(restarting this topic, new patches are in the make)
On 2017-02-17 02:30, Bryan O'Donoghue wrote:
>
>
> On 15/02/17 18:14, Jan Kiszka wrote:
>> The firmware for Quark X102x prepends a security header to the capsule
>> which is needed to support the mandatory secure boot on this processor.
>> The header can be detected by checking for the "_CSH" signature and -
>> to avoid any GUID conflict - validating its size field to contain the
>> expected value. Then we need to look for the EFI header right after the
>> security header and pass the image offset to efi_capsule_update while
>> keeping the whole image in RAM - the firmware will look for the header
>> on its own.
>>
>> Signed-off-by: Jan Kiszka <jan.kiszka@xxxxxxxxxxx>
>> ---
>> drivers/firmware/efi/capsule-loader.c | 73
>> ++++++++++++++++++++++++++++++-----
>> 1 file changed, 63 insertions(+), 10 deletions(-)
>>
>> diff --git a/drivers/firmware/efi/capsule-loader.c
>> b/drivers/firmware/efi/capsule-loader.c
>> index 63ceca9..571d931 100644
>> --- a/drivers/firmware/efi/capsule-loader.c
>> +++ b/drivers/firmware/efi/capsule-loader.c
>> @@ -26,10 +26,32 @@ struct capsule_info {
>> long index;
>> size_t count;
>> size_t total_size;
>> + unsigned int efi_hdr_offset;
>> struct page **pages;
>> size_t page_bytes_remain;
>> };
>>
>> +#define QUARK_CSH_SIGNATURE 0x5f435348 /* _CSH */
>> +#define QUARK_SECURITY_HEADER_SIZE 0x400
>> +
>> +struct efi_quark_security_header {
>> + u32 csh_signature;
>> + u32 version;
>> + u32 modulesize;
>> + u32 security_version_number_index;
>> + u32 security_version_number;
>> + u32 rsvd_module_id;
>> + u32 rsvd_module_vendor;
>> + u32 rsvd_date;
>> + u32 headersize;
>> + u32 hash_algo;
>> + u32 cryp_algo;
>> + u32 keysize;
>> + u32 signaturesize;
>> + u32 rsvd_next_header;
>> + u32 rsvd[2];
>> +};
>
> This is a real nitpick (sorry) - but it'd be nice to have a document
> reference or a link to describe this header i.e. it is officially
> documented - outside of the UEFI specification. Make life easy for
> someone reading this header and make an document reference.
>
> Also it'd be appreciated if you could describe the format of the
> structure with
>
> @member member-attribute description
Done.
>
>> +
>> /**
>> * efi_free_all_buff_pages - free all previous allocated buffer pages
>> * @cap_info: pointer to current instance of capsule_info structure
>> @@ -56,18 +78,46 @@ static void efi_free_all_buff_pages(struct
>> capsule_info *cap_info)
>> static ssize_t efi_capsule_setup_info(struct capsule_info *cap_info,
>> void *kbuff, size_t hdr_bytes)
>> {
>> + struct efi_quark_security_header *quark_hdr;
>> efi_capsule_header_t *cap_hdr;
>> size_t pages_needed;
>> int ret;
>> void *temp_page;
>>
>> - /* Only process data block that is larger than efi header size */
>> - if (hdr_bytes < sizeof(efi_capsule_header_t))
>> + /* Only process data block that is larger than the security header
>> + * (which is larger than the EFI header) */
>> + if (hdr_bytes < sizeof(struct efi_quark_security_header))
>> return 0;
>>
>> /* Reset back to the correct offset of header */
>> cap_hdr = kbuff - cap_info->count;
>> - pages_needed = ALIGN(cap_hdr->imagesize, PAGE_SIZE) >> PAGE_SHIFT;
>> +
>> + quark_hdr = (struct efi_quark_security_header *)cap_hdr;
>> +
>> + if (quark_hdr->csh_signature == QUARK_CSH_SIGNATURE &&
>> + quark_hdr->headersize == QUARK_SECURITY_HEADER_SIZE) {
>> + /* Only process data block if EFI header is included */
>> + if (hdr_bytes < QUARK_SECURITY_HEADER_SIZE +
>> + sizeof(efi_capsule_header_t))
>> + return 0;
>
> At this point if cap_info->header_obtained == false then this is an
> error - you should be barfing on this - not literally barfing - at least
> not on your keyboard :)
>
> return -ETHISHEADERSUCKS or some other sensible value -EINVAL like you
> have below.
>
> Point being you've validated the signature, the header size and
> cap_info->header_obtained is false then you definitely have a bogus
> capsule..
Nope: efi_capsule_setup_info is called whenever the user wrote some bits
to the device, not necessarily enough to evaluate all the headers. We
need to return 0 here (and not set header_obtained) until we find enough
data to declare the capsule valid or broken.
>
>
>> +
>> + pr_debug("%s: Quark security header detected\n", __func__);
>
> ... and %s __func__ is verboten don't do it. actually there's a bunch of
> those pairs all over this code - if you have the time in a supplementary
> patch please kill them - there must be a a dev pointer we can get at
> somewhere that makes sense to use dev_dbg- if not those __func__
> parameters still need to go away - please kill them.
I've written some cleanup patches for this module and refrain from
adding my own mess.
>
>> +
>> + if (quark_hdr->rsvd_next_header != 0) {
>> + pr_err("%s: multiple security headers not supported\n",
>> + __func__);
>> + return -EINVAL;
>> + }
>
>
>> +
>> + cap_hdr = (void *)cap_hdr + quark_hdr->headersize;
>
> You could have a separate void * variable and not have the cast.
>
Done.
Thanks,
Jan
--
Siemens AG, Corporate Technology, CT RDA ITP SES-DE
Corporate Competence Center Embedded Linux
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