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      1 /*
      2  * Copyright 2018-2022 The OpenSSL Project Authors. All Rights Reserved.
      3  *
      4  * Licensed under the Apache License 2.0 (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 <stdlib.h>
     11 #include <stdarg.h>
     12 #include <string.h>
     13 #include <openssl/evp.h>
     14 #include <openssl/kdf.h>
     15 #include <openssl/core_names.h>
     16 #include <openssl/proverr.h>
     17 #include "internal/cryptlib.h"
     18 #include "internal/numbers.h"
     19 #include "crypto/evp.h"
     20 #include "prov/provider_ctx.h"
     21 #include "prov/providercommon.h"
     22 #include "prov/implementations.h"
     23 #include "prov/provider_util.h"
     24 
     25 /* See RFC 4253, Section 7.2 */
     26 static OSSL_FUNC_kdf_newctx_fn kdf_sshkdf_new;
     27 static OSSL_FUNC_kdf_freectx_fn kdf_sshkdf_free;
     28 static OSSL_FUNC_kdf_reset_fn kdf_sshkdf_reset;
     29 static OSSL_FUNC_kdf_derive_fn kdf_sshkdf_derive;
     30 static OSSL_FUNC_kdf_settable_ctx_params_fn kdf_sshkdf_settable_ctx_params;
     31 static OSSL_FUNC_kdf_set_ctx_params_fn kdf_sshkdf_set_ctx_params;
     32 static OSSL_FUNC_kdf_gettable_ctx_params_fn kdf_sshkdf_gettable_ctx_params;
     33 static OSSL_FUNC_kdf_get_ctx_params_fn kdf_sshkdf_get_ctx_params;
     34 
     35 static int SSHKDF(const EVP_MD *evp_md,
     36                   const unsigned char *key, size_t key_len,
     37                   const unsigned char *xcghash, size_t xcghash_len,
     38                   const unsigned char *session_id, size_t session_id_len,
     39                   char type, unsigned char *okey, size_t okey_len);
     40 
     41 typedef struct {
     42     void *provctx;
     43     PROV_DIGEST digest;
     44     unsigned char *key; /* K */
     45     size_t key_len;
     46     unsigned char *xcghash; /* H */
     47     size_t xcghash_len;
     48     char type; /* X */
     49     unsigned char *session_id;
     50     size_t session_id_len;
     51 } KDF_SSHKDF;
     52 
     53 static void *kdf_sshkdf_new(void *provctx)
     54 {
     55     KDF_SSHKDF *ctx;
     56 
     57     if (!ossl_prov_is_running())
     58         return NULL;
     59 
     60     if ((ctx = OPENSSL_zalloc(sizeof(*ctx))) == NULL)
     61         ERR_raise(ERR_LIB_PROV, ERR_R_MALLOC_FAILURE);
     62     else
     63         ctx->provctx = provctx;
     64     return ctx;
     65 }
     66 
     67 static void kdf_sshkdf_free(void *vctx)
     68 {
     69     KDF_SSHKDF *ctx = (KDF_SSHKDF *)vctx;
     70 
     71     if (ctx != NULL) {
     72         kdf_sshkdf_reset(ctx);
     73         OPENSSL_free(ctx);
     74     }
     75 }
     76 
     77 static void kdf_sshkdf_reset(void *vctx)
     78 {
     79     KDF_SSHKDF *ctx = (KDF_SSHKDF *)vctx;
     80     void *provctx = ctx->provctx;
     81 
     82     ossl_prov_digest_reset(&ctx->digest);
     83     OPENSSL_clear_free(ctx->key, ctx->key_len);
     84     OPENSSL_clear_free(ctx->xcghash, ctx->xcghash_len);
     85     OPENSSL_clear_free(ctx->session_id, ctx->session_id_len);
     86     memset(ctx, 0, sizeof(*ctx));
     87     ctx->provctx = provctx;
     88 }
     89 
     90 static int sshkdf_set_membuf(unsigned char **dst, size_t *dst_len,
     91                              const OSSL_PARAM *p)
     92 {
     93     OPENSSL_clear_free(*dst, *dst_len);
     94     *dst = NULL;
     95     *dst_len = 0;
     96     return OSSL_PARAM_get_octet_string(p, (void **)dst, 0, dst_len);
     97 }
     98 
     99 static int kdf_sshkdf_derive(void *vctx, unsigned char *key, size_t keylen,
    100                              const OSSL_PARAM params[])
    101 {
    102     KDF_SSHKDF *ctx = (KDF_SSHKDF *)vctx;
    103     const EVP_MD *md;
    104 
    105     if (!ossl_prov_is_running() || !kdf_sshkdf_set_ctx_params(ctx, params))
    106         return 0;
    107 
    108     md = ossl_prov_digest_md(&ctx->digest);
    109     if (md == NULL) {
    110         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_MESSAGE_DIGEST);
    111         return 0;
    112     }
    113     if (ctx->key == NULL) {
    114         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_KEY);
    115         return 0;
    116     }
    117     if (ctx->xcghash == NULL) {
    118         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_XCGHASH);
    119         return 0;
    120     }
    121     if (ctx->session_id == NULL) {
    122         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_SESSION_ID);
    123         return 0;
    124     }
    125     if (ctx->type == 0) {
    126         ERR_raise(ERR_LIB_PROV, PROV_R_MISSING_TYPE);
    127         return 0;
    128     }
    129     return SSHKDF(md, ctx->key, ctx->key_len,
    130                   ctx->xcghash, ctx->xcghash_len,
    131                   ctx->session_id, ctx->session_id_len,
    132                   ctx->type, key, keylen);
    133 }
    134 
    135 static int kdf_sshkdf_set_ctx_params(void *vctx, const OSSL_PARAM params[])
    136 {
    137     const OSSL_PARAM *p;
    138     KDF_SSHKDF *ctx = vctx;
    139     OSSL_LIB_CTX *provctx = PROV_LIBCTX_OF(ctx->provctx);
    140 
    141     if (params == NULL)
    142         return 1;
    143 
    144     if (!ossl_prov_digest_load_from_params(&ctx->digest, params, provctx))
    145         return 0;
    146 
    147     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_KEY)) != NULL)
    148         if (!sshkdf_set_membuf(&ctx->key, &ctx->key_len, p))
    149             return 0;
    150 
    151     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_XCGHASH))
    152         != NULL)
    153         if (!sshkdf_set_membuf(&ctx->xcghash, &ctx->xcghash_len, p))
    154             return 0;
    155 
    156     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_SESSION_ID))
    157         != NULL)
    158         if (!sshkdf_set_membuf(&ctx->session_id, &ctx->session_id_len, p))
    159             return 0;
    160 
    161     if ((p = OSSL_PARAM_locate_const(params, OSSL_KDF_PARAM_SSHKDF_TYPE))
    162         != NULL) {
    163         const char *kdftype;
    164 
    165         if (!OSSL_PARAM_get_utf8_string_ptr(p, &kdftype))
    166             return 0;
    167         /* Expect one character (byte in this case) */
    168         if (kdftype == NULL || p->data_size != 1)
    169             return 0;
    170         if (kdftype[0] < 65 || kdftype[0] > 70) {
    171             ERR_raise(ERR_LIB_PROV, PROV_R_VALUE_ERROR);
    172             return 0;
    173         }
    174         ctx->type = kdftype[0];
    175     }
    176     return 1;
    177 }
    178 
    179 static const OSSL_PARAM *kdf_sshkdf_settable_ctx_params(ossl_unused void *ctx,
    180                                                         ossl_unused void *p_ctx)
    181 {
    182     static const OSSL_PARAM known_settable_ctx_params[] = {
    183         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_PROPERTIES, NULL, 0),
    184         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_DIGEST, NULL, 0),
    185         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_KEY, NULL, 0),
    186         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SSHKDF_XCGHASH, NULL, 0),
    187         OSSL_PARAM_octet_string(OSSL_KDF_PARAM_SSHKDF_SESSION_ID, NULL, 0),
    188         OSSL_PARAM_utf8_string(OSSL_KDF_PARAM_SSHKDF_TYPE, NULL, 0),
    189         OSSL_PARAM_END
    190     };
    191     return known_settable_ctx_params;
    192 }
    193 
    194 static int kdf_sshkdf_get_ctx_params(void *vctx, OSSL_PARAM params[])
    195 {
    196     OSSL_PARAM *p;
    197 
    198     if ((p = OSSL_PARAM_locate(params, OSSL_KDF_PARAM_SIZE)) != NULL)
    199         return OSSL_PARAM_set_size_t(p, SIZE_MAX);
    200     return -2;
    201 }
    202 
    203 static const OSSL_PARAM *kdf_sshkdf_gettable_ctx_params(ossl_unused void *ctx,
    204                                                         ossl_unused void *p_ctx)
    205 {
    206     static const OSSL_PARAM known_gettable_ctx_params[] = {
    207         OSSL_PARAM_size_t(OSSL_KDF_PARAM_SIZE, NULL),
    208         OSSL_PARAM_END
    209     };
    210     return known_gettable_ctx_params;
    211 }
    212 
    213 const OSSL_DISPATCH ossl_kdf_sshkdf_functions[] = {
    214     { OSSL_FUNC_KDF_NEWCTX, (void(*)(void))kdf_sshkdf_new },
    215     { OSSL_FUNC_KDF_FREECTX, (void(*)(void))kdf_sshkdf_free },
    216     { OSSL_FUNC_KDF_RESET, (void(*)(void))kdf_sshkdf_reset },
    217     { OSSL_FUNC_KDF_DERIVE, (void(*)(void))kdf_sshkdf_derive },
    218     { OSSL_FUNC_KDF_SETTABLE_CTX_PARAMS,
    219       (void(*)(void))kdf_sshkdf_settable_ctx_params },
    220     { OSSL_FUNC_KDF_SET_CTX_PARAMS, (void(*)(void))kdf_sshkdf_set_ctx_params },
    221     { OSSL_FUNC_KDF_GETTABLE_CTX_PARAMS,
    222       (void(*)(void))kdf_sshkdf_gettable_ctx_params },
    223     { OSSL_FUNC_KDF_GET_CTX_PARAMS, (void(*)(void))kdf_sshkdf_get_ctx_params },
    224     { 0, NULL }
    225 };
    226 
    227 static int SSHKDF(const EVP_MD *evp_md,
    228                   const unsigned char *key, size_t key_len,
    229                   const unsigned char *xcghash, size_t xcghash_len,
    230                   const unsigned char *session_id, size_t session_id_len,
    231                   char type, unsigned char *okey, size_t okey_len)
    232 {
    233     EVP_MD_CTX *md = NULL;
    234     unsigned char digest[EVP_MAX_MD_SIZE];
    235     unsigned int dsize = 0;
    236     size_t cursize = 0;
    237     int ret = 0;
    238 
    239     md = EVP_MD_CTX_new();
    240     if (md == NULL)
    241         return 0;
    242 
    243     if (!EVP_DigestInit_ex(md, evp_md, NULL))
    244         goto out;
    245 
    246     if (!EVP_DigestUpdate(md, key, key_len))
    247         goto out;
    248 
    249     if (!EVP_DigestUpdate(md, xcghash, xcghash_len))
    250         goto out;
    251 
    252     if (!EVP_DigestUpdate(md, &type, 1))
    253         goto out;
    254 
    255     if (!EVP_DigestUpdate(md, session_id, session_id_len))
    256         goto out;
    257 
    258     if (!EVP_DigestFinal_ex(md, digest, &dsize))
    259         goto out;
    260 
    261     if (okey_len < dsize) {
    262         memcpy(okey, digest, okey_len);
    263         ret = 1;
    264         goto out;
    265     }
    266 
    267     memcpy(okey, digest, dsize);
    268 
    269     for (cursize = dsize; cursize < okey_len; cursize += dsize) {
    270 
    271         if (!EVP_DigestInit_ex(md, evp_md, NULL))
    272             goto out;
    273 
    274         if (!EVP_DigestUpdate(md, key, key_len))
    275             goto out;
    276 
    277         if (!EVP_DigestUpdate(md, xcghash, xcghash_len))
    278             goto out;
    279 
    280         if (!EVP_DigestUpdate(md, okey, cursize))
    281             goto out;
    282 
    283         if (!EVP_DigestFinal_ex(md, digest, &dsize))
    284             goto out;
    285 
    286         if (okey_len < cursize + dsize) {
    287             memcpy(okey + cursize, digest, okey_len - cursize);
    288             ret = 1;
    289             goto out;
    290         }
    291 
    292         memcpy(okey + cursize, digest, dsize);
    293     }
    294 
    295     ret = 1;
    296 
    297 out:
    298     EVP_MD_CTX_free(md);
    299     OPENSSL_cleanse(digest, EVP_MAX_MD_SIZE);
    300     return ret;
    301 }
    302 
    303