fit: Don't allow verification of images with @ nodes

When searching for a node called 'fred', any unit address appended to the
name is ignored by libfdt, meaning that 'fred' can match 'fred@1'. This
means that we cannot be sure that the node originally intended is the one
that is used.

Disallow use of nodes with unit addresses.

Update the forge test also, since it uses @ addresses.

CVE-2021-27138

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>

common/image-fit-sig.c

@@ -149,6 +149,14 @@ static int fit_image_verify_sig(const void *fit, int image_noffset,
 	fdt_for_each_subnode(noffset, fit, image_noffset) {
 		const char *name = fit_get_name(fit, noffset, NULL);
 
+		/*
+		 * We don't support this since libfdt considers names with the
+		 * name root but different @ suffix to be equal
+		 */
+		if (strchr(name, '@')) {
+			err_msg = "Node name contains @";
+			goto error;
+		}
 		if (!strncmp(name, FIT_SIG_NODENAME,
 			     strlen(FIT_SIG_NODENAME))) {
 			ret = fit_image_check_sig(fit, noffset, data,
@@ -398,9 +406,10 @@ error:
 	return -EPERM;
 }
 
-int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
+static int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
-				    const void *sig_blob)
+					   const void *sig_blob)
 {
+	const char *name = fit_get_name(fit, conf_noffset, NULL);
 	int noffset;
 	int sig_node;
 	int verified = 0;
@@ -408,6 +417,15 @@ int fit_config_verify_required_sigs(const void *fit, int conf_noffset,
 	bool reqd_policy_all = true;
 	const char *reqd_mode;
 
+	/*
+	 * We don't support this since libfdt considers names with the
+	 * name root but different @ suffix to be equal
+	 */
+	if (strchr(name, '@')) {
+		printf("Configuration node '%s' contains '@'\n", name);
+		return -EPERM;
+	}
+
 	/* Work out what we need to verify */
 	sig_node = fdt_subnode_offset(sig_blob, 0, FIT_SIG_NODENAME);
 	if (sig_node < 0) {

common/image-fit.c

@@ -1369,21 +1369,31 @@ error:
  */
 int fit_image_verify(const void *fit, int image_noffset)
 {
+	const char *name = fit_get_name(fit, image_noffset, NULL);
 	const void	*data;
 	size_t		size;
-	int		noffset = 0;
 	char		*err_msg = "";
 
+	if (strchr(name, '@')) {
+		/*
+		 * We don't support this since libfdt considers names with the
+		 * name root but different @ suffix to be equal
+		 */
+		err_msg = "Node name contains @";
+		goto err;
+	}
 	/* Get image data and data length */
 	if (fit_image_get_data_and_size(fit, image_noffset, &data, &size)) {
 		err_msg = "Can't get image data/size";
-		printf("error!\n%s for '%s' hash node in '%s' image node\n",
+		goto err;
-		       err_msg, fit_get_name(fit, noffset, NULL),
-		       fit_get_name(fit, image_noffset, NULL));
-		return 0;
 	}
 
 	return fit_image_verify_with_data(fit, image_noffset, data, size);
+
+err:
+	printf("error!\n%s in '%s' image node\n", err_msg,
+	       fit_get_name(fit, image_noffset, NULL));
+	return 0;
 }
 
 /**

test/py/tests/test_fit.py

@@ -17,7 +17,7 @@ base_its = '''
         #address-cells = <1>;
 
         images {
-                kernel@1 {
+                kernel-1 {
                         data = /incbin/("%(kernel)s");
                         type = "kernel";
                         arch = "sandbox";
@@ -26,7 +26,7 @@ base_its = '''
                         load = <0x40000>;
                         entry = <0x8>;
                 };
-                kernel@2 {
+                kernel-2 {
                         data = /incbin/("%(loadables1)s");
                         type = "kernel";
                         arch = "sandbox";
@@ -35,19 +35,19 @@ base_its = '''
                         %(loadables1_load)s
                         entry = <0x0>;
                 };
-                fdt@1 {
+                fdt-1 {
                         description = "snow";
                         data = /incbin/("%(fdt)s");
                         type = "flat_dt";
                         arch = "sandbox";
                         %(fdt_load)s
                         compression = "%(compression)s";
-                        signature@1 {
+                        signature-1 {
                                 algo = "sha1,rsa2048";
                                 key-name-hint = "dev";
                         };
                 };
-                ramdisk@1 {
+                ramdisk-1 {
                         description = "snow";
                         data = /incbin/("%(ramdisk)s");
                         type = "ramdisk";
@@ -56,7 +56,7 @@ base_its = '''
                         %(ramdisk_load)s
                         compression = "%(compression)s";
                 };
-                ramdisk@2 {
+                ramdisk-2 {
                         description = "snow";
                         data = /incbin/("%(loadables2)s");
                         type = "ramdisk";
@@ -67,10 +67,10 @@ base_its = '''
                 };
         };
         configurations {
-                default = "conf@1";
+                default = "conf-1";
-                conf@1 {
+                conf-1 {
-                        kernel = "kernel@1";
+                        kernel = "kernel-1";
-                        fdt = "fdt@1";
+                        fdt = "fdt-1";
                         %(ramdisk_config)s
                         %(loadables_config)s
                 };
@@ -410,7 +410,7 @@ def test_fit(u_boot_console):
 
         # Try a ramdisk
         with cons.log.section('Kernel + FDT + Ramdisk load'):
-            params['ramdisk_config'] = 'ramdisk = "ramdisk@1";'
+            params['ramdisk_config'] = 'ramdisk = "ramdisk-1";'
             params['ramdisk_load'] = 'load = <%#x>;' % params['ramdisk_addr']
             fit = make_fit(mkimage, params)
             cons.restart_uboot()
@@ -419,7 +419,7 @@ def test_fit(u_boot_console):
 
         # Configuration with some Loadables
         with cons.log.section('Kernel + FDT + Ramdisk load + Loadables'):
-            params['loadables_config'] = 'loadables = "kernel@2", "ramdisk@2";'
+            params['loadables_config'] = 'loadables = "kernel-2", "ramdisk-2";'
             params['loadables1_load'] = ('load = <%#x>;' %
                                          params['loadables1_addr'])
             params['loadables2_load'] = ('load = <%#x>;' %

test/py/tests/vboot_forge.py

@@ -376,12 +376,12 @@ def manipulate(root, strblock):
     """
     Maliciously manipulates the structure to create a crafted FIT file
     """
-    # locate /images/kernel@1 (frankly, it just expects it to be the first one)
+    # locate /images/kernel-1 (frankly, it just expects it to be the first one)
     kernel_node = root[0][0]
     # clone it to save time filling all the properties
     fake_kernel = kernel_node.clone()
     # rename the node
-    fake_kernel.name = b'kernel@2'
+    fake_kernel.name = b'kernel-2'
     # get rid of signatures/hashes
     fake_kernel.children = []
     # NOTE: this simply replaces the first prop... either description or data
@@ -391,13 +391,13 @@ def manipulate(root, strblock):
     root[0].children.append(fake_kernel)
 
     # modify the default configuration
-    root[1].props[0].value = b'conf@2\x00'
+    root[1].props[0].value = b'conf-2\x00'
     # clone the first (only?) configuration
     fake_conf = root[1][0].clone()
     # rename and change kernel and fdt properties to select the crafted kernel
-    fake_conf.name = b'conf@2'
+    fake_conf.name = b'conf-2'
-    fake_conf.props[0].value = b'kernel@2\x00'
+    fake_conf.props[0].value = b'kernel-2\x00'
-    fake_conf.props[1].value = b'fdt@1\x00'
+    fake_conf.props[1].value = b'fdt-1\x00'
     # insert the new configuration under /configurations
     root[1].children.append(fake_conf)