1 // SPDX-License-Identifier: GPL-2.0+ 2 /* 3 * Elliptic Curve (Russian) Digital Signature Algorithm for Cryptographic API 4 * 5 * Copyright (c) 2019 Vitaly Chikunov <vt@altlinux.org> 6 * 7 * References: 8 * GOST 34.10-2018, GOST R 34.10-2012, RFC 7091, ISO/IEC 14888-3:2018. 9 * 10 * Historical references: 11 * GOST R 34.10-2001, RFC 4357, ISO/IEC 14888-3:2006/Amd 1:2010. 12 * 13 * This program is free software; you can redistribute it and/or modify it 14 * under the terms of the GNU General Public License as published by the Free 15 * Software Foundation; either version 2 of the License, or (at your option) 16 * any later version. 17 */ 18 19 #include <linux/module.h> 20 #include <linux/crypto.h> 21 #include <crypto/sig.h> 22 #include <crypto/streebog.h> 23 #include <crypto/internal/ecc.h> 24 #include <crypto/internal/sig.h> 25 #include <linux/oid_registry.h> 26 #include "ecrdsa_params.asn1.h" 27 #include "ecrdsa_pub_key.asn1.h" 28 #include "ecrdsa_defs.h" 29 30 #define ECRDSA_MAX_SIG_SIZE (2 * 512 / 8) 31 #define ECRDSA_MAX_DIGITS (512 / 64) 32 33 struct ecrdsa_ctx { 34 enum OID algo_oid; /* overall public key oid */ 35 enum OID curve_oid; /* parameter */ 36 enum OID digest_oid; /* parameter */ 37 const struct ecc_curve *curve; /* curve from oid */ 38 unsigned int digest_len; /* parameter (bytes) */ 39 const char *digest; /* digest name from oid */ 40 unsigned int key_len; /* @key length (bytes) */ 41 const char *key; /* raw public key */ 42 struct ecc_point pub_key; 43 u64 _pubp[2][ECRDSA_MAX_DIGITS]; /* point storage for @pub_key */ 44 }; 45 46 static const struct ecc_curve *get_curve_by_oid(enum OID oid) 47 { 48 switch (oid) { 49 case OID_gostCPSignA: 50 case OID_gostTC26Sign256B: 51 return &gost_cp256a; 52 case OID_gostCPSignB: 53 case OID_gostTC26Sign256C: 54 return &gost_cp256b; 55 case OID_gostCPSignC: 56 case OID_gostTC26Sign256D: 57 return &gost_cp256c; 58 case OID_gostTC26Sign512A: 59 return &gost_tc512a; 60 case OID_gostTC26Sign512B: 61 return &gost_tc512b; 62 /* The following two aren't implemented: */ 63 case OID_gostTC26Sign256A: 64 case OID_gostTC26Sign512C: 65 default: 66 return NULL; 67 } 68 } 69 70 static int ecrdsa_verify(struct crypto_sig *tfm, 71 const void *src, unsigned int slen, 72 const void *digest, unsigned int dlen) 73 { 74 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm); 75 unsigned int ndigits = dlen / sizeof(u64); 76 u64 r[ECRDSA_MAX_DIGITS]; /* witness (r) */ 77 u64 _r[ECRDSA_MAX_DIGITS]; /* -r */ 78 u64 s[ECRDSA_MAX_DIGITS]; /* second part of sig (s) */ 79 u64 e[ECRDSA_MAX_DIGITS]; /* h \mod q */ 80 u64 *v = e; /* e^{-1} \mod q */ 81 u64 z1[ECRDSA_MAX_DIGITS]; 82 u64 *z2 = _r; 83 struct ecc_point cc = ECC_POINT_INIT(s, e, ndigits); /* reuse s, e */ 84 85 /* 86 * Digest value, digest algorithm, and curve (modulus) should have the 87 * same length (256 or 512 bits), public key and signature should be 88 * twice bigger. 89 */ 90 if (!ctx->curve || 91 !ctx->digest || 92 !src || 93 !digest || 94 !ctx->pub_key.x || 95 dlen != ctx->digest_len || 96 dlen != ctx->curve->g.ndigits * sizeof(u64) || 97 ctx->pub_key.ndigits != ctx->curve->g.ndigits || 98 dlen * 2 != slen || 99 WARN_ON(slen > ECRDSA_MAX_SIG_SIZE) || 100 WARN_ON(dlen > STREEBOG512_DIGEST_SIZE)) 101 return -EBADMSG; 102 103 vli_from_be64(s, src, ndigits); 104 vli_from_be64(r, src + ndigits * sizeof(u64), ndigits); 105 106 /* Step 1: verify that 0 < r < q, 0 < s < q */ 107 if (vli_is_zero(r, ndigits) || 108 vli_cmp(r, ctx->curve->n, ndigits) >= 0 || 109 vli_is_zero(s, ndigits) || 110 vli_cmp(s, ctx->curve->n, ndigits) >= 0) 111 return -EKEYREJECTED; 112 113 /* Step 2: calculate hash (h) of the message (passed as input) */ 114 /* Step 3: calculate e = h \mod q */ 115 vli_from_le64(e, digest, ndigits); 116 if (vli_cmp(e, ctx->curve->n, ndigits) >= 0) 117 vli_sub(e, e, ctx->curve->n, ndigits); 118 if (vli_is_zero(e, ndigits)) 119 e[0] = 1; 120 121 /* Step 4: calculate v = e^{-1} \mod q */ 122 vli_mod_inv(v, e, ctx->curve->n, ndigits); 123 124 /* Step 5: calculate z_1 = sv \mod q, z_2 = -rv \mod q */ 125 vli_mod_mult_slow(z1, s, v, ctx->curve->n, ndigits); 126 vli_sub(_r, ctx->curve->n, r, ndigits); 127 vli_mod_mult_slow(z2, _r, v, ctx->curve->n, ndigits); 128 129 /* Step 6: calculate point C = z_1P + z_2Q, and R = x_c \mod q */ 130 ecc_point_mult_shamir(&cc, z1, &ctx->curve->g, z2, &ctx->pub_key, 131 ctx->curve); 132 if (vli_cmp(cc.x, ctx->curve->n, ndigits) >= 0) 133 vli_sub(cc.x, cc.x, ctx->curve->n, ndigits); 134 135 /* Step 7: if R == r signature is valid */ 136 if (!vli_cmp(cc.x, r, ndigits)) 137 return 0; 138 else 139 return -EKEYREJECTED; 140 } 141 142 int ecrdsa_param_curve(void *context, size_t hdrlen, unsigned char tag, 143 const void *value, size_t vlen) 144 { 145 struct ecrdsa_ctx *ctx = context; 146 147 ctx->curve_oid = look_up_OID(value, vlen); 148 if (!ctx->curve_oid) 149 return -EINVAL; 150 ctx->curve = get_curve_by_oid(ctx->curve_oid); 151 return 0; 152 } 153 154 /* Optional. If present should match expected digest algo OID. */ 155 int ecrdsa_param_digest(void *context, size_t hdrlen, unsigned char tag, 156 const void *value, size_t vlen) 157 { 158 struct ecrdsa_ctx *ctx = context; 159 int digest_oid = look_up_OID(value, vlen); 160 161 if (digest_oid != ctx->digest_oid) 162 return -EINVAL; 163 return 0; 164 } 165 166 int ecrdsa_parse_pub_key(void *context, size_t hdrlen, unsigned char tag, 167 const void *value, size_t vlen) 168 { 169 struct ecrdsa_ctx *ctx = context; 170 171 ctx->key = value; 172 ctx->key_len = vlen; 173 return 0; 174 } 175 176 static u8 *ecrdsa_unpack_u32(u32 *dst, void *src) 177 { 178 memcpy(dst, src, sizeof(u32)); 179 return src + sizeof(u32); 180 } 181 182 /* Parse BER encoded subjectPublicKey. */ 183 static int ecrdsa_set_pub_key(struct crypto_sig *tfm, const void *key, 184 unsigned int keylen) 185 { 186 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm); 187 unsigned int ndigits; 188 u32 algo, paramlen; 189 u8 *params; 190 int err; 191 192 err = asn1_ber_decoder(&ecrdsa_pub_key_decoder, ctx, key, keylen); 193 if (err < 0) 194 return err; 195 196 /* Key parameters is in the key after keylen. */ 197 params = ecrdsa_unpack_u32(¶mlen, 198 ecrdsa_unpack_u32(&algo, (u8 *)key + keylen)); 199 200 if (algo == OID_gost2012PKey256) { 201 ctx->digest = "streebog256"; 202 ctx->digest_oid = OID_gost2012Digest256; 203 ctx->digest_len = 256 / 8; 204 } else if (algo == OID_gost2012PKey512) { 205 ctx->digest = "streebog512"; 206 ctx->digest_oid = OID_gost2012Digest512; 207 ctx->digest_len = 512 / 8; 208 } else 209 return -ENOPKG; 210 ctx->algo_oid = algo; 211 212 /* Parse SubjectPublicKeyInfo.AlgorithmIdentifier.parameters. */ 213 err = asn1_ber_decoder(&ecrdsa_params_decoder, ctx, params, paramlen); 214 if (err < 0) 215 return err; 216 /* 217 * Sizes of algo (set in digest_len) and curve should match 218 * each other. 219 */ 220 if (!ctx->curve || 221 ctx->curve->g.ndigits * sizeof(u64) != ctx->digest_len) 222 return -ENOPKG; 223 /* 224 * Key is two 256- or 512-bit coordinates which should match 225 * curve size. 226 */ 227 if ((ctx->key_len != (2 * 256 / 8) && 228 ctx->key_len != (2 * 512 / 8)) || 229 ctx->key_len != ctx->curve->g.ndigits * sizeof(u64) * 2) 230 return -ENOPKG; 231 232 ndigits = ctx->key_len / sizeof(u64) / 2; 233 ctx->pub_key = ECC_POINT_INIT(ctx->_pubp[0], ctx->_pubp[1], ndigits); 234 vli_from_le64(ctx->pub_key.x, ctx->key, ndigits); 235 vli_from_le64(ctx->pub_key.y, ctx->key + ndigits * sizeof(u64), 236 ndigits); 237 238 if (ecc_is_pubkey_valid_partial(ctx->curve, &ctx->pub_key)) 239 return -EKEYREJECTED; 240 241 return 0; 242 } 243 244 static unsigned int ecrdsa_key_size(struct crypto_sig *tfm) 245 { 246 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm); 247 248 /* 249 * Verify doesn't need any output, so it's just informational 250 * for keyctl to determine the key bit size. 251 */ 252 return ctx->pub_key.ndigits * sizeof(u64); 253 } 254 255 static unsigned int ecrdsa_max_size(struct crypto_sig *tfm) 256 { 257 struct ecrdsa_ctx *ctx = crypto_sig_ctx(tfm); 258 259 return 2 * ctx->pub_key.ndigits * sizeof(u64); 260 } 261 262 static void ecrdsa_exit_tfm(struct crypto_sig *tfm) 263 { 264 } 265 266 static struct sig_alg ecrdsa_alg = { 267 .verify = ecrdsa_verify, 268 .set_pub_key = ecrdsa_set_pub_key, 269 .key_size = ecrdsa_key_size, 270 .max_size = ecrdsa_max_size, 271 .exit = ecrdsa_exit_tfm, 272 .base = { 273 .cra_name = "ecrdsa", 274 .cra_driver_name = "ecrdsa-generic", 275 .cra_priority = 100, 276 .cra_module = THIS_MODULE, 277 .cra_ctxsize = sizeof(struct ecrdsa_ctx), 278 }, 279 }; 280 281 static int __init ecrdsa_mod_init(void) 282 { 283 return crypto_register_sig(&ecrdsa_alg); 284 } 285 286 static void __exit ecrdsa_mod_fini(void) 287 { 288 crypto_unregister_sig(&ecrdsa_alg); 289 } 290 291 module_init(ecrdsa_mod_init); 292 module_exit(ecrdsa_mod_fini); 293 294 MODULE_LICENSE("GPL"); 295 MODULE_AUTHOR("Vitaly Chikunov <vt@altlinux.org>"); 296 MODULE_DESCRIPTION("EC-RDSA generic algorithm"); 297 MODULE_ALIAS_CRYPTO("ecrdsa"); 298 MODULE_ALIAS_CRYPTO("ecrdsa-generic"); 299