for the i386 understands how * to optimize a static rotate left of x bits, it doesn't know how to * deal with a variable rotate of x bits. So we use a bit of asm magic. */ #if (!defined (__i386__)) extern inline __u32 rotate_left(int i, __u32 word) { return (word << i) | (word >> (32 - i)); } #else extern inline __u32 rotate_left(int i, __u32 word) { __asm__("roll %%cl,%0" :"=r" (word) :"0" (word),"c" (i)); return word; } #endif /* * More asm magic.... * * For entropy estimation, we need to do an integral base 2 * logarithm. * * Note the "12bits" suffix - this is used for numbers between * 0 and 4095 only. This allows a few shortcuts. */ #if 0 /* Slow but clear version */ static inline __u32 int_ln_12bits(__u32 word) { __u32 nbits = 0; while (word >>= 1) nbits++; return nbits; } #else /* Faster (more clever) version, courtesy Colin Plumb */ static inline __u32 int_ln_12bits(__u32 word) { /* Smear msbit right to make an n-bit mask */ word |= word >> 8; word |= word >> 4; word |= word >> 2; word |= word >> 1; /* Remove one bit to make this a logarithm */ word >>= 1; /* Count the bits set in the word */ word -= (word >> 1) & 0x555; word = (word & 0x333) + ((word >> 2) & 0x333); word += (word >> 4); word += (word >> 8); return word & 15; } #endif /* * Initialize the random pool with standard stuff. * * NOTE: This is an OS-dependent function. */ static void init_std_data(struct random_bucket *r) { __u32 words[2], *p; int i; struct timeval tv; do_gettimeofday(&tv); add_entropy_words(r, tv.tv_sec, tv.tv_usec); /* * This doesnt lock system.utsname. Howeve we are generating * entropy so a race with a name set here is fine. */ p = (__u32 *)&system_utsname; for (i = sizeof(system_utsname) / sizeof(words); i; i--) { memcpy(words, p, sizeof(words)); add_entropy_words(r, words[0], words[1]); p += sizeof(words)/sizeof(*words); } } /* Clear the entropy pool and associated counters. */ static void rand_clear_pool(void) { memset(&random_state, 0, sizeof(random_state)); init_std_data(&random_state); } __initfunc(void rand_initialize(void)) { int i; rand_clear_pool(); for (i = 0; i < NR_IRQS; i++) irq_timer_state[i] = NULL; for (i = 0; i < MAX_BLKDEV; i++) blkdev_timer_state[i] = NULL; memset(&keyboard_timer_state, 0, sizeof(struct timer_rand_state)); memset(&mouse_timer_state, 0, sizeof(struct timer_rand_state)); memset(&extract_timer_state, 0, sizeof(struct timer_rand_state)); #ifdef RANDOM_BENCHMARK initialize_benchmark(&timer_benchmark, "timer", 0); #endif extract_timer_state.dont_count_entropy = 1; random_read_wait = NULL; random_write_wait = NULL; } void rand_initialize_irq(int irq) { struct timer_rand_state *state; if (irq >= NR_IRQS || irq_timer_state[irq]) return; /* * If kmalloc returns null, we just won't use that entropy * source. */ state = kmalloc(sizeof(struct timer_rand_state), GFP_KERNEL); if (state) { irq_timer_state[irq] = state; memset(state, 0, sizeof(struct timer_rand_state)); } } void rand_initialize_blkdev(int major, int mode) { struct timer_rand_state *state; if (major >= MAX_BLKDEV || blkdev_timer_state[major]) return; /* * If kmalloc returns null, we just won't use that entropy * source. */ state = kmalloc(sizeof(struct timer_rand_state), mode); if (state) { blkdev_timer_state[major] = state; memset(state, 0, sizeof(struct timer_rand_state)); } } /* * This function adds a byte into the entropy "pool". It does not * update the entropy estimate. The caller must do this if appropriate. * * This function is tuned for speed above most other considerations. * * The pool is stirred with a primitive polynomial of the appropriate degree, * and then twisted. We twist by three bits at a time because it's * cheap to do so and helps slightly in the expected case where the * entropy is concentrated in the low-order bits. */ #define MASK(x) ((x) & (POOLWORDS-1)) /* Convenient abreviation */ static inline void fast_add_entropy_words(struct random_bucket *r, __u32 x, __u32 y) { static __u32 const twist_table[8] = { 0, 0x3b6e20c8, 0x76dc4190, 0x4db26158, 0xedb88320, 0xd6d6a3e8, 0x9b64c2b0, 0xa00ae278 }; unsigned i, j; i = MASK(r->add_ptr - 2); /* i is always even */ r->add_ptr = i; #ifdef ROTATE_PARANOIA j = r->input_rotate + 14; if (i) j -= 7; r->input_rotate = j & 31; x = rotate_left(r->input_rotate, x); y = rotate_left(r->input_rotate, y); #endif /* * XOR in the various taps. Even though logically, we compute * x and then compute y, we read in y then x order because most * caches work slightly better with increasing read addresses. * If a tap is even then we can use the fact that i is even to * avoid a masking operation. Every polynomial has at least one * even tap, so j is always used. * (Is there a nicer way to arrange this code?) */ #if TAP1 & 1 y ^= r->pool[MASK(i+TAP1)]; x ^= r->pool[MASK(i+TAP1+1)]; #else j = MASK(i+TAP1); y ^= r->pool[j]; x ^= r->pool[j+1]; #endif #if TAP2 & 1 y ^= r->pool[MASK(i+TAP2)]; x ^= r->pool[MASK(i+TAP2+1)]; #else j = MASK(i+TAP2); y ^= r->pool[j]; x ^= r->pool[j+1]; #endif #if TAP3 & 1 y ^= r->pool[MASK(i+TAP3)]; x ^= r->pool[MASK(i+TAP3+1)]; #else j = MASK(i+TAP3); y ^= r->pool[j]; x ^= r->pool[j+1]; #endif #if TAP4 & 1 y ^= r->pool[MASK(i+TAP4)]; x ^= r->pool[MASK(i+TAP4+1)]; #else j = MASK(i+TAP4); y ^= r->pool[j]; x ^= r->pool[j+1]; #endif #if TAP5 == 1 /* We need to pretend to write pool[i+1] before computing y */ y ^= r->pool[i]; x ^= r->pool[i+1]; x ^= r->pool[MASK(i+TAP5+1)]; y ^= r->pool[i+1] = x = (x >> 3) ^ twist_table[x & 7]; r->pool[i] = (y >> 3) ^ twist_table[y & 7]; #else # if TAP5 & 1 y ^= r->pool[MASK(i+TAP5)]; x ^= r->pool[MASK(i+TAP5+1)]; # else j = MASK(i+TAP5); y ^= r->pool[j]; x ^= r->pool[j+1]; # endif y ^= r->pool[i]; x ^= r->pool[i+1]; r->pool[i] = (y >> 3) ^ twist_table[y & 7]; r->pool[i+1] = (x >> 3) ^ twist_table[x & 7]; #endif } /* * For places where we don't need the inlined version */ static void add_entropy_words(struct random_bucket *r, __u32 x, __u32 y) { fast_add_entropy_words(r, x, y); } /* * This function adds entropy to the entropy "pool" by using timing * delays. It uses the timer_rand_state structure to make an estimate * of how many bits of entropy this call has added to the pool. * * The number "num" is also added to the pool - it should somehow describe * the type of event which just happened. This is currently 0-255 for * keyboard scan codes, and 256 upwards for interrupts. * On the i386, this is assumed to be at most 16 bits, and the high bits * are used for a high-resolution timer. * */ static void add_timer_randomness(struct random_bucket *r, struct timer_rand_state *state, unsigned num) { __u32 time; __s32 delta, delta2, delta3; #ifdef RANDOM_BENCHMARK begin_benchmark(&timer_benchmark); #endif #if defined (__i386__) if (boot_cpu_data.x86_capability & X86_FEATURE_TSC) { __u32 high; __asm__(".byte 0x0f,0x31" :"=a" (time), "=d" (high)); num ^= high; } else { time = jiffies; } #else time = jiffies; #endif fast_add_entropy_words(r, (__u32)num, time); /* * Calculate number of bits of randomness we probably added. * We take into account the first, second and third-order deltas * in order to make our estimate. */ if ((r->entropy_count < POOLBITS) && !state->dont_count_entropy) { delta = time - state->last_time; state->last_time = time; delta2 = delta - state->last_delta; state->last_delta = delta; delta3 = delta2 - state->last_delta2; state->last_delta2 = delta2; if (delta < 0) delta = -delta; if (delta2 < 0) delta2 = -delta2; if (delta3 < 0) delta3 = -delta3; if (delta > delta2) delta = delta2; if (delta > delta3) delta = delta3; /* * delta is now minimum absolute delta. * Round down by 1 bit on general principles, * and limit entropy entimate to 12 bits. */ delta >>= 1; delta &= (1 << 12) - 1; r->entropy_count += int_ln_12bits(delta); /* Prevent overflow */ if (r->entropy_count > POOLBITS) r->entropy_count = POOLBITS; /* Wake up waiting processes, if we have enough entropy. */ if (r->entropy_count >= WAIT_INPUT_BITS) wake_up_interruptible(&random_read_wait); } #ifdef RANDOM_BENCHMARK end_benchmark(&timer_benchmark); #endif } void add_keyboard_randomness(unsigned char scancode) { add_timer_randomness(&random_state, &keyboard_timer_state, scancode); } void add_mouse_randomness(__u32 mouse_data) { add_timer_randomness(&random_state, &mouse_timer_state, mouse_data); } void add_interrupt_randomness(int irq) { if (irq >= NR_IRQS || irq_timer_state[irq] == 0) return; add_timer_randomness(&random_state, irq_timer_state[irq], 0x100+irq); } void add_blkdev_randomness(int major) { if (major >= MAX_BLKDEV) return; if (blkdev_timer_state[major] == 0) { rand_initialize_blkdev(major, GFP_ATOMIC); if (blkdev_timer_state[major] == 0) return; } add_timer_randomness(&random_state, blkdev_timer_state[major], 0x200+major); } /* * This chunk of code defines a function * void HASH_TRANSFORM(__u32 digest[HASH_BUFFER_SIZE + HASH_EXTRA_SIZE], * __u32 const data[16]) * * The function hashes the input data to produce a digest in the first * HASH_BUFFER_SIZE words of the digest[] array, and uses HASH_EXTRA_SIZE * more words for internal purposes. (This buffer is exported so the * caller can wipe it once rather than this code doing it each call, * and tacking it onto the end of the digest[] array is the quick and * dirty way of doing it.) * * It so happens that MD5 and SHA share most of the initial vector * used to initialize the digest[] array before the first call: * 1) 0x67452301 * 2) 0xefcdab89 * 3) 0x98badcfe * 4) 0x10325476 * 5) 0xc3d2e1f0 (SHA only) * * For /dev/random purposes, the length of the data being hashed is * fixed in length (at POOLWORDS words), so appending a bit count in * the usual way is not cryptographically necessary. */ #define USE_SHA #ifdef USE_SHA #define HASH_BUFFER_SIZE 5 #define HASH_EXTRA_SIZE 80 #define HASH_TRANSFORM SHATransform /* Various size/speed tradeoffs are available. Choose 0..3. */ #define SHA_CODE_SIZE 0 /* * SHA transform algorithm, taken from code written by Peter Gutmann, * and placed in the public domain. */ /* The SHA f()-functions. */ #define f1(x,y,z) ( z ^ (x & (y^z)) ) /* Rounds 0-19: x ? y : z */ #define f2(x,y,z) (x ^ y ^ z) /* Rounds 20-39: XOR */ #define f3(x,y,z) ( (x & y) + (z & (x ^ y)) ) /* Rounds 40-59: majority */ #define f4(x,y,z) (x ^ y ^ z) /* Rounds 60-79: XOR */ /* The SHA Mysterious Constants */ #define K1 0x5A827999L /* Rounds 0-19: sqrt(2) * 2^30 */ #define K2 0x6ED9EBA1L /* Rounds 20-39: sqrt(3) * 2^30 */ #define K3 0x8F1BBCDCL /* Rounds 40-59: sqrt(5) * 2^30 */ #define K4 0xCA62C1D6L /* Rounds 60-79: sqrt(10) * 2^30 */ #define ROTL(n,X) ( ( ( X ) << n ) | ( ( X ) >> ( 32 - n ) ) ) #define subRound(a, b, c, d, e, f, k, data) \ ( e += ROTL( 5, a ) + f( b, c, d ) + k + data, b = ROTL( 30, b ) ) static void SHATransform(__u32 digest[85], __u32 const data[16]) { __u32 A, B, C, D, E; /* Local vars */ __u32 TEMP; int i; #define W (digest + HASH_BUFFER_SIZE) /* Expanded data array */ /* * Do the preliminary expansion of 16 to 80 words. Doing it * out-of-line line this is faster than doing it in-line on * register-starved machines like the x86, and not really any * slower on real processors. */ memcpy(W, data, 16*sizeof(__u32)); for (i = 0; i < 64; i++) { TEMP = W[i] ^ W[i+2] ^ W[i+8] ^ W[i+13]; W[i+16] = ROTL(1, TEMP); } /* Set up first buffer and local data buffer */ A = digest[ 0 ]; B = digest[ 1 ]; C = digest[ 2 ]; D = digest[ 3 ]; E = digest[ 4 ]; /* Heavy mangling, in 4 sub-rounds of 20 iterations each. */ #if SHA_CODE_SIZE == 0 /* * Approximately 50% of the speed of the largest version, but * takes up 1/16 the space. Saves about 6k on an i386 kernel. */ for (i = 0; i < 80; i++) { if (i < 40) { if (i < 20) TEMP = f1(B, C, D) + K1; else TEMP = f2(B, C, D) + K2; } else { if (i < 60) TEMP = f3(B, C, D) + K3; else TEMP = f4(B, C, D) + K4; } TEMP += ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } #elif SHA_CODE_SIZE == 1 for (i = 0; i < 20; i++) { TEMP = f1(B, C, D) + K1 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } for (; i < 40; i++) { TEMP = f2(B, C, D) + K2 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } for (; i < 60; i++) { TEMP = f3(B, C, D) + K3 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } for (; i < 80; i++) { TEMP = f4(B, C, D) + K4 + ROTL(5, A) + E + W[i]; E = D; D = C; C = ROTL(30, B); B = A; A = TEMP; } #elif SHA_CODE_SIZE == 2 for (i = 0; i < 20; i += 5) { subRound( A, B, C, D, E, f1, K1, W[ i ] ); subRound( E, A, B, C, D, f1, K1, W[ i+1 ] ); subRound( D, E, A, B, C, f1, K1, W[ i+2 ] ); subRound( C, D, E, A, B, f1, K1, W[ i+3 ] ); subRound( B, C, D, E, A, f1, K1, W[ i+4 ] ); } for (; i < 40; i += 5) { subRound( A, B, C, D, E, f2, K2, W[ i ] ); subRound( E, A, B, C, D, f2, K2, W[ i+1 ] ); subRound( D, E, A, B, C, f2, K2, W[ i+2 ] ); subRound( C, D, E, A, B, f2, K2, W[ i+3 ] ); subRound( B, C, D, E, A, f2, K2, W[ i+4 ] ); } for (; i < 60; i += 5) { subRound( A, B, C, D, E, f3, K3, W[ i ] ); subRound( E, A, B, C, D, f3, K3, W[ i+1 ] ); subRound( D, E, A, B, C, f3, K3, W[ i+2 ] ); subRound( C, D, E, A, B, f3, K3, W[ i+3 ] ); subRound( B, C, D, E, A, f3, K3, W[ i+4 ] ); } for (; i < 80; i += 5) { subRound( A, B, C, D, E, f4, K4, W[ i ] ); subRound( E, A, B, C, D, f4, K4, W[ i+1 ] ); subRound( D, E, A, B, C, f4, K4, W[ i+2 ] ); subRound( C, D, E, A, B, f4, K4, W[ i+3 ] ); subRound( B, C, D, E, A, f4, K4, W[ i+4 ] ); } #elif SHA_CODE_SIZE == 3 /* Really large version */ subRound( A, B, C, D, E, f1, K1, W[ 0 ] ); subRound( E, A, B, C, D, f1, K1, W[ 1 ] ); subRound( D, E, A, B, C, f1, K1, W[ 2 ] ); subRound( C, D, E, A, B, f1, K1, W[ 3 ] ); subRound( B, C, D, E, A, f1, K1, W[ 4 ] ); subRound( A, B, C, D, E, f1, K1, W[ 5 ] ); subRound( E, A, B, C, D, f1, K1, W[ 6 ] ); subRound( D, E, A, B, C, f1, K1, W[ 7 ] ); subRound( C, D, E, A, B, f1, K1, W[ 8 ] ); subRound( B, C, D, E, A, f1, K1, W[ 9 ] ); subRound( A, B, C, D, E, f1, K1, W[ 10 ] ); subRound( E, A, B, C, D, f1, K1, W[ 11 ] ); subRound( D, E, A, B, C, f1, K1, W[ 12 ] ); subRound( C, D, E, A, B, f1, K1, W[ 13 ] ); subRound( B, C, D, E, A, f1, K1, W[ 14 ] ); subRound( A, B, C, D, E, f1, K1, W[ 15 ] ); subRound( E, A, B, C, D, f1, K1, W[ 16 ] ); subRound( D, E, A, B, C, f1, K1, W[ 17 ] ); subRound( C, D, E, A, B, f1, K1, W[ 18 ] ); subRound( B, C, D, E, A, f1, K1, W[ 19 ] ); subRound( A, B, C, D, E, f2, K2, W[ 20 ] ); subRound( E, A, B, C, D, f2, K2, W[ 21 ] ); subRound( D, E, A, B, C, f2, K2, W[ 22 ] ); subRound( C, D, E, A, B, f2, K2, W[ 23 ] ); subRound( B, C, D, E, A, f2, K2, W[ 24 ] ); subRound( A, B, C, D, E, f2, K2, W[ 25 ] ); subRound( E, A, B, C, D, f2, K2, W[ 26 ] ); subRound( D, E, A, B, C, f2, K2, W[ 27 ] ); subRound( C, D, E, A, B, f2, K2, W[ 28 ] ); subRound( B, C, D, E, A, f2, K2, W[ 29 ] ); subRound( A, B, C, D, E, f2, K2, W[ 30 ] ); subRound( E, A, B, C, D, f2, K2, W[ 31 ] ); subRound( D, E, A, B, C, f2, K2, W[ 32 ] ); subRound( C, D, E, A, B, f2, K2, W[ 33 ] ); subRound( B, C, D, E, A, f2, K2, W[ 34 ] ); subRound( A, B, C, D, E, f2, K2, W[ 35 ] ); subRound( E, A, B, C, D, f2, K2, W[ 36 ] ); subRound( D, E, A, B, C, f2, K2, W[ 37 ] ); subRound( C, D, E, A, B, f2, K2, W[ 38 ] ); subRound( B, C, D, E, A, f2, K2, W[ 39 ] ); subRound( A, B, C, D, E, f3, K3, W[ 40 ] ); subRound( E, A, B, C, D, f3, K3, W[ 41 ] ); subRound( D, E, A, B, C, f3, K3, W[ 42 ] ); subRound( C, D, E, A, B, f3, K3, W[ 43 ] ); subRound( B, C, D, E, A, f3, K3, W[ 44 ] ); subRound( A, B, C, D, E, f3, K3, W[ 45 ] ); subRound( E, A, B, C, D, f3, K3, W[ 46 ] ); subRound( D, E, A, B, C, f3, K3, W[ 47 ] ); subRound( C, D, E, A, B, f3, K3, W[ 48 ] ); subRound( B, C, D, E, A, f3, K3, W[ 49 ] ); subRound( A, B, C, D, E, f3, K3, W[ 50 ] ); subRound( E, A, B, C, D, f3, K3, W[ 51 ] ); subRound( D, E, A, B, C, f3, K3, W[ 52 ] ); subRound( C, D, E, A, B, f3, K3, W[ 53 ] ); subRound( B, C, D, E, A, f3, K3, W[ 54 ] ); subRound( A, B, C, D, E, f3, K3, W[ 55 ] ); subRound( E, A, B, C, D, f3, K3, W[ 56 ] ); subRound( D, E, A, B, C, f3, K3, W[ 57 ] ); subRound( C, D, E, A, B, f3, K3, W[ 58 ] ); subRound( B, C, D, E, A, f3, K3, W[ 59 ] ); subRound( A, B, C, D, E, f4, K4, W[ 60 ] ); subRound( E, A, B, C, D, f4, K4, W[ 61 ] ); subRound( D, E, A, B, C, f4, K4, W[ 62 ] ); subRound( C, D, E, A, B, f4, K4, W[ 63 ] ); subRound( B, C, D, E, A, f4, K4, W[ 64 ] ); subRound( A, B, C, D, E, f4, K4, W[ 65 ] ); subRound( E, A, B, C, D, f4, K4, W[ 66 ] ); subRound( D, E, A, B, C, f4, K4, W[ 67 ] ); subRound( C, D, E, A, B, f4, K4, W[ 68 ] ); subRound( B, C, D, E, A, f4, K4, W[ 69 ] ); subRound( A, B, C, D, E, f4, K4, W[ 70 ] ); subRound( E, A, B, C, D, f4, K4, W[ 71 ] ); subRound( D, E, A, B, C, f4, K4, W[ 72 ] ); subRound( C, D, E, A, B, f4, K4, W[ 73 ] ); subRound( B, C, D, E, A, f4, K4, W[ 74 ] ); subRound( A, B, C, D, E, f4, K4, W[ 75 ] ); subRound( E, A, B, C, D, f4, K4, W[ 76 ] ); subRound( D, E, A, B, C, f4, K4, W[ 77 ] ); subRound( C, D, E, A, B, f4, K4, W[ 78 ] ); subRound( B, C, D, E, A, f4, K4, W[ 79 ] ); #else #error Illegal SHA_CODE_SIZE #endif /* Build message digest */ digest[ 0 ] += A; digest[ 1 ] += B; digest[ 2 ] += C; digest[ 3 ] += D; digest[ 4 ] += E; /* W is wiped by the caller */ #undef W } #undef ROTL #undef f1 #undef f2 #undef f3 #undef f4 #undef K1 #undef K2 #undef K3 #undef K4 #undef subRound #else /* !USE_SHA - Use MD5 */ #define HASH_BUFFER_SIZE 4 #define HASH_EXTRA_SIZE 0 #define HASH_TRANSFORM MD5Transform /* * MD5 transform algorithm, taken from code written by Colin Plumb, * and put into the public domain * * QUESTION: Replace this with SHA, which as generally received better * reviews from the cryptographic community? */ /* The four core functions - F1 is optimized somewhat */ /* #define F1(x, y, z) (x & y | ~x & z) */ #define F1(x, y, z) (z ^ (x & (y ^ z))) #define F2(x, y, z) F1(z, x, y) #define F3(x, y, z) (x ^ y ^ z) #define F4(x, y, z) (y ^ (x | ~z)) /* This is the central step in the MD5 algorithm. */ #define MD5STEP(f, w, x, y, z, data, s) \ ( w += f(x, y, z) + data, w = w<>(32-s), w += x ) /* * The core of the MD5 algorithm, this alters an existing MD5 hash to * reflect the addition of 16 longwords of new data. MD5Update blocks * the data and converts bytes into longwords for this routine. */ static void MD5Transform(__u32 buf[HASH_BUFFER_SIZE], __u32 const in[16]) { __u32 a, b, c, d; a = buf[0]; b = buf[1]; c = buf[2]; d = buf[3]; MD5STEP(F1, a, b, c, d, in[ 0]+0xd76aa478, 7); MD5STEP(F1, d, a, b, c, in[ 1]+0xe8c7b756, 12); MD5STEP(F1, c, d, a, b, in[ 2]+0x242070db, 17); MD5STEP(F1, b, c, d, a, in[ 3]+0xc1bdceee, 22); MD5STEP(F1, a, b, c, d, in[ 4]+0xf57c0faf, 7); MD5STEP(F1, d, a, b, c, in[ 5]+0x4787c62a, 12); MD5STEP(F1, c, d, a, b, in[ 6]+0xa8304613, 17); MD5STEP(F1, b, c, d, a, in[ 7]+0xfd469501, 22); MD5STEP(F1, a, b, c, d, in[ 8]+0x698098d8, 7); MD5STEP(F1, d, a, b, c, in[ 9]+0x8b44f7af, 12); MD5STEP(F1, c, d, a, b, in[10]+0xffff5bb1, 17); MD5STEP(F1, b, c, d, a, in[11]+0x895cd7be, 22); MD5STEP(F1, a, b, c, d, in[12]+0x6b901122, 7); MD5STEP(F1, d, a, b, c, in[13]+0xfd987193, 12); MD5STEP(F1, c, d, a, b, in[14]+0xa679438e, 17); MD5STEP(F1, b, c, d, a, in[15]+0x49b40821, 22); MD5STEP(F2, a, b, c, d, in[ 1]+0xf61e2562, 5); MD5STEP(F2, d, a, b, c, in[ 6]+0xc040b340, 9); MD5STEP(F2, c, d, a, b, in[11]+0x265e5a51, 14); MD5STEP(F2, b, c, d, a, in[ 0]+0xe9b6c7aa, 20); MD5STEP(F2, a, b, c, d, in[ 5]+0xd62f105d, 5); MD5STEP(F2, d, a, b, c, in[10]+0x02441453, 9); MD5STEP(F2, c, d, a, b, in[15]+0xd8a1e681, 14); MD5STEP(F2, b, c, d, a, in[ 4]+0xe7d3fbc8, 20); MD5STEP(F2, a, b, c, d, in[ 9]+0x21e1cde6, 5); MD5STEP(F2, d, a, b, c, in[14]+0xc33707d6, 9); MD5STEP(F2, c, d, a, b, in[ 3]+0xf4d50d87, 14); MD5STEP(F2, b, c, d, a, in[ 8]+0x455a14ed, 20); MD5STEP(F2, a, b, c, d, in[13]+0xa9e3e905, 5); MD5STEP(F2, d, a, b, c, in[ 2]+0xfcefa3f8, 9); MD5STEP(F2, c, d, a, b, in[ 7]+0x676f02d9, 14); MD5STEP(F2, b, c, d, a, in[12]+0x8d2a4c8a, 20); MD5STEP(F3, a, b, c, d, in[ 5]+0xfffa3942, 4); MD5STEP(F3, d, a, b, c, in[ 8]+0x8771f681, 11); MD5STEP(F3, c, d, a, b, in[11]+0x6d9d6122, 16); MD5STEP(F3, b, c, d, a, in[14]+0xfde5380c, 23); MD5STEP(F3, a, b, c, d, in[ 1]+0xa4beea44, 4); MD5STEP(F3, d, a, b, c, in[ 4]+0x4bdecfa9, 11); MD5STEP(F3, c, d, a, b, in[ 7]+0xf6bb4b60, 16); MD5STEP(F3, b, c, d, a, in[10]+0xbebfbc70, 23); MD5STEP(F3, a, b, c, d, in[13]+0x289b7ec6, 4); MD5STEP(F3, d, a, b, c, in[ 0]+0xeaa127fa, 11); MD5STEP(F3, c, d, a, b, in[ 3]+0xd4ef3085, 16); MD5STEP(F3, b, c, d, a, in[ 6]+0x04881d05, 23); MD5STEP(F3, a, b, c, d, in[ 9]+0xd9d4d039, 4); MD5STEP(F3, d, a, b, c, in[12]+0xe6db99e5, 11); MD5STEP(F3, c, d, a, b, in[15]+0x1fa27cf8, 16); MD5STEP(F3, b, c, d, a, in[ 2]+0xc4ac5665, 23); MD5STEP(F4, a, b, c, d, in[ 0]+0xf4292244, 6); MD5STEP(F4, d, a, b, c, in[ 7]+0x432aff97, 10); MD5STEP(F4, c, d, a, b, in[14]+0xab9423a7, 15); MD5STEP(F4, b, c, d, a, in[ 5]+0xfc93a039, 21); MD5STEP(F4, a, b, c, d, in[12]+0x655b59c3, 6); MD5STEP(F4, d, a, b, c, in[ 3]+0x8f0ccc92, 10); MD5STEP(F4, c, d, a, b, in[10]+0xffeff47d, 15); MD5STEP(F4, b, c, d, a, in[ 1]+0x85845dd1, 21); MD5STEP(F4, a, b, c, d, in[ 8]+0x6fa87e4f, 6); MD5STEP(F4, d, a, b, c, in[15]+0xfe2ce6e0, 10); MD5STEP(F4, c, d, a, b, in[ 6]+0xa3014314, 15); MD5STEP(F4, b, c, d, a, in[13]+0x4e0811a1, 21); MD5STEP(F4, a, b, c, d, in[ 4]+0xf7537e82, 6); MD5STEP(F4, d, a, b, c, in[11]+0xbd3af235, 10); MD5STEP(F4, c, d, a, b, in[ 2]+0x2ad7d2bb, 15); MD5STEP(F4, b, c, d, a, in[ 9]+0xeb86d391, 21); buf[0] += a; buf[1] += b; buf[2] += c; buf[3] += d; } #undef F1 #undef F2 #undef F3 #undef F4 #undef MD5STEP #endif /* !USE_SHA */ #if POOLWORDS % 16 != 0 #error extract_entropy() assumes that POOLWORDS is a multiple of 16 words. #endif /* * This function extracts randomness from the "entropy pool", and * returns it in a buffer. This function computes how many remaining * bits of entropy are left in the pool, but it does not restrict the * number of bytes that are actually obtained. */ static ssize_t extract_entropy(struct random_bucket *r, char * buf, size_t nbytes, int to_user) { ssize_t ret, i; __u32 tmp[HASH_BUFFER_SIZE + HASH_EXTRA_SIZE]; __u32 x; add_timer_randomness(r, &extract_timer_state, nbytes); /* Redundant, but just in case... */ if (r->entropy_count > POOLBITS) r->entropy_count = POOLBITS; ret = nbytes; if (r->entropy_count / 8 >= nbytes) r->entropy_count -= nbytes*8; else r->entropy_count = 0; if (r->entropy_count < WAIT_OUTPUT_BITS) wake_up_interruptible(&random_write_wait); while (nbytes) { /* Hash the pool to get the output */ tmp[0] = 0x67452301; tmp[1] = 0xefcdab89; tmp[2] = 0x98badcfe; tmp[3] = 0x10325476; #ifdef USE_SHA tmp[4] = 0xc3d2e1f0; #endif for (i = 0; i < POOLWORDS; i += 16) HASH_TRANSFORM(tmp, r->pool+i); /* * The following code does two separate things that happen * to both work two words at a time, so are convenient * to do together. * * First, this feeds the output back into the pool so * that the next call will return different results. * Any perturbation of the pool's state would do, even * changing one bit, but this mixes the pool nicely. * * Second, this folds the output in half to hide the data * fed back into the pool from the user and further mask * any patterns in the hash output. (The exact folding * pattern is not important; the one used here is quick.) */ for (i = 0; i < HASH_BUFFER_SIZE/2; i++) { x = tmp[i + (HASH_BUFFER_SIZE+1)/2]; add_entropy_words(r, tmp[i], x); tmp[i] ^= x; } #if HASH_BUFFER_SIZE & 1 /* There's a middle word to deal with */ x = tmp[HASH_BUFFER_SIZE/2]; add_entropy_words(r, x, (__u32)buf); x ^= (x >> 16); /* Fold it in half */ ((__u16 *)tmp)[HASH_BUFFER_SIZE-1] = (__u16)x; #endif /* Copy data to destination buffer */ i = MIN(nbytes, HASH_BUFFER_SIZE*sizeof(__u32)/2); if (to_user) { i -= copy_to_user(buf, (__u8 const *)tmp, i); if (!i) { ret = -EFAULT; break; } } else memcpy(buf, (__u8 const *)tmp, i); nbytes -= i; buf += i; add_timer_randomness(r, &extract_timer_state, nbytes); if (to_user && current->need_resched) schedule(); } /* Wipe data just returned from memory */ memset(tmp, 0, sizeof(tmp)); return ret; } /* * This function is the exported kernel interface. It returns some * number of good random numbers, suitable for seeding TCP sequence * numbers, etc. */ void get_random_bytes(void *buf, int nbytes) { extract_entropy(&random_state, (char *) buf, nbytes, 0); } static ssize_t random_read(struct file * file, char * buf, size_t nbytes, loff_t *ppos) { struct wait_queue wait = { current, NULL }; ssize_t n, retval = 0, count = 0; if (nbytes == 0) return 0; add_wait_queue(&random_read_wait, &wait); while (nbytes > 0) { current->state = TASK_INTERRUPTIBLE; n = nbytes; if (n > random_state.entropy_count / 8) n = random_state.entropy_count / 8; if (n == 0) { if (file->f_flags & O_NONBLOCK) { retval = -EAGAIN; break; } if (signal_pending(current)) { retval = -ERESTARTSYS; break; } schedule(); continue; } n = extract_entropy(&random_state, buf, n, 1); if (n < 0) { retval = n; break; } count += n; buf += n; nbytes -= n; break; /* This break makes the device work */ /* like a named pipe */ } current->state = TASK_RUNNING; remove_wait_queue(&random_read_wait, &wait); /* * If we gave the user some bytes, update the access time. */ if (count != 0) { UPDATE_ATIME(file->f_dentry->d_inode); } return (count ? count : retval); } static ssize_t random_read_unlimited(struct file * file, char * buf, size_t nbytes, loff_t *ppos) { return extract_entropy(&random_state, buf, nbytes, 1); } static unsigned int random_poll(struct file *file, poll_table * wait) { unsigned int mask; poll_wait(file, &random_read_wait, wait); poll_wait(file, &random_write_wait, wait); mask = 0; if (random_state.entropy_count >= WAIT_INPUT_BITS) mask |= POLLIN | POLLRDNORM; if (random_state.entropy_count < WAIT_OUTPUT_BITS) mask |= POLLOUT | POLLWRNORM; return mask; } static ssize_t random_write(struct file * file, const char * buffer, size_t count, loff_t *ppos) { int ret = 0; size_t bytes; unsigned i; __u32 buf[16]; const char *p = buffer; size_t c = count; while (c > 0) { bytes = MIN(c, sizeof(buf)); bytes -= copy_from_user(&buf, p, bytes); if (!bytes) { ret = -EFAULT; break; } c -= bytes; p += bytes; i = (unsigned)((bytes-1) / (2 * sizeof(__u32))); do { add_entropy_words(&random_state, buf[2*i], buf[2*i+1]); } while (i--); } if (p == buffer) { return (ssize_t)ret; } else { file->f_dentry->d_inode->i_mtime = CURRENT_TIME; mark_inode_dirty(file->f_dentry->d_inode); return (ssize_t)(p - buffer); } } static int random_ioctl(struct inode * inode, struct file * file, unsigned int cmd, unsigned long arg) { int *p, size, ent_count; int retval; switch (cmd) { case RNDGETENTCNT: retval = verify_area(VERIFY_WRITE, (void *) arg, sizeof(int)); if (retval) return(retval); ent_count = random_state.entropy_count; put_user(ent_count, (int *) arg); return 0; case RNDADDTOENTCNT: if (!capable(CAP_SYS_ADMIN)) return -EPERM; retval = verify_area(VERIFY_READ, (void *) arg, sizeof(int)); if (retval) return(retval); get_user(ent_count, (int *) arg); /* * Add i to entropy_count, limiting the result to be * between 0 and POOLBITS. */ if (ent_count < -random_state.entropy_count) random_state.entropy_count = 0; else if (ent_count > POOLBITS) random_state.entropy_count = POOLBITS; else { random_state.entropy_count += ent_count; if (random_state.entropy_count > POOLBITS) random_state.entropy_count = POOLBITS; if (random_state.entropy_count < 0) random_state.entropy_count = 0; } /* * Wake up waiting processes if we have enough * entropy. */ if (random_state.entropy_count >= WAIT_INPUT_BITS) wake_up_interruptible(&random_read_wait); return 0; case RNDGETPOOL: if (!capable(CAP_SYS_ADMIN)) return -EPERM; p = (int *) arg; retval = verify_area(VERIFY_WRITE, (void *) p, sizeof(int)); if (retval) return(retval); ent_count = random_state.entropy_count; put_user(ent_count, p++); retval = verify_area(VERIFY_WRITE, (void *) p, sizeof(int)); if (retval) return(retval); get_user(size, p); put_user(POOLWORDS, p++); if (size < 0) return -EINVAL; if (size > POOLWORDS) size = POOLWORDS; if (copy_to_user(p, random_state.pool, size*sizeof(__u32))) return -EFAULT; return 0; case RNDADDENTROPY: if (!capable(CAP_SYS_ADMIN)) return -EPERM; p = (int *) arg; retval = verify_area(VERIFY_READ, (void *) p, 2*sizeof(int)); if (retval) return(retval); get_user(ent_count, p++); if (ent_count < 0) return -EINVAL; get_user(size, p++); retval = verify_area(VERIFY_READ, (void *) p, size); if (retval) return retval; retval = random_write(file, (const char *) p, size, &file->f_pos); if (retval < 0) return retval; /* * Add ent_count to entropy_count, limiting the result to be * between 0 and POOLBITS. */ if (ent_count > POOLBITS) random_state.entropy_count = POOLBITS; else { random_state.entropy_count += ent_count; if (random_state.entropy_count > POOLBITS) random_state.entropy_count = POOLBITS; if (random_state.entropy_count < 0) random_state.entropy_count = 0; } /* * Wake up waiting processes if we have enough * entropy. */ if (random_state.entropy_count >= WAIT_INPUT_BITS) wake_up_interruptible(&random_read_wait); return 0; case RNDZAPENTCNT: if (!capable(CAP_SYS_ADMIN)) return -EPERM; random_state.entropy_count = 0; return 0; case RNDCLEARPOOL: /* Clear the entropy pool and associated counters. */ if (!capable(CAP_SYS_ADMIN)) return -EPERM; rand_clear_pool(); return 0; default: return -EINVAL; } } struct file_operations random_fops = { NULL, /* random_lseek */ random_read, random_write, NULL, /* random_readdir */ random_poll, /* random_poll */ random_ioctl, NULL, /* random_mmap */ NULL, /* no special open code */ NULL, /* flush */ NULL /* no special release code */ }; struct file_operations urandom_fops = { NULL, /* unrandom_lseek */ random_read_unlimited, random_write, NULL, /* urandom_readdir */ NULL, /* urandom_poll */ random_ioctl, NULL, /* urandom_mmap */ NULL, /* no special open code */ NULL, /* flush */ NULL /* no special release code */ }; /* * TCP initial sequence number picking. This uses the random number * generator to pick an initial secret value. This value is hashed * along with the TCP endpoint information to provide a unique * starting point for each pair of TCP endpoints. This defeats * attacks which rely on guessing the initial TCP sequence number. * This algorithm was suggested by Steve Bellovin. * * Using a very strong hash was taking an appreciable amount of the total * TCP connection establishment time, so this is a weaker hash, * compensated for by changing the secret periodically. */ /* F, G and H are basic MD4 functions: selection, majority, parity */ #define F(x, y, z) ((z) ^ ((x) & ((y) ^ (z)))) #define G(x, y, z) (((x) & (y)) + (((x) ^ (y)) & (z))) #define H(x, y, z) ((x) ^ (y) ^ (z)) /* * The generic round function. The application is so specific that * we don't bother protecting all the arguments with parens, as is generally * good macro practice, in favor of extra legibility. * Rotation is separate from addition to prevent recomputation */ #define ROUND(f, a, b, c, d, x, s) \ (a += f(b, c, d) + x, a = (a << s) | (a >> (32-s))) #define K1 0 #define K2 013240474631UL #define K3 015666365641UL /* * Basic cut-down MD4 transform. Returns only 32 bits of result. */ static __u32 halfMD4Transform (__u32 const buf[4], __u32 const in[8]) { __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; /* Round 1 */ ROUND(F, a, b, c, d, in[0] + K1, 3); ROUND(F, d, a, b, c, in[1] + K1, 7); ROUND(F, c, d, a, b, in[2] + K1, 11); ROUND(F, b, c, d, a, in[3] + K1, 19); ROUND(F, a, b, c, d, in[4] + K1, 3); ROUND(F, d, a, b, c, in[5] + K1, 7); ROUND(F, c, d, a, b, in[6] + K1, 11); ROUND(F, b, c, d, a, in[7] + K1, 19); /* Round 2 */ ROUND(G, a, b, c, d, in[1] + K2, 3); ROUND(G, d, a, b, c, in[3] + K2, 5); ROUND(G, c, d, a, b, in[5] + K2, 9); ROUND(G, b, c, d, a, in[7] + K2, 13); ROUND(G, a, b, c, d, in[0] + K2, 3); ROUND(G, d, a, b, c, in[2] + K2, 5); ROUND(G, c, d, a, b, in[4] + K2, 9); ROUND(G, b, c, d, a, in[6] + K2, 13); /* Round 3 */ ROUND(H, a, b, c, d, in[3] + K3, 3); ROUND(H, d, a, b, c, in[7] + K3, 9); ROUND(H, c, d, a, b, in[2] + K3, 11); ROUND(H, b, c, d, a, in[6] + K3, 15); ROUND(H, a, b, c, d, in[1] + K3, 3); ROUND(H, d, a, b, c, in[5] + K3, 9); ROUND(H, c, d, a, b, in[0] + K3, 11); ROUND(H, b, c, d, a, in[4] + K3, 15); return buf[1] + b; /* "most hashed" word */ /* Alternative: return sum of all words? */ } #if 0 /* May be needed for IPv6 */ static __u32 twothirdsMD4Transform (__u32 const buf[4], __u32 const in[12]) { __u32 a = buf[0], b = buf[1], c = buf[2], d = buf[3]; /* Round 1 */ ROUND(F, a, b, c, d, in[ 0] + K1, 3); ROUND(F, d, a, b, c, in[ 1] + K1, 7); ROUND(F, c, d, a, b, in[ 2] + K1, 11); ROUND(F, b, c, d, a, in[ 3] + K1, 19); ROUND(F, a, b, c, d, in[ 4] + K1, 3); ROUND(F, d, a, b, c, in[ 5] + K1, 7); ROUND(F, c, d, a, b, in[ 6] + K1, 11); ROUND(F, b, c, d, a, in[ 7] + K1, 19); ROUND(F, a, b, c, d, in[ 8] + K1, 3); ROUND(F, d, a, b, c, in[ 9] + K1, 7); ROUND(F, c, d, a, b, in[10] + K1, 11); ROUND(F, b, c, d, a, in[11] + K1, 19); /* Round 2 */ ROUND(G, a, b, c, d, in[ 1] + K2, 3); ROUND(G, d, a, b, c, in[ 3] + K2, 5); ROUND(G, c, d, a, b, in[ 5] + K2, 9); ROUND(G, b, c, d, a, in[ 7] + K2, 13); ROUND(G, a, b, c, d, in[ 9] + K2, 3); ROUND(G, d, a, b, c, in[11] + K2, 5); ROUND(G, c, d, a, b, in[ 0] + K2, 9); ROUND(G, b, c, d, a, in[ 2] + K2, 13); ROUND(G, a, b, c, d, in[ 4] + K2, 3); ROUND(G, d, a, b, c, in[ 6] + K2, 5); ROUND(G, c, d, a, b, in[ 8] + K2, 9); ROUND(G, b, c, d, a, in[10] + K2, 13); /* Round 3 */ ROUND(H, a, b, c, d, in[ 3] + K3, 3); ROUND(H, d, a, b, c, in[ 7] + K3, 9); ROUND(H, c, d, a, b, in[11] + K3, 11); ROUND(H, b, c, d, a, in[ 2] + K3, 15); ROUND(H, a, b, c, d, in[ 6] + K3, 3); ROUND(H, d, a, b, c, in[10] + K3, 9); ROUND(H, c, d, a, b, in[ 1] + K3, 11); ROUND(H, b, c, d, a, in[ 5] + K3, 15); ROUND(H, a, b, c, d, in[ 9] + K3, 3); ROUND(H, d, a, b, c, in[ 0] + K3, 9); ROUND(H, c, d, a, b, in[ 4] + K3, 11); ROUND(H, b, c, d, a, in[ 8] + K3, 15); return buf[1] + b; /* "most hashed" word */ /* Alternative: return sum of all words? */ } #endif #undef ROUND #undef F #undef G #undef H #undef K1 #undef K2 #undef K3 /* This should not be decreased so low that ISNs wrap too fast. */ #define REKEY_INTERVAL 300 #define HASH_BITS 24 __u32 secure_tcp_sequence_number(__u32 saddr, __u32 daddr, __u16 sport, __u16 dport) { static __u32 rekey_time = 0; static __u32 count = 0; static __u32 secret[12]; struct timeval tv; __u32 seq; /* * Pick a random secret every REKEY_INTERVAL seconds. */ do_gettimeofday(&tv); /* We need the usecs below... */ if (!rekey_time || (tv.tv_sec - rekey_time) > REKEY_INTERVAL) { rekey_time = tv.tv_sec; /* First three words are overwritten below. */ get_random_bytes(&secret+3, sizeof(secret)-12); count = (tv.tv_sec/REKEY_INTERVAL) << HASH_BITS; } /* * Pick a unique starting offset for each TCP connection endpoints * (saddr, daddr, sport, dport). * Note that the words are placed into the first words to be * mixed in with the halfMD4. This is because the starting * vector is also a random secret (at secret+8), and further * hashing fixed data into it isn't going to improve anything, * so we should get started with the variable data. */ secret[0]=saddr; secret[1]=daddr; secret[2]=(sport << 16) + dport; seq = (halfMD4Transform(secret+8, secret) & ((1<> COOKIEBITS)) & ((__u32)-1 >> COOKIEBITS); if (diff >= maxdiff) return (__u32)-1; memcpy(tmp+3, syncookie_secret[1], sizeof(syncookie_secret[1])); tmp[0] = saddr; tmp[1] = daddr; tmp[2] = (sport << 16) + dport; tmp[3] = count - diff; /* minute counter */ HASH_TRANSFORM(tmp+16, tmp); return (cookie - tmp[17]) & COOKIEMASK; /* Leaving the data behind */ } #endif #ifdef RANDOM_BENCHMARK /* * This is so we can do some benchmarking of the random driver, to see * how much overhead add_timer_randomness really takes. This only * works on a Pentium, since it depends on the timer clock... * * Note: the results of this benchmark as of this writing (5/27/96) * * On a Pentium, add_timer_randomness() takes between 150 and 1000 * clock cycles, with an average of around 600 clock cycles. On a 75 * MHz Pentium, this translates to 2 to 13 microseconds, with an * average time of 8 microseconds. This should be fast enough so we * can use add_timer_randomness() even with the fastest of interrupts... */ static inline unsigned long long get_clock_cnt(void) { unsigned long low, high; __asm__(".byte 0x0f,0x31" :"=a" (low), "=d" (high)); return (((unsigned long long) high << 32) | low); } __initfunc(static void initialize_benchmark(struct random_benchmark *bench, const char *descr, int unit)) { bench->times = 0; bench->accum = 0; bench->max = 0; bench->min = 1 << 31; bench->descr = descr; bench->unit = unit; } static void begin_benchmark(struct random_benchmark *bench) { #ifdef BENCHMARK_NOINT save_flags(bench->flags); cli(); #endif bench->start_time = get_clock_cnt(); } static void end_benchmark(struct random_benchmark *bench) { unsigned long ticks; ticks = (unsigned long) (get_clock_cnt() - bench->start_time); #ifdef BENCHMARK_NOINT restore_flags(bench->flags); #endif if (ticks < bench->min) bench->min = ticks; if (ticks > bench->max) bench->max = ticks; bench->accum += ticks; bench->times++; if (bench->times == BENCHMARK_INTERVAL) { printk("Random benchmark: %s %d: %lu min, %lu avg, " "%lu max\n", bench->descr, bench->unit, bench->min, bench->accum / BENCHMARK_INTERVAL, bench->max); bench->times = 0; bench->accum = 0; bench->max = 0; bench->min = 1 << 31; } } #endif /* RANDOM_BENCHMARK */