From: James Bottomley <James.Bottomley@HansenPartnership.com> To: linux-integrity@vger.kernel.org Cc: Mimi Zohar <zohar@linux.ibm.com>, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>, David Woodhouse <dwmw2@infradead.org>, keyrings@vger.kernel.org, David Howells <dhowells@redhat.com> Subject: [PATCH v10 5/8] security: keys: trusted: Make sealed key properly interoperable Date: Tue, 16 Jun 2020 16:02:26 +0000 [thread overview] Message-ID: <20200616160229.8018-6-James.Bottomley@HansenPartnership.com> (raw) In-Reply-To: <20200616160229.8018-1-James.Bottomley@HansenPartnership.com> The current implementation appends a migratable flag to the end of a key, meaning the format isn't exactly interoperable because the using party needs to know to strip this extra byte. However, all other consumers of TPM sealed blobs expect the unseal to return exactly the key. Since TPM2 keys have a key property flag that corresponds to migratable, use that flag instead and make the actual key the only sealed quantity. This is secure because the key properties are bound to a hash in the private part, so if they're altered the key won't load. Backwards compatibility is implemented by detecting whether we're loading a new format key or not and correctly setting migratable from the last byte of old format keys. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> --- v2: added length checks to untrusted payload v8: recover patch --- include/linux/tpm.h | 2 + security/keys/trusted-keys/trusted_tpm2.c | 54 ++++++++++++++++------- 2 files changed, 40 insertions(+), 16 deletions(-) diff --git a/include/linux/tpm.h b/include/linux/tpm.h index 03e9b184411b..cd46ab27baa5 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -297,6 +297,8 @@ struct tpm_buf { }; enum tpm2_object_attributes { + TPM2_OA_FIXED_TPM = BIT(1), + TPM2_OA_FIXED_PARENT = BIT(4), TPM2_OA_USER_WITH_AUTH = BIT(6), }; diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 51d845da8728..905c5ca4d51c 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -231,6 +231,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, unsigned int blob_len; struct tpm_buf buf; u32 hash; + u32 flags; int i; int rc; @@ -259,32 +260,32 @@ int tpm2_seal_trusted(struct tpm_chip *chip, TPM_DIGEST_SIZE); /* sensitive */ - tpm_buf_append_u16(&buf, 4 + options->blobauth_len + - payload->key_len + 1); + tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len); 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, payload->key_len + 1); + tpm_buf_append_u16(&buf, payload->key_len); tpm_buf_append(&buf, payload->key, payload->key_len); - tpm_buf_append_u8(&buf, payload->migratable); /* public */ tpm_buf_append_u16(&buf, 14 + options->policydigest_len); tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH); tpm_buf_append_u16(&buf, hash); + /* key properties */ + flags = 0; + flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH; + flags |= payload->migratable ? (TPM2_OA_FIXED_TPM | + TPM2_OA_FIXED_PARENT) : 0; + tpm_buf_append_u32(&buf, flags); + /* policy */ - if (options->policydigest_len) { - tpm_buf_append_u32(&buf, 0); - tpm_buf_append_u16(&buf, options->policydigest_len); + tpm_buf_append_u16(&buf, options->policydigest_len); + if (options->policydigest_len) tpm_buf_append(&buf, options->policydigest, options->policydigest_len); - } else { - tpm_buf_append_u32(&buf, TPM2_OA_USER_WITH_AUTH); - tpm_buf_append_u16(&buf, 0); - } /* public parameters */ tpm_buf_append_u16(&buf, TPM_ALG_NULL); @@ -357,8 +358,9 @@ static int tpm2_load_cmd(struct tpm_chip *chip, unsigned int private_len; unsigned int public_len; unsigned int blob_len; - u8 *blob; + u8 *blob, *pub; int rc; + u32 attrs; rc = tpm2_key_decode(payload, options, &blob); if (rc) { @@ -385,6 +387,16 @@ static int tpm2_load_cmd(struct tpm_chip *chip, if (private_len + 2 + public_len + 2 > payload->blob_len) return -E2BIG; + pub = blob + 2 + private_len + 2; + /* key attributes are always at offset 4 */ + attrs = get_unaligned_be32(pub + 4); + + if ((attrs & (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) = + (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) + payload->migratable = 0; + else + payload->migratable = 1; + blob_len = private_len + public_len + 4; if (blob_len > payload->blob_len) return -E2BIG; @@ -465,7 +477,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, if (!rc) { data_len = be16_to_cpup( (__be16 *) &buf.data[TPM_HEADER_SIZE + 4]); - if (data_len < MIN_KEY_SIZE || data_len > MAX_KEY_SIZE + 1) { + if (data_len < MIN_KEY_SIZE || data_len > MAX_KEY_SIZE) { rc = -EFAULT; goto out; } @@ -476,9 +488,19 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, } data = &buf.data[TPM_HEADER_SIZE + 6]; - memcpy(payload->key, data, data_len - 1); - payload->key_len = data_len - 1; - payload->migratable = data[data_len - 1]; + if (payload->old_format) { + /* migratable flag is at the end of the key */ + memcpy(payload->key, data, data_len - 1); + payload->key_len = data_len - 1; + payload->migratable = data[data_len - 1]; + } else { + /* + * migratable flag already collected from key + * attributes + */ + memcpy(payload->key, data, data_len); + payload->key_len = data_len; + } } out: -- 2.26.2
WARNING: multiple messages have this Message-ID (diff)
From: James Bottomley <James.Bottomley@HansenPartnership.com> To: linux-integrity@vger.kernel.org Cc: Mimi Zohar <zohar@linux.ibm.com>, Jarkko Sakkinen <jarkko.sakkinen@linux.intel.com>, David Woodhouse <dwmw2@infradead.org>, keyrings@vger.kernel.org, David Howells <dhowells@redhat.com> Subject: [PATCH v10 5/8] security: keys: trusted: Make sealed key properly interoperable Date: Tue, 16 Jun 2020 09:02:26 -0700 [thread overview] Message-ID: <20200616160229.8018-6-James.Bottomley@HansenPartnership.com> (raw) In-Reply-To: <20200616160229.8018-1-James.Bottomley@HansenPartnership.com> The current implementation appends a migratable flag to the end of a key, meaning the format isn't exactly interoperable because the using party needs to know to strip this extra byte. However, all other consumers of TPM sealed blobs expect the unseal to return exactly the key. Since TPM2 keys have a key property flag that corresponds to migratable, use that flag instead and make the actual key the only sealed quantity. This is secure because the key properties are bound to a hash in the private part, so if they're altered the key won't load. Backwards compatibility is implemented by detecting whether we're loading a new format key or not and correctly setting migratable from the last byte of old format keys. Signed-off-by: James Bottomley <James.Bottomley@HansenPartnership.com> --- v2: added length checks to untrusted payload v8: recover patch --- include/linux/tpm.h | 2 + security/keys/trusted-keys/trusted_tpm2.c | 54 ++++++++++++++++------- 2 files changed, 40 insertions(+), 16 deletions(-) diff --git a/include/linux/tpm.h b/include/linux/tpm.h index 03e9b184411b..cd46ab27baa5 100644 --- a/include/linux/tpm.h +++ b/include/linux/tpm.h @@ -297,6 +297,8 @@ struct tpm_buf { }; enum tpm2_object_attributes { + TPM2_OA_FIXED_TPM = BIT(1), + TPM2_OA_FIXED_PARENT = BIT(4), TPM2_OA_USER_WITH_AUTH = BIT(6), }; diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 51d845da8728..905c5ca4d51c 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -231,6 +231,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, unsigned int blob_len; struct tpm_buf buf; u32 hash; + u32 flags; int i; int rc; @@ -259,32 +260,32 @@ int tpm2_seal_trusted(struct tpm_chip *chip, TPM_DIGEST_SIZE); /* sensitive */ - tpm_buf_append_u16(&buf, 4 + options->blobauth_len + - payload->key_len + 1); + tpm_buf_append_u16(&buf, 4 + options->blobauth_len + payload->key_len); 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, payload->key_len + 1); + tpm_buf_append_u16(&buf, payload->key_len); tpm_buf_append(&buf, payload->key, payload->key_len); - tpm_buf_append_u8(&buf, payload->migratable); /* public */ tpm_buf_append_u16(&buf, 14 + options->policydigest_len); tpm_buf_append_u16(&buf, TPM_ALG_KEYEDHASH); tpm_buf_append_u16(&buf, hash); + /* key properties */ + flags = 0; + flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH; + flags |= payload->migratable ? (TPM2_OA_FIXED_TPM | + TPM2_OA_FIXED_PARENT) : 0; + tpm_buf_append_u32(&buf, flags); + /* policy */ - if (options->policydigest_len) { - tpm_buf_append_u32(&buf, 0); - tpm_buf_append_u16(&buf, options->policydigest_len); + tpm_buf_append_u16(&buf, options->policydigest_len); + if (options->policydigest_len) tpm_buf_append(&buf, options->policydigest, options->policydigest_len); - } else { - tpm_buf_append_u32(&buf, TPM2_OA_USER_WITH_AUTH); - tpm_buf_append_u16(&buf, 0); - } /* public parameters */ tpm_buf_append_u16(&buf, TPM_ALG_NULL); @@ -357,8 +358,9 @@ static int tpm2_load_cmd(struct tpm_chip *chip, unsigned int private_len; unsigned int public_len; unsigned int blob_len; - u8 *blob; + u8 *blob, *pub; int rc; + u32 attrs; rc = tpm2_key_decode(payload, options, &blob); if (rc) { @@ -385,6 +387,16 @@ static int tpm2_load_cmd(struct tpm_chip *chip, if (private_len + 2 + public_len + 2 > payload->blob_len) return -E2BIG; + pub = blob + 2 + private_len + 2; + /* key attributes are always at offset 4 */ + attrs = get_unaligned_be32(pub + 4); + + if ((attrs & (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) == + (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT)) + payload->migratable = 0; + else + payload->migratable = 1; + blob_len = private_len + public_len + 4; if (blob_len > payload->blob_len) return -E2BIG; @@ -465,7 +477,7 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, if (!rc) { data_len = be16_to_cpup( (__be16 *) &buf.data[TPM_HEADER_SIZE + 4]); - if (data_len < MIN_KEY_SIZE || data_len > MAX_KEY_SIZE + 1) { + if (data_len < MIN_KEY_SIZE || data_len > MAX_KEY_SIZE) { rc = -EFAULT; goto out; } @@ -476,9 +488,19 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, } data = &buf.data[TPM_HEADER_SIZE + 6]; - memcpy(payload->key, data, data_len - 1); - payload->key_len = data_len - 1; - payload->migratable = data[data_len - 1]; + if (payload->old_format) { + /* migratable flag is at the end of the key */ + memcpy(payload->key, data, data_len - 1); + payload->key_len = data_len - 1; + payload->migratable = data[data_len - 1]; + } else { + /* + * migratable flag already collected from key + * attributes + */ + memcpy(payload->key, data, data_len); + payload->key_len = data_len; + } } out: -- 2.26.2
next prev parent reply other threads:[~2020-06-16 16:02 UTC|newest] Thread overview: 44+ messages / expand[flat|nested] mbox.gz Atom feed top 2020-06-16 15:49 [PATCH v10 0/8] TPM 2.0 trusted keys with attached policy James Bottomley 2020-06-16 15:49 ` James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-16 16:02 ` [PATCH v10 1/8] lib: add ASN.1 encoder James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-16 16:02 ` [PATCH v10 2/8] oid_registry: Add TCG defined OIDS for TPM keys James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-17 21:42 ` Jerry Snitselaar 2020-06-17 21:42 ` Jerry Snitselaar 2020-06-18 0:25 ` James Bottomley 2020-06-18 0:25 ` James Bottomley 2020-06-18 7:14 ` Jarkko Sakkinen 2020-06-18 7:14 ` Jarkko Sakkinen 2020-06-18 19:22 ` James Bottomley 2020-06-18 19:22 ` James Bottomley 2020-06-22 22:04 ` Jarkko Sakkinen 2020-06-22 22:04 ` Jarkko Sakkinen 2020-06-16 16:02 ` [PATCH v10 3/8] security: keys: trusted: fix TPM2 authorizations James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-16 16:02 ` [PATCH v10 4/8] security: keys: trusted: use ASN.1 TPM2 key format for the blobs James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-16 16:02 ` James Bottomley [this message] 2020-06-16 16:02 ` [PATCH v10 5/8] security: keys: trusted: Make sealed key properly interoperable James Bottomley 2020-06-17 23:46 ` Jarkko Sakkinen 2020-06-17 23:46 ` Jarkko Sakkinen 2020-06-16 16:02 ` [PATCH v10 6/8] security: keys: trusted: add PCR policy to TPM2 keys James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-17 23:44 ` Jarkko Sakkinen 2020-06-17 23:44 ` Jarkko Sakkinen 2020-06-16 16:02 ` [PATCH v10 7/8] security: keys: trusted: add ability to specify arbitrary policy James Bottomley 2020-06-16 16:02 ` James Bottomley 2020-06-17 23:42 ` Jarkko Sakkinen 2020-06-17 23:42 ` Jarkko Sakkinen 2020-06-18 0:27 ` James Bottomley 2020-06-18 0:27 ` James Bottomley 2020-06-18 7:12 ` Jarkko Sakkinen 2020-06-18 7:12 ` Jarkko Sakkinen 2020-06-18 19:45 ` James Bottomley 2020-06-18 19:45 ` James Bottomley 2020-06-23 0:46 ` Jarkko Sakkinen 2020-06-23 0:46 ` Jarkko Sakkinen 2020-06-16 16:02 ` [PATCH v10 8/8] security: keys: trusted: implement counter/timer policy James Bottomley 2020-06-16 16:02 ` James Bottomley
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