[PATCH 5/9] luks2: Improve error reporting when decrypting/verifying key

[Patrick Steinhardt]

While we already set up error messages in both `luks2_verify_key()` and
`luks2_decrypt_key()`, we do not ever print them. This makes it really
hard to discover why a given key actually failed to decrypt a disk.

Improve this by including the error message in the user-visible output.

Signed-off-by: Patrick Steinhardt <ps@pks.im>
---
 grub-core/disk/luks2.c | 6 ++++--
 1 file changed, 4 insertions(+), 2 deletions(-)

diff --git a/grub-core/disk/luks2.c b/grub-core/disk/luks2.c
index fa4b62825..7c530dd1a 100644
--- a/grub-core/disk/luks2.c
+++ b/grub-core/disk/luks2.c
@@ -611,14 +611,16 @@ luks2_recover_key (grub_disk_t disk,
                               (const grub_uint8_t *) passphrase, grub_strlen 
(passphrase));
       if (ret)
        {
-         grub_dprintf ("luks2", "Decryption with keyslot %"PRIuGRUB_SIZE" 
failed\n", i);
+         grub_dprintf ("luks2", "Decryption with keyslot %"PRIuGRUB_SIZE" 
failed: %s\n",
+                       i, grub_errmsg);
          continue;
        }
 
       ret = luks2_verify_key (&digest, candidate_key, keyslot.key_size);
       if (ret)
        {
-         grub_dprintf ("luks2", "Could not open keyslot %"PRIuGRUB_SIZE"\n", 
i);
+         grub_dprintf ("luks2", "Could not open keyslot %"PRIuGRUB_SIZE": 
%s\n",
+                       i, grub_errmsg);
          continue;
        }
 
-- 
2.28.0

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