On Thu, Jan 30, 2020 at 11:18:09AM +0100, James Bottomley wrote:
> In TPM 1.2 an authorization was a 20 byte number. The spec actually
> recommended you to hash variable length passwords and use the sha1
> hash as the authorization. Because the spec doesn't require this
> hashing, the current authorization for trusted keys is a 40 digit hex
> number. For TPM 2.0 the spec allows the passing in of variable length
> passwords and passphrases directly, so we should allow that in trusted
> keys for ease of use. Update the 'blobauth' parameter to take this
> into account, so we can now use plain text passwords for the keys.
>
> so before
>
> keyctl add trusted kmk "new 32 blobauth=f572d396fae9206628714fb2ce00f72e94f2258f"
>
> after we will accept both the old hex sha1 form as well as a new
> directly supplied password:
>
> keyctl add trusted kmk "new 32 blobauth=hello keyhandle=81000001"
>
> Since a sha1 hex code must be exactly 40 bytes long and a direct
> password must be 20 or less, we use the length as the discriminator
> for which form is input.
>
> Note this is both and enhancement and a potential bug fix. The TPM
> 2.0 spec requires us to strip leading zeros, meaning empyty
> authorization is a zero length HMAC whereas we're currently passing in
> 20 bytes of zeros. A lot of TPMs simply accept this as OK, but the
> Microsoft TPM emulator rejects it with TPM_RC_BAD_AUTH, so this patch
> makes the Microsoft TPM emulator work with trusted keys.
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
Should have a fixes tag.
> ---
> include/keys/trusted-type.h | 1 +
> security/keys/trusted-keys/trusted_tpm1.c | 26 +++++++++++++++++++++-----
> security/keys/trusted-keys/trusted_tpm2.c | 10 ++++++----
> 3 files changed, 28 insertions(+), 9 deletions(-)
>
> diff --git a/include/keys/trusted-type.h b/include/keys/trusted-type.h
> index a94c03a61d8f..b2ed3481c6a0 100644
> --- a/include/keys/trusted-type.h
> +++ b/include/keys/trusted-type.h
> @@ -30,6 +30,7 @@ struct trusted_key_options {
> uint16_t keytype;
> uint32_t keyhandle;
> unsigned char keyauth[TPM_DIGEST_SIZE];
> + uint32_t blobauth_len;
> unsigned char blobauth[TPM_DIGEST_SIZE];
> uint32_t pcrinfo_len;
> unsigned char pcrinfo[MAX_PCRINFO_SIZE];
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index d2c5ec1e040b..3f33d3f74d3c 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -781,12 +781,28 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
> return -EINVAL;
> break;
> case Opt_blobauth:
> - if (strlen(args[0].from) != 2 * SHA1_DIGEST_SIZE)
> - return -EINVAL;
> - res = hex2bin(opt->blobauth, args[0].from,
> - SHA1_DIGEST_SIZE);
> - if (res < 0)
> + /*
> + * TPM 1.2 authorizations are sha1 hashes
> + * passed in as hex strings. TPM 2.0
> + * authorizations are simple passwords
> + * (although it can take a hash as well)
Justify to the 80 character line length.
> + */
> + opt->blobauth_len = strlen(args[0].from);
> + if (opt->blobauth_len == 2 * TPM_DIGEST_SIZE) {
> + res = hex2bin(opt->blobauth, args[0].from,
> + TPM_DIGEST_SIZE);
> + if (res < 0)
> + return -EINVAL;
> +
> + opt->blobauth_len = TPM_DIGEST_SIZE;
> + } else if (tpm2 &&
> + opt->blobauth_len <= sizeof(opt->blobauth)) {
> + memcpy(opt->blobauth, args[0].from,
> + opt->blobauth_len);
> + } else {
> return -EINVAL;
> + }
This starts to be unnecessarily complicated.
This is what I would suggest:
opt->blobauth_len = strlen(args[0].from);
if (opt->blobauth_len == 2 * TPM_DIGEST_SIZE) {
res = hex2bin(opt->blobauth, args[0].from,
TPM_DIGEST_SIZE);
if (res < 0)
return -EINVAL;
opt->blobauth_len = TPM_DIGEST_SIZE;
return 0;
}
if (tpm2 && opt->blobauth_len <= sizeof(opt->blobauth)) {
memcpy(opt->blobauth, args[0].from,
opt->blobauth_len);
return 0;
}
return -EINVAL;
Easier to see quickly "when happens what".
/Jarkko
