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Message-ID: <153618457658.7946.2269119827266208835.stgit@warthog.procyon.org.uk>
Date: Wed, 05 Sep 2018 22:56:16 +0100
From: David Howells <dhowells@...hat.com>
To: jmorris@...ei.org
Cc: denkenz@...il.com, keyrings@...r.kernel.org,
linux-security-module@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: [PATCH 18/22] KEYS: asym_tpm: Implement tpm_unbind
From: Denis Kenzior <denkenz@...il.com>
Signed-off-by: Denis Kenzior <denkenz@...il.com>
Reviewed-by: James Morris <james.morris@...rosoft.com>
Signed-off-by: David Howells <dhowells@...hat.com>
---
crypto/asymmetric_keys/asym_tpm.c | 82 +++++++++++++++++++++++++++++++++++++
1 file changed, 82 insertions(+)
diff --git a/crypto/asymmetric_keys/asym_tpm.c b/crypto/asymmetric_keys/asym_tpm.c
index 6a2d33014ecc..e893b5212222 100644
--- a/crypto/asymmetric_keys/asym_tpm.c
+++ b/crypto/asymmetric_keys/asym_tpm.c
@@ -18,8 +18,10 @@
#define TPM_ORD_FLUSHSPECIFIC 186
#define TPM_ORD_LOADKEY2 65
+#define TPM_ORD_UNBIND 30
#define TPM_LOADKEY2_SIZE 59
#define TPM_FLUSHSPECIFIC_SIZE 18
+#define TPM_UNBIND_SIZE 63
#define TPM_RT_KEY 0x00000001
@@ -106,6 +108,86 @@ static int tpm_flushspecific(struct tpm_buf *tb, uint32_t handle)
return trusted_tpm_send(tb->data, MAX_BUF_SIZE);
}
+/*
+ * Decrypt a blob provided by userspace using a specific key handle.
+ * The handle is a well known handle or previously loaded by e.g. LoadKey2
+ */
+static int tpm_unbind(struct tpm_buf *tb,
+ uint32_t keyhandle, unsigned char *keyauth,
+ const unsigned char *blob, uint32_t bloblen,
+ void *out, uint32_t outlen)
+{
+ unsigned char nonceodd[TPM_NONCE_SIZE];
+ unsigned char enonce[TPM_NONCE_SIZE];
+ unsigned char authdata[SHA1_DIGEST_SIZE];
+ uint32_t authhandle = 0;
+ unsigned char cont = 0;
+ uint32_t ordinal;
+ uint32_t datalen;
+ int ret;
+
+ ordinal = htonl(TPM_ORD_UNBIND);
+ datalen = htonl(bloblen);
+
+ /* session for loading the key */
+ ret = oiap(tb, &authhandle, enonce);
+ if (ret < 0) {
+ pr_info("oiap failed (%d)\n", ret);
+ return ret;
+ }
+
+ /* generate odd nonce */
+ ret = tpm_get_random(NULL, nonceodd, TPM_NONCE_SIZE);
+ if (ret < 0) {
+ pr_info("tpm_get_random failed (%d)\n", ret);
+ return ret;
+ }
+
+ /* calculate authorization HMAC value */
+ ret = TSS_authhmac(authdata, keyauth, SHA1_DIGEST_SIZE, enonce,
+ nonceodd, cont, sizeof(uint32_t), &ordinal,
+ sizeof(uint32_t), &datalen,
+ bloblen, blob, 0, 0);
+ if (ret < 0)
+ return ret;
+
+ /* build the request buffer */
+ INIT_BUF(tb);
+ store16(tb, TPM_TAG_RQU_AUTH1_COMMAND);
+ store32(tb, TPM_UNBIND_SIZE + bloblen);
+ store32(tb, TPM_ORD_UNBIND);
+ store32(tb, keyhandle);
+ store32(tb, bloblen);
+ storebytes(tb, blob, bloblen);
+ store32(tb, authhandle);
+ storebytes(tb, nonceodd, TPM_NONCE_SIZE);
+ store8(tb, cont);
+ storebytes(tb, authdata, SHA1_DIGEST_SIZE);
+
+ ret = trusted_tpm_send(tb->data, MAX_BUF_SIZE);
+ if (ret < 0) {
+ pr_info("authhmac failed (%d)\n", ret);
+ return ret;
+ }
+
+ datalen = LOAD32(tb->data, TPM_DATA_OFFSET);
+
+ ret = TSS_checkhmac1(tb->data, ordinal, nonceodd,
+ keyauth, SHA1_DIGEST_SIZE,
+ sizeof(uint32_t), TPM_DATA_OFFSET,
+ datalen, TPM_DATA_OFFSET + sizeof(uint32_t),
+ 0, 0);
+ if (ret < 0) {
+ pr_info("TSS_checkhmac1 failed (%d)\n", ret);
+ return ret;
+ }
+
+ memcpy(out, tb->data + TPM_DATA_OFFSET + sizeof(uint32_t),
+ min(outlen, datalen));
+
+ return datalen;
+}
+
/*
* Maximum buffer size for the BER/DER encoded public key. The public key
* is of the form SEQUENCE { INTEGER n, INTEGER e } where n is a maximum 2048
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