| 1 | /* -*-c-*- |
| 2 | * |
| 3 | * Secure random number generator |
| 4 | * |
| 5 | * (c) 1999 Straylight/Edgeware |
| 6 | */ |
| 7 | |
| 8 | /*----- Licensing notice --------------------------------------------------* |
| 9 | * |
| 10 | * This file is part of Catacomb. |
| 11 | * |
| 12 | * Catacomb is free software; you can redistribute it and/or modify |
| 13 | * it under the terms of the GNU Library General Public License as |
| 14 | * published by the Free Software Foundation; either version 2 of the |
| 15 | * License, or (at your option) any later version. |
| 16 | * |
| 17 | * Catacomb is distributed in the hope that it will be useful, |
| 18 | * but WITHOUT ANY WARRANTY; without even the implied warranty of |
| 19 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the |
| 20 | * GNU Library General Public License for more details. |
| 21 | * |
| 22 | * You should have received a copy of the GNU Library General Public |
| 23 | * License along with Catacomb; if not, write to the Free |
| 24 | * Software Foundation, Inc., 59 Temple Place - Suite 330, Boston, |
| 25 | * MA 02111-1307, USA. |
| 26 | */ |
| 27 | |
| 28 | /*----- Notes on the random number generator ------------------------------* |
| 29 | * |
| 30 | * The algorithm is one of the author's own devising. It may therefore be |
| 31 | * worth a certain amount of skepticism. However, I've thought about this |
| 32 | * method for over a year before actually considering it worth implementing. |
| 33 | * With a little bit of luck, it should have received some peer review by the |
| 34 | * time this code is actually properly released, and it'll be worth a bit |
| 35 | * more confidence. My earlier generator was very similar in structure to |
| 36 | * the Linux /dev/random device. This generator is intended to address |
| 37 | * concerns I expressed about the Linux generator in a Usenet article to |
| 38 | * sci.crypt. |
| 39 | * |
| 40 | * The generator is divided into two parts: an input pool and an output |
| 41 | * buffer. New random data is placed into the pool in the way described |
| 42 | * below, which is shamelessly stolen from the Linux /dev/random generator. |
| 43 | * The only interaction that the pool has on the output buffer is through the |
| 44 | * keyed `gating' operation, which mixes up and redistributes all of the |
| 45 | * generator's state in an irreversible manner. Random bytes, when |
| 46 | * requested, are extracted from the output buffer in a linear fashion. |
| 47 | * |
| 48 | * The input pool is best seen as being eight shift registers in parallel. |
| 49 | * Data is added to the pool one octet at a time. Each bit of a new octet is |
| 50 | * added to a different shift register, by adding it (mod 2) with other bits |
| 51 | * according to the coefficients of a primitive polynomial. Each new byte is |
| 52 | * rotated before being added into the pool, in a half-hearted attempt to |
| 53 | * protect against biases in the input data (e.g., top bits being clear on |
| 54 | * ASCII text). |
| 55 | * |
| 56 | * The gating operation takes a keyed hash of the entire generator state, |
| 57 | * uses it as the key for a symmetric cipher, and encrypts the state. The |
| 58 | * key is then discarded. The result is that every ouptut bit of the |
| 59 | * operation depends in a complex way on every input bit, but the operation |
| 60 | * cannot be reversed. |
| 61 | * |
| 62 | * As an added wrinkle, 160 bits of the output buffer are never actually |
| 63 | * output. They are used in the gating operation only, as an extra item that |
| 64 | * an adversary has to guess before predicting generator output. |
| 65 | */ |
| 66 | |
| 67 | #ifndef CATACOMB_RAND_H |
| 68 | #define CATACOMB_RAND_H |
| 69 | |
| 70 | #ifdef __cplusplus |
| 71 | extern "C" { |
| 72 | #endif |
| 73 | |
| 74 | /*----- Header files ------------------------------------------------------*/ |
| 75 | |
| 76 | #include <stddef.h> |
| 77 | |
| 78 | #ifndef CATACOMB_GRAND_H |
| 79 | # include "grand.h" |
| 80 | #endif |
| 81 | |
| 82 | #ifndef CATACOMB_RMD160_HMAC_H |
| 83 | # include "rmd160-hmac.h" |
| 84 | #endif |
| 85 | |
| 86 | /*----- Magic numbers -----------------------------------------------------*/ |
| 87 | |
| 88 | #define RAND_POOLSZ 128 /* Input pool size in bytes */ |
| 89 | #define RAND_BUFSZ 512 /* Output buffer size in bytes */ |
| 90 | #define RAND_SECSZ 32 /* Secret octets in output buffer */ |
| 91 | #define RAND_KEYSZ 32 /* Recommended random key size */ |
| 92 | |
| 93 | #define RAND_IBITS (RAND_POOLSZ * 8) |
| 94 | #define RAND_OBITS (RAND_BUFSZ * 8) |
| 95 | |
| 96 | /*----- Data structures ---------------------------------------------------*/ |
| 97 | |
| 98 | /* --- A random number generator pool --- */ |
| 99 | |
| 100 | typedef struct rand_pool { |
| 101 | octet pool[RAND_POOLSZ]; /* Actual contents of the pool */ |
| 102 | unsigned gen; /* Generation number */ |
| 103 | unsigned short i; /* Current index into pool */ |
| 104 | unsigned short irot; /* Current rotation applied */ |
| 105 | unsigned ibits; /* Number of good bits in pool */ |
| 106 | octet buf[RAND_BUFSZ]; /* Random octet output buffer */ |
| 107 | unsigned o; /* Current index into buffer */ |
| 108 | unsigned obits; /* Number of good bits in buffer */ |
| 109 | union { octet k[RAND_KEYSZ]; rmd160_mackey _; } k; /* Key for the pool */ |
| 110 | const struct rand_source *s; /* System-specific noise source */ |
| 111 | } rand_pool; |
| 112 | |
| 113 | #define RAND_GLOBAL ((rand_pool *)0) /* The global randomness pool */ |
| 114 | |
| 115 | /* --- A noise source --- */ |
| 116 | |
| 117 | typedef struct rand_source { |
| 118 | void (*getnoise)(rand_pool */*r*/); /* Acquire more noise */ |
| 119 | int (*timer)(rand_pool */*r*/); /* Get noise from current time */ |
| 120 | } rand_source; |
| 121 | |
| 122 | /*----- Functions provided ------------------------------------------------*/ |
| 123 | |
| 124 | /* --- @rand_init@ --- * |
| 125 | * |
| 126 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 127 | * |
| 128 | * Returns: --- |
| 129 | * |
| 130 | * Use: Initializes a randomness pool. The pool doesn't start out |
| 131 | * very random: that's your job to sort out. |
| 132 | */ |
| 133 | |
| 134 | extern void rand_init(rand_pool */*r*/); |
| 135 | |
| 136 | /* --- @rand_generation@ --- * |
| 137 | * |
| 138 | * Arguments: --- |
| 139 | * |
| 140 | * Returns: A nonzero generation number. |
| 141 | * |
| 142 | * Use: Returns a generation number for the current process. Each |
| 143 | * pool has its own number. If this matches the process number |
| 144 | * then all is well. If it doesn't match, then the pool needs |
| 145 | * to be cleaned before its next use. |
| 146 | */ |
| 147 | |
| 148 | extern unsigned rand_generation(void); |
| 149 | |
| 150 | /* --- @rand_noisesrc@ --- * |
| 151 | * |
| 152 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 153 | * @const rand_source *s@ = pointer to source definition |
| 154 | * |
| 155 | * Returns: --- |
| 156 | * |
| 157 | * Use: Sets a noise source for a randomness pool. When the pool's |
| 158 | * estimate of good random bits falls to zero, the @getnoise@ |
| 159 | * function is called, passing the pool handle as an argument. |
| 160 | * It is expected to increase the number of good bits by at |
| 161 | * least one, because it'll be called over and over again until |
| 162 | * there are enough bits to satisfy the caller. The @timer@ |
| 163 | * function is called frequently throughout the generator's |
| 164 | * operation. |
| 165 | */ |
| 166 | |
| 167 | extern void rand_noisesrc(rand_pool */*r*/, const rand_source */*s*/); |
| 168 | |
| 169 | /* --- @rand_seed@ --- * |
| 170 | * |
| 171 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 172 | * @unsigned bits@ = number of bits to ensure |
| 173 | * |
| 174 | * Returns: --- |
| 175 | * |
| 176 | * Use: Ensures that there are at least @bits@ good bits of entropy |
| 177 | * in the pool. It is recommended that you call this after |
| 178 | * initializing a new pool. Requesting @bits > RAND_IBITS@ is |
| 179 | * doomed to failure (and is an error). |
| 180 | */ |
| 181 | |
| 182 | extern void rand_seed(rand_pool */*r*/, unsigned /*bits*/); |
| 183 | |
| 184 | /* --- @rand_key@ --- * |
| 185 | * |
| 186 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 187 | * @const void *k@ = pointer to key data |
| 188 | * @size_t sz@ = size of key data |
| 189 | * |
| 190 | * Returns: --- |
| 191 | * |
| 192 | * Use: Sets the secret key for a randomness pool. The key is used |
| 193 | * when mixing in new random bits. |
| 194 | */ |
| 195 | |
| 196 | extern void rand_key(rand_pool */*r*/, const void */*k*/, size_t /*sz*/); |
| 197 | |
| 198 | /* --- @rand_quick@ --- * |
| 199 | * |
| 200 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 201 | * |
| 202 | * Returns: Zero on success; @-1@ on failure. |
| 203 | * |
| 204 | * Use Attempts to use some machine-specific `quick' source of |
| 205 | * entropy to top up @r@. This may not do anything at all on |
| 206 | * many systems. |
| 207 | */ |
| 208 | |
| 209 | extern int rand_quick(rand_pool */*r*/); |
| 210 | |
| 211 | /* --- @rand_add@ --- * |
| 212 | * |
| 213 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 214 | * @const void *p@ = pointer a buffer of data to add |
| 215 | * @size_t sz@ = size of the data buffer |
| 216 | * @unsigned goodbits@ = number of good bits estimated in buffer |
| 217 | * |
| 218 | * Returns: --- |
| 219 | * |
| 220 | * Use: Mixes the data in the buffer with the contents of the |
| 221 | * pool. The estimate of the number of good bits is added to |
| 222 | * the pool's own count. The mixing operation is not |
| 223 | * cryptographically strong. However, data in the input pool |
| 224 | * isn't output directly, only through the one-way gating |
| 225 | * operation, so that shouldn't matter. |
| 226 | */ |
| 227 | |
| 228 | extern void rand_add(rand_pool */*r*/, |
| 229 | const void */*p*/, size_t /*sz*/, |
| 230 | unsigned /*goodbits*/); |
| 231 | |
| 232 | /* --- @rand_goodbits@ --- * |
| 233 | * |
| 234 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 235 | * |
| 236 | * Returns: Estimate of the number of good bits remaining in the pool. |
| 237 | */ |
| 238 | |
| 239 | extern unsigned rand_goodbits(rand_pool */*r*/); |
| 240 | |
| 241 | /* --- @rand_gate@ --- * |
| 242 | * |
| 243 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 244 | * |
| 245 | * Returns: --- |
| 246 | * |
| 247 | * Use: Mixes up the entire state of the generator in a nonreversible |
| 248 | * way. |
| 249 | */ |
| 250 | |
| 251 | extern void rand_gate(rand_pool */*r*/); |
| 252 | |
| 253 | /* --- @rand_stretch@ --- * |
| 254 | * |
| 255 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 256 | * |
| 257 | * Returns: --- |
| 258 | * |
| 259 | * Use: Stretches the contents of the output buffer by transforming |
| 260 | * it in a nonreversible way. This doesn't add any entropy |
| 261 | * worth speaking about, but it works well enough when the |
| 262 | * caller doesn't care about that sort of thing. |
| 263 | */ |
| 264 | |
| 265 | extern void rand_stretch(rand_pool */*r*/); |
| 266 | |
| 267 | /* --- @rand_get@ --- * |
| 268 | * |
| 269 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 270 | * @void *p@ = pointer to output buffer |
| 271 | * @size_t sz@ = size of output buffer |
| 272 | * |
| 273 | * Returns: --- |
| 274 | * |
| 275 | * Use: Gets random data from the pool. The pool's contents can't be |
| 276 | * determined from the output of this function; nor can the |
| 277 | * output data be determined from a knowledge of the data input |
| 278 | * to the pool without also having knowledge of the secret key. |
| 279 | * The good bits counter is decremented, although no special |
| 280 | * action is taken if it reaches zero. |
| 281 | */ |
| 282 | |
| 283 | extern void rand_get(rand_pool */*r*/, void */*p*/, size_t /*sz*/); |
| 284 | |
| 285 | /* --- @rand_getgood@ --- * |
| 286 | * |
| 287 | * Arguments: @rand_pool *r@ = pointer to a randomness pool |
| 288 | * @void *p@ = pointer to output buffer |
| 289 | * @size_t sz@ = size of output buffer |
| 290 | * |
| 291 | * Returns: --- |
| 292 | * |
| 293 | * Use: Gets random data from the pool. The pool's contents can't be |
| 294 | * determined from the output of this function; nor can the |
| 295 | * output data be determined from a knowledge of the data input |
| 296 | * to the pool wihtout also having knowledge of the secret key. |
| 297 | * If a noise source is attached to the pool in question, it is |
| 298 | * called to replenish the supply of good bits in the pool; |
| 299 | * otherwise this call is equivalent to @rand_get@. |
| 300 | */ |
| 301 | |
| 302 | extern void rand_getgood(rand_pool */*r*/, void */*p*/, size_t /*sz*/); |
| 303 | |
| 304 | /*----- Generic random number generator interface -------------------------*/ |
| 305 | |
| 306 | /* --- Miscellaneous operations --- */ |
| 307 | |
| 308 | enum { |
| 309 | RAND_GATE = GRAND_SPECIFIC('R'), /* No args */ |
| 310 | RAND_STRETCH, /* No args */ |
| 311 | RAND_KEY, /* @const void *k, size_t sz@ */ |
| 312 | RAND_NOISESRC, /* @const rand_source *s@ */ |
| 313 | RAND_SEED, /* @unsigned bits@ */ |
| 314 | RAND_TIMER, /* No args */ |
| 315 | RAND_GOODBITS, /* No args */ |
| 316 | RAND_ADD /* @const void *p, size_t sz,@ |
| 317 | * @unsigned goodbits */ |
| 318 | }; |
| 319 | |
| 320 | /* --- Default random number generator --- */ |
| 321 | |
| 322 | #ifdef RAND__HACKS |
| 323 | extern struct rand__gctx rand_global; |
| 324 | #else |
| 325 | extern grand rand_global; |
| 326 | #endif |
| 327 | |
| 328 | /* --- @rand_create@ --- * |
| 329 | * |
| 330 | * Arguments: --- |
| 331 | * |
| 332 | * Returns: Pointer to a generic generator. |
| 333 | * |
| 334 | * Use: Constructs a generic generator interface over a Catacomb |
| 335 | * entropy pool generator. |
| 336 | */ |
| 337 | |
| 338 | extern grand *rand_create(void); |
| 339 | |
| 340 | /*----- That's all, folks -------------------------------------------------*/ |
| 341 | |
| 342 | #ifdef __cplusplus |
| 343 | } |
| 344 | #endif |
| 345 | |
| 346 | #endif |