[U-Boot] [PATCH 5/9] arm: omap-common: secure ROM signature verify API

[Lokesh Vutla]

On Wednesday 22 June 2016 05:26 AM, Tom Rini wrote:
> On Tue, Jun 21, 2016 at 10:01:54AM +0530, Lokesh Vutla wrote:
>>
>>
>> On Tuesday 21 June 2016 09:04 AM, Andreas Dannenberg wrote:
>>> Adds an API that verifies a signature attached to an image (binary
>>> blob). This API is basically a entry to a secure ROM service provided by
>>> the device and accessed via an SMC call, using a particular calling
>>> convention.
>>>
>>> Signed-off-by: Daniel Allred <d-allred at ti.com>
>>> Signed-off-by: Andreas Dannenberg <dannenberg at ti.com>
>>> ---
>>>  arch/arm/cpu/armv7/omap-common/sec-common.c | 76 +++++++++++++++++++++++++++++
>>>  arch/arm/include/asm/omap_common.h          |  9 ++++
>>>  2 files changed, 85 insertions(+)
>>>
>>> diff --git a/arch/arm/cpu/armv7/omap-common/sec-common.c b/arch/arm/cpu/armv7/omap-common/sec-common.c
>>> index b9c0a42..dbb9078 100644
>>> --- a/arch/arm/cpu/armv7/omap-common/sec-common.c
>>> +++ b/arch/arm/cpu/armv7/omap-common/sec-common.c
>>> @@ -16,6 +16,9 @@
>>>  #include <asm/arch/sys_proto.h>
>>>  #include <asm/omap_common.h>
>>>  
>>> +/* Index for signature verify ROM API */
>>> +#define API_HAL_KM_VERIFYCERTIFICATESIGNATURE_INDEX	(0x0000000E)
>>> +
>>>  static uint32_t secure_rom_call_args[5] __aligned(ARCH_DMA_MINALIGN);
>>>  
>>>  u32 secure_rom_call(u32 service, u32 proc_id, u32 flag, ...)
>>> @@ -47,3 +50,76 @@ u32 secure_rom_call(u32 service, u32 proc_id, u32 flag, ...)
>>>  
>>>  	return omap_smc_sec(service, proc_id, flag, secure_rom_call_args);
>>>  }
>>> +
>>> +static u32 find_sig_start(char *image, size_t size)
>>> +{
>>> +	char *image_end = image + size;
>>> +	char *sig_start_magic = "CERT_";
>>> +	int magic_str_len = strlen(sig_start_magic);
>>> +	char *ch;
>>> +
>>> +	while (--image_end > image) {
>>> +		if (*image_end == '_') {
>>> +			ch = image_end - magic_str_len + 1;
>>> +			if (!strncmp(ch, sig_start_magic, magic_str_len))
>>> +				return (u32)ch;
>>> +		}
>>> +	}
>>> +	return 0;
>>> +}
>>> +
>>> +int secure_boot_verify_image(void **image, size_t *size)
>>> +{
>>> +	int result = 1;
>>> +	u32 cert_addr, sig_addr;
>>> +	size_t cert_size;
>>> +
>>> +	/* Perform cache writeback on input buffer */
>>> +	flush_dcache_range(
>>> +		(u32)*image,
>>> +		(u32)*image + roundup(*size, ARCH_DMA_MINALIGN));
>>> +
>>> +	cert_addr = (uint32_t)*image;
>>> +	sig_addr = find_sig_start((char *)*image, *size);
>>> +
>>> +	if (sig_addr == 0) {
>>> +		printf("No signature found in image.\n");
>>> +		result = 1;
>>> +		goto auth_exit;
>>> +	}
>>> +
>>> +	*size = sig_addr - cert_addr;	/* Subtract out the signature size */
>>> +	cert_size = *size;
>>> +
>>> +	/* Check if image load address is 32-bit aligned */
>>> +	if (0 != (0x3 & cert_addr)) {
>>
>> 	if (!IS_ALIGNED(cert_addr, 4)) { ?
>>
>>> +		printf("Image is not 4-byte aligned.\n");
>>> +		result = 1;
>>> +		goto auth_exit;
>>> +	}
>>> +
>>> +	/* Image size also should be multiple of 4 */
>>> +	if (0 != (0x3 & cert_size)) {
>>
>> 	if (!IS_ALIGNED(cert_size, 4)) { ?
>>
>>> +		printf("Image size is not 4-byte aligned.\n");
>>> +		result = 1;
>>> +		goto auth_exit;
>>> +	}
>>> +
>>> +	/* Call ROM HAL API to verify certificate signature */
>>> +	debug("%s: load_addr = %x, size = %x, sig_addr = %x\n", __func__,
>>> +	      cert_addr, cert_size, sig_addr);
>>> +
>>> +	result = secure_rom_call(
>>> +		API_HAL_KM_VERIFYCERTIFICATESIGNATURE_INDEX, 0, 0,
>>> +		4, cert_addr, cert_size, sig_addr, 0xFFFFFFFF);
>>> +auth_exit:
>>> +	if (result != 0) {
>>> +		printf("Authentication failed!\n");
>>> +		printf("Return Value = %08X\n", result);
>>> +		hang();
>>> +	}
>>> +
>>> +	printf("Authentication passed: %s\n", (char *)sig_addr);
>>
>> Uart boot will break because of these prints during the FIT loading. Can
>> you make this as debug?
> 
> Are you sure it will break?  There's usually a print in between loading
> SPL via UART and then U-Boot itself via UART and Y-MODEM is smart enough
> to re-transmit.
> 

Yes, if the print is in between while Y-MODEM is transferring. The above
print falls in this case.

Thanks and regards,
Lokesh