crypto/asymmetric_keys/public_key.c

   1 /* In-software asymmetric public-key crypto subtype
   2  *
   3  * See Documentation/crypto/asymmetric-keys.txt
   4  *
   5  * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
   6  * Written by David Howells (dhowells@redhat.com)
   7  *
   8  * This program is free software; you can redistribute it and/or
   9  * modify it under the terms of the GNU General Public Licence
  10  * as published by the Free Software Foundation; either version
  11  * 2 of the Licence, or (at your option) any later version.
  12  */
  13
  14 #define pr_fmt(fmt) "PKEY: "fmt
  15 #include <linux/module.h>
  16 #include <linux/export.h>
  17 #include <linux/kernel.h>
  18 #include <linux/slab.h>
  19 #include <linux/seq_file.h>
  20 #include <linux/scatterlist.h>
  21 #include <keys/asymmetric-subtype.h>
  22 #include <crypto/public_key.h>
  23 #include <crypto/akcipher.h>
  24
  25 MODULE_LICENSE("GPL");
  26
  27 /*
  28  * Provide a part of a description of the key for /proc/keys.
  29  */
  30 static void public_key_describe(const struct key *asymmetric_key,
  31                                 struct seq_file *m)
  32 {
  33         struct public_key *key = asymmetric_key->payload.data[asym_crypto];
  34
  35         if (key)
  36                 seq_printf(m, "%s.%s", key->id_type, key->pkey_algo);
  37 }
  38
  39 /*
  40  * Destroy a public key algorithm key.
  41  */
  42 void public_key_free(struct public_key *key)
  43 {
  44         if (key) {
  45                 kfree(key->key);
  46                 kfree(key);
  47         }
  48 }
  49 EXPORT_SYMBOL_GPL(public_key_free);
  50
  51 /*
  52  * Destroy a public key algorithm key.
  53  */
  54 static void public_key_destroy(void *payload0, void *payload3)
  55 {
  56         public_key_free(payload0);
  57         public_key_signature_free(payload3);
  58 }
  59
  60 struct public_key_completion {
  61         struct completion completion;
  62         int err;
  63 };
  64
  65 static void public_key_verify_done(struct crypto_async_request *req, int err)
  66 {
  67         struct public_key_completion *compl = req->data;
  68
  69         if (err == -EINPROGRESS)
  70                 return;
  71
  72         compl->err = err;
  73         complete(&compl->completion);
  74 }
  75
  76 /*
  77  * Verify a signature using a public key.
  78  */
  79 int public_key_verify_signature(const struct public_key *pkey,
  80                                 const struct public_key_signature *sig)
  81 {
  82         struct public_key_completion compl;
  83         struct crypto_akcipher *tfm;
  84         struct akcipher_request *req;
  85         struct scatterlist sig_sg, digest_sg;
  86         const char *alg_name;
  87         char alg_name_buf[CRYPTO_MAX_ALG_NAME];
  88         void *output;
  89         unsigned int outlen;
  90         int ret = -ENOMEM;
  91
  92         pr_devel("==>%s()\n", __func__);
  93
  94         BUG_ON(!pkey);
  95         BUG_ON(!sig);
  96         BUG_ON(!sig->digest);
  97         BUG_ON(!sig->s);
  98
  99         alg_name = sig->pkey_algo;
 100         if (strcmp(sig->pkey_algo, "rsa") == 0) {
 101                 /* The data wangled by the RSA algorithm is typically padded
 102                  * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447
 103                  * sec 8.2].
 104                  */
 105                 if (snprintf(alg_name_buf, CRYPTO_MAX_ALG_NAME,
 106                              "pkcs1pad(rsa,%s)", sig->hash_algo
 107                              ) >= CRYPTO_MAX_ALG_NAME)
 108                         return -EINVAL;
 109                 alg_name = alg_name_buf;
 110         }
 111
 112         tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 113         if (IS_ERR(tfm))
 114                 return PTR_ERR(tfm);
 115
 116         req = akcipher_request_alloc(tfm, GFP_KERNEL);
 117         if (!req)
 118                 goto error_free_tfm;
 119
 120         ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
 121         if (ret)
 122                 goto error_free_req;
 123
 124         ret = -ENOMEM;
 125         outlen = crypto_akcipher_maxsize(tfm);
 126         output = kmalloc(outlen, GFP_KERNEL);
 127         if (!output)
 128                 goto error_free_req;
 129
 130         sg_init_one(&sig_sg, sig->s, sig->s_size);
 131         sg_init_one(&digest_sg, output, outlen);
 132         akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
 133                                    outlen);
 134         init_completion(&compl.completion);
 135         akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 136                                       CRYPTO_TFM_REQ_MAY_SLEEP,
 137                                       public_key_verify_done, &compl);
 138
 139         /* Perform the verification calculation.  This doesn't actually do the
 140          * verification, but rather calculates the hash expected by the
 141          * signature and returns that to us.
 142          */
 143         ret = crypto_akcipher_verify(req);
 144         if (ret == -EINPROGRESS) {
 145                 wait_for_completion(&compl.completion);
 146                 ret = compl.err;
 147         }
 148         if (ret < 0)
 149                 goto out_free_output;
 150
 151         /* Do the actual verification step. */
 152         if (req->dst_len != sig->digest_size ||
 153             memcmp(sig->digest, output, sig->digest_size) != 0)
 154                 ret = -EKEYREJECTED;
 155
 156 out_free_output:
 157         kfree(output);
 158 error_free_req:
 159         akcipher_request_free(req);
 160 error_free_tfm:
 161         crypto_free_akcipher(tfm);
 162         pr_devel("<==%s() = %d\n", __func__, ret);
 163         return ret;
 164 }
 165 EXPORT_SYMBOL_GPL(public_key_verify_signature);
 166
 167 static int public_key_verify_signature_2(const struct key *key,
 168                                          const struct public_key_signature *sig)
 169 {
 170         const struct public_key *pk = key->payload.data[asym_crypto];
 171         return public_key_verify_signature(pk, sig);
 172 }
 173
 174 /*
 175  * Public key algorithm asymmetric key subtype
 176  */
 177 struct asymmetric_key_subtype public_key_subtype = {
 178         .owner                  = THIS_MODULE,
 179         .name                   = "public_key",
 180         .name_len               = sizeof("public_key") - 1,
 181         .describe               = public_key_describe,
 182         .destroy                = public_key_destroy,
 183         .verify_signature       = public_key_verify_signature_2,
 184 };
 185 EXPORT_SYMBOL_GPL(public_key_subtype);