1 /* 2 * echainiv: Encrypted Chain IV Generator 3 * 4 * This generator generates an IV based on a sequence number by xoring it 5 * 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/mm.h> 28 #include <linux/module.h> 29 #include <linux/percpu.h> 30 #include <linux/spinlock.h> 31 #include <linux/string.h> 32 33 #define MAX_IV_SIZE 16 34 35 static DEFINE_PER_CPU(u32 [MAX_IV_SIZE / sizeof(u32)], echainiv_iv); 36 37 /* We don't care if we get preempted and read/write IVs from the next CPU. */ 38 static void echainiv_read_iv(u8 *dst, unsigned size) 39 { 40 u32 *a = (u32 *)dst; 41 u32 __percpu *b = echainiv_iv; 42 43 for (; size >= 4; size -= 4) { 44 *a++ = this_cpu_read(*b); 45 b++; 46 } 47 } 48 49 static void echainiv_write_iv(const u8 *src, unsigned size) 50 { 51 const u32 *a = (const u32 *)src; 52 u32 __percpu *b = echainiv_iv; 53 54 for (; size >= 4; size -= 4) { 55 this_cpu_write(*b, *a); 56 a++; 57 b++; 58 } 59 } 60 61 static void echainiv_encrypt_complete2(struct aead_request *req, int err) 62 { 63 struct aead_request *subreq = aead_request_ctx(req); 64 struct crypto_aead *geniv; 65 unsigned int ivsize; 66 67 if (err == -EINPROGRESS) 68 return; 69 70 if (err) 71 goto out; 72 73 geniv = crypto_aead_reqtfm(req); 74 ivsize = crypto_aead_ivsize(geniv); 75 76 echainiv_write_iv(subreq->iv, ivsize); 77 78 if (req->iv != subreq->iv) 79 memcpy(req->iv, subreq->iv, ivsize); 80 81 out: 82 if (req->iv != subreq->iv) 83 kzfree(subreq->iv); 84 } 85 86 static void echainiv_encrypt_complete(struct crypto_async_request *base, 87 int err) 88 { 89 struct aead_request *req = base->data; 90 91 echainiv_encrypt_complete2(req, err); 92 aead_request_complete(req, err); 93 } 94 95 static int echainiv_encrypt(struct aead_request *req) 96 { 97 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 98 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 99 struct aead_request *subreq = aead_request_ctx(req); 100 crypto_completion_t compl; 101 void *data; 102 u8 *info; 103 unsigned int ivsize = crypto_aead_ivsize(geniv); 104 int err; 105 106 if (req->cryptlen < ivsize) 107 return -EINVAL; 108 109 aead_request_set_tfm(subreq, ctx->child); 110 111 compl = echainiv_encrypt_complete; 112 data = req; 113 info = req->iv; 114 115 if (req->src != req->dst) { 116 SKCIPHER_REQUEST_ON_STACK(nreq, ctx->sknull); 117 118 skcipher_request_set_tfm(nreq, ctx->sknull); 119 skcipher_request_set_callback(nreq, req->base.flags, 120 NULL, NULL); 121 skcipher_request_set_crypt(nreq, req->src, req->dst, 122 req->assoclen + req->cryptlen, 123 NULL); 124 125 err = crypto_skcipher_encrypt(nreq); 126 if (err) 127 return err; 128 } 129 130 if (unlikely(!IS_ALIGNED((unsigned long)info, 131 crypto_aead_alignmask(geniv) + 1))) { 132 info = kmalloc(ivsize, req->base.flags & 133 CRYPTO_TFM_REQ_MAY_SLEEP ? GFP_KERNEL: 134 GFP_ATOMIC); 135 if (!info) 136 return -ENOMEM; 137 138 memcpy(info, req->iv, ivsize); 139 } 140 141 aead_request_set_callback(subreq, req->base.flags, compl, data); 142 aead_request_set_crypt(subreq, req->dst, req->dst, 143 req->cryptlen, info); 144 aead_request_set_ad(subreq, req->assoclen); 145 146 crypto_xor(info, ctx->salt, ivsize); 147 scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1); 148 echainiv_read_iv(info, ivsize); 149 150 err = crypto_aead_encrypt(subreq); 151 echainiv_encrypt_complete2(req, err); 152 return err; 153 } 154 155 static int echainiv_decrypt(struct aead_request *req) 156 { 157 struct crypto_aead *geniv = crypto_aead_reqtfm(req); 158 struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv); 159 struct aead_request *subreq = aead_request_ctx(req); 160 crypto_completion_t compl; 161 void *data; 162 unsigned int ivsize = crypto_aead_ivsize(geniv); 163 164 if (req->cryptlen < ivsize) 165 return -EINVAL; 166 167 aead_request_set_tfm(subreq, ctx->child); 168 169 compl = req->base.complete; 170 data = req->base.data; 171 172 aead_request_set_callback(subreq, req->base.flags, compl, data); 173 aead_request_set_crypt(subreq, req->src, req->dst, 174 req->cryptlen - ivsize, req->iv); 175 aead_request_set_ad(subreq, req->assoclen + ivsize); 176 177 scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0); 178 179 return crypto_aead_decrypt(subreq); 180 } 181 182 static int echainiv_aead_create(struct crypto_template *tmpl, 183 struct rtattr **tb) 184 { 185 struct aead_instance *inst; 186 struct crypto_aead_spawn *spawn; 187 struct aead_alg *alg; 188 int err; 189 190 inst = aead_geniv_alloc(tmpl, tb, 0, 0); 191 192 if (IS_ERR(inst)) 193 return PTR_ERR(inst); 194 195 spawn = aead_instance_ctx(inst); 196 alg = crypto_spawn_aead_alg(spawn); 197 198 err = -EINVAL; 199 if (inst->alg.ivsize & (sizeof(u32) - 1) || 200 inst->alg.ivsize > MAX_IV_SIZE) 201 goto free_inst; 202 203 inst->alg.encrypt = echainiv_encrypt; 204 inst->alg.decrypt = echainiv_decrypt; 205 206 inst->alg.init = aead_init_geniv; 207 inst->alg.exit = aead_exit_geniv; 208 209 inst->alg.base.cra_alignmask |= __alignof__(u32) - 1; 210 inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx); 211 inst->alg.base.cra_ctxsize += inst->alg.ivsize; 212 213 inst->free = aead_geniv_free; 214 215 err = aead_register_instance(tmpl, inst); 216 if (err) 217 goto free_inst; 218 219 out: 220 return err; 221 222 free_inst: 223 aead_geniv_free(inst); 224 goto out; 225 } 226 227 static void echainiv_free(struct crypto_instance *inst) 228 { 229 aead_geniv_free(aead_instance(inst)); 230 } 231 232 static struct crypto_template echainiv_tmpl = { 233 .name = "echainiv", 234 .create = echainiv_aead_create, 235 .free = echainiv_free, 236 .module = THIS_MODULE, 237 }; 238 239 static int __init echainiv_module_init(void) 240 { 241 return crypto_register_template(&echainiv_tmpl); 242 } 243 244 static void __exit echainiv_module_exit(void) 245 { 246 crypto_unregister_template(&echainiv_tmpl); 247 } 248 249 module_init(echainiv_module_init); 250 module_exit(echainiv_module_exit); 251 252 MODULE_LICENSE("GPL"); 253 MODULE_DESCRIPTION("Encrypted Chain IV Generator"); 254 MODULE_ALIAS_CRYPTO("echainiv"); 255