From 5a690183091c2c161481123b17e1925148e516e4 Mon Sep 17 00:00:00 2001 From: Daniel Axtens Date: Tue, 30 Nov 2021 15:00:57 +1100 Subject: [PATCH 23/23] x509: allow Digitial Signature plus other Key Usages Currently the x509 certificate parser for appended signature verification requires that the certificate have the Digitial Signature key usage and _only_ the Digitial Signature use. This is overly strict and becomes policy enforcement rather than a security property. Require that the Digitial Signature usage is present, but do not require that it is the only usage present. Reported-by: Michal Suchanek Signed-off-by: Daniel Axtens --- grub-core/commands/appendedsig/x509.c | 6 +++--- 1 file changed, 3 insertions(+), 3 deletions(-) diff --git a/grub-core/commands/appendedsig/x509.c b/grub-core/commands/appendedsig/x509.c index 70480aa73..6ae985b30 100644 --- a/grub-core/commands/appendedsig/x509.c +++ b/grub-core/commands/appendedsig/x509.c @@ -547,7 +547,7 @@ cleanup: /* * Verify the Key Usage extension. - * We only permit the Digital signature usage. + * We require the Digital signature usage. */ static grub_err_t verify_key_usage (grub_uint8_t *value, int value_size) @@ -586,10 +586,10 @@ verify_key_usage (grub_uint8_t *value, int value_size) goto cleanup; } - if (usage != digitalSignatureUsage) + if (!(usage & digitalSignatureUsage)) { err = - grub_error (GRUB_ERR_BAD_FILE_TYPE, "Unexpected Key Usage value: %x", + grub_error (GRUB_ERR_BAD_FILE_TYPE, "Key Usage (0x%x) missing Digital Signature usage", usage); goto cleanup; } -- 2.31.1