Re: [PATCH v2 2/2] cmd: mvebu/bubt: Check for A38x/A37xx OTP secure bits and secure boot

On Tuesday 23 August 2022 07:05:33 Stefan Roese wrote:

Hi Pali,

On 09.08.22 21:42, Pali Rohár wrote:

...

For obvious reasons BootROMS rejects unsigned images when secure boot is enabled in OTP secure bits. So check for OPT secure bits and do not allow flashing unsigned images when secure boot is enabled. Access to OTP via U-Boot fuse API is currently implemented only for A38x and A37xx SoCs.

Additionally Armada 3700 BootROM rejects signed trusted image when secure boot is not enabled in OTP. So add also check for this case. On the other hand Armada 38x BootROM acceps images with secure boot header when secure boot is not enabled in OTP.

OTP secure bits may have burned also boot device source. Check it also and reject flashing images to target storage which does not match OTP.

Signed-off-by: Pali Rohár pali@kernel.org

---

Changes in v2:

• Add missing dependency on MVEBU_EFUSE
• Use only for A38x and A37xx

Running a world CI build leads to these errors:

$ make clearfog_gt_8k_defconfig ... $ make -sj cmd/mvebu/bubt.c:809:12: warning: 'fuse_read_u64' defined but not used [-Wunused-function] 809 | static u64 fuse_read_u64(u32 bank) | ^~~~~~~~~~~~~

Could you please please take a look and fix this issue?

There is missing guard to not compile that function for A7k/A8k. I will fix it in v3.

Thanks, Stefan

...

---

cmd/mvebu/Kconfig | 1 + cmd/mvebu/bubt.c | 127 +++++++++++++++++++++++++++++++++++++++++++--- 2 files changed, 120 insertions(+), 8 deletions(-)

diff --git a/cmd/mvebu/Kconfig b/cmd/mvebu/Kconfig index 120397d6d4d0..9ec3aa983a51 100644 --- a/cmd/mvebu/Kconfig +++ b/cmd/mvebu/Kconfig @@ -5,6 +5,7 @@ config CMD_MVEBU_BUBT bool "bubt" select SHA256 if ARMADA_3700 select SHA512 if ARMADA_3700

• select MVEBU_EFUSE if ARMADA_38X || ARMADA_3700 help bubt - Burn a u-boot image to flash For details about bubt command please see the documentation

diff --git a/cmd/mvebu/bubt.c b/cmd/mvebu/bubt.c index 3b6ffb7ffd1f..feb1e778a98c 100644 --- a/cmd/mvebu/bubt.c +++ b/cmd/mvebu/bubt.c @@ -13,6 +13,8 @@ #include <vsprintf.h> #include <errno.h> #include <dm.h> +#include <fuse.h> +#include <mach/efuse.h> #include <spi_flash.h> #include <spi.h> @@ -121,6 +123,17 @@ struct a38x_main_hdr_v1 { u8 checksum; /* 0x1F */ }; +/*

• • Header for the optional headers, version 1 (Armada 370/XP/375/38x/39x)
• */

+struct a38x_opt_hdr_v1 {

• u8 headertype;
• u8 headersz_msb;
• u16 headersz_lsb;
• u8 data[0];

+}; +#define A38X_OPT_HDR_V1_SECURE_TYPE 0x1

• struct a38x_boot_mode { unsigned int id; const char *name;

@@ -706,6 +719,7 @@ static int check_image_header(void) { u8 checksum; u32 checksum32, exp_checksum32;

• u32 offset, size; const struct a38x_main_hdr_v1 *hdr = (struct a38x_main_hdr_v1 *)get_load_addr(); const size_t image_size = a38x_header_size(hdr);

@@ -752,6 +766,38 @@ static int check_image_header(void) printf("Image checksum...OK!\n"); return 0; }

+#if defined(CONFIG_ARMADA_38X) +static int a38x_image_is_secure(const struct a38x_main_hdr_v1 *hdr) +{

• u32 image_size = a38x_header_size(hdr);
• struct a38x_opt_hdr_v1 *ohdr;
• u32 ohdr_size;
• if (hdr->version != 1)

• return 0;
  

• if (!hdr->ext)

• return 0;
  

• ohdr = (struct a38x_opt_hdr_v1 *)(hdr + 1);
• do {

• if (ohdr->headertype == A38X_OPT_HDR_V1_SECURE_TYPE)
  

• 	return 1;
  

• ohdr_size = (ohdr->headersz_msb << 16) | le16_to_cpu(ohdr->headersz_lsb);
  

• if (!*((u8 *)ohdr + ohdr_size - 4))
  

• 	break;
  

• ohdr = (struct a38x_opt_hdr_v1 *)((u8 *)ohdr + ohdr_size);
  

• if ((u8 *)ohdr >= (u8 *)hdr + image_size)
  

• 	break;
  

• } while (1);
• return 0;

+} +#endif #else /* Not ARMADA? */ static int check_image_header(void) { @@ -760,20 +806,58 @@ static int check_image_header(void) } #endif +static u64 fuse_read_u64(u32 bank) +{

• u32 val[2];
• int ret;
• ret = fuse_read(bank, 0, &val[0]);
• if (ret < 0)

• return -1;
  

• ret = fuse_read(bank, 1, &val[1]);
• if (ret < 0)

• return -1;
  

• return ((u64)val[1] << 32) | val[0];

+}

+#if defined(CONFIG_ARMADA_3700) +static inline u8 maj3(u8 val) +{

• /* return majority vote of 3 bits */
• return ((val & 0x7) == 3 || (val & 0x7) > 4) ? 1 : 0;

+} +#endif

• static int bubt_check_boot_mode(const struct bubt_dev *dst) { #if defined(CONFIG_ARMADA_3700) || defined(CONFIG_ARMADA_32BIT)

• int mode;

• int mode, secure_mode; #if defined(CONFIG_ARMADA_3700) const struct tim_boot_flash_sign *boot_modes = tim_boot_flash_signs; const struct common_tim_data *hdr = (struct common_tim_data *)get_load_addr(); u32 id = hdr->boot_flash_sign;
• int is_secure = hdr->trusted != 0;
• u64 otp_secure_bits = fuse_read_u64(1);
• int otp_secure_boot = ((maj3(otp_secure_bits >> 0) << 0) |

• 	       (maj3(otp_secure_bits >> 4) << 1)) == 2;
  

• unsigned int otp_boot_device = (maj3(otp_secure_bits >> 48) << 0) |

• 		       (maj3(otp_secure_bits >> 52) << 1) |
  

• 		       (maj3(otp_secure_bits >> 56) << 2) |
  

• 		       (maj3(otp_secure_bits >> 60) << 3);
  

  #elif defined(CONFIG_ARMADA_32BIT) const struct a38x_boot_mode *boot_modes = a38x_boot_modes; const struct a38x_main_hdr_v1 *hdr = (struct a38x_main_hdr_v1 *)get_load_addr(); u32 id = hdr->blockid;

+#if defined(CONFIG_ARMADA_38X)

• int is_secure = a38x_image_is_secure(hdr);
• u64 otp_secure_bits = fuse_read_u64(EFUSE_LINE_SECURE_BOOT);
• int otp_secure_boot = otp_secure_bits & 0x1;
• unsigned int otp_boot_device = (otp_secure_bits >> 8) & 0x7;

+#endif #endif for (mode = 0; boot_modes[mode].name; mode++) { @@ -786,15 +870,42 @@ static int bubt_check_boot_mode(const struct bubt_dev *dst) return -ENOEXEC; }

• if (strcmp(boot_modes[mode].name, dst->name) == 0)

• return 0;
  

• if (strcmp(boot_modes[mode].name, dst->name) != 0) {

• printf("Error: image meant to be booted from \"%s\", not \"%s\"!\n",
  

•        boot_modes[mode].name, dst->name);
  

• return -ENOEXEC;
  

• }

• printf("Error: image meant to be booted from "%s", not "%s"!\n",

•       boot_modes[mode].name, dst->name);
  

• return -ENOEXEC;

-#else

• return 0;

+#if defined(CONFIG_ARMADA_38X) || defined(CONFIG_ARMADA_3700)

• if (otp_secure_bits == (u64)-1) {

• printf("Error: cannot read OTP secure bits\n");
  

• return -ENOEXEC;
  

• } else {

• if (otp_secure_boot && !is_secure) {
  

• 	printf("Error: secure boot is enabled in OTP but image does not have secure boot header!\n");
  

• 	return -ENOEXEC;
  

• } else if (!otp_secure_boot && is_secure) {
  

+#if defined(CONFIG_ARMADA_3700)

• 	/*
  

• 	 * Armada 3700 BootROM rejects trusted image when secure boot is not enabled.
  

• 	 * Armada 385 BootROM accepts image with secure boot header also when secure boot is not enabled.
  

• 	 */
  

• 	printf("Error: secure boot is disabled in OTP but image has secure boot header!\n");
  

• 	return -ENOEXEC;
  

  #endif

• } else if (otp_boot_device && otp_boot_device != id) {
  

• 	for (secure_mode = 0; boot_modes[secure_mode].name; secure_mode++) {
  

• 		if (boot_modes[secure_mode].id == otp_boot_device)
  

• 			break;
  

• 	}
  

• 	printf("Error: boot source is set to \"%s\" in OTP but image is for \"%s\"!\n",
  

• 	       boot_modes[secure_mode].name ?: "unknown", dst->name);
  

• 	return -ENOEXEC;
  

• }
  

• }

+#endif +#endif

• return 0; } static int bubt_verify(const struct bubt_dev *dst)

Viele Grüße, Stefan Roese

-- DENX Software Engineering GmbH, Managing Director: Wolfgang Denk HRB 165235 Munich, Office: Kirchenstr.5, D-82194 Groebenzell, Germany Phone: (+49)-8142-66989-51 Fax: (+49)-8142-66989-80 Email: sr@denx.de