tpm_lite: implement TPM_GetRandom

Provide TPM_GetRandom function to library callers.

BUG=chromium-os:22172
TEST=lumpy build & manual testing

Change-Id: Id604fd92490ba697033158a580b0b4df1d975932
Signed-off-by: Kees Cook <keescook@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/17120
Reviewed-by: Luigi Semenzato <semenzato@chromium.org>

6 files changed, 88 insertions, 5 deletions

diff --git a/firmware/include/tlcl.h b/firmware/include/tlcl.h
index 6f0db1b6..c8632e43 100644
--- a/firmware/include/tlcl.h
+++ b/firmware/include/tlcl.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
@@ -150,4 +150,9 @@ uint32_t TlclGetPermanentFlags(TPM_PERMANENT_FLAGS* pflags);
  */
 uint32_t TlclGetSTClearFlags(TPM_STCLEAR_FLAGS* pflags);
 
+/* Requests [length] bytes from TPM RNG to be stored in [data]. Actual
+ * number of bytes read is stored in [size]. The TPM error code is returned.
+ */
+uint32_t TlclGetRandom(uint8_t* data, uint32_t length, uint32_t* size);
+
 #endif  /* TPM_LITE_TLCL_H_ */
diff --git a/firmware/include/tss_constants.h b/firmware/include/tss_constants.h
index 68a9c6ff..b28c3c60 100644
--- a/firmware/include/tss_constants.h
+++ b/firmware/include/tss_constants.h
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010-2011 The Chromium OS Authors. All rights reserved.
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
@@ -36,6 +36,7 @@
 #define TPM_E_MUST_REBOOT            ((uint32_t)0x00005002)  /* vboot local */
 #define TPM_E_CORRUPTED_STATE        ((uint32_t)0x00005003)  /* vboot local */
 #define TPM_E_COMMUNICATION_ERROR    ((uint32_t)0x00005004)  /* vboot local */
+#define TPM_E_RESPONSE_TOO_LARGE     ((uint32_t)0x00005005)  /* vboot local */
 
 #define TPM_NV_INDEX0 ((uint32_t)0x00000000)
 #define TPM_NV_INDEX_LOCK ((uint32_t)0xffffffff)
diff --git a/firmware/lib/tpm_lite/include/tlcl_structures.h b/firmware/lib/tpm_lite/include/tlcl_structures.h
index e0a7a46b..c4d80ba3 100644
--- a/firmware/lib/tpm_lite/include/tlcl_structures.h
+++ b/firmware/lib/tpm_lite/include/tlcl_structures.h
@@ -7,6 +7,12 @@ const struct s_tpm_extend_cmd{
 } tpm_extend_cmd = {{0x0, 0xc1, 0x0, 0x0, 0x0, 0x22, 0x0, 0x0, 0x0, 0x14, },
 10, 14, };
 
+const struct s_tpm_get_random_cmd{
+  uint8_t buffer[14];
+  uint16_t bytesRequested;
+} tpm_get_random_cmd = {{0x0, 0xc1, 0x0, 0x0, 0x0, 0xe, 0x0, 0x0, 0x0, 0x46, },
+10, };
+
 const struct s_tpm_getpermissions_cmd{
   uint8_t buffer[22];
   uint16_t index;
diff --git a/firmware/lib/tpm_lite/tlcl.c b/firmware/lib/tpm_lite/tlcl.c
index 338e2f67..9e9ece84 100644
--- a/firmware/lib/tpm_lite/tlcl.c
+++ b/firmware/lib/tpm_lite/tlcl.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2011 The Chromium OS Authors. All rights reserved.
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
@@ -396,3 +396,34 @@ uint32_t TlclGetPermissions(uint32_t index, uint32_t* permissions) {
   FromTpmUint32(nvdata + kNvDataPublicPermissionsOffset, permissions);
   return result;
 }
+
+uint32_t TlclGetRandom(uint8_t* data, uint32_t length, uint32_t *size) {
+  struct s_tpm_get_random_cmd cmd;
+  uint8_t response[TPM_LARGE_ENOUGH_COMMAND_SIZE];
+  uint32_t result;
+
+  VBDEBUG(("TPM: TlclGetRandom(%d)\n", length));
+  Memcpy(&cmd, &tpm_get_random_cmd, sizeof(cmd));
+  ToTpmUint32(cmd.buffer + tpm_get_random_cmd.bytesRequested, length);
+  /* There must be room in the response buffer for the bytes. */
+  if (length > TPM_LARGE_ENOUGH_COMMAND_SIZE - kTpmResponseHeaderLength
+               - sizeof(uint32_t)) {
+    return TPM_E_IOERROR;
+  }
+
+  result = TlclSendReceive(cmd.buffer, response, sizeof(response));
+  if (result == TPM_SUCCESS) {
+    uint8_t* get_random_cursor;
+    FromTpmUint32(response + kTpmResponseHeaderLength, size);
+
+    /* There must be room in the target buffer for the bytes. */
+    if (*size > length) {
+      return TPM_E_RESPONSE_TOO_LARGE;
+    }
+    get_random_cursor = response + kTpmResponseHeaderLength
+                                 + sizeof(uint32_t);
+    Memcpy(data, get_random_cursor, *size);
+  }
+
+  return result;
+}
diff --git a/utility/tlcl_generator.c b/utility/tlcl_generator.c
index f905784f..bbc379c1 100644
--- a/utility/tlcl_generator.c
+++ b/utility/tlcl_generator.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
@@ -362,6 +362,14 @@ Command* BuildGetPermissionsCommand(void) {
   return cmd;
 }
 
+Command* BuildGetRandomCommand(void) {
+  int size = kTpmRequestHeaderLength + sizeof(uint32_t);
+  Command* cmd = newCommand(TPM_ORD_GetRandom, size);
+  cmd->name = "tpm_get_random_cmd";
+  AddVisibleField(cmd, "bytesRequested", kTpmRequestHeaderLength);
+  return cmd;
+}
+
 /* Output the fields of a structure.
  */
 void OutputFields(Field* fld) {
@@ -480,6 +488,7 @@ Command* (*builders[])(void) = {
   BuildGetFlagsCommand,
   BuildGetSTClearFlagsCommand,
   BuildGetPermissionsCommand,
+  BuildGetRandomCommand,
   BuildExtendCommand,
 };
 
diff --git a/utility/tpmc.c b/utility/tpmc.c
index d8fb07a5..68ce6d3f 100644
--- a/utility/tpmc.c
+++ b/utility/tpmc.c
@@ -1,4 +1,4 @@
-/* Copyright (c) 2010 The Chromium OS Authors. All rights reserved.
+/* Copyright (c) 2012 The Chromium OS Authors. All rights reserved.
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  *
@@ -228,6 +228,35 @@ static uint32_t HandlerGetPermissions(void) {
   return result;
 }
 
+static uint32_t HandlerGetRandom(void) {
+  uint32_t length, size;
+  uint8_t* bytes;
+  uint32_t result;
+  int i;
+  if (nargs != 3) {
+    fprintf(stderr, "usage: tpmc getrandom <size>\n");
+    exit(OTHER_ERROR);
+  }
+  if (HexStringToUint32(args[2], &length) != 0) {
+    fprintf(stderr, "<size> must be 32-bit hex (0x[0-9a-f]+)\n");
+    exit(OTHER_ERROR);
+  }
+  bytes = calloc(1, length);
+  if (bytes == NULL) {
+    perror("calloc");
+    exit(OTHER_ERROR);
+  }
+  result = TlclGetRandom(bytes, length, &size);
+  if (result == 0 && size > 0) {
+    for (i = 0; i < size; i++) {
+      printf("%02x", bytes[i]);
+    }
+    printf("\n");
+  }
+  free(bytes);
+  return result;
+}
+
 static uint32_t HandlerGetPermanentFlags(void) {
   TPM_PERMANENT_FLAGS pflags;
   uint32_t result = TlclGetPermanentFlags(&pflags);
@@ -312,6 +341,8 @@ command_record command_table[] = {
     HandlerGetPermissions },
   { "getpermanentflags", "getpf", "print all permanent flags",
     HandlerGetPermanentFlags },
+  { "getrandom", "rand", "read bytes from RNG (rand <size>)",
+    HandlerGetRandom },
   { "getstclearflags", "getvf", "print all volatile (ST_CLEAR) flags",
     HandlerGetSTClearFlags },
   { "resume", "res", "execute TPM_Startup(ST_STATE)", TlclResume },