tpm2: add tpm2_get_name()

This adds functions to get the "name" of a key. The key "name", as defined
by the TPM2 spec, includes its entire public area (with attribute fields),
not only its key fingerprint.

A function is added to calculate the name of a provided key public area,
as well as a function to get the name of a key which is present in the TPM.

diff --git a/src/shared/tpm2-util.c b/src/shared/tpm2-util.c
index a39a28351baa696e4a0c32b35b28796ffde7b5e4..73282787777fe62808a546dc111dc055a92183f9 100644 (file)
--- a/src/shared/tpm2-util.c
+++ b/src/shared/tpm2-util.c
@@ -68,6 +68,8 @@ TSS2_RC (*sym_Tss2_MU_TPM2B_PRIVATE_Marshal)(TPM2B_PRIVATE const *src, uint8_t b
 TSS2_RC (*sym_Tss2_MU_TPM2B_PRIVATE_Unmarshal)(uint8_t const buffer[], size_t buffer_size, size_t *offset, TPM2B_PRIVATE  *dest) = NULL;
 TSS2_RC (*sym_Tss2_MU_TPM2B_PUBLIC_Marshal)(TPM2B_PUBLIC const *src, uint8_t buffer[], size_t buffer_size, size_t *offset) = NULL;
 TSS2_RC (*sym_Tss2_MU_TPM2B_PUBLIC_Unmarshal)(uint8_t const buffer[], size_t buffer_size, size_t *offset, TPM2B_PUBLIC *dest) = NULL;
+TSS2_RC (*sym_Tss2_MU_TPMT_HA_Marshal)(TPMT_HA const *src, uint8_t buffer[], size_t buffer_size, size_t *offset) = NULL;
+TSS2_RC (*sym_Tss2_MU_TPMT_PUBLIC_Marshal)(TPMT_PUBLIC const *src, uint8_t buffer[], size_t buffer_size, size_t *offset) = NULL;
 
 int dlopen_tpm2(void) {
         int r;
@@ -117,7 +119,9 @@ int dlopen_tpm2(void) {
                         DLSYM_ARG(Tss2_MU_TPM2B_PRIVATE_Marshal),
                         DLSYM_ARG(Tss2_MU_TPM2B_PRIVATE_Unmarshal),
                         DLSYM_ARG(Tss2_MU_TPM2B_PUBLIC_Marshal),
-                        DLSYM_ARG(Tss2_MU_TPM2B_PUBLIC_Unmarshal));
+                        DLSYM_ARG(Tss2_MU_TPM2B_PUBLIC_Unmarshal),
+                        DLSYM_ARG(Tss2_MU_TPMT_HA_Marshal),
+                        DLSYM_ARG(Tss2_MU_TPMT_PUBLIC_Marshal));
 }
 
 static Tpm2Context *tpm2_context_free(Tpm2Context *c) {
@@ -977,6 +981,11 @@ static void tpm2_log_debug_digest(const TPM2B_DIGEST *digest, const char *msg) {
                 tpm2_log_debug_buffer(digest->buffer, digest->size, msg ?: "Digest");
 }
 
+static void tpm2_log_debug_name(const TPM2B_NAME *name, const char *msg) {
+        if (name)
+                tpm2_log_debug_buffer(name->name, name->size, msg ?: "Name");
+}
+
 static int tpm2_get_policy_digest(
                 Tpm2Context *c,
                 const Tpm2Handle *session,
@@ -1826,6 +1835,100 @@ static int find_signature(
 #endif
 }
 
+/* Calculates the "name" of a public key.
+ *
+ * As specified in TPM2 spec "Part 1: Architecture", a key's "name" is its nameAlg value followed by a hash
+ * of its TPM2 public area, all properly marshalled. This allows a key's "name" to be dependent not only on
+ * the key fingerprint, but also on the TPM2-specific fields that associated with the key (i.e. all fields in
+ * TPMT_PUBLIC). Note that this means an existing key may not change any of its TPMT_PUBLIC fields, since
+ * that would also change the key name.
+ *
+ * Since we (currently) hardcode to always using SHA256 for hashing, this returns an error if the public key
+ * nameAlg is not TPM2_ALG_SHA256. */
+int tpm2_calculate_name(const TPMT_PUBLIC *public, TPM2B_NAME *ret_name) {
+        TSS2_RC rc;
+        int r;
+
+        assert(public);
+        assert(ret_name);
+
+        r = dlopen_tpm2();
+        if (r < 0)
+                return log_error_errno(r, "TPM2 support not installed: %m");
+
+        if (public->nameAlg != TPM2_ALG_SHA256)
+                return log_error_errno(SYNTHETIC_ERRNO(EOPNOTSUPP),
+                                       "Unsupported nameAlg: 0x%x",
+                                       public->nameAlg);
+
+        _cleanup_free_ uint8_t *buf = NULL;
+        size_t size = 0;
+
+        buf = (uint8_t*) new(TPMT_PUBLIC, 1);
+        if (!buf)
+                return log_oom();
+
+        rc = sym_Tss2_MU_TPMT_PUBLIC_Marshal(public, buf, sizeof(TPMT_PUBLIC), &size);
+        if (rc != TSS2_RC_SUCCESS)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
+                                       "Failed to marshal public key: %s", sym_Tss2_RC_Decode(rc));
+
+        TPM2B_DIGEST digest = {};
+        r = tpm2_digest_buffer(TPM2_ALG_SHA256, &digest, buf, size, /* extend= */ false);
+        if (r < 0)
+                return r;
+
+        TPMT_HA ha = {
+                .hashAlg = TPM2_ALG_SHA256,
+        };
+        assert(digest.size <= sizeof(ha.digest.sha256));
+        memcpy_safe(ha.digest.sha256, digest.buffer, digest.size);
+
+        TPM2B_NAME name;
+        size = 0;
+        rc = sym_Tss2_MU_TPMT_HA_Marshal(&ha, name.name, sizeof(name.name), &size);
+        if (rc != TSS2_RC_SUCCESS)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
+                                       "Failed to marshal key name: %s", sym_Tss2_RC_Decode(rc));
+        name.size = size;
+
+        tpm2_log_debug_name(&name, "Calculated name");
+
+        *ret_name = name;
+
+        return 0;
+}
+
+/* Get the "name" of a key from the TPM.
+ *
+ * The "name" of a key is explained above in tpm2_calculate_name().
+ *
+ * The handle must reference a key already present in the TPM. It may be either a public key only, or a
+ * public/private keypair. */
+static int tpm2_get_name(
+                Tpm2Context *c,
+                const Tpm2Handle *handle,
+                TPM2B_NAME **ret_name) {
+
+        _cleanup_(Esys_Freep) TPM2B_NAME *name = NULL;
+        TSS2_RC rc;
+
+        assert(c);
+        assert(handle);
+        assert(ret_name);
+
+        rc = sym_Esys_TR_GetName(c->esys_context, handle->esys_handle, &name);
+        if (rc != TSS2_RC_SUCCESS)
+                return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
+                                       "Failed to get name of public key from TPM: %s", sym_Tss2_RC_Decode(rc));
+
+        tpm2_log_debug_name(name, "Object name");
+
+        *ret_name = TAKE_PTR(name);
+
+        return 0;
+}
+
 static int tpm2_build_sealing_policy(
                 Tpm2Context *c,
                 const Tpm2Handle *session,
@@ -1894,13 +1997,9 @@ static int tpm2_build_sealing_policy(
 
                 /* Acquire the "name" of what we just loaded */
                 _cleanup_(Esys_Freep) TPM2B_NAME *pubkey_name = NULL;
-                rc = sym_Esys_TR_GetName(
-                                c->esys_context,
-                                pubkey_handle->esys_handle,
-                                &pubkey_name);
-                if (rc != TSS2_RC_SUCCESS)
-                        return log_error_errno(SYNTHETIC_ERRNO(ENOTRECOVERABLE),
-                                               "Failed to get name of public key from TPM: %s", sym_Tss2_RC_Decode(rc));
+                r = tpm2_get_name(c, pubkey_handle, &pubkey_name);
+                if (r < 0)
+                        return r;
 
                 /* Put together the PCR policy we want to use */
                 TPML_PCR_SELECTION pcr_selection;

diff --git a/src/shared/tpm2-util.h b/src/shared/tpm2-util.h
index 7f9f0737ff675db25326edb45973ff37e66f52b3..12aad22a0f0b6f85fcb5be129b3723aada59e085 100644 (file)
--- a/src/shared/tpm2-util.h
+++ b/src/shared/tpm2-util.h
@@ -70,6 +70,8 @@ extern TSS2_RC (*sym_Tss2_MU_TPM2B_PRIVATE_Marshal)(TPM2B_PRIVATE const *src, ui
 extern TSS2_RC (*sym_Tss2_MU_TPM2B_PRIVATE_Unmarshal)(uint8_t const buffer[], size_t buffer_size, size_t *offset, TPM2B_PRIVATE  *dest);
 extern TSS2_RC (*sym_Tss2_MU_TPM2B_PUBLIC_Marshal)(TPM2B_PUBLIC const *src, uint8_t buffer[], size_t buffer_size, size_t *offset);
 extern TSS2_RC (*sym_Tss2_MU_TPM2B_PUBLIC_Unmarshal)(uint8_t const buffer[], size_t buffer_size, size_t *offset, TPM2B_PUBLIC *dest);
+extern TSS2_RC (*sym_Tss2_MU_TPMT_HA_Marshal)(TPMT_HA const *src, uint8_t buffer[], size_t buffer_size, size_t *offset);
+extern TSS2_RC (*sym_Tss2_MU_TPMT_PUBLIC_Marshal)(TPMT_PUBLIC const *src, uint8_t buffer[], size_t buffer_size, size_t *offset);
 
 int dlopen_tpm2(void);
 
@@ -85,6 +87,8 @@ static inline int tpm2_digest_init(TPMI_ALG_HASH alg, TPM2B_DIGEST *digest) {
         return tpm2_digest_many(alg, digest, NULL, 0, false);
 }
 
+int tpm2_calculate_name(const TPMT_PUBLIC *public, TPM2B_NAME *ret_name);
+
 int tpm2_seal(const char *device, uint32_t hash_pcr_mask, const void *pubkey, size_t pubkey_size, uint32_t pubkey_pcr_mask, const char *pin, void **ret_secret, size_t *ret_secret_size, void **ret_blob, size_t *ret_blob_size, void **ret_pcr_hash, size_t *ret_pcr_hash_size, uint16_t *ret_pcr_bank, uint16_t *ret_primary_alg, void **ret_srk_buf, size_t *ret_srk_buf_size);
 int tpm2_unseal(const char *device, uint32_t hash_pcr_mask, uint16_t pcr_bank, const void *pubkey, size_t pubkey_size, uint32_t pubkey_pcr_mask, JsonVariant *signature, const char *pin, uint16_t primary_alg, const void *blob, size_t blob_size, const void *policy_hash, size_t policy_hash_size, const void *srk_buf, size_t srk_buf_size, void **ret_secret, size_t *ret_secret_size);
 

diff --git a/src/test/test-tpm2.c b/src/test/test-tpm2.c
index 3b009606910d0dbaa425d68d0e3ae0536b8673ea..df64a4a106ac6da7f007a50d80f194b43a3fe764 100644 (file)
--- a/src/test/test-tpm2.c
+++ b/src/test/test-tpm2.c
@@ -647,6 +647,49 @@ TEST(digest_many) {
         assert_se(digest_check(&d, "02ecb0628264235111e0053e271092981c8b15d59cd46617836bee3149a4ecb0"));
 }
 
+static void tpm2b_public_init(TPM2B_PUBLIC *public) {
+        TPMT_PUBLIC tpmt = {
+                .type = TPM2_ALG_RSA,
+                .nameAlg = TPM2_ALG_SHA256,
+                .objectAttributes = TPMA_OBJECT_RESTRICTED|TPMA_OBJECT_DECRYPT|TPMA_OBJECT_FIXEDTPM|TPMA_OBJECT_FIXEDPARENT|TPMA_OBJECT_SENSITIVEDATAORIGIN|TPMA_OBJECT_USERWITHAUTH,
+                .parameters.rsaDetail = {
+                        .symmetric = {
+                                .algorithm = TPM2_ALG_AES,
+                                .keyBits.aes = 128,
+                                .mode.aes = TPM2_ALG_CFB,
+                        },
+                        .scheme.scheme = TPM2_ALG_NULL,
+                        .keyBits = 2048,
+                },
+        };
+
+        const char *key = "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";
+        _cleanup_free_ void *mem = NULL;
+        size_t len = 0;
+        assert_se(unhexmem(key, strlen(key), &mem, &len) == 0);
+        assert_se(len <= sizeof(tpmt.unique.rsa.buffer));
+        memcpy_safe(tpmt.unique.rsa.buffer, mem, len);
+        tpmt.unique.rsa.size = len;
+
+        public->publicArea = tpmt;
+}
+
+TEST(calculate_name) {
+        TPM2B_PUBLIC public;
+        TPM2B_NAME name;
+
+        tpm2b_public_init(&public);
+        assert_se(tpm2_calculate_name(&public.publicArea, &name) == 0);
+        assert_se(name.size == SHA256_DIGEST_SIZE + 2);
+
+        const char *expect = "000be78f74a470dd92e979ca067cdb2293a35f075e8560b436bd2ccea5da21486a07";
+        _cleanup_free_ char *h = hexmem(name.name, name.size);
+        assert_se(h);
+
+        assert_se(strlen(expect) == strlen(h));
+        assert_se(streq(expect, h));
+}
+
 #endif /* HAVE_TPM2 */
 
 DEFINE_TEST_MAIN(LOG_DEBUG);