lgl/gc.h

   1 /* gc.h --- Header file for implementation agnostic crypto wrapper API.
   2  * Copyright (C) 2002, 2003, 2004, 2005, 2007, 2008  Simon Josefsson
   3  *
   4  * This file is free software; you can redistribute it and/or modify
   5  * it under the terms of the GNU Lesser General Public License as published
   6  * by the Free Software Foundation; either version 2.1, or (at your
   7  * option) any later version.
   8  *
   9  * This file is distributed in the hope that it will be useful, but
  10  * WITHOUT ANY WARRANTY; without even the implied warranty of
  11  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  12  * General Public License for more details.
  13  *
  14  * You should have received a copy of the GNU Lesser General Public License
  15  * along with this file; if not, write to the Free Software
  16  * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
  17  * 02110-1301, USA.
  18  *
  19  */
  20
  21 #ifndef GC_H
  22 # define GC_H
  23
  24 /* Get size_t. */
  25 # include <stddef.h>
  26
  27 enum Gc_rc
  28 {
  29   GC_OK = 0,
  30   GC_MALLOC_ERROR,
  31   GC_INIT_ERROR,
  32   GC_RANDOM_ERROR,
  33   GC_INVALID_CIPHER,
  34   GC_INVALID_HASH,
  35   GC_PKCS5_INVALID_ITERATION_COUNT,
  36   GC_PKCS5_INVALID_DERIVED_KEY_LENGTH,
  37   GC_PKCS5_DERIVED_KEY_TOO_LONG
  38 };
  39 typedef enum Gc_rc Gc_rc;
  40
  41 /* Hash types. */
  42 enum Gc_hash
  43 {
  44   GC_MD4,
  45   GC_MD5,
  46   GC_SHA1,
  47   GC_MD2,
  48   GC_RMD160,
  49   GC_SHA256,
  50   GC_SHA384,
  51   GC_SHA512,
  52   GC_SHA224
  53 };
  54 typedef enum Gc_hash Gc_hash;
  55
  56 enum Gc_hash_mode
  57 {
  58   GC_HMAC = 1
  59 };
  60 typedef enum Gc_hash_mode Gc_hash_mode;
  61
  62 typedef void *gc_hash_handle;
  63
  64 #define GC_MD2_DIGEST_SIZE 16
  65 #define GC_MD4_DIGEST_SIZE 16
  66 #define GC_MD5_DIGEST_SIZE 16
  67 #define GC_RMD160_DIGEST_SIZE 20
  68 #define GC_SHA1_DIGEST_SIZE 20
  69 #define GC_SHA256_DIGEST_SIZE 32
  70 #define GC_SHA384_DIGEST_SIZE 48
  71 #define GC_SHA512_DIGEST_SIZE 64
  72 #define GC_SHA224_DIGEST_SIZE 24
  73
  74 /* Cipher types. */
  75 enum Gc_cipher
  76 {
  77   GC_AES128,
  78   GC_AES192,
  79   GC_AES256,
  80   GC_3DES,
  81   GC_DES,
  82   GC_ARCFOUR128,
  83   GC_ARCFOUR40,
  84   GC_ARCTWO40,
  85   GC_CAMELLIA128,
  86   GC_CAMELLIA256
  87 };
  88 typedef enum Gc_cipher Gc_cipher;
  89
  90 enum Gc_cipher_mode
  91 {
  92   GC_ECB,
  93   GC_CBC,
  94   GC_STREAM
  95 };
  96 typedef enum Gc_cipher_mode Gc_cipher_mode;
  97
  98 typedef void *gc_cipher_handle;
  99
 100 /* Call before respectively after any other functions. */
 101 extern Gc_rc gc_init (void);
 102 extern void gc_done (void);
 103
 104 /* Memory allocation (avoid). */
 105 typedef void *(*gc_malloc_t) (size_t n);
 106 typedef int (*gc_secure_check_t) (const void *);
 107 typedef void *(*gc_realloc_t) (void *p, size_t n);
 108 typedef void (*gc_free_t) (void *);
 109 extern void gc_set_allocators (gc_malloc_t func_malloc,
 110                                gc_malloc_t secure_malloc,
 111                                gc_secure_check_t secure_check,
 112                                gc_realloc_t func_realloc,
 113                                gc_free_t func_free);
 114
 115 /* Randomness. */
 116 extern Gc_rc gc_nonce (char *data, size_t datalen);
 117 extern Gc_rc gc_pseudo_random (char *data, size_t datalen);
 118 extern Gc_rc gc_random (char *data, size_t datalen);
 119
 120 /* Ciphers. */
 121 extern Gc_rc gc_cipher_open (Gc_cipher cipher, Gc_cipher_mode mode,
 122                              gc_cipher_handle *outhandle);
 123 extern Gc_rc gc_cipher_setkey (gc_cipher_handle handle,
 124                                size_t keylen, const char *key);
 125 extern Gc_rc gc_cipher_setiv (gc_cipher_handle handle,
 126                               size_t ivlen, const char *iv);
 127 extern Gc_rc gc_cipher_encrypt_inline (gc_cipher_handle handle,
 128                                        size_t len, char *data);
 129 extern Gc_rc gc_cipher_decrypt_inline (gc_cipher_handle handle,
 130                                        size_t len, char *data);
 131 extern Gc_rc gc_cipher_close (gc_cipher_handle handle);
 132
 133 /* Hashes. */
 134
 135 extern Gc_rc gc_hash_open (Gc_hash hash, Gc_hash_mode mode,
 136                            gc_hash_handle *outhandle);
 137 extern Gc_rc gc_hash_clone (gc_hash_handle handle, gc_hash_handle *outhandle);
 138 extern size_t gc_hash_digest_length (Gc_hash hash);
 139 extern void gc_hash_hmac_setkey (gc_hash_handle handle,
 140                                  size_t len, const char *key);
 141 extern void gc_hash_write (gc_hash_handle handle,
 142                            size_t len, const char *data);
 143 extern const char *gc_hash_read (gc_hash_handle handle);
 144 extern void gc_hash_close (gc_hash_handle handle);
 145
 146 /* Compute a hash value over buffer IN of INLEN bytes size using the
 147    algorithm HASH, placing the result in the pre-allocated buffer OUT.
 148    The required size of OUT depends on HASH, and is generally
 149    GC_<HASH>_DIGEST_SIZE.  For example, for GC_MD5 the output buffer
 150    must be 16 bytes.  The return value is 0 (GC_OK) on success, or
 151    another Gc_rc error code. */
 152 extern Gc_rc
 153 gc_hash_buffer (Gc_hash hash, const void *in, size_t inlen, char *out);
 154
 155 /* One-call interface. */
 156 extern Gc_rc gc_md2 (const void *in, size_t inlen, void *resbuf);
 157 extern Gc_rc gc_md4 (const void *in, size_t inlen, void *resbuf);
 158 extern Gc_rc gc_md5 (const void *in, size_t inlen, void *resbuf);
 159 extern Gc_rc gc_sha1 (const void *in, size_t inlen, void *resbuf);
 160 extern Gc_rc gc_hmac_md5 (const void *key, size_t keylen,
 161                           const void *in, size_t inlen, char *resbuf);
 162 extern Gc_rc gc_hmac_sha1 (const void *key, size_t keylen,
 163                            const void *in, size_t inlen, char *resbuf);
 164
 165 /* Derive cryptographic keys from a password P of length PLEN, with
 166    salt S of length SLEN, placing the result in pre-allocated buffer
 167    DK of length DKLEN.  An iteration count is specified in C, where a
 168    larger value means this function take more time (typical iteration
 169    counts are 1000-20000).  This function "stretches" the key to be
 170    exactly dkLen bytes long.  GC_OK is returned on success, otherwise
 171    an Gc_rc error code is returned.  */
 172 extern Gc_rc
 173 gc_pbkdf2_sha1 (const char *P, size_t Plen,
 174                 const char *S, size_t Slen,
 175                 unsigned int c, char *DK, size_t dkLen);
 176
 177 /*
 178   TODO:
 179
 180   From: Simon Josefsson <jas@extundo.com>
 181   Subject: Re: generic crypto
 182   Newsgroups: gmane.comp.lib.gnulib.bugs
 183   Cc: bug-gnulib@gnu.org
 184   Date: Fri, 07 Oct 2005 12:50:57 +0200
 185   Mail-Copies-To: nobody
 186
 187   Paul Eggert <eggert@CS.UCLA.EDU> writes:
 188
 189   > Simon Josefsson <jas@extundo.com> writes:
 190   >
 191   >> * Perhaps the /dev/?random reading should be separated into a separate
 192   >>   module?  It might be useful outside of the gc layer too.
 193   >
 194   > Absolutely.  I've been meaning to do that for months (for a "shuffle"
 195   > program I want to add to coreutils), but hadn't gotten around to it.
 196   > It would have to be generalized a bit.  I'd like to have the file
 197   > descriptor cached, for example.
 198
 199   I'll write a separate module for that part.
 200
 201   I think we should even add a good PRNG that is re-seeded from
 202   /dev/?random frequently.  GnuTLS can need a lot of random data on a
 203   big server, more than /dev/random can supply.  And /dev/urandom might
 204   not be strong enough.  Further, the security of /dev/?random can also
 205   be questionable.
 206
 207   >>   I'm also not sure about the names of those functions, they suggest
 208   >>   a more higher-level API than what is really offered (i.e., the
 209   >>   names "nonce" and "pseudo_random" and "random" imply certain
 210   >>   cryptographic properties).
 211   >
 212   > Could you expand a bit more on that?  What is the relationship between
 213   > nonce/pseudorandom/random and the /dev/ values you are using?
 214
 215   There is none, that is the problem.
 216
 217   Applications generally need different kind of "random" numbers.
 218   Sometimes they just need some random data and doesn't care whether it
 219   is possible for an attacker to compute the string (aka a "nonce").
 220   Sometimes they need data that is very difficult to compute (i.e.,
 221   computing it require inverting SHA1 or similar).  Sometimes they need
 222   data that is not possible to compute, i.e., it wants real entropy
 223   collected over time on the system.  Collecting the last kind of random
 224   data is very expensive, so it must not be used too often.  The second
 225   kind of random data ("pseudo random") is typically generated by
 226   seeding a good PRNG with a couple of hundred bytes of real entropy
 227   from the "real random" data pool.  The "nonce" is usually computed
 228   using the PRNG as well, because PRNGs are usually fast.
 229
 230   Pseudo-random data is typically used for session keys.  Strong random
 231   data is often used to generate long-term keys (e.g., private RSA
 232   keys).
 233
 234   Of course, there are many subtleties.  There are several different
 235   kind of nonce:s.  Sometimes a nonce is just an ever-increasing
 236   integer, starting from 0.  Sometimes it is assumed to be unlikely to
 237   be the same as previous nonces, but without a requirement that the
 238   nonce is possible to guess.  MD5(system clock) would thus suffice, if
 239   it isn't called too often.  You can guess what the next value will be,
 240   but it will always be different.
 241
 242   The problem is that /dev/?random doesn't offer any kind of semantic
 243   guarantees.  But applications need an API that make that promise.
 244
 245   I think we should do this in several steps:
 246
 247   1) Write a module that can read from /dev/?random.
 248
 249   2) Add a module for a known-good PRNG suitable for random number
 250   generation, that can be continuously re-seeded.
 251
 252   3) Add a high-level module that provide various different randomness
 253   functions.  One for nonces, perhaps even different kind of nonces,
 254   one for pseudo random data, and one for strong random data.  It is
 255   not clear whether we can hope to achieve the last one in a portable
 256   way.
 257
 258   Further, it would be useful to allow users to provide their own
 259   entropy source as a file, used to seed the PRNG or initialize the
 260   strong randomness pool.  This is used on embedded platforms that
 261   doesn't have enough interrupts to hope to generate good random data.
 262
 263   > For example, why not use OpenBSD's /dev/arandom?
 264
 265   I don't trust ARC4.  For example, recent cryptographic efforts
 266   indicate that you must throw away the first 512 bytes generated from
 267   the PRNG for it to be secure.  I don't know whether OpenBSD do this.
 268   Further, I recall some eprint paper on RC4 security that didn't
 269   inspire confidence.
 270
 271   While I trust the random devices in OpenBSD more than
 272   Solaris/AIX/HPUX/etc, I think that since we need something better on
 273   Solaris/AIX/HPUX we'd might as well use it on OpenBSD or even Linux
 274   too.
 275
 276   > Here is one thought.  The user could specify a desired quality level
 277   > range, and the implementation then would supply random data that is at
 278   > least as good as the lower bound of the range.  I.e., ihe
 279   > implementation refuses to produce any random data if it can't generate
 280   > data that is at least as good as the lower end of the range.  The
 281   > upper bound of the range is advice from the user not to be any more
 282   > expensive than that, but the implementation can ignore the advice if
 283   > it doesn't have anything cheaper.
 284
 285   I'm not sure this is a good idea.  Users can't really be expected to
 286   understand this.  Further, applications need many different kind of
 287   random data.  Selecting the randomness level for each by the user will
 288   be too complicated.
 289
 290   I think it is better if the application decide, from its cryptographic
 291   requirement, what entropy quality it require, and call the proper API.
 292   Meeting the implied semantic properties should be the job for gnulib.
 293
 294   >> Perhaps gc_dev_random and gc_dev_urandom?
 295   >
 296   > To some extent.  I'd rather insulate the user from the details of
 297   > where the random numbers come from.  On the other hand we need to
 298   > provide a way for applications to specify a file that contains
 299   > random bits, so that people can override the defaults.
 300
 301   Agreed.
 302
 303   This may require some thinking before it is finalized.  Is it ok to
 304   install the GC module as-is meanwhile?  Then I can continue to add the
 305   stuff that GnuTLS need, and then come back to re-working the
 306   randomness module.  That way, we have two different projects that use
 307   the code.  GnuTLS includes the same randomness code that was in GNU
 308   SASL and that is in the current gc module.  I feel much more
 309   comfortable working in small steps at a time, rather then working on
 310   this for a long time in gnulib and only later integrate the stuff in
 311   GnuTLS.
 312
 313   Thanks,
 314   Simon
 315  */
 316
 317 #endif /* GC_H */