Re: [PATCH 4/5] efi_capsule: Add a weak function to get the public key needed for capsule authentication

On 4/7/21 1:53 PM, Sughosh Ganu wrote:

Define a weak function which would be used in the scenario where the public key is stored on the platform's dtb. This dtb is concatenated with the u-boot binary during the build process. Platforms which have a different mechanism for getting the public key would define their own platform specific function.

Storing the public key in U-Boot's dtb is reasonable. But what is the use case for a weak function?

Best regards

Heinrich

Signed-off-by: Sughosh Ganu sughosh.ganu@linaro.org

lib/efi_loader/efi_capsule.c | 38 ++++++++++++++++++++++++++++++++---- 1 file changed, 34 insertions(+), 4 deletions(-)

diff --git a/lib/efi_loader/efi_capsule.c b/lib/efi_loader/efi_capsule.c index 1423b675c8..fc5e1c0856 100644 --- a/lib/efi_loader/efi_capsule.c +++ b/lib/efi_loader/efi_capsule.c @@ -14,10 +14,13 @@ #include <mapmem.h> #include <sort.h>

+#include <asm/global_data.h> #include <crypto/pkcs7.h> #include <crypto/pkcs7_parser.h> #include <linux/err.h>

+DECLARE_GLOBAL_DATA_PTR;

• const efi_guid_t efi_guid_capsule_report = EFI_CAPSULE_REPORT_GUID; static const efi_guid_t efi_guid_firmware_management_capsule_id = EFI_FIRMWARE_MANAGEMENT_CAPSULE_ID_GUID;

@@ -210,11 +213,38 @@ const efi_guid_t efi_guid_capsule_root_cert_guid =

__weak int efi_get_public_key_data(void **pkey, efi_uintn_t *pkey_len) {

• /* The platform is supposed to provide

• * a method for getting the public key
  

• * stored in the form of efi signature
  

• * list
  

• /*

• * This is a function for retrieving the public key from the
  

• * platform's device tree. The platform's device tree has been
  

• * concatenated with the u-boot binary.
  

• * If a platform has a different mechanism to get the public
  

• * key, it can define it's own function.
  

  */
• const void *fdt_blob = gd->fdt_blob;
• const void *blob;
• const char *cnode_name = "capsule-key";
• const char *snode_name = "signature";
• int sig_node;
• int len;
• sig_node = fdt_subnode_offset(fdt_blob, 0, snode_name);
• if (sig_node < 0) {

• EFI_PRINT("Unable to get signature node offset\n");
  

• return -FDT_ERR_NOTFOUND;
  

• }
• blob = fdt_getprop(fdt_blob, sig_node, cnode_name, &len);
• if (!blob || len < 0) {

• EFI_PRINT("Unable to get capsule-key value\n");
  

• *pkey = NULL;
  

• *pkey_len = 0;
  

• return -FDT_ERR_NOTFOUND;
  

• }
• *pkey = (void *)blob;
• *pkey_len = len;
• return 0; }