crypto/include/internal/evp_int.h

   1 /*
   2  * Copyright 2015-2018 The OpenSSL Project Authors. All Rights Reserved.
   3  *
   4  * Licensed under the OpenSSL license (the "License").  You may not use
   5  * this file except in compliance with the License.  You can obtain a copy
   6  * in the file LICENSE in the source distribution or at
   7  * https://www.openssl.org/source/license.html
   8  */
   9
  10 #include <openssl/evp.h>
  11 #include "internal/refcount.h"
  12
  13 /*
  14  * Don't free up md_ctx->pctx in EVP_MD_CTX_reset, use the reserved flag
  15  * values in evp.h
  16  */
  17 #define EVP_MD_CTX_FLAG_KEEP_PKEY_CTX   0x0400
  18
  19 struct evp_pkey_ctx_st {
  20     /* Method associated with this operation */
  21     const EVP_PKEY_METHOD *pmeth;
  22     /* Engine that implements this method or NULL if builtin */
  23     ENGINE *engine;
  24     /* Key: may be NULL */
  25     EVP_PKEY *pkey;
  26     /* Peer key for key agreement, may be NULL */
  27     EVP_PKEY *peerkey;
  28     /* Actual operation */
  29     int operation;
  30     /* Algorithm specific data */
  31     void *data;
  32     /* Application specific data */
  33     void *app_data;
  34     /* Keygen callback */
  35     EVP_PKEY_gen_cb *pkey_gencb;
  36     /* implementation specific keygen data */
  37     int *keygen_info;
  38     int keygen_info_count;
  39 } /* EVP_PKEY_CTX */ ;
  40
  41 #define EVP_PKEY_FLAG_DYNAMIC   1
  42
  43 struct evp_pkey_method_st {
  44     int pkey_id;
  45     int flags;
  46     int (*init) (EVP_PKEY_CTX *ctx);
  47     int (*copy) (EVP_PKEY_CTX *dst, EVP_PKEY_CTX *src);
  48     void (*cleanup) (EVP_PKEY_CTX *ctx);
  49     int (*paramgen_init) (EVP_PKEY_CTX *ctx);
  50     int (*paramgen) (EVP_PKEY_CTX *ctx, EVP_PKEY *pkey);
  51     int (*keygen_init) (EVP_PKEY_CTX *ctx);
  52     int (*keygen) (EVP_PKEY_CTX *ctx, EVP_PKEY *pkey);
  53     int (*sign_init) (EVP_PKEY_CTX *ctx);
  54     int (*sign) (EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
  55                  const unsigned char *tbs, size_t tbslen);
  56     int (*verify_init) (EVP_PKEY_CTX *ctx);
  57     int (*verify) (EVP_PKEY_CTX *ctx,
  58                    const unsigned char *sig, size_t siglen,
  59                    const unsigned char *tbs, size_t tbslen);
  60     int (*verify_recover_init) (EVP_PKEY_CTX *ctx);
  61     int (*verify_recover) (EVP_PKEY_CTX *ctx,
  62                            unsigned char *rout, size_t *routlen,
  63                            const unsigned char *sig, size_t siglen);
  64     int (*signctx_init) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
  65     int (*signctx) (EVP_PKEY_CTX *ctx, unsigned char *sig, size_t *siglen,
  66                     EVP_MD_CTX *mctx);
  67     int (*verifyctx_init) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
  68     int (*verifyctx) (EVP_PKEY_CTX *ctx, const unsigned char *sig, int siglen,
  69                       EVP_MD_CTX *mctx);
  70     int (*encrypt_init) (EVP_PKEY_CTX *ctx);
  71     int (*encrypt) (EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen,
  72                     const unsigned char *in, size_t inlen);
  73     int (*decrypt_init) (EVP_PKEY_CTX *ctx);
  74     int (*decrypt) (EVP_PKEY_CTX *ctx, unsigned char *out, size_t *outlen,
  75                     const unsigned char *in, size_t inlen);
  76     int (*derive_init) (EVP_PKEY_CTX *ctx);
  77     int (*derive) (EVP_PKEY_CTX *ctx, unsigned char *key, size_t *keylen);
  78     int (*ctrl) (EVP_PKEY_CTX *ctx, int type, int p1, void *p2);
  79     int (*ctrl_str) (EVP_PKEY_CTX *ctx, const char *type, const char *value);
  80     int (*digestsign) (EVP_MD_CTX *ctx, unsigned char *sig, size_t *siglen,
  81                        const unsigned char *tbs, size_t tbslen);
  82     int (*digestverify) (EVP_MD_CTX *ctx, const unsigned char *sig,
  83                          size_t siglen, const unsigned char *tbs,
  84                          size_t tbslen);
  85     int (*check) (EVP_PKEY *pkey);
  86     int (*public_check) (EVP_PKEY *pkey);
  87     int (*param_check) (EVP_PKEY *pkey);
  88
  89     int (*digest_custom) (EVP_PKEY_CTX *ctx, EVP_MD_CTX *mctx);
  90 } /* EVP_PKEY_METHOD */ ;
  91
  92 DEFINE_STACK_OF_CONST(EVP_PKEY_METHOD)
  93
  94 void evp_pkey_set_cb_translate(BN_GENCB *cb, EVP_PKEY_CTX *ctx);
  95
  96 extern const EVP_PKEY_METHOD cmac_pkey_meth;
  97 extern const EVP_PKEY_METHOD dh_pkey_meth;
  98 extern const EVP_PKEY_METHOD dhx_pkey_meth;
  99 extern const EVP_PKEY_METHOD dsa_pkey_meth;
 100 extern const EVP_PKEY_METHOD ec_pkey_meth;
 101 extern const EVP_PKEY_METHOD sm2_pkey_meth;
 102 extern const EVP_PKEY_METHOD ecx25519_pkey_meth;
 103 extern const EVP_PKEY_METHOD ecx448_pkey_meth;
 104 extern const EVP_PKEY_METHOD ed25519_pkey_meth;
 105 extern const EVP_PKEY_METHOD ed448_pkey_meth;
 106 extern const EVP_PKEY_METHOD hmac_pkey_meth;
 107 extern const EVP_PKEY_METHOD rsa_pkey_meth;
 108 extern const EVP_PKEY_METHOD rsa_pss_pkey_meth;
 109 extern const EVP_PKEY_METHOD scrypt_pkey_meth;
 110 extern const EVP_PKEY_METHOD tls1_prf_pkey_meth;
 111 extern const EVP_PKEY_METHOD hkdf_pkey_meth;
 112 extern const EVP_PKEY_METHOD poly1305_pkey_meth;
 113 extern const EVP_PKEY_METHOD siphash_pkey_meth;
 114
 115 struct evp_md_st {
 116     int type;
 117     int pkey_type;
 118     int md_size;
 119     unsigned long flags;
 120     int (*init) (EVP_MD_CTX *ctx);
 121     int (*update) (EVP_MD_CTX *ctx, const void *data, size_t count);
 122     int (*final) (EVP_MD_CTX *ctx, unsigned char *md);
 123     int (*copy) (EVP_MD_CTX *to, const EVP_MD_CTX *from);
 124     int (*cleanup) (EVP_MD_CTX *ctx);
 125     int block_size;
 126     int ctx_size;               /* how big does the ctx->md_data need to be */
 127     /* control function */
 128     int (*md_ctrl) (EVP_MD_CTX *ctx, int cmd, int p1, void *p2);
 129 } /* EVP_MD */ ;
 130
 131 struct evp_cipher_st {
 132     int nid;
 133     int block_size;
 134     /* Default value for variable length ciphers */
 135     int key_len;
 136     int iv_len;
 137     /* Various flags */
 138     unsigned long flags;
 139     /* init key */
 140     int (*init) (EVP_CIPHER_CTX *ctx, const unsigned char *key,
 141                  const unsigned char *iv, int enc);
 142     /* encrypt/decrypt data */
 143     int (*do_cipher) (EVP_CIPHER_CTX *ctx, unsigned char *out,
 144                       const unsigned char *in, size_t inl);
 145     /* cleanup ctx */
 146     int (*cleanup) (EVP_CIPHER_CTX *);
 147     /* how big ctx->cipher_data needs to be */
 148     int ctx_size;
 149     /* Populate a ASN1_TYPE with parameters */
 150     int (*set_asn1_parameters) (EVP_CIPHER_CTX *, ASN1_TYPE *);
 151     /* Get parameters from a ASN1_TYPE */
 152     int (*get_asn1_parameters) (EVP_CIPHER_CTX *, ASN1_TYPE *);
 153     /* Miscellaneous operations */
 154     int (*ctrl) (EVP_CIPHER_CTX *, int type, int arg, void *ptr);
 155     /* Application data */
 156     void *app_data;
 157 } /* EVP_CIPHER */ ;
 158
 159 /* Macros to code block cipher wrappers */
 160
 161 /* Wrapper functions for each cipher mode */
 162
 163 #define EVP_C_DATA(kstruct, ctx) \
 164         ((kstruct *)EVP_CIPHER_CTX_get_cipher_data(ctx))
 165
 166 #define BLOCK_CIPHER_ecb_loop() \
 167         size_t i, bl; \
 168         bl = EVP_CIPHER_CTX_cipher(ctx)->block_size;    \
 169         if (inl < bl) return 1;\
 170         inl -= bl; \
 171         for (i=0; i <= inl; i+=bl)
 172
 173 #define BLOCK_CIPHER_func_ecb(cname, cprefix, kstruct, ksched) \
 174 static int cname##_ecb_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, const unsigned char *in, size_t inl) \
 175 {\
 176         BLOCK_CIPHER_ecb_loop() \
 177             cprefix##_ecb_encrypt(in + i, out + i, &EVP_C_DATA(kstruct,ctx)->ksched, EVP_CIPHER_CTX_encrypting(ctx)); \
 178         return 1;\
 179 }
 180
 181 #define EVP_MAXCHUNK ((size_t)1<<(sizeof(long)*8-2))
 182
 183 #define BLOCK_CIPHER_func_ofb(cname, cprefix, cbits, kstruct, ksched) \
 184     static int cname##_ofb_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, const unsigned char *in, size_t inl) \
 185 {\
 186         while(inl>=EVP_MAXCHUNK) {\
 187             int num = EVP_CIPHER_CTX_num(ctx);\
 188             cprefix##_ofb##cbits##_encrypt(in, out, (long)EVP_MAXCHUNK, &EVP_C_DATA(kstruct,ctx)->ksched, EVP_CIPHER_CTX_iv_noconst(ctx), &num); \
 189             EVP_CIPHER_CTX_set_num(ctx, num);\
 190             inl-=EVP_MAXCHUNK;\
 191             in +=EVP_MAXCHUNK;\
 192             out+=EVP_MAXCHUNK;\
 193         }\
 194         if (inl) {\
 195             int num = EVP_CIPHER_CTX_num(ctx);\
 196             cprefix##_ofb##cbits##_encrypt(in, out, (long)inl, &EVP_C_DATA(kstruct,ctx)->ksched, EVP_CIPHER_CTX_iv_noconst(ctx), &num); \
 197             EVP_CIPHER_CTX_set_num(ctx, num);\
 198         }\
 199         return 1;\
 200 }
 201
 202 #define BLOCK_CIPHER_func_cbc(cname, cprefix, kstruct, ksched) \
 203 static int cname##_cbc_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, const unsigned char *in, size_t inl) \
 204 {\
 205         while(inl>=EVP_MAXCHUNK) \
 206             {\
 207             cprefix##_cbc_encrypt(in, out, (long)EVP_MAXCHUNK, &EVP_C_DATA(kstruct,ctx)->ksched, EVP_CIPHER_CTX_iv_noconst(ctx), EVP_CIPHER_CTX_encrypting(ctx));\
 208             inl-=EVP_MAXCHUNK;\
 209             in +=EVP_MAXCHUNK;\
 210             out+=EVP_MAXCHUNK;\
 211             }\
 212         if (inl)\
 213             cprefix##_cbc_encrypt(in, out, (long)inl, &EVP_C_DATA(kstruct,ctx)->ksched, EVP_CIPHER_CTX_iv_noconst(ctx), EVP_CIPHER_CTX_encrypting(ctx));\
 214         return 1;\
 215 }
 216
 217 #define BLOCK_CIPHER_func_cfb(cname, cprefix, cbits, kstruct, ksched)  \
 218 static int cname##_cfb##cbits##_cipher(EVP_CIPHER_CTX *ctx, unsigned char *out, const unsigned char *in, size_t inl) \
 219 {\
 220     size_t chunk = EVP_MAXCHUNK;\
 221     if (cbits == 1)  chunk >>= 3;\
 222     if (inl < chunk) chunk = inl;\
 223     while (inl && inl >= chunk)\
 224     {\
 225         int num = EVP_CIPHER_CTX_num(ctx);\
 226         cprefix##_cfb##cbits##_encrypt(in, out, (long) \
 227             ((cbits == 1) \
 228                 && !EVP_CIPHER_CTX_test_flags(ctx, EVP_CIPH_FLAG_LENGTH_BITS) \
 229                 ? chunk*8 : chunk), \
 230             &EVP_C_DATA(kstruct, ctx)->ksched, EVP_CIPHER_CTX_iv_noconst(ctx),\
 231             &num, EVP_CIPHER_CTX_encrypting(ctx));\
 232         EVP_CIPHER_CTX_set_num(ctx, num);\
 233         inl -= chunk;\
 234         in += chunk;\
 235         out += chunk;\
 236         if (inl < chunk) chunk = inl;\
 237     }\
 238     return 1;\
 239 }
 240
 241 #define BLOCK_CIPHER_all_funcs(cname, cprefix, cbits, kstruct, ksched) \
 242         BLOCK_CIPHER_func_cbc(cname, cprefix, kstruct, ksched) \
 243         BLOCK_CIPHER_func_cfb(cname, cprefix, cbits, kstruct, ksched) \
 244         BLOCK_CIPHER_func_ecb(cname, cprefix, kstruct, ksched) \
 245         BLOCK_CIPHER_func_ofb(cname, cprefix, cbits, kstruct, ksched)
 246
 247 #define BLOCK_CIPHER_def1(cname, nmode, mode, MODE, kstruct, nid, block_size, \
 248                           key_len, iv_len, flags, init_key, cleanup, \
 249                           set_asn1, get_asn1, ctrl) \
 250 static const EVP_CIPHER cname##_##mode = { \
 251         nid##_##nmode, block_size, key_len, iv_len, \
 252         flags | EVP_CIPH_##MODE##_MODE, \
 253         init_key, \
 254         cname##_##mode##_cipher, \
 255         cleanup, \
 256         sizeof(kstruct), \
 257         set_asn1, get_asn1,\
 258         ctrl, \
 259         NULL \
 260 }; \
 261 const EVP_CIPHER *EVP_##cname##_##mode(void) { return &cname##_##mode; }
 262
 263 #define BLOCK_CIPHER_def_cbc(cname, kstruct, nid, block_size, key_len, \
 264                              iv_len, flags, init_key, cleanup, set_asn1, \
 265                              get_asn1, ctrl) \
 266 BLOCK_CIPHER_def1(cname, cbc, cbc, CBC, kstruct, nid, block_size, key_len, \
 267                   iv_len, flags, init_key, cleanup, set_asn1, get_asn1, ctrl)
 268
 269 #define BLOCK_CIPHER_def_cfb(cname, kstruct, nid, key_len, \
 270                              iv_len, cbits, flags, init_key, cleanup, \
 271                              set_asn1, get_asn1, ctrl) \
 272 BLOCK_CIPHER_def1(cname, cfb##cbits, cfb##cbits, CFB, kstruct, nid, 1, \
 273                   key_len, iv_len, flags, init_key, cleanup, set_asn1, \
 274                   get_asn1, ctrl)
 275
 276 #define BLOCK_CIPHER_def_ofb(cname, kstruct, nid, key_len, \
 277                              iv_len, cbits, flags, init_key, cleanup, \
 278                              set_asn1, get_asn1, ctrl) \
 279 BLOCK_CIPHER_def1(cname, ofb##cbits, ofb, OFB, kstruct, nid, 1, \
 280                   key_len, iv_len, flags, init_key, cleanup, set_asn1, \
 281                   get_asn1, ctrl)
 282
 283 #define BLOCK_CIPHER_def_ecb(cname, kstruct, nid, block_size, key_len, \
 284                              flags, init_key, cleanup, set_asn1, \
 285                              get_asn1, ctrl) \
 286 BLOCK_CIPHER_def1(cname, ecb, ecb, ECB, kstruct, nid, block_size, key_len, \
 287                   0, flags, init_key, cleanup, set_asn1, get_asn1, ctrl)
 288
 289 #define BLOCK_CIPHER_defs(cname, kstruct, \
 290                           nid, block_size, key_len, iv_len, cbits, flags, \
 291                           init_key, cleanup, set_asn1, get_asn1, ctrl) \
 292 BLOCK_CIPHER_def_cbc(cname, kstruct, nid, block_size, key_len, iv_len, flags, \
 293                      init_key, cleanup, set_asn1, get_asn1, ctrl) \
 294 BLOCK_CIPHER_def_cfb(cname, kstruct, nid, key_len, iv_len, cbits, \
 295                      flags, init_key, cleanup, set_asn1, get_asn1, ctrl) \
 296 BLOCK_CIPHER_def_ofb(cname, kstruct, nid, key_len, iv_len, cbits, \
 297                      flags, init_key, cleanup, set_asn1, get_asn1, ctrl) \
 298 BLOCK_CIPHER_def_ecb(cname, kstruct, nid, block_size, key_len, flags, \
 299                      init_key, cleanup, set_asn1, get_asn1, ctrl)
 300
 301 /*-
 302 #define BLOCK_CIPHER_defs(cname, kstruct, \
 303                                 nid, block_size, key_len, iv_len, flags,\
 304                                  init_key, cleanup, set_asn1, get_asn1, ctrl)\
 305 static const EVP_CIPHER cname##_cbc = {\
 306         nid##_cbc, block_size, key_len, iv_len, \
 307         flags | EVP_CIPH_CBC_MODE,\
 308         init_key,\
 309         cname##_cbc_cipher,\
 310         cleanup,\
 311         sizeof(EVP_CIPHER_CTX)-sizeof((((EVP_CIPHER_CTX *)NULL)->c))+\
 312                 sizeof((((EVP_CIPHER_CTX *)NULL)->c.kstruct)),\
 313         set_asn1, get_asn1,\
 314         ctrl, \
 315         NULL \
 316 };\
 317 const EVP_CIPHER *EVP_##cname##_cbc(void) { return &cname##_cbc; }\
 318 static const EVP_CIPHER cname##_cfb = {\
 319         nid##_cfb64, 1, key_len, iv_len, \
 320         flags | EVP_CIPH_CFB_MODE,\
 321         init_key,\
 322         cname##_cfb_cipher,\
 323         cleanup,\
 324         sizeof(EVP_CIPHER_CTX)-sizeof((((EVP_CIPHER_CTX *)NULL)->c))+\
 325                 sizeof((((EVP_CIPHER_CTX *)NULL)->c.kstruct)),\
 326         set_asn1, get_asn1,\
 327         ctrl,\
 328         NULL \
 329 };\
 330 const EVP_CIPHER *EVP_##cname##_cfb(void) { return &cname##_cfb; }\
 331 static const EVP_CIPHER cname##_ofb = {\
 332         nid##_ofb64, 1, key_len, iv_len, \
 333         flags | EVP_CIPH_OFB_MODE,\
 334         init_key,\
 335         cname##_ofb_cipher,\
 336         cleanup,\
 337         sizeof(EVP_CIPHER_CTX)-sizeof((((EVP_CIPHER_CTX *)NULL)->c))+\
 338                 sizeof((((EVP_CIPHER_CTX *)NULL)->c.kstruct)),\
 339         set_asn1, get_asn1,\
 340         ctrl,\
 341         NULL \
 342 };\
 343 const EVP_CIPHER *EVP_##cname##_ofb(void) { return &cname##_ofb; }\
 344 static const EVP_CIPHER cname##_ecb = {\
 345         nid##_ecb, block_size, key_len, iv_len, \
 346         flags | EVP_CIPH_ECB_MODE,\
 347         init_key,\
 348         cname##_ecb_cipher,\
 349         cleanup,\
 350         sizeof(EVP_CIPHER_CTX)-sizeof((((EVP_CIPHER_CTX *)NULL)->c))+\
 351                 sizeof((((EVP_CIPHER_CTX *)NULL)->c.kstruct)),\
 352         set_asn1, get_asn1,\
 353         ctrl,\
 354         NULL \
 355 };\
 356 const EVP_CIPHER *EVP_##cname##_ecb(void) { return &cname##_ecb; }
 357 */
 358
 359 #define IMPLEMENT_BLOCK_CIPHER(cname, ksched, cprefix, kstruct, nid, \
 360                                block_size, key_len, iv_len, cbits, \
 361                                flags, init_key, \
 362                                cleanup, set_asn1, get_asn1, ctrl) \
 363         BLOCK_CIPHER_all_funcs(cname, cprefix, cbits, kstruct, ksched) \
 364         BLOCK_CIPHER_defs(cname, kstruct, nid, block_size, key_len, iv_len, \
 365                           cbits, flags, init_key, cleanup, set_asn1, \
 366                           get_asn1, ctrl)
 367
 368 #define IMPLEMENT_CFBR(cipher,cprefix,kstruct,ksched,keysize,cbits,iv_len,fl) \
 369         BLOCK_CIPHER_func_cfb(cipher##_##keysize,cprefix,cbits,kstruct,ksched) \
 370         BLOCK_CIPHER_def_cfb(cipher##_##keysize,kstruct, \
 371                              NID_##cipher##_##keysize, keysize/8, iv_len, cbits, \
 372                              (fl)|EVP_CIPH_FLAG_DEFAULT_ASN1, \
 373                              cipher##_init_key, NULL, NULL, NULL, NULL)
 374
 375
 376 # ifndef OPENSSL_NO_EC
 377
 378 #define X25519_KEYLEN        32
 379 #define X448_KEYLEN          56
 380 #define ED448_KEYLEN         57
 381
 382 #define MAX_KEYLEN  ED448_KEYLEN
 383
 384 typedef struct {
 385     unsigned char pubkey[MAX_KEYLEN];
 386     unsigned char *privkey;
 387 } ECX_KEY;
 388
 389 #endif
 390
 391 /*
 392  * Type needs to be a bit field Sub-type needs to be for variations on the
 393  * method, as in, can it do arbitrary encryption....
 394  */
 395 struct evp_pkey_st {
 396     int type;
 397     int save_type;
 398     CRYPTO_REF_COUNT references;
 399     const EVP_PKEY_ASN1_METHOD *ameth;
 400     ENGINE *engine;
 401     ENGINE *pmeth_engine; /* If not NULL public key ENGINE to use */
 402     union {
 403         void *ptr;
 404 # ifndef OPENSSL_NO_RSA
 405         struct rsa_st *rsa;     /* RSA */
 406 # endif
 407 # ifndef OPENSSL_NO_DSA
 408         struct dsa_st *dsa;     /* DSA */
 409 # endif
 410 # ifndef OPENSSL_NO_DH
 411         struct dh_st *dh;       /* DH */
 412 # endif
 413 # ifndef OPENSSL_NO_EC
 414         struct ec_key_st *ec;   /* ECC */
 415         ECX_KEY *ecx;           /* X25519, X448, Ed25519, Ed448 */
 416 # endif
 417     } pkey;
 418     int save_parameters;
 419     STACK_OF(X509_ATTRIBUTE) *attributes; /* [ 0 ] */
 420     CRYPTO_RWLOCK *lock;
 421 } /* EVP_PKEY */ ;
 422
 423
 424 void openssl_add_all_ciphers_int(void);
 425 void openssl_add_all_digests_int(void);
 426 void evp_cleanup_int(void);
 427 void evp_app_cleanup_int(void);
 428
 429 /* Pulling defines out of C source files */
 430
 431 #define EVP_RC4_KEY_SIZE 16
 432 #ifndef TLS1_1_VERSION
 433 # define TLS1_1_VERSION   0x0302
 434 #endif
 435
 436 void evp_encode_ctx_set_flags(EVP_ENCODE_CTX *ctx, unsigned int flags);
 437
 438 /* EVP_ENCODE_CTX flags */
 439 /* Don't generate new lines when encoding */
 440 #define EVP_ENCODE_CTX_NO_NEWLINES          1
 441 /* Use the SRP base64 alphabet instead of the standard one */
 442 #define EVP_ENCODE_CTX_USE_SRP_ALPHABET     2