linux-kernel - [PATCH 3.16 160/204] KEYS: trusted: sanitize all key material

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Message-ID: <lsq.1514480744.955797951@decadent.org.uk>
Date:   Thu, 28 Dec 2017 17:05:44 +0000
From:   Ben Hutchings <ben@...adent.org.uk>
To:     linux-kernel@...r.kernel.org, stable@...r.kernel.org
CC:     akpm@...ux-foundation.org, "Mimi Zohar" <zohar@...ux.vnet.ibm.com>,
        "David Howells" <dhowells@...hat.com>,
        "James Morris" <james.l.morris@...cle.com>,
        "David Safford" <safford@...ibm.com>,
        "Eric Biggers" <ebiggers@...gle.com>
Subject: [PATCH 3.16 160/204] KEYS: trusted: sanitize all key material

3.16.52-rc1 review patch.  If anyone has any objections, please let me know.

------------------

From: Eric Biggers <ebiggers@...gle.com>

commit ee618b4619b72527aaed765f0f0b74072b281159 upstream.

As the previous patch did for encrypted-keys, zero sensitive any
potentially sensitive data related to the "trusted" key type before it
is freed.  Notably, we were not zeroing the tpm_buf structures in which
the actual key is stored for TPM seal and unseal, nor were we zeroing
the trusted_key_payload in certain error paths.

Cc: Mimi Zohar <zohar@...ux.vnet.ibm.com>
Cc: David Safford <safford@...ibm.com>
Signed-off-by: Eric Biggers <ebiggers@...gle.com>
Signed-off-by: David Howells <dhowells@...hat.com>
Signed-off-by: James Morris <james.l.morris@...cle.com>
[bwh: Backported to 3.16:
 - Drop one unapplicable change
 - Adjust context]
Signed-off-by: Ben Hutchings <ben@...adent.org.uk>
---
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -69,7 +69,7 @@ static int TSS_sha1(const unsigned char
 	}
 
 	ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
-	kfree(sdesc);
+	kzfree(sdesc);
 	return ret;
 }
 
@@ -113,7 +113,7 @@ static int TSS_rawhmac(unsigned char *di
 	if (!ret)
 		ret = crypto_shash_final(&sdesc->shash, digest);
 out:
-	kfree(sdesc);
+	kzfree(sdesc);
 	return ret;
 }
 
@@ -164,7 +164,7 @@ static int TSS_authhmac(unsigned char *d
 				  paramdigest, TPM_NONCE_SIZE, h1,
 				  TPM_NONCE_SIZE, h2, 1, &c, 0, 0);
 out:
-	kfree(sdesc);
+	kzfree(sdesc);
 	return ret;
 }
 
@@ -245,7 +245,7 @@ static int TSS_checkhmac1(unsigned char
 	if (memcmp(testhmac, authdata, SHA1_DIGEST_SIZE))
 		ret = -EINVAL;
 out:
-	kfree(sdesc);
+	kzfree(sdesc);
 	return ret;
 }
 
@@ -346,7 +346,7 @@ static int TSS_checkhmac2(unsigned char
 	if (memcmp(testhmac2, authdata2, SHA1_DIGEST_SIZE))
 		ret = -EINVAL;
 out:
-	kfree(sdesc);
+	kzfree(sdesc);
 	return ret;
 }
 
@@ -563,7 +563,7 @@ static int tpm_seal(struct tpm_buf *tb,
 		*bloblen = storedsize;
 	}
 out:
-	kfree(td);
+	kzfree(td);
 	return ret;
 }
 
@@ -677,7 +677,7 @@ static int key_seal(struct trusted_key_p
 	if (ret < 0)
 		pr_info("trusted_key: srkseal failed (%d)\n", ret);
 
-	kfree(tb);
+	kzfree(tb);
 	return ret;
 }
 
@@ -702,7 +702,7 @@ static int key_unseal(struct trusted_key
 		/* pull migratable flag out of sealed key */
 		p->migratable = p->key[--p->key_len];
 
-	kfree(tb);
+	kzfree(tb);
 	return ret;
 }
 
@@ -961,12 +961,12 @@ static int trusted_instantiate(struct ke
 	if (!ret && options->pcrlock)
 		ret = pcrlock(options->pcrlock);
 out:
-	kfree(datablob);
-	kfree(options);
+	kzfree(datablob);
+	kzfree(options);
 	if (!ret)
 		rcu_assign_keypointer(key, payload);
 	else
-		kfree(payload);
+		kzfree(payload);
 	return ret;
 }
 
@@ -975,8 +975,7 @@ static void trusted_rcu_free(struct rcu_
 	struct trusted_key_payload *p;
 
 	p = container_of(rcu, struct trusted_key_payload, rcu);
-	memset(p->key, 0, p->key_len);
-	kfree(p);
+	kzfree(p);
 }
 
 /*
@@ -1015,7 +1014,7 @@ static int trusted_update(struct key *ke
 	ret = datablob_parse(datablob, new_p, new_o);
 	if (ret != Opt_update) {
 		ret = -EINVAL;
-		kfree(new_p);
+		kzfree(new_p);
 		goto out;
 	}
 	/* copy old key values, and reseal with new pcrs */
@@ -1028,22 +1027,22 @@ static int trusted_update(struct key *ke
 	ret = key_seal(new_p, new_o);
 	if (ret < 0) {
 		pr_info("trusted_key: key_seal failed (%d)\n", ret);
-		kfree(new_p);
+		kzfree(new_p);
 		goto out;
 	}
 	if (new_o->pcrlock) {
 		ret = pcrlock(new_o->pcrlock);
 		if (ret < 0) {
 			pr_info("trusted_key: pcrlock failed (%d)\n", ret);
-			kfree(new_p);
+			kzfree(new_p);
 			goto out;
 		}
 	}
 	rcu_assign_keypointer(key, new_p);
 	call_rcu(&p->rcu, trusted_rcu_free);
 out:
-	kfree(datablob);
-	kfree(new_o);
+	kzfree(datablob);
+	kzfree(new_o);
 	return ret;
 }
 
@@ -1072,24 +1071,19 @@ static long trusted_read(const struct ke
 	for (i = 0; i < p->blob_len; i++)
 		bufp = hex_byte_pack(bufp, p->blob[i]);
 	if ((copy_to_user(buffer, ascii_buf, 2 * p->blob_len)) != 0) {
-		kfree(ascii_buf);
+		kzfree(ascii_buf);
 		return -EFAULT;
 	}
-	kfree(ascii_buf);
+	kzfree(ascii_buf);
 	return 2 * p->blob_len;
 }
 
 /*
- * trusted_destroy - before freeing the key, clear the decrypted data
+ * trusted_destroy - clear and free the key's payload
  */
 static void trusted_destroy(struct key *key)
 {
-	struct trusted_key_payload *p = key->payload.data;
-
-	if (!p)
-		return;
-	memset(p->key, 0, p->key_len);
-	kfree(key->payload.data);
+	kzfree(key->payload.data);
 }
 
 struct key_type key_type_trusted = {