include/linux/mpi.h

   1 /* SPDX-License-Identifier: GPL-2.0-or-later */
   2 /* mpi.h  -  Multi Precision Integers
   3  *      Copyright (C) 1994, 1996, 1998, 1999,
   4  *                    2000, 2001 Free Software Foundation, Inc.
   5  *
   6  * This file is part of GNUPG.
   7  *
   8  * Note: This code is heavily based on the GNU MP Library.
   9  *       Actually it's the same code with only minor changes in the
  10  *       way the data is stored; this is to support the abstraction
  11  *       of an optional secure memory allocation which may be used
  12  *       to avoid revealing of sensitive data due to paging etc.
  13  *       The GNU MP Library itself is published under the LGPL;
  14  *       however I decided to publish this code under the plain GPL.
  15  */
  16
  17 #ifndef G10_MPI_H
  18 #define G10_MPI_H
  19
  20 #include <linux/types.h>
  21 #include <linux/scatterlist.h>
  22
  23 #define BYTES_PER_MPI_LIMB      (BITS_PER_LONG / 8)
  24 #define BITS_PER_MPI_LIMB       BITS_PER_LONG
  25
  26 typedef unsigned long int mpi_limb_t;
  27 typedef signed long int mpi_limb_signed_t;
  28
  29 struct gcry_mpi {
  30         int alloced;            /* array size (# of allocated limbs) */
  31         int nlimbs;             /* number of valid limbs */
  32         int nbits;              /* the real number of valid bits (info only) */
  33         int sign;               /* indicates a negative number */
  34         unsigned flags;         /* bit 0: array must be allocated in secure memory space */
  35         /* bit 1: not used */
  36         /* bit 2: the limb is a pointer to some m_alloced data */
  37         mpi_limb_t *d;          /* array with the limbs */
  38 };
  39
  40 typedef struct gcry_mpi *MPI;
  41
  42 #define mpi_get_nlimbs(a)     ((a)->nlimbs)
  43 #define mpi_has_sign(a)       ((a)->sign)
  44
  45 /*-- mpiutil.c --*/
  46 MPI mpi_alloc(unsigned nlimbs);
  47 void mpi_clear(MPI a);
  48 void mpi_free(MPI a);
  49 int mpi_resize(MPI a, unsigned nlimbs);
  50
  51 static inline MPI mpi_new(unsigned int nbits)
  52 {
  53         return mpi_alloc((nbits + BITS_PER_MPI_LIMB - 1) / BITS_PER_MPI_LIMB);
  54 }
  55
  56 MPI mpi_copy(MPI a);
  57 MPI mpi_alloc_like(MPI a);
  58 void mpi_snatch(MPI w, MPI u);
  59 MPI mpi_set(MPI w, MPI u);
  60 MPI mpi_set_ui(MPI w, unsigned long u);
  61 MPI mpi_alloc_set_ui(unsigned long u);
  62 void mpi_swap_cond(MPI a, MPI b, unsigned long swap);
  63
  64 /* Constants used to return constant MPIs.  See mpi_init if you
  65  * want to add more constants.
  66  */
  67 #define MPI_NUMBER_OF_CONSTANTS 6
  68 enum gcry_mpi_constants {
  69         MPI_C_ZERO,
  70         MPI_C_ONE,
  71         MPI_C_TWO,
  72         MPI_C_THREE,
  73         MPI_C_FOUR,
  74         MPI_C_EIGHT
  75 };
  76
  77 MPI mpi_const(enum gcry_mpi_constants no);
  78
  79 /*-- mpicoder.c --*/
  80
  81 /* Different formats of external big integer representation. */
  82 enum gcry_mpi_format {
  83         GCRYMPI_FMT_NONE = 0,
  84         GCRYMPI_FMT_STD = 1,    /* Twos complement stored without length. */
  85         GCRYMPI_FMT_PGP = 2,    /* As used by OpenPGP (unsigned only). */
  86         GCRYMPI_FMT_SSH = 3,    /* As used by SSH (like STD but with length). */
  87         GCRYMPI_FMT_HEX = 4,    /* Hex format. */
  88         GCRYMPI_FMT_USG = 5,    /* Like STD but unsigned. */
  89         GCRYMPI_FMT_OPAQUE = 8  /* Opaque format (some functions only). */
  90 };
  91
  92 MPI mpi_read_raw_data(const void *xbuffer, size_t nbytes);
  93 MPI mpi_read_from_buffer(const void *buffer, unsigned *ret_nread);
  94 int mpi_fromstr(MPI val, const char *str);
  95 MPI mpi_scanval(const char *string);
  96 MPI mpi_read_raw_from_sgl(struct scatterlist *sgl, unsigned int len);
  97 void *mpi_get_buffer(MPI a, unsigned *nbytes, int *sign);
  98 int mpi_read_buffer(MPI a, uint8_t *buf, unsigned buf_len, unsigned *nbytes,
  99                     int *sign);
 100 int mpi_write_to_sgl(MPI a, struct scatterlist *sg, unsigned nbytes,
 101                      int *sign);
 102 int mpi_print(enum gcry_mpi_format format, unsigned char *buffer,
 103                         size_t buflen, size_t *nwritten, MPI a);
 104
 105 /*-- mpi-mod.c --*/
 106 void mpi_mod(MPI rem, MPI dividend, MPI divisor);
 107
 108 /* Context used with Barrett reduction.  */
 109 struct barrett_ctx_s;
 110 typedef struct barrett_ctx_s *mpi_barrett_t;
 111
 112 mpi_barrett_t mpi_barrett_init(MPI m, int copy);
 113 void mpi_barrett_free(mpi_barrett_t ctx);
 114 void mpi_mod_barrett(MPI r, MPI x, mpi_barrett_t ctx);
 115 void mpi_mul_barrett(MPI w, MPI u, MPI v, mpi_barrett_t ctx);
 116
 117 /*-- mpi-pow.c --*/
 118 int mpi_powm(MPI res, MPI base, MPI exp, MPI mod);
 119
 120 /*-- mpi-cmp.c --*/
 121 int mpi_cmp_ui(MPI u, ulong v);
 122 int mpi_cmp(MPI u, MPI v);
 123 int mpi_cmpabs(MPI u, MPI v);
 124
 125 /*-- mpi-sub-ui.c --*/
 126 int mpi_sub_ui(MPI w, MPI u, unsigned long vval);
 127
 128 /*-- mpi-bit.c --*/
 129 void mpi_normalize(MPI a);
 130 unsigned mpi_get_nbits(MPI a);
 131 int mpi_test_bit(MPI a, unsigned int n);
 132 void mpi_set_bit(MPI a, unsigned int n);
 133 void mpi_set_highbit(MPI a, unsigned int n);
 134 void mpi_clear_highbit(MPI a, unsigned int n);
 135 void mpi_clear_bit(MPI a, unsigned int n);
 136 void mpi_rshift_limbs(MPI a, unsigned int count);
 137 void mpi_rshift(MPI x, MPI a, unsigned int n);
 138 void mpi_lshift_limbs(MPI a, unsigned int count);
 139 void mpi_lshift(MPI x, MPI a, unsigned int n);
 140
 141 /*-- mpi-add.c --*/
 142 void mpi_add_ui(MPI w, MPI u, unsigned long v);
 143 void mpi_add(MPI w, MPI u, MPI v);
 144 void mpi_sub(MPI w, MPI u, MPI v);
 145 void mpi_addm(MPI w, MPI u, MPI v, MPI m);
 146 void mpi_subm(MPI w, MPI u, MPI v, MPI m);
 147
 148 /*-- mpi-mul.c --*/
 149 void mpi_mul(MPI w, MPI u, MPI v);
 150 void mpi_mulm(MPI w, MPI u, MPI v, MPI m);
 151
 152 /*-- mpi-div.c --*/
 153 void mpi_tdiv_r(MPI rem, MPI num, MPI den);
 154 void mpi_fdiv_r(MPI rem, MPI dividend, MPI divisor);
 155 void mpi_fdiv_q(MPI quot, MPI dividend, MPI divisor);
 156
 157 /*-- mpi-inv.c --*/
 158 int mpi_invm(MPI x, MPI a, MPI n);
 159
 160 /*-- ec.c --*/
 161
 162 /* Object to represent a point in projective coordinates */
 163 struct gcry_mpi_point {
 164         MPI x;
 165         MPI y;
 166         MPI z;
 167 };
 168
 169 typedef struct gcry_mpi_point *MPI_POINT;
 170
 171 /* Models describing an elliptic curve */
 172 enum gcry_mpi_ec_models {
 173         /* The Short Weierstrass equation is
 174          *      y^2 = x^3 + ax + b
 175          */
 176         MPI_EC_WEIERSTRASS = 0,
 177         /* The Montgomery equation is
 178          *      by^2 = x^3 + ax^2 + x
 179          */
 180         MPI_EC_MONTGOMERY,
 181         /* The Twisted Edwards equation is
 182          *      ax^2 + y^2 = 1 + bx^2y^2
 183          * Note that we use 'b' instead of the commonly used 'd'.
 184          */
 185         MPI_EC_EDWARDS
 186 };
 187
 188 /* Dialects used with elliptic curves */
 189 enum ecc_dialects {
 190         ECC_DIALECT_STANDARD = 0,
 191         ECC_DIALECT_ED25519,
 192         ECC_DIALECT_SAFECURVE
 193 };
 194
 195 /* This context is used with all our EC functions. */
 196 struct mpi_ec_ctx {
 197         enum gcry_mpi_ec_models model; /* The model describing this curve. */
 198         enum ecc_dialects dialect;     /* The ECC dialect used with the curve. */
 199         int flags;                     /* Public key flags (not always used). */
 200         unsigned int nbits;            /* Number of bits.  */
 201
 202         /* Domain parameters.  Note that they may not all be set and if set
 203          * the MPIs may be flagged as constant.
 204          */
 205         MPI p;         /* Prime specifying the field GF(p).  */
 206         MPI a;         /* First coefficient of the Weierstrass equation.  */
 207         MPI b;         /* Second coefficient of the Weierstrass equation.  */
 208         MPI_POINT G;   /* Base point (generator).  */
 209         MPI n;         /* Order of G.  */
 210         unsigned int h;       /* Cofactor.  */
 211
 212         /* The actual key.  May not be set.  */
 213         MPI_POINT Q;   /* Public key.   */
 214         MPI d;         /* Private key.  */
 215
 216         const char *name;      /* Name of the curve.  */
 217
 218         /* This structure is private to mpi/ec.c! */
 219         struct {
 220                 struct {
 221                         unsigned int a_is_pminus3:1;
 222                         unsigned int two_inv_p:1;
 223                 } valid; /* Flags to help setting the helper vars below.  */
 224
 225                 int a_is_pminus3;  /* True if A = P - 3. */
 226
 227                 MPI two_inv_p;
 228
 229                 mpi_barrett_t p_barrett;
 230
 231                 /* Scratch variables.  */
 232                 MPI scratch[11];
 233
 234                 /* Helper for fast reduction.  */
 235                 /*   int nist_nbits; /\* If this is a NIST curve, the # of bits. *\/ */
 236                 /*   MPI s[10]; */
 237                 /*   MPI c; */
 238         } t;
 239
 240         /* Curve specific computation routines for the field.  */
 241         void (*addm)(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx);
 242         void (*subm)(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ec);
 243         void (*mulm)(MPI w, MPI u, MPI v, struct mpi_ec_ctx *ctx);
 244         void (*pow2)(MPI w, const MPI b, struct mpi_ec_ctx *ctx);
 245         void (*mul2)(MPI w, MPI u, struct mpi_ec_ctx *ctx);
 246 };
 247
 248 void mpi_ec_init(struct mpi_ec_ctx *ctx, enum gcry_mpi_ec_models model,
 249                         enum ecc_dialects dialect,
 250                         int flags, MPI p, MPI a, MPI b);
 251 void mpi_ec_deinit(struct mpi_ec_ctx *ctx);
 252 MPI_POINT mpi_point_new(unsigned int nbits);
 253 void mpi_point_release(MPI_POINT p);
 254 void mpi_point_init(MPI_POINT p);
 255 void mpi_point_free_parts(MPI_POINT p);
 256 int mpi_ec_get_affine(MPI x, MPI y, MPI_POINT point, struct mpi_ec_ctx *ctx);
 257 void mpi_ec_add_points(MPI_POINT result,
 258                         MPI_POINT p1, MPI_POINT p2,
 259                         struct mpi_ec_ctx *ctx);
 260 void mpi_ec_mul_point(MPI_POINT result,
 261                         MPI scalar, MPI_POINT point,
 262                         struct mpi_ec_ctx *ctx);
 263 int mpi_ec_curve_point(MPI_POINT point, struct mpi_ec_ctx *ctx);
 264
 265 /* inline functions */
 266
 267 /**
 268  * mpi_get_size() - returns max size required to store the number
 269  *
 270  * @a:  A multi precision integer for which we want to allocate a buffer
 271  *
 272  * Return: size required to store the number
 273  */
 274 static inline unsigned int mpi_get_size(MPI a)
 275 {
 276         return a->nlimbs * BYTES_PER_MPI_LIMB;
 277 }
 278 #endif /*G10_MPI_H */