[systemd-devel] [PATCH] cryptsetup: add keyfile-size= support

[Tom Gundersen]

This is useful e.g. if the keyfile is a raw device, where only parts of it
should be read. It is typically used whenever the keyfile-offset= option is
specified.

Tested-by: Erik Westrup <erik.westrup at gmail.com>
---
 man/crypttab.xml            | 12 ++++++++++++
 src/cryptsetup/cryptsetup.c | 22 +++++++++++++++-------
 2 files changed, 27 insertions(+), 7 deletions(-)

diff --git a/man/crypttab.xml b/man/crypttab.xml
index 2fa8e89..8711272 100644
--- a/man/crypttab.xml
+++ b/man/crypttab.xml
@@ -131,6 +131,18 @@
 
 
                         <varlistentry>
+                                <term><varname>keyfile-size=</varname></term>
+
+                                <listitem><para>Specifies the maximum number
+                                of bytes to read from the keyfile; see
+                                <citerefentry><refentrytitle>cryptsetup</refentrytitle><manvolnum>8</manvolnum></citerefentry>
+                                for possible values and the default
+                                value of this option. This option is ignored
+                                in plain encryption mode, as the keyfile-size is then given by the key size.</para></listitem>
+                        </varlistentry>
+
+
+                        <varlistentry>
                                 <term><varname>keyfile-offset=</varname></term>
 
                                 <listitem><para>Specifies the number
diff --git a/src/cryptsetup/cryptsetup.c b/src/cryptsetup/cryptsetup.c
index cc30e50..916509a 100644
--- a/src/cryptsetup/cryptsetup.c
+++ b/src/cryptsetup/cryptsetup.c
@@ -37,6 +37,7 @@
 static const char *opt_type = NULL; /* LUKS1 or PLAIN */
 static char *opt_cipher = NULL;
 static unsigned opt_key_size = 0;
+static unsigned opt_keyfile_size = 0;
 static unsigned opt_keyfile_offset = 0;
 static char *opt_hash = NULL;
 static unsigned opt_tries = 0;
@@ -80,6 +81,13 @@ static int parse_one_option(const char *option) {
                         return 0;
                 }
 
+        } else if (startswith(option, "keyfile-size=")) {
+
+                if (safe_atou(option+13, &opt_keyfile_size) < 0) {
+                        log_error("keyfile-size= parse failure, ignoring.");
+                        return 0;
+                }
+
         } else if (startswith(option, "keyfile-offset=")) {
 
                 if (safe_atou(option+15, &opt_keyfile_offset) < 0) {
@@ -238,7 +246,6 @@ int main(int argc, char *argv[]) {
         char **passwords = NULL, *truncated_cipher = NULL;
         const char *cipher = NULL, *cipher_mode = NULL, *hash = NULL, *name = NULL;
         char *description = NULL, *name_buffer = NULL, *mount_point = NULL;
-        unsigned keyfile_size = 0;
 
         if (argc <= 1) {
                 help();
@@ -437,6 +444,11 @@ int main(int argc, char *argv[]) {
                                 zero(params);
                                 params.hash = hash;
 
+                                /* for CRYPT_PLAIN limit reads
+                                * from keyfile to key length, and
+                                * ignore keyfile-size */
+                                opt_keyfile_size = opt_key_size / 8;
+
                                 /* In contrast to what the name
                                  * crypt_setup() might suggest this
                                  * doesn't actually format anything,
@@ -448,14 +460,10 @@ int main(int argc, char *argv[]) {
                                                  cipher_mode,
                                                  NULL,
                                                  NULL,
-                                                 opt_key_size / 8,
+                                                 opt_keyfile_size,
                                                  &params);
 
                                 pass_volume_key = streq(hash, "plain");
-
-                               /* for CRYPT_PLAIN limit reads
-                                * from keyfile to key length */
-                                keyfile_size = opt_key_size / 8;
                         }
 
                         if (k < 0) {
@@ -470,7 +478,7 @@ int main(int argc, char *argv[]) {
                                  argv[3]);
 
                         if (key_file)
-                                k = crypt_activate_by_keyfile_offset(cd, argv[2], CRYPT_ANY_SLOT, key_file, keyfile_size,
+                                k = crypt_activate_by_keyfile_offset(cd, argv[2], CRYPT_ANY_SLOT, key_file, opt_keyfile_size,
                                             opt_keyfile_offset, flags);
                         else {
                                 char **p;
-- 
1.7.11.4