Attachment 115162 Details for Bug 87717 – cryptsetup: Implement offset and skip options

[patch] cryptsetup: Implement offset and skip options

0001-cryptsetup-Implement-offset-and-skip-options.patch (text/plain), 4.38 KB, created by Martin Pitt on 2015-04-17 14:37:46 UTC

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Creator: Martin Pitt

Created: 2015-04-17 14:37:46 UTC

Size: 4.38 KB

patch

obsolete

>From 8fa1668c9ddf1b05194e0da8edcbdcae7519a883 Mon Sep 17 00:00:00 2001
>From: Martin Pitt <martin.pitt@ubuntu.com>
>Date: Thu, 16 Apr 2015 06:44:07 -0500
>Subject: [PATCH] cryptsetup: Implement offset and skip options
>
>These are useful for plain devices as they don't have any metadata by
>themselves. Instead of using an unreliable hardcoded device name in crypttab
>you can then put static metadata at the start of the partition for a stable
>UUID or label.
>
>https://bugs.freedesktop.org/show_bug.cgi?id=87717
>https://bugs.debian.org/751707
>https://launchpad.net/bugs/953875
>---
> man/crypttab.xml            | 24 ++++++++++++++++++++++++
> src/cryptsetup/cryptsetup.c | 31 ++++++++++++++++++++++++++++---
> 2 files changed, 52 insertions(+), 3 deletions(-)
>
>diff --git a/man/crypttab.xml b/man/crypttab.xml
>index 3e249ad..d4ff760 100644
>--- a/man/crypttab.xml
>+++ b/man/crypttab.xml
>@@ -146,6 +146,30 @@
>       </varlistentry>
> 
>       <varlistentry>
>+        <term><option>offset=</option></term>
>+
>+        <listitem><para>Start offset in the backend device, in 512-byte sectors.
>+        This option is only relevant for plain devices.
>+        </para></listitem>
>+      </varlistentry>
>+
>+      <varlistentry>
>+        <term><option>skip=</option></term>
>+
>+        <listitem><para>How many 512-byte sectors of the encrypted data to skip
>+        at the beginning. This is different from the <option>--offset</option>
>+        option with respect to the sector numbers used in initialization vector
>+        (IV) calculation. Using <option>--offset</option> will shift the IV
>+        calculation by the same negative amount.  Hence, if <option>--offset n</option>,
>+        sector n will  get a sector number of 0 for the IV calculation.
>+        Using <option>--skip</option> causes sector n to also be the first
>+        sector of the mapped device, but with its number for IV generation is n.</para>
>+
>+        <para>This option is only relevant for plain devices.</para>
>+        </listitem>
>+      </varlistentry>
>+
>+      <varlistentry>
>         <term><option>keyfile-offset=</option></term>
> 
>         <listitem><para>Specifies the number of bytes to skip at the
>diff --git a/src/cryptsetup/cryptsetup.c b/src/cryptsetup/cryptsetup.c
>index ba0ef72..a5018f1 100644
>--- a/src/cryptsetup/cryptsetup.c
>+++ b/src/cryptsetup/cryptsetup.c
>@@ -50,12 +50,12 @@ static bool arg_discards = false;
> static bool arg_tcrypt_hidden = false;
> static bool arg_tcrypt_system = false;
> static char **arg_tcrypt_keyfiles = NULL;
>+static uint64_t arg_offset = 0;
>+static uint64_t arg_skip = 0;
> static usec_t arg_timeout = 0;
> 
> /* Options Debian's crypttab knows we don't:
> 
>-    offset=
>-    skip=
>     precheck=
>     check=
>     checkargs=
>@@ -185,6 +185,20 @@ static int parse_one_option(const char *option) {
>                         return 0;
>                 }
> 
>+        } else if (startswith(option, "offset=")) {
>+
>+                if (safe_atou64(option+7, &arg_offset) < 0) {
>+                        log_error("offset= parse failure, refusing.");
>+                        return -EINVAL;
>+                }
>+
>+        } else if (startswith(option, "skip=")) {
>+
>+                if (safe_atou64(option+5, &arg_skip) < 0) {
>+                        log_error("skip= parse failure, refusing.");
>+                        return -EINVAL;
>+                }
>+
>         } else if (!streq(option, "none"))
>                 log_error("Encountered unknown /etc/crypttab option '%s', ignoring.", option);
> 
>@@ -209,6 +223,14 @@ static int parse_options(const char *options) {
>                         return r;
>         }
> 
>+        /* sanity-check options */
>+        if (arg_type != NULL && !streq(arg_type, CRYPT_PLAIN)) {
>+                if (arg_offset)
>+                      log_warning("offset= ignored with type %s", arg_type);
>+                if (arg_skip)
>+                      log_warning("skip= ignored with type %s", arg_type);
>+        }
>+
>         return 0;
> }
> 
>@@ -410,7 +432,10 @@ static int attach_luks_or_plain(struct crypt_device *cd,
>         }
> 
>         if ((!arg_type && r < 0) || streq_ptr(arg_type, CRYPT_PLAIN)) {
>-                struct crypt_params_plain params = {};
>+                struct crypt_params_plain params = {
>+                        .offset = arg_offset,
>+                        .skip = arg_skip,
>+                };
>                 const char *cipher, *cipher_mode;
>                 _cleanup_free_ char *truncated_cipher = NULL;
> 
>-- 
>2.1.4
>

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