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_destroy(void *payload)
  43 {
  44         struct public_key *key = payload;
  45
  46         if (key)
  47                 kfree(key->key);
  48         kfree(key);
  49 }
  50 EXPORT_SYMBOL_GPL(public_key_destroy);
  51
  52 struct public_key_completion {
  53         struct completion completion;
  54         int err;
  55 };
  56
  57 static void public_key_verify_done(struct crypto_async_request *req, int err)
  58 {
  59         struct public_key_completion *compl = req->data;
  60
  61         if (err == -EINPROGRESS)
  62                 return;
  63
  64         compl->err = err;
  65         complete(&compl->completion);
  66 }
  67
  68 /*
  69  * Verify a signature using a public key.
  70  */
  71 int public_key_verify_signature(const struct public_key *pkey,
  72                                 const struct public_key_signature *sig)
  73 {
  74         struct public_key_completion compl;
  75         struct crypto_akcipher *tfm;
  76         struct akcipher_request *req;
  77         struct scatterlist sig_sg, digest_sg;
  78         const char *alg_name;
  79         char alg_name_buf[CRYPTO_MAX_ALG_NAME];
  80         void *output;
  81         unsigned int outlen;
  82         int ret = -ENOMEM;
  83
  84         pr_devel("==>%s()\n", __func__);
  85
  86         BUG_ON(!pkey);
  87         BUG_ON(!sig);
  88         BUG_ON(!sig->digest);
  89         BUG_ON(!sig->s);
  90
  91         alg_name = sig->pkey_algo;
  92         if (strcmp(sig->pkey_algo, "rsa") == 0) {
  93                 /* The data wangled by the RSA algorithm is typically padded
  94                  * and encoded in some manner, such as EMSA-PKCS1-1_5 [RFC3447
  95                  * sec 8.2].
  96                  */
  97                 if (snprintf(alg_name_buf, CRYPTO_MAX_ALG_NAME,
  98                              "pkcs1pad(rsa,%s)", sig->hash_algo
  99                              ) >= CRYPTO_MAX_ALG_NAME)
 100                         return -EINVAL;
 101                 alg_name = alg_name_buf;
 102         }
 103
 104         tfm = crypto_alloc_akcipher(alg_name, 0, 0);
 105         if (IS_ERR(tfm))
 106                 return PTR_ERR(tfm);
 107
 108         req = akcipher_request_alloc(tfm, GFP_KERNEL);
 109         if (!req)
 110                 goto error_free_tfm;
 111
 112         ret = crypto_akcipher_set_pub_key(tfm, pkey->key, pkey->keylen);
 113         if (ret)
 114                 goto error_free_req;
 115
 116         outlen = crypto_akcipher_maxsize(tfm);
 117         output = kmalloc(outlen, GFP_KERNEL);
 118         if (!output)
 119                 goto error_free_req;
 120
 121         sg_init_one(&sig_sg, sig->s, sig->s_size);
 122         sg_init_one(&digest_sg, output, outlen);
 123         akcipher_request_set_crypt(req, &sig_sg, &digest_sg, sig->s_size,
 124                                    outlen);
 125         init_completion(&compl.completion);
 126         akcipher_request_set_callback(req, CRYPTO_TFM_REQ_MAY_BACKLOG |
 127                                       CRYPTO_TFM_REQ_MAY_SLEEP,
 128                                       public_key_verify_done, &compl);
 129
 130         /* Perform the verification calculation.  This doesn't actually do the
 131          * verification, but rather calculates the hash expected by the
 132          * signature and returns that to us.
 133          */
 134         ret = crypto_akcipher_verify(req);
 135         if (ret == -EINPROGRESS) {
 136                 wait_for_completion(&compl.completion);
 137                 ret = compl.err;
 138         }
 139         if (ret < 0)
 140                 goto out_free_output;
 141
 142         /* Do the actual verification step. */
 143         if (req->dst_len != sig->digest_size ||
 144             memcmp(sig->digest, output, sig->digest_size) != 0)
 145                 ret = -EKEYREJECTED;
 146
 147 out_free_output:
 148         kfree(output);
 149 error_free_req:
 150         akcipher_request_free(req);
 151 error_free_tfm:
 152         crypto_free_akcipher(tfm);
 153         pr_devel("<==%s() = %d\n", __func__, ret);
 154         return ret;
 155 }
 156 EXPORT_SYMBOL_GPL(public_key_verify_signature);
 157
 158 static int public_key_verify_signature_2(const struct key *key,
 159                                          const struct public_key_signature *sig)
 160 {
 161         const struct public_key *pk = key->payload.data[asym_crypto];
 162         return public_key_verify_signature(pk, sig);
 163 }
 164
 165 /*
 166  * Public key algorithm asymmetric key subtype
 167  */
 168 struct asymmetric_key_subtype public_key_subtype = {
 169         .owner                  = THIS_MODULE,
 170         .name                   = "public_key",
 171         .name_len               = sizeof("public_key") - 1,
 172         .describe               = public_key_describe,
 173         .destroy                = public_key_destroy,
 174         .verify_signature       = public_key_verify_signature_2,
 175 };
 176 EXPORT_SYMBOL_GPL(public_key_subtype);