| 1 | |
| 2 | |
| 3 | * echainiv: Encrypted Chain IV Generator
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| 4 | *
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| 5 | * This generator generates an IV based on a sequence number by multiplying
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| 6 | * it with a salt and then encrypting it with the same key as used to encrypt
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| 7 | * the plain text. This algorithm requires that the block size be equal
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| 8 | * to the IV size. It is mainly useful for CBC.
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| 9 | *
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| 10 | * This generator can only be used by algorithms where authentication
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| 11 | * is performed after encryption (i.e., authenc).
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| 12 | *
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| 13 | * Copyright (c) 2015 Herbert Xu <[email protected]>
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| 14 |
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| 15 |
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| 16 | #include <crypto/internal/geniv.h>
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| 17 | #include <crypto/scatterwalk.h>
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| 18 | #include <crypto/skcipher.h>
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| 19 | #include <linux/err.h>
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| 20 | #include <linux/init.h>
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| 21 | #include <linux/kernel.h>
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| 22 | #include <linux/module.h>
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| 23 | #include <linux/slab.h>
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| 24 | #include <linux/string.h>
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| 25 |
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| 26 | static int echainiv_encrypt(struct aead_request *req)
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| 27 | {
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| 28 | struct crypto_aead *geniv = crypto_aead_reqtfm(req);
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| 29 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
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| 30 | struct aead_request *subreq = aead_request_ctx(req);
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| 31 | __be64 nseqno;
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| 32 | u64 seqno;
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| 33 | u8 *info;
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| 34 | unsigned int ivsize = crypto_aead_ivsize(geniv);
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| 35 |
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| 36 | if (req->cryptlen < ivsize)
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| 37 | return -EINVAL;
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| 38 |
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| 39 | aead_request_set_tfm(subreq, ctx->child);
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| 40 |
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| 41 | info = req->iv;
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| 42 |
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| 43 | if (req->src != req->dst)
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| 44 | memcpy_sglist(req->dst, req->src,
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| 45 | req->assoclen + req->cryptlen);
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| 46 |
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| 47 | aead_request_set_callback(subreq, req->base.flags,
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| 48 | req->base.complete, req->base.data);
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| 49 | aead_request_set_crypt(subreq, req->dst, req->dst,
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| 50 | req->cryptlen, info);
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| 51 | aead_request_set_ad(subreq, req->assoclen);
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| 52 |
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| 53 | memcpy(&nseqno, info + ivsize - 8, 8);
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| 54 | seqno = be64_to_cpu(nseqno);
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| 55 | memset(info, 0, ivsize);
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| 56 |
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| 57 | scatterwalk_map_and_copy(info, req->dst, req->assoclen, ivsize, 1);
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| 58 |
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| 59 | do {
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| 60 | u64 a;
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| 61 |
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| 62 | memcpy(&a, ctx->salt + ivsize - 8, 8);
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| 63 |
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| 64 | a |= 1;
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| 65 | a *= seqno;
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| 66 |
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| 67 | memcpy(info + ivsize - 8, &a, 8);
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| 68 | } while ((ivsize -= 8));
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| 69 |
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| 70 | return crypto_aead_encrypt(subreq);
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| 71 | }
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| 72 |
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| 73 | static int echainiv_decrypt(struct aead_request *req)
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| 74 | {
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| 75 | struct crypto_aead *geniv = crypto_aead_reqtfm(req);
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| 76 | struct aead_geniv_ctx *ctx = crypto_aead_ctx(geniv);
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| 77 | struct aead_request *subreq = aead_request_ctx(req);
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| 78 | crypto_completion_t compl;
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| 79 | void *data;
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| 80 | unsigned int ivsize = crypto_aead_ivsize(geniv);
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| 81 |
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| 82 | if (req->cryptlen < ivsize)
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| 83 | return -EINVAL;
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| 84 |
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| 85 | aead_request_set_tfm(subreq, ctx->child);
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| 86 |
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| 87 | compl = req->base.complete;
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| 88 | data = req->base.data;
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| 89 |
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| 90 | aead_request_set_callback(subreq, req->base.flags, compl, data);
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| 91 | aead_request_set_crypt(subreq, req->src, req->dst,
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| 92 | req->cryptlen - ivsize, req->iv);
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| 93 | aead_request_set_ad(subreq, req->assoclen + ivsize);
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| 94 |
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| 95 | scatterwalk_map_and_copy(req->iv, req->src, req->assoclen, ivsize, 0);
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| 96 |
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| 97 | return crypto_aead_decrypt(subreq);
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| 98 | }
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| 99 |
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| 100 | static int echainiv_aead_create(struct crypto_template *tmpl,
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| 101 | struct rtattr **tb)
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| 102 | {
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| 103 | struct aead_instance *inst;
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| 104 | int err;
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| 105 |
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| 106 | inst = aead_geniv_alloc(tmpl, tb);
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| 107 |
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| 108 | if (IS_ERR(inst))
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| 109 | return PTR_ERR(inst);
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| 110 |
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| 111 | err = -EINVAL;
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| 112 | if (inst->alg.ivsize & (sizeof(u64) - 1) || !inst->alg.ivsize)
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| 113 | goto free_inst;
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| 114 |
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| 115 | inst->alg.encrypt = echainiv_encrypt;
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| 116 | inst->alg.decrypt = echainiv_decrypt;
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| 117 |
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| 118 | inst->alg.init = aead_init_geniv;
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| 119 | inst->alg.exit = aead_exit_geniv;
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| 120 |
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| 121 | inst->alg.base.cra_ctxsize = sizeof(struct aead_geniv_ctx);
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| 122 | inst->alg.base.cra_ctxsize += inst->alg.ivsize;
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| 123 |
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| 124 | err = aead_register_instance(tmpl, inst);
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| 125 | if (err) {
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| 126 | free_inst:
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| 127 | inst->free(inst);
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| 128 | }
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| 129 | return err;
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| 130 | }
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| 131 |
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| 132 | static struct crypto_template echainiv_tmpl = {
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| 133 | .name = "echainiv",
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| 134 | .create = echainiv_aead_create,
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| 135 | .module = THIS_MODULE,
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| 136 | };
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| 137 |
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| 138 | static int __init echainiv_module_init(void)
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| 139 | {
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| 140 | return crypto_register_template(&echainiv_tmpl);
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| 141 | }
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| 142 |
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| 143 | static void __exit echainiv_module_exit(void)
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| 144 | {
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| 145 | crypto_unregister_template(&echainiv_tmpl);
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| 146 | }
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| 147 |
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| 148 | module_init(echainiv_module_init);
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| 149 | module_exit(echainiv_module_exit);
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| 150 |
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| 151 | MODULE_LICENSE("GPL");
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| 152 | MODULE_DESCRIPTION("Encrypted Chain IV Generator");
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| 153 | MODULE_ALIAS_CRYPTO("echainiv");
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