1 /* 2 * echainiv: Encrypted Chain IV Generator 3 * 4 * This generator generates an IV based on a sequence number by multiplying 5 * it with a salt and then encrypting it with the same key as used to encrypt 6 * the plain text. This algorithm requires that the block size be equal 7 * to the IV size. It is mainly useful for CBC. 8 * 9 * This generator can only be used by algorithms where authentication 10 * is performed after encryption (i.e., authenc). 11 * 12 * Copyright (c) 2015 Herbert Xu <herbert@gondor.apana.org.au> 13 * 14 * This program is free software; you can redistribute it and/or modify it 15 * under the terms of the GNU General Public License as published by the Free 16 * Software Foundation; either version 2 of the License, or (at your option) 17 * any later version. 18 * 19 */ 20 21 #include <crypto/internal/geniv.h> 22 #include <crypto/scatterwalk.h> 23 #include <crypto/skcipher.h> 24 #include <linux/err.h> 25 #include <linux/init.h> 26 #include <linux/kernel.h> 27 #include <linux/module.h> 28 #include <linux/slab.h> 29 #include <linux/string.h> 30 31 static int echainiv_encrypt(struct aead_request *req) 32 { 33 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 34 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 35 struct aead_request *subreq = aead_request_ctx(req); 36 __be64 nseqno; 37 u64 seqno; 38 u8 *info; 39 unsigned int ivsize = crypto_aead_ivsize(geniv); 40 int err; 41 42 if (req->cryptlen < ivsize) 43 return -EINVAL; 44 45 aead_request_set_tfm(subreq, ctx->child); 46 47 info = req->iv; 48 49 if (req->src != req->dst) { 50 SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull); 51 52 skcipher_request_set_tfm(nreq, ctx->sknull); 53 skcipher_request_set_callback(nreq, req->base.flags, 54 NULL, NULL); 55 skcipher_request_set_crypt(nreq, req->src, req->dst, 56 req->assoclen + req->cryptlen, 57 NULL); 58 59 err = crypto_skcipher_encrypt(nreq); 60 if (err) 61 return err; 62 } 63 64 aead_request_set_callback(subreq, req->base.flags, 65 req->base.complete, req->base.data); 66 aead_request_set_crypt(subreq, req->dst, req->dst, 67 req->cryptlen, info); 68 aead_request_set_ad(subreq, req->assoclen); 69 70 memcpy(&nseqno, info + ivsize - 8, 8); 71 seqno = be64_to_cpu(nseqno); 72 memset(info, 0, ivsize); 73 74 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); 75 76 do { 77 u64 a; 78 79 memcpy(&a, ctx->salt + ivsize - 8, 8); 80 81 a |= 1; 82 a *= seqno; 83 84 memcpy(info + ivsize - 8, &a, 8); 85 } while ((ivsize -= 8)); 86 87 return crypto_aead_encrypt(subreq); 88 } 89 90 static int echainiv_decrypt(struct aead_request *req) 91 { 92 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 93 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 94 struct aead_request *subreq = aead_request_ctx(req); 95 crypto_completion_t compl; 96 void *data; 97 unsigned int ivsize = crypto_aead_ivsize(geniv); 98 99 if (req->cryptlen < ivsize) 100 return -EINVAL; 101 102 aead_request_set_tfm(subreq, ctx->child); 103 104 compl = req->base.complete; 105 data = req->base.data; 106 107 aead_request_set_callback(subreq, req->base.flags, compl, data); 108 aead_request_set_crypt(subreq, req->src, req->dst, 109 req->cryptlen - ivsize, req->iv); 110 aead_request_set_ad(subreq, req->assoclen + ivsize); 111 112 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); 113 114 return crypto_aead_decrypt(subreq); 115 } 116 117 static int echainiv_aead_create(struct crypto_template *tmpl, 118 struct rtattr **tb) 119 { 120 struct aead_instance *inst; 121 struct crypto_aead_spawn *spawn; 122 struct aead_alg *alg; 123 int err; 124 125 inst = aead_geniv_alloc(tmpl, tb, 0, 0); 126 127 if (IS_ERR(inst)) 128 return PTR_ERR(inst); 129 130 spawn = aead_instance_ctx(inst); 131 alg = crypto_spawn_aead_alg(spawn); 132 133 err = -EINVAL; 134 if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize) 135 goto free_inst; 136 137 inst->alg.encrypt = echainiv_encrypt; 138 inst->alg.decrypt = echainiv_decrypt; 139 140 inst->alg.init = aead_init_geniv; 141 inst->alg.exit = aead_exit_geniv; 142 143 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); 144 inst->alg.base.cra_ctxsize += inst->alg.ivsize; 145 146 inst->free = aead_geniv_free; 147 148 err = aead_register_instance(tmpl, inst); 149 if (err) 150 goto free_inst; 151 152 out: 153 return err; 154 155 free_inst: 156 aead_geniv_free(inst); 157 goto out; 158 } 159 160 static void echainiv_free(struct crypto_instance *inst) 161 { 162 aead_geniv_free(aead_instance(inst)); 163 } 164 165 static struct crypto_template echainiv_tmpl = { 166 .name = "echainiv", 167 .create = echainiv_aead_create, 168 .free = echainiv_free, 169 .module = THIS_MODULE, 170 }; 171 172 static int __init echainiv_module_init(void) 173 { 174 return crypto_register_template(&echainiv_tmpl); 175 } 176 177 static void __exit echainiv_module_exit(void) 178 { 179 crypto_unregister_template(&echainiv_tmpl); 180 } 181 182 module_init(echainiv_module_init); 183 module_exit(echainiv_module_exit); 184 185 MODULE_LICENSE("GPL"); 186 MODULE_DESCRIPTION("Encrypted Chain IV Generator"); 187 MODULE_ALIAS_CRYPTO("echainiv"); 188