ccd_config: Simplify open and password

Allow setting password from the AP, but not from USB.  Remove the old
password control logic, which is no longer needed.

Allow open if:
- Not explicitly blocked
- Not blocked via FWMP
- One of the following is true:
  - A password is set
  - Battery is removed (also doesn't require physical presence)
  - Dev mode is on, and request came from the AP

Reduces cr50 binary by 152 bytes.

BUG=b:79983505
BRANCH=cr50
TEST=manual, with a CR50_DEV=1 build

	ccd oops
	ccd lock
	ccd unlock -> fails
	gsctool -U -> fails from host
	gsctool -t -U -> fails from AP

	ccd oops
	ccd password foo -> fails from console
	gsctool -P -> fails from host
	gsctool -t -P -> works from AP
	ccd get -> confirms password set

	ccd lock
	ccd unlock foo -> works
	ccd lock
	gsctool -U -> works from host, if correct password supplied
	ccd lock
	gsctool -t -U -> works from AP, if correct password supplied

	ccd open foo -> works
	ccd lock
	gsctool -O -> works from host, if correct password supplied
	ccd lock
	gsctool -t -O -> works from AP, if correct password supplied

	ccd oops
	ccd lock
	(remove battery)
	ccd open -> works without physical presence
	(reattach battery)
	ccd lock
	gsctool -O -> works from host
	ccd lock
	gsctool -t -O -> works from AP, if dev mode is enabled

Change-Id: I364b322d03db250e7dd140767d7a22dbb3ac1eef
Signed-off-by: Randall Spangler <rspangler@chromium.org>
Reviewed-on: https://chromium-review.googlesource.com/1072957
Reviewed-by: Vadim Bendebury <vbendeb@chromium.org>

3 files changed, 60 insertions, 116 deletions

diff --git a/board/cr50/tpm2/platform.c b/board/cr50/tpm2/platform.c
index 3068c903e3..a275a82264 100644
--- a/board/cr50/tpm2/platform.c
+++ b/board/cr50/tpm2/platform.c
@@ -66,5 +66,20 @@ void   _plat__GetFwVersion(uint32_t *firmwareV1, uint32_t *firmwareV2)
 void _plat__ResetCallback(void)
 {
 	pinweaver_init();
-	ccd_tpm_reset_callback();
+
+	/*
+	 * Eventually, we'll want to allow CCD unlock with no password, so
+	 * enterprise policy can set a password to block CCD instead of locking
+	 * it out via the FWMP.
+	 *
+	 * When we do that, we'll allow unlock without password between a real
+	 * TPM startup (not just a resume) - which is this callback - and
+	 * explicit disabling of that feature via a to-be-created vendor
+	 * command.  That vendor command will be called after enterprize policy
+	 * is updated, or the device is determined not to be enrolled.
+	 *
+	 * But for now, we'll just block unlock entirely if no password is set,
+	 * so we don't yet need to tell CCD that a real TPM startup has
+	 * occurred.
+	 */
 }
diff --git a/common/ccd_config.c b/common/ccd_config.c
index 677eb025ca..28f393d87d 100644
--- a/common/ccd_config.c
+++ b/common/ccd_config.c
@@ -838,26 +838,26 @@ static enum vendor_cmd_rc ccd_open(struct vendor_cmd_params *p)
 	int need_pp = 1;
 	int rv;
 	char *buffer = p->buffer;
+	const char *why_denied = "forced";
 
-	if (force_disabled) {
-		p->out_size = 1;
-		buffer[0] = EC_ERROR_ACCESS_DENIED;
-		return VENDOR_RC_NOT_ALLOWED;
-	}
+	if (force_disabled)
+		goto denied;
 
 	if (ccd_state == CCD_STATE_OPENED)
 		return VENDOR_RC_SUCCESS;
 
 	/* FWMP blocks open even if a password is set */
 	if (!board_fwmp_allows_unlock()) {
-		p->out_size = 1;
-		buffer[0] = EC_ERROR_ACCESS_DENIED;
-		return VENDOR_RC_NOT_ALLOWED;
+		why_denied = "fwmp";
+		goto denied;
 	}
 
-	/* If a password is set, check it */
+	/* Make sure open is allowed */
 	if (raw_has_password()) {
+		/* Open allowed if correct password is specified */
+
 		if (!p->in_size) {
+			/* ...which it wasn't */
 			p->out_size = 1;
 			buffer[0] = EC_ERROR_PARAM_COUNT;
 			return VENDOR_RC_PASSWORD_REQUIRED;
@@ -874,6 +874,22 @@ static enum vendor_cmd_rc ccd_open(struct vendor_cmd_params *p)
 			buffer[0] = rv;
 			return VENDOR_RC_INTERNAL_ERROR;
 		}
+	} else if (!board_battery_is_present()) {
+		/* Open allowed with no password if battery is removed */
+	} else if (board_vboot_dev_mode_enabled() &&
+		   !(p->flags & VENDOR_CMD_FROM_USB)) {
+		/*
+		 * Open allowed with no password if dev mode enabled and
+		 * command came from the AP.
+		 */
+	} else {
+		/*
+		 * - Password not set
+		 * - Battery is present
+		 * - Either not in developer mode or the command came from USB
+		 */
+		why_denied = "nopwd";
+		goto denied;
 	}
 
 	/* Fail and abort if already checking physical presence */
@@ -912,6 +928,13 @@ static enum vendor_cmd_rc ccd_open(struct vendor_cmd_params *p)
 	ccd_open_done(1);
 
 	return VENDOR_RC_SUCCESS;
+
+denied:
+	/* Open not allowed for some reason */
+	CPRINTS("%s denied: %s", __func__, why_denied);
+	p->out_size = 1;
+	buffer[0] = EC_ERROR_ACCESS_DENIED;
+	return VENDOR_RC_NOT_ALLOWED;
 }
 
 static enum vendor_cmd_rc ccd_unlock(struct vendor_cmd_params *p)
@@ -1177,104 +1200,6 @@ DECLARE_SAFE_CONSOLE_COMMAND(ccd, command_ccd,
 			     "Configure case-closed debugging");
 
 /*
- * Password handling on Cr50 passes the following states:
- *
- * - password setting is not allowed after Cr50 reset until an upstart (as
- *   opposed to resume) TPM startup happens, as signalled by the TPM callback.
- *   After the proper TPM reset the state changes to 'POST_RESET_STATE' which
- *   means that the device was just reset/rebooted (not resumed) and no user
- *   logged in yet.
- *
- *  - if the owner logs in in this state, the state changes to
- *    'PASSWORD_ALLOWED_STATE'. The owner can open crosh session and set the
- *    password.
- *
- *   - when the owner logs out or any user but the owner logs in, the state
- *     changes to PASSWORD_NOT_ALLOWED_STATE and does not change until TPM is
- *     reset. This makes sure that password can be set only by the owner and
- *     only before anybody else logged in.
- */
-enum password_reset_phase {
-	POST_RESET_STATE,
-	PASSWORD_ALLOWED_STATE,
-	PASSWORD_NOT_ALLOWED_STATE
-};
-
-static uint8_t password_state = PASSWORD_NOT_ALLOWED_STATE;
-
-void ccd_tpm_reset_callback(void)
-{
-	CPRINTS("%s: TPM Startup processed", __func__);
-	password_state = POST_RESET_STATE;
-}
-
-/*
- * Handle the VENDOR_CC_MANAGE_CCD_PASSWORD command.
- *
- * The payload of the command is a single byte Boolean which sets the controls
- * if CCD password can be set or not.
- *
- * After reset the pasword can not be set using VENDOR_CC_CCD_PASSWORD; once
- * this command is received with value of True, the phase stars when the
- * password can be set. As soon as this command is received with a value of
- * False, the password can not be set any more until device is rebooted, even
- * if this command is re-sent with the value of True.
- */
-static enum vendor_cmd_rc manage_ccd_password(enum vendor_cmd_cc code,
-					      void *buf,
-					      size_t input_size,
-					      size_t *response_size)
-{
-	uint8_t prev_state = password_state;
-	/* The vendor command status code. */
-	enum vendor_cmd_rc rv = VENDOR_RC_SUCCESS;
-	/* Actual error code. */
-	uint8_t error_code = EC_SUCCESS;
-
-	do {
-		int value;
-
-		if (input_size != 1) {
-			rv = VENDOR_RC_INTERNAL_ERROR;
-			error_code = EC_ERROR_PARAM1;
-			break;
-		}
-
-		value = *((uint8_t *)buf);
-
-		if (!value) {
-			/* No more password setting allowed. */
-			password_state = PASSWORD_NOT_ALLOWED_STATE;
-			break;
-		}
-
-		if (password_state == POST_RESET_STATE) {
-			/* The only way to allow password setting. */
-			password_state = PASSWORD_ALLOWED_STATE;
-			break;
-		}
-
-		password_state = PASSWORD_NOT_ALLOWED_STATE;
-		rv = VENDOR_RC_BOGUS_ARGS;
-		error_code = EC_ERROR_INVAL;
-	} while (0);
-
-	if (prev_state != password_state)
-		CPRINTF("%s: state change from %d to %d\n",
-			__func__, prev_state, password_state);
-
-	if (rv == VENDOR_RC_SUCCESS) {
-		*response_size = 0;
-	} else {
-		*response_size = 1;
-		((uint8_t *)buf)[0] = error_code;
-	}
-
-	return rv;
-}
-DECLARE_VENDOR_COMMAND(VENDOR_CC_MANAGE_CCD_PWD, manage_ccd_password);
-
-/*
  * Handle the CCVD_PASSWORD subcommand.
  *
  * The payload of the command is a text string to use to set or clear the
@@ -1286,7 +1211,15 @@ static enum vendor_cmd_rc ccd_password(struct vendor_cmd_params *p)
 	char password[CCD_MAX_PASSWORD_SIZE + 1];
 	char *response = p->buffer;
 
-	if (password_state != PASSWORD_ALLOWED_STATE) {
+	/*
+	 * Only allow setting a password from the AP, not USB.  This increases
+	 * the effort required for an attacker to set one externally, even if
+	 * they have access to a system someone left in the opened state.
+	 *
+	 * An attacker can still set testlab mode or open up the CCD config,
+	 * but those changes are reversible by the device owner.
+	 */
+	if (p->flags & VENDOR_CMD_FROM_USB) {
 		p->out_size = 1;
 		*response = EC_ERROR_ACCESS_DENIED;
 		return VENDOR_RC_NOT_ALLOWED;
diff --git a/include/tpm_vendor_cmds.h b/include/tpm_vendor_cmds.h
index 2d460badfa..72dc670b7d 100644
--- a/include/tpm_vendor_cmds.h
+++ b/include/tpm_vendor_cmds.h
@@ -35,9 +35,7 @@ enum vendor_cmd_cc {
 	VENDOR_CC_IMMEDIATE_RESET = 19,
 	VENDOR_CC_INVALIDATE_INACTIVE_RW = 20,
 	VENDOR_CC_COMMIT_NVMEM = 21,
-
-	/* A gap left for the deep sleep control command. */
-
+	/* DEPRECATED(22): deep sleep control command. */
 	VENDOR_CC_REPORT_TPM_STATE = 23,
 	VENDOR_CC_TURN_UPDATE_ON = 24,
 	VENDOR_CC_GET_BOARD_ID = 25,
@@ -46,11 +44,9 @@ enum vendor_cmd_cc {
 	VENDOR_CC_POP_LOG_ENTRY = 28,
 	VENDOR_CC_GET_REC_BTN = 29,
 	VENDOR_CC_RMA_CHALLENGE_RESPONSE = 30,
-
-	/* A gap left for the no longer supported CCD password command. */
-
+	/* DEPRECATED(31): CCD password command (now part of VENDOR_CC_CCD) */
 	VENDOR_CC_DISABLE_RMA = 32,
-	VENDOR_CC_MANAGE_CCD_PWD = 33,
+	/* DEPRECATED(33): Manage CCD password phase */
 	VENDOR_CC_CCD = 34,
 	VENDOR_CC_GET_ALERTS_DATA = 35,
 	VENDOR_CC_SPI_HASH = 36,