From patchwork Mon Nov 27 19:08:52 2023 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: James Bottomley X-Patchwork-Id: 13470222 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="UhtWXhSZ" Received: from bedivere.hansenpartnership.com (bedivere.hansenpartnership.com [96.44.175.130]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id EA578D5F; Mon, 27 Nov 2023 11:20:04 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=hansenpartnership.com; s=20151216; t=1701112804; bh=IXTaYPhs+Z47ZssITLiRDv+1XDVv5UgqtsfBBLD02kI=; h=From:To:Subject:Date:Message-Id:In-Reply-To:References:From; b=UhtWXhSZi0l37AheYT+XURoCx3Ku9FzbXm+KAsvdBzObvjatepSKUKIY7LGOqfJYj kMqyxDHeQpeBYij1PBJU1kRVm48ZodlmYch1LIZUzJPXaW3NGyL4LP6l2dXqKwW0fl PXASiNUHqhFKgKzAsVQmiEftLhJi+BilAHWSf2JE= Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id B478B1286989; Mon, 27 Nov 2023 14:20:04 -0500 (EST) Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavis, port 10024) with ESMTP id xlQseFj98Brn; Mon, 27 Nov 2023 14:20:04 -0500 (EST) Received: from lingrow.int.hansenpartnership.com (unknown [153.66.160.227]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 1966B1286954; Mon, 27 Nov 2023 14:20:04 -0500 (EST) From: James Bottomley To: linux-integrity@vger.kernel.org Cc: Jarkko Sakkinen , keyrings@vger.kernel.org, Ard Biesheuvel Subject: [PATCH v5 15/17] KEYS: trusted: Add session encryption protection to the seal/unseal path Date: Mon, 27 Nov 2023 14:08:52 -0500 Message-Id: <20231127190854.13310-16-James.Bottomley@HansenPartnership.com> X-Mailer: git-send-email 2.35.3 In-Reply-To: <20231127190854.13310-1-James.Bottomley@HansenPartnership.com> References: <20231127190854.13310-1-James.Bottomley@HansenPartnership.com> Precedence: bulk X-Mailing-List: linux-integrity@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 If some entity is snooping the TPM bus, the can see the data going in to be sealed and the data coming out as it is unsealed. Add parameter and response encryption to these cases to ensure that no secrets are leaked even if the bus is snooped. As part of doing this conversion it was discovered that policy sessions can't work with HMAC protected authority because of missing pieces (the tpm Nonce). I've added code to work the same way as before, which will result in potential authority exposure (while still adding security for the command and the returned blob), and a fixme to redo the API to get rid of this security hole. Signed-off-by: James Bottomley --- v2: fix unseal with policy and password v3: fix session memory leak --- security/keys/trusted-keys/trusted_tpm2.c | 88 ++++++++++++++++------- 1 file changed, 61 insertions(+), 27 deletions(-) diff --git a/security/keys/trusted-keys/trusted_tpm2.c b/security/keys/trusted-keys/trusted_tpm2.c index 97b1dfca2dba..dfeec06301ce 100644 --- a/security/keys/trusted-keys/trusted_tpm2.c +++ b/security/keys/trusted-keys/trusted_tpm2.c @@ -253,26 +253,26 @@ int tpm2_seal_trusted(struct tpm_chip *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) { - tpm_put_ops(chip); - return rc; + tpm2_end_auth_session(chip); + goto out_put; } rc = tpm_buf_init_sized(&sized); if (rc) { tpm_buf_destroy(&buf); - tpm_put_ops(chip); - return rc; + tpm2_end_auth_session(chip); + goto out_put; } - tpm_buf_reset(&buf, TPM2_ST_SESSIONS, TPM2_CC_CREATE); - tpm_buf_append_u32(&buf, options->keyhandle); - tpm2_buf_append_auth(&buf, TPM2_RS_PW, - NULL /* nonce */, 0, - 0 /* session_attributes */, - options->keyauth /* hmac */, - TPM_DIGEST_SIZE); + tpm_buf_append_name(chip, &buf, options->keyhandle, NULL); + tpm_buf_append_hmac_session(chip, &buf, TPM2_SA_DECRYPT, + options->keyauth, TPM_DIGEST_SIZE); /* sensitive */ tpm_buf_append_u16(&sized, options->blobauth_len); @@ -314,10 +314,13 @@ int tpm2_seal_trusted(struct tpm_chip *chip, if (buf.flags & TPM_BUF_OVERFLOW) { rc = -E2BIG; + tpm2_end_auth_session(chip); goto out; } + tpm_buf_fill_hmac_session(chip, &buf); rc = tpm_transmit_cmd(chip, &buf, 4, "sealing data"); + rc = tpm_buf_check_hmac_response(chip, &buf, rc); if (rc) goto out; @@ -348,6 +351,7 @@ int tpm2_seal_trusted(struct tpm_chip *chip, else payload->blob_len = blob_len; +out_put: tpm_put_ops(chip); return rc; } @@ -417,25 +421,31 @@ static int tpm2_load_cmd(struct tpm_chip *chip, if (blob_len > payload->blob_len) return -E2BIG; - rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD); + rc = tpm2_start_auth_session(chip); if (rc) return rc; - tpm_buf_append_u32(&buf, options->keyhandle); - tpm2_buf_append_auth(&buf, TPM2_RS_PW, - NULL /* nonce */, 0, - 0 /* session_attributes */, - options->keyauth /* hmac */, - TPM_DIGEST_SIZE); + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_LOAD); + if (rc) { + tpm2_end_auth_session(chip); + return rc; + } + + tpm_buf_append_name(chip, &buf, options->keyhandle, NULL); + 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; } + tpm_buf_fill_hmac_session(chip, &buf); 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]); @@ -473,20 +483,44 @@ static int tpm2_unseal_cmd(struct tpm_chip *chip, u8 *data; int rc; - rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL); + rc = tpm2_start_auth_session(chip); if (rc) return rc; - tpm_buf_append_u32(&buf, blob_handle); - tpm2_buf_append_auth(&buf, - options->policyhandle ? - options->policyhandle : TPM2_RS_PW, - NULL /* nonce */, 0, - TPM2_SA_CONTINUE_SESSION, - options->blobauth /* hmac */, - options->blobauth_len); + rc = tpm_buf_init(&buf, TPM2_ST_SESSIONS, TPM2_CC_UNSEAL); + if (rc) { + tpm2_end_auth_session(chip); + return rc; + } + + tpm_buf_append_name(chip, &buf, blob_handle, NULL); + + 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); + tpm_buf_append_hmac_session_opt(chip, &buf, TPM2_SA_ENCRYPT, + NULL, 0); + } + tpm_buf_fill_hmac_session(chip, &buf); rc = tpm_transmit_cmd(chip, &buf, 6, "unsealing"); + rc = tpm_buf_check_hmac_response(chip, &buf, rc); if (rc > 0) rc = -EPERM;