linux-kernel - [PATCH v3] KEYS: trusted: allow trusted.ko to initialize w/o a TPM

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Message-Id: <20190326121158.13499-1-jarkko.sakkinen@linux.intel.com>
Date:   Tue, 26 Mar 2019 14:11:58 +0200
From:   Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
To:     linux-integrity@...r.kernel.org
Cc:     linux-security-module@...r.kernel.org,
        Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>,
        James Morris <jmorris@...ei.org>,
        James Bottomley <jejb@...ux.ibm.com>,
        Mimi Zohar <zohar@...uxibm.com>,
        David Howells <dhowells@...hat.com>,
        "Serge E. Hallyn" <serge@...lyn.com>,
        keyrings@...r.kernel.org (open list:KEYS-TRUSTED),
        linux-kernel@...r.kernel.org (open list)
Subject: [PATCH v3] KEYS: trusted: allow trusted.ko to initialize w/o a TPM

Allow trusted.ko to initialize w/o a TPM. This commit adds checks to the
key type callbacks and exported functions to fail when a TPM is not
available.

Cc: James Morris <jmorris@...ei.org>
Reported-by: Dan Williams <dan.j.williams@...el.com>
Tested-by: Dan Williams <dan.j.williams@...el.com>
Fixes: 240730437deb ("KEYS: trusted: explicitly use tpm_chip structure...")
Signed-off-by: Jarkko Sakkinen <jarkko.sakkinen@...ux.intel.com>
---
v3:
- remove unnecessary check for chip in init_trusted()
v2:
- Remove checks from the key type callbacks because the key type will
  not be registered.
- Cc to James Morris because hopefully we can land this 5.1.0.
 security/keys/trusted.c | 28 +++++++++++++++++++++++-----
 1 file changed, 23 insertions(+), 5 deletions(-)

diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index ecec672d3a77..efdbf17f3915 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -135,6 +135,9 @@ int TSS_authhmac(unsigned char *digest, const unsigned char *key,
 	int ret;
 	va_list argp;
 
+	if (!chip)
+		return -ENODEV;
+
 	sdesc = init_sdesc(hashalg);
 	if (IS_ERR(sdesc)) {
 		pr_info("trusted_key: can't alloc %s\n", hash_alg);
@@ -196,6 +199,9 @@ int TSS_checkhmac1(unsigned char *buffer,
 	va_list argp;
 	int ret;
 
+	if (!chip)
+		return -ENODEV;
+
 	bufsize = LOAD32(buffer, TPM_SIZE_OFFSET);
 	tag = LOAD16(buffer, 0);
 	ordinal = command;
@@ -363,6 +369,9 @@ int trusted_tpm_send(unsigned char *cmd, size_t buflen)
 {
 	int rc;
 
+	if (!chip)
+		return -ENODEV;
+
 	dump_tpm_buf(cmd);
 	rc = tpm_send(chip, cmd, buflen);
 	dump_tpm_buf(cmd);
@@ -429,6 +438,9 @@ int oiap(struct tpm_buf *tb, uint32_t *handle, unsigned char *nonce)
 {
 	int ret;
 
+	if (!chip)
+		return -ENODEV;
+
 	INIT_BUF(tb);
 	store16(tb, TPM_TAG_RQU_COMMAND);
 	store32(tb, TPM_OIAP_SIZE);
@@ -1245,9 +1257,13 @@ static int __init init_trusted(void)
 {
 	int ret;
 
+	/* encrypted_keys.ko depends on successful load of this module even if
+	 * TPM is not used.
+	 */
 	chip = tpm_default_chip();
 	if (!chip)
-		return -ENOENT;
+		return 0;
+
 	ret = init_digests();
 	if (ret < 0)
 		goto err_put;
@@ -1269,10 +1285,12 @@ static int __init init_trusted(void)
 
 static void __exit cleanup_trusted(void)
 {
-	put_device(&chip->dev);
-	kfree(digests);
-	trusted_shash_release();
-	unregister_key_type(&key_type_trusted);
+	if (chip) {
+		put_device(&chip->dev);
+		kfree(digests);
+		trusted_shash_release();
+		unregister_key_type(&key_type_trusted);
+	}
 }
 
 late_initcall(init_trusted);
-- 
2.19.1