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From f42b774020839b1e07c5fa0ad7be4735d35cc705 Mon Sep 17 00:00:00 2001
From: Maxim Fomin <maxim@fomin.one>
Date: Fri, 8 Jan 2021 20:00:31 +0000
Subject: [PATCH] Support for multiple LUKS passphrase attempts
---
grub-core/disk/luks.c | 273 ++++++++++++++++++++++--------------------
1 file changed, 141 insertions(+), 132 deletions(-)
diff --git a/grub-core/disk/luks.c b/grub-core/disk/luks.c
index eea85338d..3f98df287 100644
--- a/grub-core/disk/luks.c
+++ b/grub-core/disk/luks.c
@@ -34,6 +34,8 @@ GRUB_MOD_LICENSE ("GPLv3+");
#define LUKS_KEY_ENABLED 0x00AC71F3
+#define LUKS_PASSPHRASE_ATTEMPTS 3
+
/* On disk LUKS header */
struct grub_luks_phdr
{
@@ -182,6 +184,7 @@ luks_recover_key (grub_disk_t source,
grub_size_t max_stripes = 1;
char *tmp;
grub_uint32_t sector;
+ unsigned int attempts = LUKS_PASSPHRASE_ATTEMPTS;
err = GRUB_ERR_NONE;
@@ -211,145 +214,151 @@ luks_recover_key (grub_disk_t source,
if (!split_key)
return grub_errno;
- if (keyfile_bytes)
- {
- /* Use bytestring from key file as passphrase */
- passphrase = keyfile_bytes;
- passphrase_length = keyfile_bytes_size;
- }
- else
+ while (attempts)
{
- /* Get the passphrase from the user. */
- tmp = NULL;
- if (source->partition)
- tmp = grub_partition_get_name (source->partition);
- grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
- source->partition ? "," : "", tmp ? : "", dev->uuid);
- grub_free (tmp);
- if (!grub_password_get (interactive_passphrase, MAX_PASSPHRASE))
+ if (keyfile_bytes)
{
- grub_free (split_key);
- return grub_error (GRUB_ERR_BAD_ARGUMENT, "Passphrase not supplied");
+ /* Use bytestring from key file as passphrase */
+ passphrase = keyfile_bytes;
+ passphrase_length = keyfile_bytes_size;
+ keyfile_bytes = NULL; /* use it only once */
+ }
+ else
+ {
+ /* Get the passphrase from the user. */
+ tmp = NULL;
+ if (source->partition)
+ tmp = grub_partition_get_name (source->partition);
+ grub_printf_ (N_("Enter passphrase for %s%s%s (%s): "), source->name,
+ source->partition ? "," : "", tmp ? : "", dev->uuid);
+ grub_free (tmp);
+ if (!grub_password_get (interactive_passphrase, MAX_PASSPHRASE))
+ {
+ grub_free (split_key);
+ return grub_error (GRUB_ERR_BAD_ARGUMENT, "Passphrase not supplied");
+ }
+
+ passphrase = (grub_uint8_t *)interactive_passphrase;
+ passphrase_length = grub_strlen (interactive_passphrase);
}
- passphrase = (grub_uint8_t *)interactive_passphrase;
- passphrase_length = grub_strlen (interactive_passphrase);
+ /* Try to recover master key from each active keyslot. */
+ for (i = 0; i < ARRAY_SIZE (header.keyblock); i++)
+ {
+ gcry_err_code_t gcry_err;
+ grub_uint8_t candidate_key[GRUB_CRYPTODISK_MAX_KEYLEN];
+ grub_uint8_t digest[GRUB_CRYPTODISK_MAX_KEYLEN];
+
+ /* Check if keyslot is enabled. */
+ if (grub_be_to_cpu32 (header.keyblock[i].active) != LUKS_KEY_ENABLED)
+ continue;
+
+ grub_dprintf ("luks", "Trying keyslot %d\n", i);
+
+ /* Calculate the PBKDF2 of the user supplied passphrase. */
+ gcry_err = grub_crypto_pbkdf2 (dev->hash, (grub_uint8_t *) passphrase,
+ passphrase_length,
+ header.keyblock[i].passwordSalt,
+ sizeof (header.keyblock[i].passwordSalt),
+ grub_be_to_cpu32 (header.keyblock[i].
+ passwordIterations),
+ digest, keysize);
+
+ if (gcry_err)
+ {
+ grub_free (split_key);
+ return grub_crypto_gcry_error (gcry_err);
+ }
+
+ grub_dprintf ("luks", "PBKDF2 done\n");
+
+ gcry_err = grub_cryptodisk_setkey (dev, digest, keysize);
+ if (gcry_err)
+ {
+ grub_free (split_key);
+ return grub_crypto_gcry_error (gcry_err);
+ }
+
+ sector = grub_be_to_cpu32 (header.keyblock[i].keyMaterialOffset);
+ length = (keysize * grub_be_to_cpu32 (header.keyblock[i].stripes));
+
+ /* Read and decrypt the key material from the disk. */
+ if (hdr)
+ {
+ grub_file_seek (hdr, sector * 512);
+ if (grub_file_read (hdr, split_key, length) != (grub_ssize_t)length)
+ err = GRUB_ERR_READ_ERROR;
+ }
+ else
+ err = grub_disk_read (source, sector, 0, length, split_key);
+ if (err)
+ {
+ grub_free (split_key);
+ return err;
+ }
+
+ gcry_err = grub_cryptodisk_decrypt (dev, split_key, length, 0,
+ GRUB_LUKS1_LOG_SECTOR_SIZE);
+ if (gcry_err)
+ {
+ grub_free (split_key);
+ return grub_crypto_gcry_error (gcry_err);
+ }
+
+ /* Merge the decrypted key material to get the candidate master key. */
+ gcry_err = AF_merge (dev->hash, split_key, candidate_key, keysize,
+ grub_be_to_cpu32 (header.keyblock[i].stripes));
+ if (gcry_err)
+ {
+ grub_free (split_key);
+ return grub_crypto_gcry_error (gcry_err);
+ }
+
+ grub_dprintf ("luks", "candidate key recovered\n");
+
+ /* Calculate the PBKDF2 of the candidate master key. */
+ gcry_err = grub_crypto_pbkdf2 (dev->hash, candidate_key,
+ grub_be_to_cpu32 (header.keyBytes),
+ header.mkDigestSalt,
+ sizeof (header.mkDigestSalt),
+ grub_be_to_cpu32
+ (header.mkDigestIterations),
+ candidate_digest,
+ sizeof (candidate_digest));
+ if (gcry_err)
+ {
+ grub_free (split_key);
+ return grub_crypto_gcry_error (gcry_err);
+ }
+
+ /* Compare the calculated PBKDF2 to the digest stored
+ in the header to see if it's correct. */
+ if (grub_memcmp (candidate_digest, header.mkDigest,
+ sizeof (header.mkDigest)) != 0)
+ {
+ grub_dprintf ("luks", "bad digest\n");
+ continue;
+ }
+
+ /* TRANSLATORS: It's a cryptographic key slot: one element of an array
+ where each element is either empty or holds a key. */
+ grub_printf_ (N_("Slot %d opened\n"), i);
+
+ /* Set the master key. */
+ gcry_err = grub_cryptodisk_setkey (dev, candidate_key, keysize);
+ if (gcry_err)
+ {
+ grub_free (split_key);
+ return grub_crypto_gcry_error (gcry_err);
+ }
- }
+ grub_free (split_key);
- /* Try to recover master key from each active keyslot. */
- for (i = 0; i < ARRAY_SIZE (header.keyblock); i++)
- {
- gcry_err_code_t gcry_err;
- grub_uint8_t candidate_key[GRUB_CRYPTODISK_MAX_KEYLEN];
- grub_uint8_t digest[GRUB_CRYPTODISK_MAX_KEYLEN];
-
- /* Check if keyslot is enabled. */
- if (grub_be_to_cpu32 (header.keyblock[i].active) != LUKS_KEY_ENABLED)
- continue;
-
- grub_dprintf ("luks", "Trying keyslot %d\n", i);
-
- /* Calculate the PBKDF2 of the user supplied passphrase. */
- gcry_err = grub_crypto_pbkdf2 (dev->hash, (grub_uint8_t *) passphrase,
- passphrase_length,
- header.keyblock[i].passwordSalt,
- sizeof (header.keyblock[i].passwordSalt),
- grub_be_to_cpu32 (header.keyblock[i].
- passwordIterations),
- digest, keysize);
-
- if (gcry_err)
- {
- grub_free (split_key);
- return grub_crypto_gcry_error (gcry_err);
- }
-
- grub_dprintf ("luks", "PBKDF2 done\n");
-
- gcry_err = grub_cryptodisk_setkey (dev, digest, keysize);
- if (gcry_err)
- {
- grub_free (split_key);
- return grub_crypto_gcry_error (gcry_err);
- }
-
- sector = grub_be_to_cpu32 (header.keyblock[i].keyMaterialOffset);
- length = (keysize * grub_be_to_cpu32 (header.keyblock[i].stripes));
-
- /* Read and decrypt the key material from the disk. */
- if (hdr)
- {
- grub_file_seek (hdr, sector * 512);
- if (grub_file_read (hdr, split_key, length) != (grub_ssize_t)length)
- err = GRUB_ERR_READ_ERROR;
+ return GRUB_ERR_NONE;
}
- else
- err = grub_disk_read (source, sector, 0, length, split_key);
- if (err)
- {
- grub_free (split_key);
- return err;
- }
-
- gcry_err = grub_cryptodisk_decrypt (dev, split_key, length, 0,
- GRUB_LUKS1_LOG_SECTOR_SIZE);
- if (gcry_err)
- {
- grub_free (split_key);
- return grub_crypto_gcry_error (gcry_err);
- }
-
- /* Merge the decrypted key material to get the candidate master key. */
- gcry_err = AF_merge (dev->hash, split_key, candidate_key, keysize,
- grub_be_to_cpu32 (header.keyblock[i].stripes));
- if (gcry_err)
- {
- grub_free (split_key);
- return grub_crypto_gcry_error (gcry_err);
- }
-
- grub_dprintf ("luks", "candidate key recovered\n");
-
- /* Calculate the PBKDF2 of the candidate master key. */
- gcry_err = grub_crypto_pbkdf2 (dev->hash, candidate_key,
- grub_be_to_cpu32 (header.keyBytes),
- header.mkDigestSalt,
- sizeof (header.mkDigestSalt),
- grub_be_to_cpu32
- (header.mkDigestIterations),
- candidate_digest,
- sizeof (candidate_digest));
- if (gcry_err)
- {
- grub_free (split_key);
- return grub_crypto_gcry_error (gcry_err);
- }
-
- /* Compare the calculated PBKDF2 to the digest stored
- in the header to see if it's correct. */
- if (grub_memcmp (candidate_digest, header.mkDigest,
- sizeof (header.mkDigest)) != 0)
- {
- grub_dprintf ("luks", "bad digest\n");
- continue;
- }
-
- /* TRANSLATORS: It's a cryptographic key slot: one element of an array
- where each element is either empty or holds a key. */
- grub_printf_ (N_("Slot %d opened\n"), i);
-
- /* Set the master key. */
- gcry_err = grub_cryptodisk_setkey (dev, candidate_key, keysize);
- if (gcry_err)
- {
- grub_free (split_key);
- return grub_crypto_gcry_error (gcry_err);
- }
-
- grub_free (split_key);
-
- return GRUB_ERR_NONE;
+ grub_printf_ (N_("Failed to decrypt master key.\n"));
+ if (--attempts) grub_printf_ (N_("%u attempt%s remaining.\n"), attempts,
+ (attempts==1) ? "" : "s");
}
grub_free (split_key);
--
2.30.0
|