On Fri May 24, 2024 at 4:04 PM EEST, James Bottomley wrote:
> This patch adds a policy= argument to key creation. The policy is the
> standard tss policymaker format and each separate policy line must
> have a newline after it.
>
> Thus to construct a policy requiring authorized value and pcr 16
> locking using a sha256 hash, the policy (policy.txt) file would be two
> lines:
>
> 0000017F00000001000B03000001303095B49BE85E381E5B20E557E46363EF55B0F43B132C2D8E3DE9AC436656F2
> 0000016b
>
> This can be inserted into the key with
>
> keyctl add trusted kmk "new 32 policy=`cat policy.txt` keyhandle=0x81000001 hash=sha256" @u
>
> Note that although a few policies work like this, most require special
> handling which must be added to the kernel policy construction
> routine.
>
> Signed-off-by: James Bottomley <James.Bottomley@xxxxxxxxxxxxxxxxxxxxx>
> ---
> .../security/keys/trusted-encrypted.rst | 17 +++++-
> security/keys/trusted-keys/tpm2-policy.c | 53 +++++++++++++++++++
> security/keys/trusted-keys/tpm2-policy.h | 5 ++
> security/keys/trusted-keys/trusted_tpm1.c | 15 ++++++
> 4 files changed, 89 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/security/keys/trusted-encrypted.rst b/Documentation/security/keys/trusted-encrypted.rst
> index c37c08956ec1..fbb41cf16f30 100644
> --- a/Documentation/security/keys/trusted-encrypted.rst
> +++ b/Documentation/security/keys/trusted-encrypted.rst
> @@ -233,6 +233,9 @@ Usage::
> policyhandle= handle to an authorization policy session that defines the
> same policy and with the same hash algorithm as was used to
> seal the key.
> + policy= specify an arbitrary set of policies. These must
> + be in policymaker format with each separate
> + policy line newline terminated.
>
> "keyctl print" returns an ascii hex copy of the sealed key, which is in standard
> TPM_STORED_DATA format. The key length for new keys are always in bytes.
> @@ -377,6 +380,19 @@ the sha1 pcr16 bank you'd say::
>
> because the trailing hash is the sha256sum of 20 zero bytes.
>
> +You can also specify arbitrary policy in policymaker format, so a two
> +value policy (the pcr example above and authvalue) would look like
> +this in policymaker format::
> +
> + 0000017F000000010004030000016768033e216468247bd031a0a2d9876d79818f8f
> + 0000016b
> +
> +This can be placed in a file (say policy.txt) and then added to the key as::
> +
> + $ keyctl add trusted kmk "new 32 keyhandle=0x81000001 hash=sha1 policy=`cat policy.txt`" @u
> +
> +The newlines in the file policy.txt will be automatically processed.
> +
> Reseal (TPM specific) a trusted key under new PCR values::
>
> $ keyctl update 268728824 "update pcrinfo=`cat pcr.blob`"
> @@ -447,7 +463,6 @@ Another new format 'enc32' has been defined in order to support encrypted keys
> with payload size of 32 bytes. This will initially be used for nvdimm security
> but may expand to other usages that require 32 bytes payload.
>
> -
> TPM 2.0 ASN.1 Key Format
> ------------------------
>
> diff --git a/security/keys/trusted-keys/tpm2-policy.c b/security/keys/trusted-keys/tpm2-policy.c
> index 8c3a09762c10..a731c10d9bba 100644
> --- a/security/keys/trusted-keys/tpm2-policy.c
> +++ b/security/keys/trusted-keys/tpm2-policy.c
Ditto.
> @@ -323,3 +323,56 @@ int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols)
>
> return 0;
> }
> +
> +int tpm2_parse_policies(struct tpm2_policies **ppols, char *str)
> +{
> + struct tpm2_policies *pols;
> + char *p;
> + u8 *ptr;
> + int i = 0, left = PAGE_SIZE, res;
> +
> + pols = kmalloc(left, GFP_KERNEL);
> + if (!pols)
> + return -ENOMEM;
> +
> + ptr = (u8 *)(pols + 1);
> + left -= ptr - (u8 *)pols;
> +
> + while ((p = strsep(&str, "\n"))) {
> + if (*p == '\0' || *p == '\n')
> + continue;
> +
> + pols->len[i] = strlen(p)/2;
> + if (pols->len[i] > left) {
> + res = -E2BIG;
> + goto err;
> + }
> +
> + res = hex2bin(ptr, p, pols->len[i]);
> + if (res)
> + goto err;
> +
> + /* get command code and skip past */
> + pols->code[i] = get_unaligned_be32(ptr);
> + pols->policies[i] = ptr + 4;
> + ptr += pols->len[i];
> + left -= pols->len[i];
> + pols->len[i] -= 4;
> +
> + /*
> + * FIXME: this does leave the code embedded in dead
> + * regions of the memory, but it's easier than
> + * hexdumping to a temporary or copying over
> + */
> + i++;
> + }
> +
> + pols->count = i;
> + *ppols = pols;
> +
> + return 0;
> +
> + err:
> + kfree(pols);
> + return res;
> +}
> diff --git a/security/keys/trusted-keys/tpm2-policy.h b/security/keys/trusted-keys/tpm2-policy.h
> index b20e9c3e2f06..8ddf235b3fec 100644
> --- a/security/keys/trusted-keys/tpm2-policy.h
> +++ b/security/keys/trusted-keys/tpm2-policy.h
> @@ -28,6 +28,7 @@ int tpm2_generate_policy_digest(struct tpm2_policies *pols, u32 hash,
> u8 *policydigest, u32 *plen);
> int tpm2_encode_policy(struct tpm2_policies *pols, u8 **data, u32 *len);
> int tpm2_get_policy_session(struct tpm_chip *chip, struct tpm2_policies *pols);
> +int tpm2_parse_policies(struct tpm2_policies **ppols, char *str);
> #else
> static inline int tpm2_key_policy_process(struct tpm2_key_context *ctx,
> struct trusted_key_payload *payload)
> @@ -50,4 +51,8 @@ static inline int tpm2_get_policy_session(struct tpm_chip *chip,
> {
> return -EINVAL;
> }
> +static inline int tpm2_parse_policies(struct tpm2_policies **ppols, char *str)
> +{
> + return -EINVAL;
> +}
> #endif
> diff --git a/security/keys/trusted-keys/trusted_tpm1.c b/security/keys/trusted-keys/trusted_tpm1.c
> index 89c9798d1800..4dcc1373dd05 100644
> --- a/security/keys/trusted-keys/trusted_tpm1.c
> +++ b/security/keys/trusted-keys/trusted_tpm1.c
> @@ -22,6 +22,8 @@
>
> #include <keys/trusted_tpm.h>
>
> +#include "tpm2-policy.h"
> +
> static const char hmac_alg[] = "hmac(sha1)";
> static const char hash_alg[] = "sha1";
> static struct tpm_chip *chip;
> @@ -724,6 +726,7 @@ enum {
> Opt_hash,
> Opt_policydigest,
> Opt_policyhandle,
> + Opt_policy,
> };
>
> static const match_table_t key_tokens = {
> @@ -736,6 +739,7 @@ static const match_table_t key_tokens = {
> {Opt_hash, "hash=%s"},
> {Opt_policydigest, "policydigest=%s"},
> {Opt_policyhandle, "policyhandle=%s"},
> + {Opt_policy, "policy=%s"},
> {Opt_err, NULL}
> };
>
> @@ -869,6 +873,17 @@ static int getoptions(char *c, struct trusted_key_payload *pay,
> return -EINVAL;
> opt->policyhandle = handle;
> break;
> +
> + case Opt_policy:
> + if (pay->policies)
> + return -EINVAL;
> + if (!tpm2)
> + return -EINVAL;
> + res = tpm2_parse_policies(&pay->policies, args[0].from);
> + if (res)
> + return res;
> + break;
> +
> default:
> return -EINVAL;
> }
BR, Jarkko
