Re: [PATCH 01/11] keys-encrypted: add nvdimm key format type to encrypted keys

From: Mimi Zohar <zohar@linux.ibm.com>
To: Dave Jiang <dave.jiang@intel.com>,
	Dan Williams <dan.j.williams@intel.com>
Cc: keyrings@vger.kernel.org, Mimi Zohar <zohar@linux.vnet.ibm.com>,
	linux-nvdimm <linux-nvdimm@lists.01.org>
Subject: Re: [PATCH 01/11] keys-encrypted: add nvdimm key format type to encrypted keys
Date: Tue, 27 Nov 2018 13:24:14 -0500	[thread overview]
Message-ID: <1543343054.3902.192.camel@linux.ibm.com> (raw)
In-Reply-To: <5c0d66c2-d628-54eb-b16e-8a6a8eb990c1@intel.com>

On Tue, 2018-11-27 at 09:20 -0700, Dave Jiang wrote:
> 
> On 11/27/18 12:20 AM, Dan Williams wrote:
> > On Fri, Nov 9, 2018 at 2:13 PM Dave Jiang <dave.jiang@intel.com> wrote:
> >>
> >> Adding nvdimm key format type to encrypted keys in order to limit the size
> > 
> > s/Adding/Add an/
> > 
> >> of the key to 32-bytes.
> >>
> >> Signed-off-by: Dave Jiang <dave.jiang@intel.com>
> >> ---
> >>  security/keys/encrypted-keys/encrypted.c |   29 ++++++++++++++++++++---------
> >>  1 file changed, 20 insertions(+), 9 deletions(-)
> >>
> >> diff --git a/security/keys/encrypted-keys/encrypted.c b/security/keys/encrypted-keys/encrypted.c
> >> index d92cbf9687c3..182b4f136bdf 100644
> >> --- a/security/keys/encrypted-keys/encrypted.c
> >> +++ b/security/keys/encrypted-keys/encrypted.c
> >> @@ -45,6 +45,7 @@ static const char hmac_alg[] = "hmac(sha256)";
> >>  static const char blkcipher_alg[] = "cbc(aes)";
> >>  static const char key_format_default[] = "default";
> >>  static const char key_format_ecryptfs[] = "ecryptfs";
> >> +static const char key_format_nvdimm[] = "nvdimm";
> >>  static unsigned int ivsize;
> >>  static int blksize;
> >>
> >> @@ -54,6 +55,7 @@ static int blksize;
> >>  #define HASH_SIZE SHA256_DIGEST_SIZE
> >>  #define MAX_DATA_SIZE 4096
> >>  #define MIN_DATA_SIZE  20
> >> +#define KEY_NVDIMM_PAYLOAD_LEN 32
> >>
> >>  static struct crypto_shash *hash_tfm;
> >>
> >> @@ -62,12 +64,13 @@ enum {
> >>  };
> >>
> >>  enum {
> >> -       Opt_error = -1, Opt_default, Opt_ecryptfs
> >> +       Opt_error = -1, Opt_default, Opt_ecryptfs, Opt_nvdimm
> >>  };
> >>
> >>  static const match_table_t key_format_tokens = {
> >>         {Opt_default, "default"},
> >>         {Opt_ecryptfs, "ecryptfs"},
> >> +       {Opt_nvdimm, "nvdimm"},
> >>         {Opt_error, NULL}
> >>  };
> >>
> >> @@ -195,6 +198,7 @@ static int datablob_parse(char *datablob, const char **format,
> >>         key_format = match_token(p, key_format_tokens, args);
> >>         switch (key_format) {
> >>         case Opt_ecryptfs:
> >> +       case Opt_nvdimm:
> >>         case Opt_default:
> >>                 *format = p;
> >>                 *master_desc = strsep(&datablob, " \t");
> >> @@ -625,15 +629,22 @@ static struct encrypted_key_payload *encrypted_key_alloc(struct key *key,
> >>         format_len = (!format) ? strlen(key_format_default) : strlen(format);
> >>         decrypted_datalen = dlen;
> >>         payload_datalen = decrypted_datalen;
> >> -       if (format && !strcmp(format, key_format_ecryptfs)) {
> >> -               if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
> >> -                       pr_err("encrypted_key: keylen for the ecryptfs format "
> >> -                              "must be equal to %d bytes\n",
> >> -                              ECRYPTFS_MAX_KEY_BYTES);
> >> -                       return ERR_PTR(-EINVAL);
> >> +       if (format) {
> >> +               if (!strcmp(format, key_format_ecryptfs)) {
> >> +                       if (dlen != ECRYPTFS_MAX_KEY_BYTES) {
> >> +                               pr_err("encrypted_key: keylen for the ecryptfs format must be equal to %d bytes\n",
> >> +                                       ECRYPTFS_MAX_KEY_BYTES);
> >> +                               return ERR_PTR(-EINVAL);
> >> +                       }
> >> +                       decrypted_datalen = ECRYPTFS_MAX_KEY_BYTES;
> >> +                       payload_datalen = sizeof(struct ecryptfs_auth_tok);
> >> +               } else if (!strcmp(format, key_format_nvdimm)) {
> >> +                       if (decrypted_datalen != KEY_NVDIMM_PAYLOAD_LEN) {
> >> +                               pr_err("encrypted_key: nvdimm key payload incorrect length: %d\n",
> >> +                                               decrypted_datalen);
> >> +                               return ERR_PTR(-EINVAL);
> >> +                       }
> > 
> > I suspect this may not be the last key type that gets added, but I
> > wonder if we should instead create key-types based on the dlen size.
> > I.e. create a generic 32-byte key-type "enc32"? That way if another
> > 32-byte requirement key comes along we don't need to come touch this
> > routine again.
> > 
> 
> I'm ok with that if Mimi is.

If the usage (eg. format: ecryptfs, nvdimm) limits the dlen size(s),
how will defining generic key-types help?  If there are no usage size
limitations, then there would be no usage specific definition.

I must be missing something.

Mimi

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