mdw@git.distorted.org.uk Git - catacomb/blob - symm/strobe.h

   1 /* -*-c-*-
   2  *
   3  * The STROBE protocol framework
   4  *
   5  * (c) 2018 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 it
  13  * under the terms of the GNU Library General Public License as published
  14  * by the Free Software Foundation; either version 2 of the License, or
  15  * (at your option) any later version.
  16  *
  17  * Catacomb is distributed in the hope that it will be useful, but
  18  * WITHOUT ANY WARRANTY; without even the implied warranty of
  19  * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  20  * 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 Software
  24  * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307,
  25  * USA.
  26  */
  27
  28 /*----- Notes on the STROBE framework -------------------------------------*
  29  *
  30  * Mike Hamburg's STROBE framework is an attempt to do pretty much all the
  31  * obvious parts of symmetric cryptography using a single primitive: the
  32  * Keccak-p[1600, 24] sponge function which underlies the SHA3.  This works
  33  * excellently on tiny devices, because it's possible to implement
  34  * Keccak-p[1600, 24] with a very small amount of code, and STROBE requires
  35  * minimal additional state beyond the 200-byte Keccak-p[1600, n] state,
  36  * which can be updated more-or-less in place.
  37  *
  38  * STROBE is stateful.  The idea is that the two parties' STROBE states
  39  * should evolve in lockstep with each other.  This will obviously go wrong
  40  * if messages cross over, or are reordered or duplicated.
  41  *
  42  * The model for a single STROBE-based endpoint consists of the application,
  43  * and a transport for communicating with a peer.  All data gets mixed into
  44  * the STROBE state.  Some operations mix input data with a keystream
  45  * generated by the sponge function (used in duplexing mode), which can then
  46  * be used to encrypt and authenticate messages.
  47  */
  48
  49 #ifndef CATACOMB_STROBE_H
  50 #define CATACOMB_STROBE_H
  51
  52 #ifdef __cplusplus
  53   extern "C" {
  54 #endif
  55
  56 /*----- Header files ------------------------------------------------------*/
  57
  58 #include <mLib/bits.h>
  59
  60 #ifndef CATACOMB_KECCAK1600_H
  61 #  include "keccak1600.h"
  62 #endif
  63
  64 /*----- Data structures ---------------------------------------------------*/
  65
  66 #define STRBF_I 0x01                    /* inbound */
  67 #define STRBF_A 0x02                    /* application */
  68 #define STRBF_C 0x04                    /* cipher */
  69 #define STRBF_T 0x08                    /* transport */
  70 #define STRBF_M 0x10                    /* metadata */
  71 #define STRBF_K 0x20                    /* key-tree (not implemented) */
  72 #define STRBF_VALIDMASK 0x1f            /* valid bits */
  73 #define STRBF_OPMASK 0xff               /* observable operation bits */
  74
  75 typedef struct strobe_ctx {
  76   keccak1600_state k;
  77   octet buf[200];
  78   unsigned f, r, n0, n;
  79 #define STRBF_I0 0x0001                 /* initiator/responder role */
  80 #define STRBF_INIT 0x0100               /* initiator/responder role set? */
  81 #define STRBF_STMASK 0x01ff             /* mask for persistent state bits */
  82 #define STRBF_ACTIVE 0x0200             /* operation in progress */
  83 #define STRBF_WANTIN 0x0400             /* expect input buffer */
  84 #define STRBF_WANTOUT 0x0800            /* expect output buffer */
  85 #define STRBF_VRFOUT 0x1000             /* verify that output is nonzero */
  86 #define STRBF_NZERO 0x2000              /* nonzero output from update */
  87 #define STRBF_MIXOUT 0x4000             /* mix output into state */
  88 #define STRBF_CRYPTO 0x8000             /* mix sponge state into output */
  89 } strobe_ctx;
  90
  91 #define STROBE_KEY                (STRBF_A | STRBF_C)
  92 #define STROBE_AD                 (STRBF_A)
  93 #define STROBE_PRF      (STRBF_I | STRBF_A | STRBF_C)
  94 #define STROBE_CLROUT             (STRBF_A |           STRBF_T)
  95 #define STROBE_CLRIN    (STRBF_I | STRBF_A |           STRBF_T)
  96 #define STROBE_ENCOUT             (STRBF_A | STRBF_C | STRBF_T)
  97 #define STROBE_ENCIN    (STRBF_I | STRBF_A | STRBF_C | STRBF_T)
  98 #define STROBE_MACOUT                       (STRBF_C | STRBF_T)
  99 #define STROBE_MACIN    (STRBF_I |           STRBF_C | STRBF_T)
 100 #define STROBE_RATCHET                      (STRBF_C)
 101
 102 #define STROBE_ROLEMASK (STRBF_I0 | STRBF_INIT)
 103 #define STRBRL_UNDCD    (0)                     /* undecided */
 104 #define STRBRL_INIT                (STRBF_INIT) /* initiator */
 105 #define STRBRL_RESP     (STRBF_I0 | STRBF_INIT) /* responder */
 106
 107 /*----- Functions provided ------------------------------------------------*/
 108
 109 /* --- @strobe_init@ --- *
 110  *
 111  * Arguments:   @strobe_ctx *ctx@ = pointer to context block to initialize
 112  *              @unsigned lambda@ = security parameter, in bits (must be a
 113  *                      multiple of 32)
 114  *
 115  * Returns:     ---
 116  *
 117  * Use:         Initialize a STROBE context for use.
 118  */
 119
 120 extern void strobe_init(strobe_ctx */*ctx*/, unsigned /*lambda*/);
 121
 122 /* --- @strobe_begin@ --- *
 123  *
 124  * Arguments:   @strobe_ctx *ctx@ = pointer to context block
 125  *              @unsigned op@ = bitmask of flags
 126  *
 127  * Returns:     ---
 128  *
 129  * Use:         Begin a STROBE operation.  The flags determine the behaviour
 130  *              of the @strobe_process@ and @strobe_done@ functions.
 131  *
 132  *                * The @I@ bit determines the primary direction of data
 133  *                  movement.  If it's clear, data comes from the application
 134  *                  into STROBE.  If it's set, data comes from STROBE towards
 135  *                  the application.
 136  *
 137  *                * The @C@ bit activates cryptographic processing.  If it's
 138  *                  clear, then the input and output data would be equal, so
 139  *                  @dest@ must be null.  If it's set, then input data is
 140  *                  XORed with the keystream on its way to the output.
 141  *
 142  *                * The @A@ bit determines whether the application is
 143  *                  engaged.  If it's set, then the input or output buffer
 144  *                  (according to whether @I@ is clear or set, respectively)
 145  *                  holds the application data.  If it's clear, and @I@ is
 146  *                  clear, then zero bytes are fed in; if @I@ is set, then
 147  *                  the output is compared with zero, and @strobe_done@
 148  *                  reports the outcome of this comparison.
 149  *
 150  *                * The @T@ bit determines whether the transport is engaged.
 151  *                  If it's set, then the input or output buffer (according
 152  *                  to whether @I@ is set or clear, respectively) holds
 153  *                  transport data.  If it's clear, and @I@ is set, then zero
 154  *                  bytes are fed in; if @I@ is clear, then the output is
 155  *                  discarded.
 156  *
 157  *                * The @M@ bit marks the data as metadata, but has no other
 158  *                  effect.
 159  */
 160
 161 extern void strobe_begin(strobe_ctx */*ctx*/, unsigned /*op*/);
 162
 163 /* --- @strobe_process@ --- *
 164  *
 165  * Arguments:   @strobe_ctx *ctx@ = pointer to context block
 166  *              @const void *src@ = pointer to input data, or null
 167  *              @void *dest@ = pointer to output data, or null
 168  *              @size_t sz@ = common buffer length
 169  *
 170  * Returns:     ---
 171  *
 172  * Use:         Process data through the active STROBE operation.  The exact
 173  *              behaviour depends on the flags passed to @strobe_begin@; see
 174  *              that function for details.  If @src@ is null, then the
 175  *              behaviour is as if the input consists of @sz@ zero bytes.  If
 176  *              @dest@ in null, then the output is discarded.
 177  */
 178
 179 extern void strobe_process(strobe_ctx */*ctx*/, const void */*src*/,
 180                            void */*dest*/, size_t /*sz*/);
 181
 182 /* --- @strobe_done@ --- *
 183  *
 184  * Arguments:   @strobe_ctx *ctx@ = pointer to context block
 185  *
 186  * Returns:     Zero on success; @-1@ on verification failure (if @I@ and @T@
 187  *                      are set and @A@ is clear)
 188  *
 189  * Use:         Concludes a STROBE operation, returning the result.
 190  */
 191
 192 extern int strobe_done(strobe_ctx */*ctx*/);
 193
 194 /* --- @strobe_key@, @strobe_ad@, @strobe_@prf@, @strobe_clrout@,
 195  *     @strobe_clrin@, @strobe_encout@, @strobe_encin@, @strobe_macout@,
 196  *     @strobe_macin@, @strobe_ratchet@ --- *
 197  *
 198  * Arguments:   @strobe_ctx *ctx@ = pointer to context block
 199  *
 200  * Returns:     @strobe_macin@ returns zero on success, or @-1@ on
 201  *                      verification failure
 202  *
 203  * Use:         Perform a STROBE operation on a single buffer.
 204  */
 205
 206 extern void strobe_key(strobe_ctx */*ctx*/, unsigned /*f*/,
 207                        const void */*k*/, size_t /*sz*/);
 208 extern void strobe_ad(strobe_ctx */*ctx*/, unsigned /*f*/,
 209                       const void */*h*/, size_t /*sz*/);
 210 extern void strobe_prf(strobe_ctx */*ctx*/, unsigned /*f*/,
 211                        void */*t*/, size_t /*sz*/);
 212 extern void strobe_clrout(strobe_ctx */*ctx*/, unsigned /*f*/,
 213                           const void */*m*/, size_t /*sz*/);
 214 extern void strobe_clrin(strobe_ctx */*ctx*/, unsigned /*f*/,
 215                          const void */*m*/, size_t /*sz*/);
 216 extern void strobe_encout(strobe_ctx */*ctx*/, unsigned /*f*/,
 217                           const void */*m*/, void */*c*/, size_t /*sz*/);
 218 extern void strobe_encin(strobe_ctx */*ctx*/, unsigned /*f*/,
 219                          const void */*c*/, void */*m*/, size_t /*sz*/);
 220 extern void strobe_macout(strobe_ctx */*ctx*/, unsigned /*f*/,
 221                           void */*t*/, size_t /*sz*/);
 222 extern int strobe_macin(strobe_ctx */*ctx*/, unsigned /*f*/,
 223                         const void */*t*/, size_t /*sz*/);
 224 extern void strobe_ratchet(strobe_ctx */*ctx*/, unsigned /*f*/,
 225                            size_t /*sz*/);
 226
 227 /*----- That's all, folks -------------------------------------------------*/
 228
 229 #ifdef __cplusplus
 230   }
 231 #endif
 232
 233 #endif