KEYS: asym_tpm: Implement tpm_sign [ver #2]

Signed-off-by: Denis Kenzior <denkenz@gmail.com>
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Marcel Holtmann <marcel@holtmann.org>
Signed-off-by: James Morris <james.morris@microsoft.com>

diff --git a/crypto/asymmetric_keys/asym_tpm.c b/crypto/asymmetric_keys/asym_tpm.c
index a38ba375675ee2f33bdd1d9ba4ed9a8770fd20ce..a5a5f913a74f351d67fa7e90a2afd751bee9d3c2 100644 (file)
--- a/crypto/asymmetric_keys/asym_tpm.c
+++ b/crypto/asymmetric_keys/asym_tpm.c
@@ -20,9 +20,11 @@
 #define TPM_ORD_FLUSHSPECIFIC  186
 #define TPM_ORD_LOADKEY2       65
 #define TPM_ORD_UNBIND         30
+#define TPM_ORD_SIGN           60
 #define TPM_LOADKEY2_SIZE              59
 #define TPM_FLUSHSPECIFIC_SIZE         18
 #define TPM_UNBIND_SIZE                        63
+#define TPM_SIGN_SIZE                  63
 
 #define TPM_RT_KEY                      0x00000001
 
@@ -189,6 +191,91 @@ static int tpm_unbind(struct tpm_buf *tb,
        return datalen;
 }
 
+/*
+ * Sign a blob provided by userspace (that has had the hash function applied)
+ * using a specific key handle.  The handle is assumed to have been previously
+ * loaded by e.g. LoadKey2.
+ *
+ * Note that the key signature scheme of the used key should be set to
+ * TPM_SS_RSASSAPKCS1v15_DER.  This allows the hashed input to be of any size
+ * up to key_length_in_bytes - 11 and not be limited to size 20 like the
+ * TPM_SS_RSASSAPKCS1v15_SHA1 signature scheme.
+ */
+static int tpm_sign(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_SIGN);
+       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_SIGN_SIZE + bloblen);
+       store32(tb, TPM_ORD_SIGN);
+       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(datalen, outlen));
+
+       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