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SubjectRe: [PATCH encrypted swsusp 1/3] core functionality
Rafael J. Wysocki wrote:
> Hi,
>
> On Monday, 11 of April 2005 18:11, Andreas Steinmetz wrote:
>
>>Pavel Machek wrote:
>>
>>>Was it really neccessary to include "union u"? I don't like its name,
>>
>>Here comes the patch with this reverted. I'm now using casts when
>>'abusing' the space for encryption. Furthermore the iv set up in the tfm
>>is used instead of the local copy.
>
>
> I had no time to review your patch earlier, sorry. I'm inlining it so that I can
> comment it:
>
>
>>--- linux-2.6.11.2/kernel/power/swsusp.c.ast 2005-04-10 14:08:55.000000000 +0200
>>+++ linux-2.6.11.2/kernel/power/swsusp.c 2005-04-11 18:05:58.000000000 +0200
>>@@ -31,6 +31,9 @@
>> * Alex Badea <vampire@go.ro>:
>> * Fixed runaway init
>> *
>>+ * Andreas Steinmetz <ast@domdv.de>:
>>+ * Added encrypted suspend option
>>+ *
>> * More state savers are welcome. Especially for the scsi layer...
>> *
>> * For TODOs,FIXMEs also look in Documentation/power/swsusp.txt
>>@@ -72,6 +75,16 @@
>>
>> #include "power.h"
>>
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+#include <linux/random.h>
>>+#include <linux/crypto.h>
>>+#include <asm/scatterlist.h>
>>+#endif
>>+
>>+#define CIPHER "aes"
>>+#define MAXKEY 32
>>+#define MAXIV 32
>
>
> Why not to put these definitions under #ifdef?
>

I keep it the way Pavel likes it here if you don't mind.

>
>>+
>> /* References to section boundaries */
>> extern const void __nosave_begin, __nosave_end;
>>
>>@@ -104,7 +117,9 @@
>> #define SWSUSP_SIG "S1SUSPEND"
>>
>> static struct swsusp_header {
>>- char reserved[PAGE_SIZE - 20 - sizeof(swp_entry_t)];
>
>
> I would add #ifdef here as well.

Same as above.

>
>
>>+ char reserved[PAGE_SIZE - 20 - MAXKEY - MAXIV - sizeof(swp_entry_t)];
>>+ u8 key[MAXKEY];
>>+ u8 iv[MAXIV];
>> swp_entry_t swsusp_info;
>> char orig_sig[10];
>> char sig[10];
>>@@ -112,6 +127,11 @@
>>
>> static struct swsusp_info swsusp_info;
>>
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+static u8 key[MAXKEY];
>>+static u8 iv[MAXIV];
>>+#endif
>>+
>> /*
>> * XXX: We try to keep some more pages free so that I/O operations succeed
>> * without paging. Might this be more?
>>@@ -130,6 +150,52 @@
>> static unsigned short swapfile_used[MAX_SWAPFILES];
>> static unsigned short root_swap;
>>
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+static struct crypto_tfm *crypto_init(int mode)
>
>
> I think it's better if this function returns an int error code and the
> messages are printed where it's called from. This way, the essential
> part of the code would be easier to grasp (Pavel?).
>

Pavel doesn't mind printing the errors here as far as I can see. The
messages will be adapted to suspend/resume stae.

>
>>+{
>>+ struct crypto_tfm *tfm;
>>+ int len;
>>+
>>+ tfm = crypto_alloc_tfm(CIPHER, CRYPTO_TFM_MODE_CBC);
>>+ if(!tfm) {
>>+ printk(KERN_ERR "swsusp: no tfm, suspend not possible\n");
>>+ return NULL;
>>+ }
>>+
>>+ if(sizeof(key) < crypto_tfm_alg_min_keysize(tfm)) {
>>+ printk("swsusp: key buffer too small, suspend not possible\n");
>>+ crypto_free_tfm(tfm);
>>+ return NULL;
>>+ }
>>+
>>+ if (sizeof(iv) < crypto_tfm_alg_ivsize(tfm)) {
>>+ printk("swsusp: iv buffer too small, suspend not possible\n");
>>+ crypto_free_tfm(tfm);
>>+ return NULL;
>>+ }
>>+
>>+ if (mode) {
>>+ get_random_bytes(key, MAXKEY);
>
>
> I hope you realize that this may give you a sequence of bits that you should
> not use as a key ...

I don't get what you mean here. As far as I know aes has no weak keys.
The only danger I can see here is that get_get_random_bytes returns a
consecutive sequence of zeroes (or some other constant value) on every
invocation. Otherwise a sequence of zeroes is just one of 2^256 possible
keys. I prefer to keep the key space as wide open as possible.
Please let me know if you did mean something different.

>
>
>>+ get_random_bytes(iv, MAXIV);
>>+ }
>>+
>>+ len = crypto_tfm_alg_max_keysize(tfm);
>
>
> You have used this value earlier. Why don't you initialize len at that time?
>

Not correct. Earlieron it is crypto_tfm_alg_min_keysize().
^^^
>
>>+ if (len > sizeof(key))
>>+ len = sizeof(key);
>>+
>>+ if (crypto_cipher_setkey(tfm, key, len)) {
>>+ printk(KERN_ERR "swsusp: key setup failure, suspend not possible\n");
>>+ crypto_free_tfm(tfm);
>
>
> On any error, you call crypto_free_tfm(tfm) and return. I would use a common
> error handling code, like that:
>
> if (error)
> goto Error;
> /* some code */
> Error:
> crypto_free_tfm(tfm);
> return error;
>

Will do.

>
>>+ return NULL;
>>+ }
>>+
>>+ len = crypto_tfm_alg_blocksize(tfm);
>>+ crypto_cipher_set_iv(tfm, iv, len);
>
>
> I would use crypto_tfm_alg_blocksize(tfm) here directly (shorter code).
>

I reworked this a bit. New patch will follow later.

>
>>+
>>+ return tfm;
>>+}
>>+#endif
>>+
>> static int mark_swapfiles(swp_entry_t prev)
>> {
>> int error;
>>@@ -141,6 +207,10 @@
>
>
> If you used -p while making diffs, it would be easier to find out where the
> changes actually started.
>

I'll try to remember.

>
>> !memcmp("SWAPSPACE2",swsusp_header.sig, 10)) {
>> memcpy(swsusp_header.orig_sig,swsusp_header.sig, 10);
>> memcpy(swsusp_header.sig,SWSUSP_SIG, 10);
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ memcpy(swsusp_header.key, key, MAXKEY);
>>+ memcpy(swsusp_header.iv, iv, MAXIV);
>>+#endif
>> swsusp_header.swsusp_info = prev;
>> error = rw_swap_page_sync(WRITE,
>> swp_entry(root_swap, 0),
>>@@ -294,6 +364,19 @@
>
>
> This change will not apply to the current swsusp.c (eg as in 2.6.12-rc2).
>

Going to have a look at 2.6.12-rc2 later today.

>
>> int error = 0;
>> int i;
>> unsigned int mod = nr_copy_pages / 100;
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ struct crypto_tfm *tfm;
>>+ struct scatterlist src, dst;
>>+
>>+ if (!(tfm = crypto_init(1)))
>>+ return -EINVAL;
>
>
> It's not necessarily -EINVAL, I think. It's better to return different
> error codes on different error conditions.
>

Different error codes are on their way.

>
>>+
>>+ src.offset = 0;
>>+ src.length = PAGE_SIZE;
>>+ dst.page = virt_to_page((void *)&swsusp_header);
>>+ dst.offset = 0;
>>+ dst.length = PAGE_SIZE;
>>+#endif
>>
>> if (!mod)
>> mod = 1;
>>@@ -302,10 +385,21 @@
>
>
> This change will not apply to the current swsusp.c (eg as in 2.6.12-rc2).
>

As above.

>
>> for (i = 0; i < nr_copy_pages && !error; i++) {
>> if (!(i%mod))
>> printk( "\b\b\b\b%3d%%", i / mod );
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ src.page = virt_to_page((pagedir_nosave+i)->address);
>>+ error = crypto_cipher_encrypt(tfm, &dst, &src, PAGE_SIZE);
>>+ if (!error)
>>+ error = write_page((unsigned long)&swsusp_header,
>>+ &((pagedir_nosave+i)->swap_address));
>
>
> I wouldn't use swsusp_header directly in this statement. It's a bit confusing.
>

Hmm, I tried to solve this with a union which Pavel didn't like. An
extra buffer doesn't make sense here as it would be a lost page. Any
ideas? BTW, I need to use a buffer here as when swsusp fails later the
pages would have been encrypted in-place...

>
>>+#else
>> error = write_page((pagedir_nosave+i)->address,
>> &((pagedir_nosave+i)->swap_address));
>>+#endif
>> }
>> printk("\b\b\b\bdone\n");
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ crypto_free_tfm(tfm);
>>+#endif
>> return error;
>> }
>>
>>@@ -404,6 +498,10 @@
>> if ((error = close_swap()))
>> goto FreePagedir;
>> Done:
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ memset(key, 0, MAXKEY);
>>+ memset(iv, 0, MAXIV);
>>+#endif
>> return error;
>> FreePagedir:
>> free_pagedir_entries();
>>@@ -1124,6 +1222,12 @@
>> if (!memcmp(SWSUSP_SIG, swsusp_header.sig, 10)) {
>> memcpy(swsusp_header.sig, swsusp_header.orig_sig, 10);
>>
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ memcpy(key, swsusp_header.key, MAXKEY);
>>+ memcpy(iv, swsusp_header.iv, MAXIV);
>>+ memset(swsusp_header.key, 0, MAXKEY);
>>+ memset(swsusp_header.iv, 0, MAXIV);
>>+#endif
>> /*
>> * Reset swap signature now.
>> */
>>@@ -1150,6 +1254,18 @@
>
>
> This change will not apply to the current swsusp.c (eg as in 2.6.12-rc2).
>

As above.

>
>> int error;
>> int i;
>> int mod = nr_copy_pages / 100;
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ struct crypto_tfm *tfm;
>>+ struct scatterlist src, dst;
>>+
>>+ if (!(tfm = crypto_init(0)))
>>+ return -EINVAL;
>
>
> Same as in data_write() (ie not necessarily -EINVAL).
>

As above, consider this done.

>
>>+
>>+ src.offset = 0;
>>+ src.length = PAGE_SIZE;
>>+ dst.offset = 0;
>>+ dst.length = PAGE_SIZE;
>>+#endif
>>
>> if (!mod)
>> mod = 1;
>>@@ -1163,8 +1279,18 @@
>> printk( "\b\b\b\b%3d%%", i / mod );
>> error = bio_read_page(swp_offset(p->swap_address),
>> (void *)p->address);
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ if (!error) {
>>+ src.page = dst.page = virt_to_page((void *)p->address);
>>+ error = crypto_cipher_decrypt(tfm, &dst, &src,
>>+ PAGE_SIZE);
>>+ }
>>+#endif
>> }
>> printk(" %d done.\n",i);
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ crypto_free_tfm(tfm);
>>+#endif
>> return error;
>>
>> }
>>@@ -1233,6 +1359,11 @@
>> } else
>> error = PTR_ERR(resume_bdev);
>>
>>+#ifdef CONFIG_SWSUSP_ENCRYPT
>>+ memset(key, 0, MAXKEY);
>>+ memset(iv, 0, MAXIV);
>>+#endif
>>+
>> if (!error)
>> pr_debug("Reading resume file was successful\n");
>> else
>
>
> Greets,
> Rafael
>
>


--
Andreas Steinmetz SPAMmers use robotrap@domdv.de
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