diff options
Diffstat (limited to 'security/keys/trusted-keys/trusted_tpm2.c')
| -rw-r--r-- | security/keys/trusted-keys/trusted_tpm2.c | 605 |
1 files changed, 605 insertions, 0 deletions
diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c new file mode 100644 index 000000000000..a7ea4a1c3bed --- /dev/null +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -0,0 +1,605 @@ +// SPDX-License-Identifier: GPL-2.0-only +/* + * Copyright (C) 2004 IBM Corporation + * Copyright (C) 2014 Intel Corporation + */ + +#include <linux/asn1_encoder.h> +#include <linux/oid_registry.h> +#include <linux/string.h> +#include <linux/err.h> +#include <linux/tpm.h> +#include <linux/tpm_command.h> + +#include <keys/trusted-type.h> +#include <keys/trusted_tpm.h> + +#include <linux/unaligned.h> + +#include "tpm2key.asn1.h" + +static u32 tpm2key_oid[] = { 2, 23, 133, 10, 1, 5 }; + +static int tpm2_key_encode(struct trusted_key_payload *payload, + struct trusted_key_options *options, + u8 *src, u32 len) +{ + const int SCRATCH_SIZE = PAGE_SIZE; + u8 *scratch = kmalloc(SCRATCH_SIZE, GFP_KERNEL); + u8 *work = scratch, *work1; + u8 *end_work = scratch + SCRATCH_SIZE; + u8 *priv, *pub; + u16 priv_len, pub_len; + int ret; + + priv_len = get_unaligned_be16(src) + 2; + priv = src; + + src += priv_len; + + pub_len = get_unaligned_be16(src) + 2; + pub = src; + + if (!scratch) + return -ENOMEM; + + work = asn1_encode_oid(work, end_work, tpm2key_oid, + asn1_oid_len(tpm2key_oid)); + + if (options->blobauth_len == 0) { + unsigned char bool[3], *w = bool; + /* tag 0 is emptyAuth */ + w = asn1_encode_boolean(w, w + sizeof(bool), true); + if (WARN(IS_ERR(w), "BUG: Boolean failed to encode")) { + ret = PTR_ERR(w); + goto err; + } + work = asn1_encode_tag(work, end_work, 0, bool, w - bool); + } + + /* + * Assume both octet strings will encode to a 2 byte definite length + * + * Note: For a well behaved TPM, this warning should never + * trigger, so if it does there's something nefarious going on + */ + if (WARN(work - scratch + pub_len + priv_len + 14 > SCRATCH_SIZE, + "BUG: scratch buffer is too small")) { + ret = -EINVAL; + goto err; + } + + work = asn1_encode_integer(work, end_work, options->keyhandle); + work = asn1_encode_octet_string(work, end_work, pub, pub_len); + work = asn1_encode_octet_string(work, end_work, priv, priv_len); + + work1 = payload->blob; + work1 = asn1_encode_sequence(work1, work1 + sizeof(payload->blob), + scratch, work - scratch); + if (IS_ERR(work1)) { + ret = PTR_ERR(work1); + pr_err("BUG: ASN.1 encoder failed with %d\n", ret); + goto err; + } + + kfree(scratch); + return work1 - payload->blob; + +err: + kfree(scratch); + return ret; +} + +struct tpm2_key_context { + u32 parent; + const u8 *pub; + u32 pub_len; + const u8 *priv; + u32 priv_len; +}; + +static int tpm2_key_decode(struct trusted_key_payload *payload, + struct trusted_key_options *options, + u8 **buf) +{ + int ret; + struct tpm2_key_context ctx; + u8 *blob; + + memset(&ctx, 0, sizeof(ctx)); + + ret = asn1_ber_decoder(&tpm2key_decoder, &ctx, payload->blob, + payload->blob_len); + if (ret < 0) + return ret; + + if (ctx.priv_len + ctx.pub_len > MAX_BLOB_SIZE) + return -EINVAL; + + blob = kmalloc(ctx.priv_len + ctx.pub_len + 4, GFP_KERNEL); + if (!blob) + return -ENOMEM; + + *buf = blob; + options->keyhandle = ctx.parent; + + memcpy(blob, ctx.priv, ctx.priv_len); + blob += ctx.priv_len; + + memcpy(blob, ctx.pub, ctx.pub_len); + + return 0; +} + +int tpm2_key_parent(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct tpm2_key_context *ctx = context; + const u8 *v = value; + int i; + + ctx->parent = 0; + for (i = 0; i < vlen; i++) { + ctx->parent <<= 8; + ctx->parent |= v[i]; + } + + return 0; +} + +int tpm2_key_type(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + enum OID oid = look_up_OID(value, vlen); + + if (oid != OID_TPMSealedData) { + char buffer[50]; + + sprint_oid(value, vlen, buffer, sizeof(buffer)); + pr_debug("OID is \"%s\" which is not TPMSealedData\n", + buffer); + return -EINVAL; + } + + return 0; +} + +int tpm2_key_pub(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct tpm2_key_context *ctx = context; + + ctx->pub = value; + ctx->pub_len = vlen; + + return 0; +} + +int tpm2_key_priv(void *context, size_t hdrlen, + unsigned char tag, + const void *value, size_t vlen) +{ + struct tpm2_key_context *ctx = context; + + ctx->priv = value; + ctx->priv_len = vlen; + + return 0; +} + +/** + * tpm2_buf_append_auth() - append TPMS_AUTH_COMMAND to the buffer. + * + * @buf: an allocated tpm_buf instance + * @session_handle: session handle + * @nonce: the session nonce, may be NULL if not used + * @nonce_len: the session nonce length, may be 0 if not used + * @attributes: the session attributes + * @hmac: the session HMAC or password, may be NULL if not used + * @hmac_len: the session HMAC or password length, maybe 0 if not used + */ +static void tpm2_buf_append_auth(struct tpm_buf *buf, u32 session_handle, + const u8 *nonce, u16 nonce_len, + u8 attributes, + const u8 *hmac, u16 hmac_len) +{ + tpm_buf_append_u32(buf, 9 + nonce_len + hmac_len); + tpm_buf_append_u32(buf, session_handle); + tpm_buf_append_u16(buf, nonce_len); + + if (nonce && nonce_len) + tpm_buf_append(buf, nonce, nonce_len); + + tpm_buf_append_u8(buf, attributes); + tpm_buf_append_u16(buf, hmac_len); + + if (hmac && hmac_len) + tpm_buf_append(buf, hmac, hmac_len); +} + +/** + * tpm2_seal_trusted() - seal the payload of a trusted key + * + * @chip: TPM chip to use + * @payload: the key data in clear and encrypted form + * @options: authentication values and other options + * + * Return: < 0 on error and 0 on success. + */ +int tpm2_seal_trusted(struct tpm_chip *chip, + struct trusted_key_payload *payload, + struct trusted_key_options *options) +{ + off_t offset = TPM_HEADER_SIZE; + struct tpm_buf buf, sized; + int blob_len = 0; + int hash; + u32 flags; + int rc; + + hash = tpm2_find_hash_alg(options->hash); + if (hash < 0) + return hash; + + if (!options->keyhandle) + return -EINVAL; + + rc = tpm_try_get_ops(chip); + if (rc) + return rc; + + rc = tpm2_start_auth_session(chip); + if (rc) + goto out_put; + + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE); + if (rc) { + tpm2_end_auth_session(chip); + goto out_put; + } + + rc = tpm_buf_init_sized(&sized); + if (rc) { + tpm_buf_destroy(&buf); + tpm2_end_auth_session(chip); + goto out_put; + } + + rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL); + if (rc) + goto out; + + tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT, + options->keyauth, TPM_DIGEST_SIZE); + + /* sensitive */ + tpm_buf_append_u16(&sized, options->blobauth_len); + + if (options->blobauth_len) + tpm_buf_append(&sized, options->blobauth, options->blobauth_len); + + tpm_buf_append_u16(&sized, payload->key_len); + tpm_buf_append(&sized, payload->key, payload->key_len); + tpm_buf_append(&buf, sized.data, sized.length); + + /* public */ + tpm_buf_reset_sized(&sized); + tpm_buf_append_u16(&sized, TPM_ALG_KEYEDHASH); + tpm_buf_append_u16(&sized, hash); + + /* key properties */ + flags = 0; + flags |= options->policydigest_len ? 0 : TPM2_OA_USER_WITH_AUTH; + flags |= payload->migratable ? 0 : (TPM2_OA_FIXED_TPM | TPM2_OA_FIXED_PARENT); + tpm_buf_append_u32(&sized, flags); + + /* policy */ + tpm_buf_append_u16(&sized, options->policydigest_len); + if (options->policydigest_len) + tpm_buf_append(&sized, options->policydigest, options->policydigest_len); + + /* public parameters */ + tpm_buf_append_u16(&sized, TPM_ALG_NULL); + tpm_buf_append_u16(&sized, 0); + + tpm_buf_append(&buf, sized.data, sized.length); + + /* outside info */ + tpm_buf_append_u16(&buf, 0); + + /* creation PCR */ + tpm_buf_append_u32(&buf, 0); + + if (buf.flags & TPM_BUF_OVERFLOW) { + rc = -E2BIG; + tpm2_end_auth_session(chip); + goto out; + } + + rc = tpm_buf_fill_hmac_session(chip, &buf); + if (rc) + goto out; + + rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data"); + rc = tpm_buf_check_hmac_response(chip, &buf, rc); + if (rc) + goto out; + + blob_len = tpm_buf_read_u32(&buf, &offset); + if (blob_len > MAX_BLOB_SIZE || buf.flags & TPM_BUF_BOUNDARY_ERROR) { + rc = -E2BIG; + goto out; + } + if (buf.length - offset < blob_len) { + rc = -EFAULT; + goto out; + } + + blob_len = tpm2_key_encode(payload, options, &buf.data[offset], blob_len); + if (blob_len < 0) + rc = blob_len; + +out: + tpm_buf_destroy(&sized); + tpm_buf_destroy(&buf); + + if (!rc) + payload->blob_len = blob_len; + +out_put: + tpm_put_ops(chip); + return tpm_ret_to_err(rc); +} + +/** + * tpm2_load_cmd() - execute a TPM2_Load command + * + * @chip: TPM chip to use + * @payload: the key data in clear and encrypted form + * @options: authentication values and other options + * @blob_handle: returned blob handle + * + * Return: 0 on success. + * -E2BIG on wrong payload size. + * -EPERM on tpm error status. + * < 0 error from tpm_send. + */ +static int tpm2_load_cmd(struct tpm_chip *chip, + struct trusted_key_payload *payload, + struct trusted_key_options *options, + u32 *blob_handle) +{ + u8 *blob_ref __free(kfree) = NULL; + struct tpm_buf buf; + unsigned int private_len; + unsigned int public_len; + unsigned int blob_len; + u8 *blob, *pub; + int rc; + u32 attrs; + + rc = tpm2_key_decode(payload, options, &blob); + if (rc) { + /* old form */ + blob = payload->blob; + payload->old_format = 1; + } else { + /* Bind for cleanup: */ + blob_ref = blob; + } + + /* new format carries keyhandle but old format doesn't */ + if (!options->keyhandle) + return -EINVAL; + + /* must be big enough for at least the two be16 size counts */ + if (payload->blob_len < 4) + return -EINVAL; + + private_len = get_unaligned_be16(blob); + + /* must be big enough for following public_len */ + if (private_len + 2 + 2 > (payload->blob_len)) + return -E2BIG; + + public_len = get_unaligned_be16(blob + 2 + private_len); + 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; + + rc = tpm2_start_auth_session(chip); + if (rc) + return rc; + + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD); + if (rc) { + tpm2_end_auth_session(chip); + return rc; + } + + rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL); + if (rc) + goto out; + + tpm_buf_append_hmac_session(chip, &buf, 0, options->keyauth, + TPM_DIGEST_SIZE); + + tpm_buf_append(&buf, blob, blob_len); + + if (buf.flags & TPM_BUF_OVERFLOW) { + rc = -E2BIG; + tpm2_end_auth_session(chip); + goto out; + } + + rc = tpm_buf_fill_hmac_session(chip, &buf); + if (rc) + goto out; + + rc = tpm_transmit_cmd(chip, &buf, 4, "loading blob"); + rc = tpm_buf_check_hmac_response(chip, &buf, rc); + if (!rc) + *blob_handle = be32_to_cpup( + (__be32 *) &buf.data[TPM_HEADER_SIZE]); + +out: + tpm_buf_destroy(&buf); + + return tpm_ret_to_err(rc); +} + +/** + * tpm2_unseal_cmd() - execute a TPM2_Unload command + * + * @chip: TPM chip to use + * @payload: the key data in clear and encrypted form + * @options: authentication values and other options + * @blob_handle: blob handle + * + * Return: 0 on success + * -EPERM on tpm error status + * < 0 error from tpm_send + */ +static int tpm2_unseal_cmd(struct tpm_chip *chip, + struct trusted_key_payload *payload, + struct trusted_key_options *options, + u32 blob_handle) +{ + struct tpm_header *head; + struct tpm_buf buf; + u16 data_len; + int offset; + u8 *data; + int rc; + + rc = tpm2_start_auth_session(chip); + if (rc) + return rc; + + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL); + if (rc) { + tpm2_end_auth_session(chip); + return rc; + } + + rc = tpm_buf_append_name(chip, &buf, options->keyhandle, NULL); + if (rc) + goto out; + + if (!options->policyhandle) { + tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT, + options->blobauth, + options->blobauth_len); + } else { + /* + * FIXME: The policy session was generated outside the + * kernel so we don't known the nonce and thus can't + * calculate a HMAC on it. Therefore, the user can + * only really use TPM2_PolicyPassword and we must + * send down the plain text password, which could be + * intercepted. We can still encrypt the returned + * key, but that's small comfort since the interposer + * could repeat our actions with the exfiltrated + * password. + */ + tpm2_buf_append_auth(&buf, options->policyhandle, + NULL /* nonce */, 0, 0, + options->blobauth, options->blobauth_len); + if (tpm2_chip_auth(chip)) { + tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_ENCRYPT, NULL, 0); + } else { + offset = buf.handles * 4 + TPM_HEADER_SIZE; + head = (struct tpm_header *)buf.data; + if (tpm_buf_length(&buf) == offset) + head->tag = cpu_to_be16(TPM2_ST_NO_SESSIONS); + } + } + + rc = tpm_buf_fill_hmac_session(chip, &buf); + if (rc) + goto out; + + rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing"); + rc = tpm_buf_check_hmac_response(chip, &buf, rc); + + 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) { + rc = -EFAULT; + goto out; + } + + if (tpm_buf_length(&buf) < TPM_HEADER_SIZE + 6 + data_len) { + rc = -EFAULT; + goto out; + } + data = &buf.data[TPM_HEADER_SIZE + 6]; + + 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: + tpm_buf_destroy(&buf); + return tpm_ret_to_err(rc); +} + +/** + * tpm2_unseal_trusted() - unseal the payload of a trusted key + * + * @chip: TPM chip to use + * @payload: the key data in clear and encrypted form + * @options: authentication values and other options + * + * Return: Same as with tpm_send. + */ +int tpm2_unseal_trusted(struct tpm_chip *chip, + struct trusted_key_payload *payload, + struct trusted_key_options *options) +{ + u32 blob_handle; + int rc; + + rc = tpm_try_get_ops(chip); + if (rc) + return rc; + + rc = tpm2_load_cmd(chip, payload, options, &blob_handle); + if (rc) + goto out; + + rc = tpm2_unseal_cmd(chip, payload, options, blob_handle); + tpm2_flush_context(chip, blob_handle); + +out: + tpm_put_ops(chip); + return tpm_ret_to_err(rc); +} |