From 708ae9f5241fcbae0b41e8beead5509a056e2e99 Mon Sep 17 00:00:00 2001 From: Daniel Kiper Date: Wed, 26 Sep 2018 13:17:52 +0200 Subject: [PATCH] verifiers: Add possibility to defer verification to other verifiers This way if a verifier requires verification of a given file it can defer task to another verifier (another authority) if it is not able to do it itself. E.g. shim_lock verifier, posted as a subsequent patch, is able to verify only PE files. This means that it is not able to verify any of GRUB2 modules which have to be trusted on UEFI systems with secure boot enabled. So, it can defer verification to other verifier, e.g. PGP one. I silently assume that other verifiers are trusted and will do good job for us. Or at least they will not do any harm. Signed-off-by: Daniel Kiper Reviewed-by: Ross Philipson --- grub-core/commands/verifiers.c | 23 ++++++++++++++++++++--- include/grub/verify.h | 4 +++- 2 files changed, 23 insertions(+), 4 deletions(-) diff --git a/grub-core/commands/verifiers.c b/grub-core/commands/verifiers.c index 59ea418a2..c638d5f43 100644 --- a/grub-core/commands/verifiers.c +++ b/grub-core/commands/verifiers.c @@ -83,6 +83,7 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type) void *context; grub_file_t ret = 0; grub_err_t err; + int defer = 0; grub_dprintf ("verify", "file: %s type: %d\n", io->name, type); @@ -102,13 +103,27 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type) err = ver->init (io, type, &context, &flags); if (err) goto fail_noclose; + if (flags & GRUB_VERIFY_FLAGS_DEFER_AUTH) + { + defer = 1; + continue; + } if (!(flags & GRUB_VERIFY_FLAGS_SKIP_VERIFICATION)) break; } if (!ver) - /* No verifiers wanted to verify. Just return underlying file. */ - return io; + { + if (defer) + { + grub_error (GRUB_ERR_ACCESS_DENIED, + N_("verification requested but nobody cares: %s"), io->name); + goto fail_noclose; + } + + /* No verifiers wanted to verify. Just return underlying file. */ + return io; + } ret = grub_malloc (sizeof (*ret)); if (!ret) @@ -160,7 +175,9 @@ grub_verifiers_open (grub_file_t io, enum grub_file_type type) err = ver->init (io, type, &context, &flags); if (err) goto fail_noclose; - if (flags & GRUB_VERIFY_FLAGS_SKIP_VERIFICATION) + if (flags & GRUB_VERIFY_FLAGS_SKIP_VERIFICATION || + /* Verification done earlier. So, we are happy here. */ + flags & GRUB_VERIFY_FLAGS_DEFER_AUTH) continue; err = ver->write (context, verified->buf, ret->size); if (err) diff --git a/include/grub/verify.h b/include/grub/verify.h index 9f892d8fe..79022b422 100644 --- a/include/grub/verify.h +++ b/include/grub/verify.h @@ -22,7 +22,9 @@ enum grub_verify_flags { GRUB_VERIFY_FLAGS_SKIP_VERIFICATION = 1, - GRUB_VERIFY_FLAGS_SINGLE_CHUNK = 2 + GRUB_VERIFY_FLAGS_SINGLE_CHUNK = 2, + /* Defer verification to another authority. */ + GRUB_VERIFY_FLAGS_DEFER_AUTH = 4 }; enum grub_verify_string_type