On Mon, Sep 21, 2020 at 07:28:07PM -0700, 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=f572d396fae9206628714fb2ce00f72e94f2258fkeyhandle=81000001" @u
>
> 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" @u
>
> 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.
>
> Fixes: 0fe5480303a1 ("keys, trusted: seal/unseal with TPM 2.0 chips")
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> Reviewed-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
>
> ---
>
> v6: change comment, eliminate else clauses and add fixes tag
> v7: fixes before signoff
> v12: fix mismerge from v6 to make processing continue after blobauth
>
> Merge with auth fix
> ---
> include/keys/trusted-type.h | 1 +
> security/keys/trusted-keys/trusted_tpm1.c | 32 ++++++++++++++++++-----
> security/keys/trusted-keys/trusted_tpm2.c | 10 ++++---
> 3 files changed, 33 insertions(+), 10 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 b9fe02e5f84f..eaa2e7ca136e 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -781,13 +781,33 @@ 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)
> - return -EINVAL;
> + /*
> + * 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)
> + */
> + 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;
> + break;
> + }
> +
> + if (tpm2 && opt->blobauth_len <= sizeof(opt->blobauth)) {
> + memcpy(opt->blobauth, args[0].from,
> + opt->blobauth_len);
> + break;
> + }
> +
> + return -EINVAL;
> +
> break;
> +
> case Opt_migratable:
> if (*args[0].from == '0')
> pay->migratable = 0;
> diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c
> index 08ec7f48f01d..b4a5058107c2 100644
> --- a/security/keys/trusted-keys/trusted_tpm2.c
> +++ b/security/keys/trusted-keys/trusted_tpm2.c
> @@ -91,10 +91,12 @@ int tpm2_seal_trusted(struct tpm_chip *chip,
> TPM_DIGEST_SIZE);
>
> /* sensitive */
> - tpm_buf_append_u16(&buf, 4 + TPM_DIGEST_SIZE + payload->key_len + 1);
> + tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len + 1);
> +
> + tpm_buf_append_u16(&buf, options->blobauth_len);
> + if (options->blobauth_len)
> + tpm_buf_append(&buf, options->blobauth, options->blobauth_len);
>
> - tpm_buf_append_u16(&buf, TPM_DIGEST_SIZE);
> - tpm_buf_append(&buf, options->blobauth, TPM_DIGEST_SIZE);
> tpm_buf_append_u16(&buf, payload->key_len + 1);
> tpm_buf_append(&buf, payload->key, payload->key_len);
> tpm_buf_append_u8(&buf, payload->migratable);
> @@ -258,7 +260,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip,
> NULL /* nonce */, 0,
> TPM2_SA_CONTINUE_SESSION,
> options->blobauth /* hmac */,
> - TPM_DIGEST_SIZE);
> + options->blobauth_len);
>
> rc = tpm_send(chip, buf.data, tpm_buf_length(&buf));
> if (rc > 0)
> --
> 2.26.2
>
Tested-by: Jarkko Sakkinen <jarkko.sakkinen@xxxxxxxxxxxxxxx>
Transcript:
➜ tpm2-scripts (master) ✗ sudo ./tpm2-root-key
0x80000000
➜ tpm2-scripts (master) ✗ sudo keyctl add trusted kmk "new 32 blobauth=hello keyhandle=80000000" @u
751240563
/Jarkko
