From: Simon Glass <sjg@chromium.org>
Date: Tue, 16 Feb 2021 00:08:10 +0000 (-0700)
Subject: image: Add an option to do a full check of the FIT
X-Git-Tag: archive/raspbian/2021.01+dfsg-5+rpi1+deb11u2^2~3
X-Git-Url: https://dgit.raspbian.org/?a=commitdiff_plain;h=7aca3f15e1ff9c4e4083c5d522209fe840c46423;p=u-boot.git

image: Add an option to do a full check of the FIT

Some strange modifications of the FIT can introduce security risks. Add an
option to check it thoroughly, using libfdt's fdt_check_full() function.

Enable this by default if signature verification is enabled.

CVE-2021-27097

Signed-off-by: Simon Glass <sjg@chromium.org>
Reported-by: Bruce Monroe <bruce.monroe@intel.com>
Reported-by: Arie Haenel <arie.haenel@intel.com>
Reported-by: Julien Lenoir <julien.lenoir@intel.com>

Reviewed-By: Daniel Leidert <dleidert@debian.org>
Origin: https://github.com/u-boot/u-boot/commit/6f3c2d8aa5e6cbd80b5e869bbbddecb66c329d01
Bug: https://github.com/advisories/GHSA-3w66-96j7-fmcp
Bug-Debian: https://bugs.debian.org/983270
Bug-Debian-Security: https://security-tracker.debian.org/tracker/CVE-2021-27097
Bug-Freexian-Security: https://deb.freexian.com/extended-lts/tracker/CVE-2021-27097

Gbp-Pq: Name CVE-2021-27097-3.patch
---

diff --git a/common/Kconfig.boot b/common/Kconfig.boot
index 3f6d9c1a2..af906306d 100644
--- a/common/Kconfig.boot
+++ b/common/Kconfig.boot
@@ -63,6 +63,15 @@ config FIT_ENABLE_SHA512_SUPPORT
 	  SHA512 checksum is a 512-bit (64-byte) hash value used to check that
 	  the image contents have not been corrupted.
 
+config FIT_FULL_CHECK
+	bool "Do a full check of the FIT before using it"
+	default y
+	help
+	  Enable this do a full check of the FIT to make sure it is valid. This
+	  helps to protect against carefully crafted FITs which take advantage
+	  of bugs or omissions in the code. This includes a bad structure,
+	  multiple root nodes and the like.
+
 config FIT_SIGNATURE
 	bool "Enable signature verification of FIT uImages"
 	depends on DM
@@ -70,6 +79,7 @@ config FIT_SIGNATURE
 	select RSA
 	select RSA_VERIFY
 	select IMAGE_SIGN_INFO
+	select FIT_FULL_CHECK
 	help
 	  This option enables signature verification of FIT uImages,
 	  using a hash signed and verified using RSA. If
@@ -153,6 +163,15 @@ config SPL_FIT_PRINT
 	help
 	  Support printing the content of the fitImage in a verbose manner in SPL.
 
+config SPL_FIT_FULL_CHECK
+	bool "Do a full check of the FIT before using it"
+	help
+	  Enable this do a full check of the FIT to make sure it is valid. This
+	  helps to protect against carefully crafted FITs which take advantage
+	  of bugs or omissions in the code. This includes a bad structure,
+	  multiple root nodes and the like.
+
+
 config SPL_FIT_SIGNATURE
 	bool "Enable signature verification of FIT firmware within SPL"
 	depends on SPL_DM
@@ -162,6 +181,7 @@ config SPL_FIT_SIGNATURE
 	select SPL_RSA
 	select SPL_RSA_VERIFY
 	select SPL_IMAGE_SIGN_INFO
+	select SPL_FIT_FULL_CHECK
 
 config SPL_LOAD_FIT
 	bool "Enable SPL loading U-Boot as a FIT (basic fitImage features)"
diff --git a/common/image-fit.c b/common/image-fit.c
index 442433e55..b9edcc7a4 100644
--- a/common/image-fit.c
+++ b/common/image-fit.c
@@ -1564,6 +1564,22 @@ int fit_check_format(const void *fit, ulong size)
 		return -ENOEXEC;
 	}
 
+	if (CONFIG_IS_ENABLED(FIT_FULL_CHECK)) {
+		/*
+		 * If we are not given the size, make do wtih calculating it.
+		 * This is not as secure, so we should consider a flag to
+		 * control this.
+		 */
+		if (size == IMAGE_SIZE_INVAL)
+			size = fdt_totalsize(fit);
+		ret = fdt_check_full(fit, size);
+
+		if (ret) {
+			log_debug("FIT check error %d\n", ret);
+			return -EINVAL;
+		}
+	}
+
 	/* mandatory / node 'description' property */
 	if (!fdt_getprop(fit, 0, FIT_DESC_PROP, NULL)) {
 		log_debug("Wrong FIT format: no description\n");