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Use new crypt_generate_volume_key to generate weaker keys.

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There were two different use cases for weaker keys:

1) empty keys (zero filled buffer)
2) weak 'random' keys not sucking entropy while being generated

Those key types must not be used to encrypt real data. It's used either
to check cipher can be configured sucessfully on the system or as
a fake envelope during metadata repair.
This commit is contained in:
Ondrej Kozina
2025-01-29 14:49:12 +01:00
parent 1326dfbac1
commit 88b3da6042
2 changed files with 12 additions and 11 deletions
Download Patch File Download Diff File Expand all files Collapse all files

18
lib/luks1/keymanage.c
View File

@@ -378,7 +378,7 @@ static int _keyslot_repair(struct luks_phdr *phdr, struct crypt_device *ctx)
{
struct luks_phdr temp_phdr;
const unsigned char *sector = (const unsigned char*)phdr;
struct volume_key *vk;
struct volume_key *fake_vk;
int i, bad, r, need_write = 0;
if (phdr->keyBytes != 16 && phdr->keyBytes != 32 && phdr->keyBytes != 64) {
@@ -424,8 +424,8 @@ static int _keyslot_repair(struct luks_phdr *phdr, struct crypt_device *ctx)
if (r < 0)
return -EINVAL;
vk = crypt_alloc_volume_key(phdr->keyBytes, NULL);
if (!vk)
fake_vk = crypt_generate_volume_key(ctx, phdr->keyBytes, KEY_QUALITY_EMPTY);
if (!fake_vk)
return -ENOMEM;
log_verbose(ctx, _("Repairing keyslots."));
@@ -433,7 +433,7 @@ static int _keyslot_repair(struct luks_phdr *phdr, struct crypt_device *ctx)
log_dbg(ctx, "Generating second header with the same parameters for check.");
/* cipherName, cipherMode, hashSpec, uuid are already null terminated */
/* payloadOffset - cannot check */
r = LUKS_generate_phdr(&temp_phdr, vk, phdr->cipherName, phdr->cipherMode,
r = LUKS_generate_phdr(&temp_phdr, fake_vk, phdr->cipherName, phdr->cipherMode,
phdr->hashSpec, phdr->uuid,
phdr->payloadOffset * SECTOR_SIZE, 0, 0, ctx);
if (r < 0)
@@ -492,7 +492,7 @@ static int _keyslot_repair(struct luks_phdr *phdr, struct crypt_device *ctx)
out:
if (r)
log_err(ctx, _("Repair failed."));
crypt_free_volume_key(vk);
crypt_free_volume_key(fake_vk);
crypt_safe_memzero(&temp_phdr, sizeof(temp_phdr));
return r;
}
@@ -710,14 +710,12 @@ int LUKS_check_cipher(struct crypt_device *ctx, size_t keylength, const char *ci
log_dbg(ctx, "Checking if cipher %s-%s is usable.", cipher, cipher_mode);
empty_key = crypt_alloc_volume_key(keylength, NULL);
/* No need to get KEY quality random but it must avoid known weak keys. */
empty_key = crypt_generate_volume_key(ctx, keylength, KEY_QUALITY_NORMAL);
if (!empty_key)
return -ENOMEM;
/* No need to get KEY quality random but it must avoid known weak keys. */
r = crypt_random_get(ctx, empty_key->key, empty_key->keylength, CRYPT_RND_NORMAL);
if (!r)
r = LUKS_decrypt_from_storage(buf, sizeof(buf), cipher, cipher_mode, empty_key, 0, ctx);
r = LUKS_decrypt_from_storage(buf, sizeof(buf), cipher, cipher_mode, empty_key, 0, ctx);
crypt_free_volume_key(empty_key);
crypt_safe_memzero(buf, sizeof(buf));

5
lib/setup.c
View File

@@ -3016,7 +3016,10 @@ static int _crypt_format_integrity(struct crypt_device *cd,
cd->u.integrity.params.journal_crypt = journal_crypt;
if (params->integrity_key_size) {
ik = crypt_alloc_volume_key(params->integrity_key_size, integrity_key);
if (!integrity_key)
ik = crypt_generate_volume_key(cd, params->integrity_key_size, KEY_QUALITY_EMPTY);
else
ik = crypt_alloc_volume_key(params->integrity_key_size, integrity_key);
if (!ik) {
r = -ENOMEM;
goto out;