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Subject[PATCH 4/5] KEYS: trusted: sanitize all key material
Date
From: Eric Biggers <ebiggers@google.com>

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@linux.vnet.ibm.com>
Cc: David Safford <safford@us.ibm.com>
Signed-off-by: Eric Biggers <ebiggers@google.com>
---
security/keys/trusted.c | 50 ++++++++++++++++++++++---------------------------
1 file changed, 22 insertions(+), 28 deletions(-)

diff --git a/security/keys/trusted.c b/security/keys/trusted.c
index 2ae31c5a87de..435e86e13879 100644
--- a/security/keys/trusted.c
+++ b/security/keys/trusted.c
@@ -70,7 +70,7 @@ static int TSS_sha1(const unsigned char *data, unsigned int datalen,
}

ret = crypto_shash_digest(&sdesc->shash, data, datalen, digest);
- kfree(sdesc);
+ kzfree(sdesc);
return ret;
}

@@ -114,7 +114,7 @@ static int TSS_rawhmac(unsigned char *digest, const unsigned char *key,
if (!ret)
ret = crypto_shash_final(&sdesc->shash, digest);
out:
- kfree(sdesc);
+ kzfree(sdesc);
return ret;
}

@@ -165,7 +165,7 @@ static int TSS_authhmac(unsigned char *digest, const unsigned char *key,
paramdigest, TPM_NONCE_SIZE, h1,
TPM_NONCE_SIZE, h2, 1, &c, 0, 0);
out:
- kfree(sdesc);
+ kzfree(sdesc);
return ret;
}

@@ -246,7 +246,7 @@ static int TSS_checkhmac1(unsigned char *buffer,
if (memcmp(testhmac, authdata, SHA1_DIGEST_SIZE))
ret = -EINVAL;
out:
- kfree(sdesc);
+ kzfree(sdesc);
return ret;
}

@@ -347,7 +347,7 @@ static int TSS_checkhmac2(unsigned char *buffer,
if (memcmp(testhmac2, authdata2, SHA1_DIGEST_SIZE))
ret = -EINVAL;
out:
- kfree(sdesc);
+ kzfree(sdesc);
return ret;
}

@@ -564,7 +564,7 @@ static int tpm_seal(struct tpm_buf *tb, uint16_t keytype,
*bloblen = storedsize;
}
out:
- kfree(td);
+ kzfree(td);
return ret;
}

@@ -678,7 +678,7 @@ static int key_seal(struct trusted_key_payload *p,
if (ret < 0)
pr_info("trusted_key: srkseal failed (%d)\n", ret);

- kfree(tb);
+ kzfree(tb);
return ret;
}

@@ -703,7 +703,7 @@ static int key_unseal(struct trusted_key_payload *p,
/* pull migratable flag out of sealed key */
p->migratable = p->key[--p->key_len];

- kfree(tb);
+ kzfree(tb);
return ret;
}

@@ -1037,12 +1037,12 @@ static int trusted_instantiate(struct key *key,
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;
}

@@ -1051,8 +1051,7 @@ static void trusted_rcu_free(struct rcu_head *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);
}

/*
@@ -1094,13 +1093,13 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
ret = datablob_parse(datablob, new_p, new_o);
if (ret != Opt_update) {
ret = -EINVAL;
- kfree(new_p);
+ kzfree(new_p);
goto out;
}

if (!new_o->keyhandle) {
ret = -EINVAL;
- kfree(new_p);
+ kzfree(new_p);
goto out;
}

@@ -1114,22 +1113,22 @@ static int trusted_update(struct key *key, struct key_preparsed_payload *prep)
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;
}

@@ -1158,24 +1157,19 @@ static long trusted_read(const struct key *key, char __user *buffer,
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[0];
-
- if (!p)
- return;
- memset(p->key, 0, p->key_len);
- kfree(key->payload.data[0]);
+ kzfree(key->payload.data[0]);
}

struct key_type key_type_trusted = {
--
2.12.2
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