[PATCH 1/2] tools: add fdt_add_pubkey
Jan Kiszka
jan.kiszka at siemens.com
Wed Nov 10 22:15:36 CET 2021
On 08.11.21 16:28, Roman Kopytin wrote:
> Having to use the -K option to mkimage to populate U-Boot's .dtb with the
> public key while signing the kernel FIT image is often a little
> awkward. In particular, when using a meta-build system such as
> bitbake/Yocto, having the tasks of the kernel and U-Boot recipes
> intertwined, modifying deployed artifacts and rebuilding U-Boot with
> an updated .dtb is quite cumbersome. Also, in some scenarios one may
> wish to build U-Boot complete with the public key(s) embedded in the
> .dtb without the corresponding private keys being present on the same
> build host.
>
> So this adds a simple tool that allows one to disentangle the kernel
> and U-Boot builds, by simply copy-pasting just enough of the mkimage
> code to allow one to add a public key to a .dtb. When using mkimage,
> some of the information is taken from the .its used to build the
> kernel (algorithm and key name), so that of course needs to be
> supplied on the command line.
>
> Signed-off-by: Roman Kopytin <Roman.Kopytin at kaspersky.com>
> Cc: Rasmus Villemoes <rasmus.villemoes at prevas.dk>
> ---
> tools/.gitignore | 1 +
> tools/Makefile | 3 ++
> tools/fdt_add_pubkey.c | 97 ++++++++++++++++++++++++++++++++++++++++++
> 3 files changed, 101 insertions(+)
> create mode 100755 tools/fdt_add_pubkey.c
>
> diff --git a/tools/.gitignore b/tools/.gitignore
> index a88453f64d..f312b760e4 100644
> --- a/tools/.gitignore
> +++ b/tools/.gitignore
> @@ -6,6 +6,7 @@
> /dumpimage
> /easylogo/easylogo
> /envcrc
> +/fdt_add_pubkey
> /fdtgrep
> /file2include
> /fit_check_sign
> diff --git a/tools/Makefile b/tools/Makefile
> index 4a86321f64..44f25dda18 100644
> --- a/tools/Makefile
> +++ b/tools/Makefile
> @@ -73,6 +73,7 @@ mkenvimage-objs := mkenvimage.o os_support.o lib/crc32.o
>
> hostprogs-y += dumpimage mkimage
> hostprogs-$(CONFIG_TOOLS_LIBCRYPTO) += fit_info fit_check_sign
> +hostprogs-$(CONFIG_TOOLS_LIBCRYPTO) += fdt_add_pubkey
>
> hostprogs-$(CONFIG_CMD_BOOTEFI_SELFTEST) += file2include
>
> @@ -153,6 +154,7 @@ dumpimage-objs := $(dumpimage-mkimage-objs) dumpimage.o
> mkimage-objs := $(dumpimage-mkimage-objs) mkimage.o
> fit_info-objs := $(dumpimage-mkimage-objs) fit_info.o
> fit_check_sign-objs := $(dumpimage-mkimage-objs) fit_check_sign.o
> +fdt_add_pubkey-objs := $(dumpimage-mkimage-objs) fdt_add_pubkey.o
> file2include-objs := file2include.o
>
> ifneq ($(CONFIG_MX23)$(CONFIG_MX28)$(CONFIG_TOOLS_LIBCRYPTO),)
> @@ -190,6 +192,7 @@ HOSTCFLAGS_fit_image.o += -DMKIMAGE_DTC=\"$(CONFIG_MKIMAGE_DTC_PATH)\"
> HOSTLDLIBS_dumpimage := $(HOSTLDLIBS_mkimage)
> HOSTLDLIBS_fit_info := $(HOSTLDLIBS_mkimage)
> HOSTLDLIBS_fit_check_sign := $(HOSTLDLIBS_mkimage)
> +HOSTLDLIBS_fdt_add_pubkey := $(HOSTLDLIBS_mkimage)
>
> hostprogs-$(CONFIG_EXYNOS5250) += mkexynosspl
> hostprogs-$(CONFIG_EXYNOS5420) += mkexynosspl
> diff --git a/tools/fdt_add_pubkey.c b/tools/fdt_add_pubkey.c
> new file mode 100755
> index 0000000000..9306ecedd1
> --- /dev/null
> +++ b/tools/fdt_add_pubkey.c
> @@ -0,0 +1,97 @@
> +#include <image.h>
> +#include "fit_common.h"
> +
> +static const char *cmdname;
> +
> +static const char *algo_name = "sha1,rsa2048"; /* -a <algo> */
> +static const char *keydir = "."; /* -k <keydir> */
> +static const char *keyname = "key"; /* -n <keyname> */
> +static const char *require_keys; /* -r <conf|image> */
> +static const char *keydest; /* argv[n] */
> +
> +static void usage(const char *msg)
> +{
> + fprintf(stderr, "Error: %s\n", msg);
> + fprintf(stderr, "Usage: %s [-a <algo>] [-k <keydir>] [-n <keyname>] [-r <conf|image>] <fdt blob>\n",
> + cmdname);
> + exit(EXIT_FAILURE);
> +}
> +
> +static void process_args(int argc, char *argv[])
> +{
> + int opt;
> +
> + while((opt = getopt(argc, argv, "a:k:n:r:")) != -1) {
> + switch (opt) {
> + case 'k':
> + keydir = optarg;
> + break;
> + case 'a':
> + algo_name = optarg;
> + break;
> + case 'n':
> + keyname = optarg;
> + break;
> + case 'r':
> + require_keys = optarg;
> + break;
> + default:
> + usage("Invalid option");
> + }
> + }
> + /* The last parameter is expected to be the .dtb to add the public key to */
> + if (optind < argc)
> + keydest = argv[optind];
> +
> + if (!keydest)
> + usage("Missing dtb file to update");
> +}
> +
> +int main(int argc, char *argv[])
> +{
> + struct image_sign_info info;
> + int destfd, ret;
> + void *dest_blob = NULL;
> + struct stat dest_sbuf;
> + size_t size_inc = 0;
> +
> + cmdname = argv[0];
> +
> + process_args(argc, argv);
> +
> + memset(&info, 0, sizeof(info));
> +
> + info.keydir = keydir;
> + info.keyname = keyname;
> + info.name = algo_name;
> + info.require_keys = require_keys;
> + info.crypto = image_get_crypto_algo(algo_name);
> + if (!info.crypto) {
> + fprintf(stderr, "Unsupported signature algorithm '%s'\n", algo_name);
> + exit(EXIT_FAILURE);
> + }
> +
> + while (1) {
> + destfd = mmap_fdt(cmdname, keydest, size_inc, &dest_blob, &dest_sbuf, false, false);
> + if (destfd < 0)
> + exit(EXIT_FAILURE);
> +
> + ret = info.crypto->add_verify_data(&info, dest_blob);
> +
> + munmap(dest_blob, dest_sbuf.st_size);
> + close(destfd);
> + if (!ret || ret != -ENOSPC)
> + break;
> + fprintf(stderr, ".dtb too small, increasing size by 1024 bytes\n");
> + size_inc = 1024;
> + }
> +
> + if (ret) {
> + fprintf(stderr, "%s: Cannot add public key to FIT blob: %s\n",
> + cmdname, strerror(-ret));
> + exit(EXIT_FAILURE);
> + }
> +
> + exit(EXIT_SUCCESS);
> +}
> +
>
I'm playing with this diff on top in order to support embedding into SPL
control FDTs:
diff --git a/tools/fdt_add_pubkey.c b/tools/fdt_add_pubkey.c
index 9306ecedd1..176b6bd37d 100755
--- a/tools/fdt_add_pubkey.c
+++ b/tools/fdt_add_pubkey.c
@@ -50,10 +50,11 @@ static void process_args(int argc, char *argv[])
int main(int argc, char *argv[])
{
struct image_sign_info info;
- int destfd, ret;
+ int signode, keynode, ret;
void *dest_blob = NULL;
struct stat dest_sbuf;
size_t size_inc = 0;
+ int destfd = -1;
cmdname = argv[0];
@@ -71,20 +72,41 @@ int main(int argc, char *argv[])
exit(EXIT_FAILURE);
}
- while (1) {
+ do {
+ if (destfd >= 0) {
+ munmap(dest_blob, dest_sbuf.st_size);
+ close(destfd);
+
+ fprintf(stderr, ".dtb too small, increasing size by 1024 bytes\n");
+ size_inc = 1024;
+ }
+
destfd = mmap_fdt(cmdname, keydest, size_inc, &dest_blob, &dest_sbuf, false, false);
if (destfd < 0)
exit(EXIT_FAILURE);
ret = info.crypto->add_verify_data(&info, dest_blob);
-
- munmap(dest_blob, dest_sbuf.st_size);
- close(destfd);
- if (!ret || ret != -ENOSPC)
+ if (ret == -ENOSPC)
+ continue;
+ else if (ret)
break;
- fprintf(stderr, ".dtb too small, increasing size by 1024 bytes\n");
- size_inc = 1024;
- }
+
+ signode = fdt_path_offset(dest_blob, "/signature");
+ if (signode < 0) {
+ fprintf(stderr, "%s: /signature node not found?!\n",
+ cmdname);
+ exit(EXIT_FAILURE);
+ }
+
+ keynode = fdt_first_subnode(dest_blob, signode);
+ if (keynode < 0) {
+ fprintf(stderr, "%s: /signature/<key> node not found?!\n",
+ cmdname);
+ exit(EXIT_FAILURE);
+ }
+
+ ret = fdt_appendprop(dest_blob, keynode, "u-boot,dm-spl", NULL, 0);
+ } while (ret == -ENOSPC);
if (ret) {
fprintf(stderr, "%s: Cannot add public key to FIT blob: %s\n",
@@ -94,4 +116,3 @@ int main(int argc, char *argv[])
exit(EXIT_SUCCESS);
}
-
This is step one. Step two is a diff - actually still rather a hack due
to some hard-coded options - to use the tool during dtb builds:
diff --git a/common/Kconfig.boot b/common/Kconfig.boot
index d3a12be228..a9ed4d4ec4 100644
--- a/common/Kconfig.boot
+++ b/common/Kconfig.boot
@@ -279,6 +279,14 @@ config SPL_FIT_GENERATOR
endif # SPL
+config FIT_SIGNATURE_PUB_KEYS
+ string "Public keys to use for FIT image verification"
+ depends on FIT_SIGNATURE || SPL_FIT_SIGNATURE
+ help
+ Public keys, or certificate files to extract them from, that shall
+ be used to verify signed FIT images. The keys will be embedded into
+ the control device tree of U-Boot.
+
endif # FIT
config LEGACY_IMAGE_FORMAT
diff --git a/scripts/Makefile.lib b/scripts/Makefile.lib
index 39f03398ed..65852dc1d9 100644
--- a/scripts/Makefile.lib
+++ b/scripts/Makefile.lib
@@ -326,9 +326,12 @@ cmd_dtc = mkdir -p $(dir ${dtc-tmp}) ; \
-d $(depfile).dtc.tmp $(dtc-tmp) || \
(echo "Check $(shell pwd)/$(pre-tmp) for errors" && false) \
; \
+ $(foreach key,$(subst $(quote),,$(CONFIG_FIT_SIGNATURE_PUB_KEYS)), \
+ tools/fdt_add_pubkey -a sha256,rsa4096 -k $(shell dirname $(key)) \
+ -n $(subst .key,,$(shell basename $(key))) -r conf $@;) \
sed "s:$(pre-tmp):$(<):" $(depfile).pre.tmp $(depfile).dtc.tmp > $(depfile)
-$(obj)/%.dtb: $(src)/%.dts FORCE
+$(obj)/%.dtb: $(src)/%.dts tools/fdt_add_pubkey FORCE
$(call if_changed_dep,dtc)
pre-tmp = $(subst $(comma),_,$(dot-target).pre.tmp)
This permits the workflow:
- make flash.bin (via binman)
- mkimage -r -F fit at 0x280000.fit (an embedded FIT in flash.bin)
- binman replace -i flash.bin -f fit at 0x280000.fit fit at 0x280000
(the latter on in theory, that command is broken ATM)
Jan
--
Siemens AG, T RDA IOT
Corporate Competence Center Embedded Linux
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