Revert "common: replace safe_memcmp with cryptoc version"

This reverts commit 85554f0a843daa1c85ba252c7a27a389968d347b.

Reason for revert: Broke gitlab (https://gitlab.com/zephyr-ec/ec/-/pipelines/651162463) and also CQ emerge builds (https://ci.chromium.org/ui/p/chromeos/builders/postsubmit/nissa-postsubmit/16030/overview)

Original change's description:
> common: replace safe_memcmp with cryptoc version
>
> We now have to always link against cryptoc, but it does not increase
> code size on our most constrained boards:
>
> Before and after both show:
>
> Smallest free spaces in RO flash (bytes):
> pdeval-stm32f072: 88
> servo_v4  :       104
> fusb307bgevb:     156
>
> Smallest free spaces in RW flash (bytes):
> volteer   :    516
> bobba     :    712
> meep      :    716
>
> Tightest boards' RW RAM images, bytes free:
> whiskers  :    212
> minimuffin:    284
> zinger    :    284
>
> BRANCH=none
> BUG=b:169156874
> TEST=make buildall
>
> Signed-off-by: Tom Hughes <tomhughes@chromium.org>
> Change-Id: I98422eccb3e903bd82ddb386087dd2d55d1f845e
> Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/2424068
> Reviewed-by: Denis Brockus <dbrockus@chromium.org>
> Code-Coverage: Zoss <zoss-cl-coverage@prod.google.com>

Bug: b:169156874
Change-Id: I794ae31f9e217677471b0ff164fadc9623571a33
Reviewed-on: https://chromium-review.googlesource.com/c/chromiumos/platform/ec/+/3919500
Commit-Queue: Raul Rangel <rrangel@chromium.org>
Commit-Queue: Jeremy Bettis <jbettis@chromium.org>
Reviewed-by: Raul Rangel <rrangel@chromium.org>
Tested-by: Jeremy Bettis <jbettis@chromium.org>
Auto-Submit: Jeremy Bettis <jbettis@chromium.org>

7 files changed, 34 insertions, 15 deletions

diff --git a/board/host/board.h b/board/host/board.h
index a0099c38fe..165331ce4c 100644
--- a/board/host/board.h
+++ b/board/host/board.h
@@ -25,6 +25,8 @@
 
 #define CONFIG_WP_ACTIVE_HIGH
 
+#define CONFIG_LIBCRYPTOC
+
 #define CONFIG_USB_PD_CUSTOM_PDO
 #define CONFIG_USB_PD_DUAL_ROLE
 
diff --git a/common/rollback.c b/common/rollback.c
index 3d61cd4d95..20dcbe4aa9 100644
--- a/common/rollback.c
+++ b/common/rollback.c
@@ -8,7 +8,9 @@
 #include "builtin/assert.h"
 #include "common.h"
 #include "console.h"
+#ifdef CONFIG_LIBCRYPTOC
 #include "cryptoc/util.h"
+#endif
 #include "flash.h"
 #include "hooks.h"
 #include "host_command.h"
diff --git a/common/util.c b/common/util.c
index b19fcd1d99..7672dc1325 100644
--- a/common/util.c
+++ b/common/util.c
@@ -8,7 +8,6 @@
 #include "builtin/assert.h"
 #include "common.h"
 #include "console.h"
-#include "cryptoc/util.h"
 #include "util.h"
 
 int find_base(int base, int *c, const char **nptr)
@@ -86,7 +85,21 @@ int parse_bool(const char *s, int *dest)
 /* Constant-time memory comparison */
 int safe_memcmp(const void *s1, const void *s2, size_t size)
 {
-	return ct_memeq(s1, s2, size);
+	const uint8_t *us1 = s1;
+	const uint8_t *us2 = s2;
+	int result = 0;
+
+	if (size == 0)
+		return 0;
+
+	/*
+	 * Code snippet without data-dependent branch due to Nate Lawson
+	 * (nate@root.org) of Root Labs.
+	 */
+	while (size--)
+		result |= *us1++ ^ *us2++;
+
+	return result != 0;
 }
 
 void reverse(void *dest, size_t len)
diff --git a/include/config.h b/include/config.h
index 9257a5884e..8ca7973093 100644
--- a/include/config.h
+++ b/include/config.h
@@ -396,6 +396,9 @@
 /* Define which ALS sensor is used for dimming the lightbar when dark */
 #undef CONFIG_ALS_LIGHTBAR_DIMMING
 
+/* Link against third_party/cryptoc. */
+#undef CONFIG_LIBCRYPTOC
+
 /* Support AP hang detection host command and state machine */
 #undef CONFIG_AP_HANG_DETECT
 
@@ -6248,6 +6251,14 @@
 
 /*****************************************************************************/
 /*
+ * Define CONFIG_LIBCRYPTOC if a board needs to read secret data from the
+ * anti-rollback block.
+ */
+#ifdef CONFIG_ROLLBACK_SECRET_SIZE
+#define CONFIG_LIBCRYPTOC
+#endif
+
+/*
  * Handle task-dependent configs.
  *
  * This prevent sub-modules from being compiled when the task and parent module
diff --git a/third_party/rules.mk b/third_party/rules.mk
index 38ebcf8d3f..eb4391b70c 100644
--- a/third_party/rules.mk
+++ b/third_party/rules.mk
@@ -9,6 +9,7 @@
 
 # Build and link against libcryptoc.
 # See https://chromium.googlesource.com/chromiumos/third_party/cryptoc .
+ifeq ($(CONFIG_LIBCRYPTOC),y)
 
 # The cryptoc path can be overridden on invocation, as in the following example:
 # $ make CRYPTOC_DIR=~/src/cryptoc BOARD=bloonchipper
@@ -52,3 +53,5 @@ test-targets=$(foreach test,$(test-list-y),\
 	$(out)/RW/$(test).RW.elf $(out)/RO/$(test).RO.elf)
 $(test-targets): LDFLAGS_EXTRA += $(CRYPTOC_LDFLAGS)
 $(test-targets): $(out)/cryptoc/libcryptoc.a
+
+endif # CONFIG_LIBCRYPTOC
diff --git a/util/config_allowed.txt b/util/config_allowed.txt
index f9180640c8..7a8e3ffbba 100644
--- a/util/config_allowed.txt
+++ b/util/config_allowed.txt
@@ -600,6 +600,7 @@ CONFIG_LED_PWM_ACTIVE_CHARGE_PORT_ONLY
 CONFIG_LED_PWM_CHARGE_STATE_ONLY
 CONFIG_LED_PWM_COUNT
 CONFIG_LFW_OFFSET
+CONFIG_LIBCRYPTOC
 CONFIG_LID_ANGLE_INVALID_CHECK
 CONFIG_LID_ANGLE_SENSOR_BASE
 CONFIG_LID_ANGLE_SENSOR_LID
diff --git a/zephyr/CMakeLists.txt b/zephyr/CMakeLists.txt
index 6f57cb5d40..7a71823bc8 100644
--- a/zephyr/CMakeLists.txt
+++ b/zephyr/CMakeLists.txt
@@ -130,19 +130,6 @@ endif()
 
 add_subdirectory("subsys")
 
-set(cryptoc_dir "../../../third_party/cryptoc")
-zephyr_library_sources(
-        ${cryptoc_dir}/hmac.c
-        ${cryptoc_dir}/md5.c
-        ${cryptoc_dir}/p256.c
-        ${cryptoc_dir}/p256_ec.c
-        ${cryptoc_dir}/p256_ecdsa.c
-        ${cryptoc_dir}/p256_prng.c
-        ${cryptoc_dir}/sha224.c
-        ${cryptoc_dir}/util.c
-)
-zephyr_library_include_directories(${cryptoc_dir}/include)
-
 # Creates a phony target all.libraries in case you only want to build the
 # libraries and not the binaries. For example for creating the initial zero
 # coverage files.