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

[Tom Rini]

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.

-- 
Tom
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