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cryptsetup: Add optional support for linking volume key in keyring.

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cryptsetup 2.7.0 adds feature to link effective volume key in custom
kernel keyring during device activation. It can be used later to pass
linked volume key to other services.

For example: kdump enabled systems installed on LUKS2 device.
This feature allows it to store volume key linked in a kernel keyring
to the kdump reserved memory and reuse it to reactivate LUKS2 device
in case of kernel crash.
This commit is contained in:
Ondrej Kozina 2024-01-31 13:11:21 +01:00 committed by Lennart Poettering
parent 10048b2e20
commit c5daf14c88
3 changed files with 90 additions and 1 deletions
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23
man/crypttab.xml
View File

@ -260,6 +260,29 @@
<xi:include href="version-info.xml" xpointer="v243"/></listitem>
</varlistentry>
<varlistentry>
<term><option>link-volume-key=</option></term>
<listitem><para>Specifies the kernel keyring and key description
(see <citerefentry project='man-pages'><refentrytitle>keyrings</refentrytitle><manvolnum>7</manvolnum></citerefentry>)
where LUKS2 volume key gets linked during device activation. The kernel keyring
description and key description must be separated by <literal>::</literal>.</para>
<para>The kernel keyring part can be a string description or a predefined
kernel keyring prefixed with <literal>@</literal> (e.g.: to use <literal>@s</literal> session or
<literal>@u</literal> user keyring directly). The type prefix text in the kernel keyring description
is not required. The specified kernel keyring must already exist at the time of device activation.</para>
<para>The key part is a string description optionally prefixed by a <literal>%key_type:</literal>.
If no type is specified, the <literal>user</literal> type key is linked by default. See
<citerefentry project='man-pages'><refentrytitle>keyctl</refentrytitle><manvolnum>1</manvolnum></citerefentry>
for more information on key descriptions (KEY IDENTIFIERS section).</para>
<para>Note that the linked volume key is not cleaned up automatically when the device is detached.</para>
<xi:include href="version-info.xml" xpointer="v256"/></listitem>
</varlistentry>
<varlistentry>
<term><option>luks</option></term>

3
meson.build
View File

@ -1260,7 +1260,8 @@ foreach ident : ['crypt_set_metadata_size',
'crypt_token_max',
'crypt_reencrypt_init_by_passphrase',
'crypt_reencrypt',
'crypt_set_data_offset']
'crypt_set_data_offset',
'crypt_set_keyring_to_link']
have_ident = have and cc.has_function(
ident,
prefix : '#include <libcryptsetup.h>',

65
src/cryptsetup/cryptsetup.c
View File

@ -105,6 +105,9 @@ static bool arg_headless = false;
static usec_t arg_token_timeout_usec = 30*USEC_PER_SEC;
static unsigned arg_tpm2_measure_pcr = UINT_MAX; /* This and the following field is about measuring the unlocked volume key to the local TPM */
static char **arg_tpm2_measure_banks = NULL;
static char *arg_link_keyring = NULL;
static char *arg_link_key_type = NULL;
static char *arg_link_key_description = NULL;
STATIC_DESTRUCTOR_REGISTER(arg_cipher, freep);
STATIC_DESTRUCTOR_REGISTER(arg_hash, freep);
@ -118,6 +121,9 @@ STATIC_DESTRUCTOR_REGISTER(arg_tpm2_device, freep);
STATIC_DESTRUCTOR_REGISTER(arg_tpm2_signature, freep);
STATIC_DESTRUCTOR_REGISTER(arg_tpm2_measure_banks, strv_freep);
STATIC_DESTRUCTOR_REGISTER(arg_tpm2_pcrlock, freep);
STATIC_DESTRUCTOR_REGISTER(arg_link_keyring, freep);
STATIC_DESTRUCTOR_REGISTER(arg_link_key_type, freep);
STATIC_DESTRUCTOR_REGISTER(arg_link_key_description, freep);
static const char* const passphrase_type_table[_PASSPHRASE_TYPE_MAX] = {
[PASSPHRASE_REGULAR] = "passphrase",
@ -508,6 +514,56 @@ static int parse_one_option(const char *option) {
if (r < 0)
log_warning_errno(r, "Failed to parse %s, ignoring: %m", option);
} else if ((val = startswith(option, "link-volume-key="))) {
#ifdef HAVE_CRYPT_SET_KEYRING_TO_LINK
const char *sep, *c;
_cleanup_free_ char *keyring = NULL, *key_type = NULL, *key_description = NULL;
/* Stick with cryptsetup --link-vk-to-keyring format
* <keyring_description>::%<key_type>:<key_description>,
* where %<key_type> is optional and defaults to 'user'.
*/
if (!(sep = strstr(val, "::")))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to parse link-volume-key= option value: %m");
/* cryptsetup (cli) supports <keyring_description> passed in various formats:
* - well-known keyrings prefixed with '@' (@u user, @s session, etc)
* - text descriptions prefixed with "%:" or "%keyring:".
* - text desription with no prefix.
* - numeric keyring id (ignored in current patch set). */
if (*val == '@' || *val == '%')
keyring = strndup(val, sep - val);
else
/* add type prefix if missing (crypt_set_keyring_to_link() expects it) */
keyring = strnappend("%:", val, sep - val);
if (!keyring)
return log_oom();
sep += 2;
/* %<key_type> is optional (and defaults to 'user') */
if (*sep == '%') {
/* must be separated by colon */
if (!(c = strchr(sep, ':')))
return log_error_errno(SYNTHETIC_ERRNO(EINVAL), "Failed to parse link-volume-key= option value: %m");
key_type = strndup(sep + 1, c - sep - 1);
if (!key_type)
return log_oom();
sep = c + 1;
}
key_description = strdup(sep);
if (!key_description)
return log_oom();
free_and_replace(arg_link_keyring, keyring);
free_and_replace(arg_link_key_type, key_type);
free_and_replace(arg_link_key_description, key_description);
#else
log_error("Build lacks libcryptsetup support for linking volume keys in user specified kernel keyrings upon device activation, ignoring: %s", option);
#endif
} else if (!streq(option, "x-initrd.attach"))
log_warning("Encountered unknown /etc/crypttab option '%s', ignoring.", option);
@ -2287,6 +2343,15 @@ static int run(int argc, char *argv[]) {
if (r < 0)
return log_error_errno(r, "Failed to load LUKS superblock on device %s: %m", crypt_get_device_name(cd));
/* since cryptsetup 2.7.0 (Jan 2024) */
#if HAVE_CRYPT_SET_KEYRING_TO_LINK
if (arg_link_key_description) {
r = crypt_set_keyring_to_link(cd, arg_link_key_description, NULL, arg_link_key_type, arg_link_keyring);
if (r < 0)
log_warning_errno(r, "Failed to set keyring or key description to link volume key in, ignoring: %m");
}
#endif
if (arg_header) {
r = crypt_set_data_device(cd, source);
if (r < 0)