dm crypt: add multi key capability

This patch adds generic multikey handling to be used
in following patch for Loop-AES mode compatibility.

This patch extends mapping table to optional keycount and
implements generic multi-key capability.

With more keys defined the <key> string is divided into
several <keycount> sections and these are used for tfms.

The tfm is used according to sector offset
(sector 0->tfm[0], sector 1->tfm[1], sector N->tfm[N modulo keycount])
(only power of two values supported for keycount here).

Because of tfms per-cpu allocation, this mode can be take
a lot of memory on large smp systems.

Signed-off-by: Milan Broz <mbroz@redhat.com>
Signed-off-by: Alasdair G Kergon <agk@redhat.com>
Cc: Max Vozeler <max@hinterhof.net>

2 files changed, 70 insertions, 22 deletions

diff --git a/Documentation/device-mapper/dm-crypt.txt b/Documentation/device-mapper/dm-crypt.txt
index 524de926290d..59293ac4a5d0 100644
--- a/Documentation/device-mapper/dm-crypt.txt
+++ b/Documentation/device-mapper/dm-crypt.txt
@@ -8,7 +8,7 @@ Parameters: <cipher> <key> <iv_offset> <device path> <offset>
 
 <cipher>
     Encryption cipher and an optional IV generation mode.
-    (In format cipher-chainmode-ivopts:ivmode).
+    (In format cipher[:keycount]-chainmode-ivopts:ivmode).
     Examples:
        des
        aes-cbc-essiv:sha256
@@ -20,6 +20,11 @@ Parameters: <cipher> <key> <iv_offset> <device path> <offset>
     Key used for encryption. It is encoded as a hexadecimal number.
     You can only use key sizes that are valid for the selected cipher.
 
+<keycount>
+    Multi-key compatibility mode. You can define <keycount> keys and
+    then sectors are encrypted according to their offsets (sector 0 uses key0;
+    sector 1 uses key1 etc.).  <keycount> must be a power of two.
+
 <iv_offset>
     The IV offset is a sector count that is added to the sector number
     before creating the IV.
diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c
index e0ebe685be6a..b8b9267c4dbb 100644
--- a/drivers/md/dm-crypt.c
+++ b/drivers/md/dm-crypt.c
@@ -101,10 +101,9 @@ enum flags { DM_CRYPT_SUSPENDED, DM_CRYPT_KEY_VALID };
  */
 struct crypt_cpu {
         struct ablkcipher_request *req;
-        struct crypto_ablkcipher *tfm;
-
         /* ESSIV: struct crypto_cipher *essiv_tfm */
         void *iv_private;
+        struct crypto_ablkcipher *tfms[0];
 };
 
 /*
@@ -143,6 +142,7 @@ struct crypt_config {
          * per_cpu_ptr() only.
          */
         struct crypt_cpu __percpu *cpu;
+        unsigned tfms_count;
 
         /*
          * Layout of each crypto request:
@@ -161,6 +161,7 @@ struct crypt_config {
 
         unsigned long flags;
         unsigned int key_size;
+        unsigned int key_parts;
         u8 key[0];
 };
 
@@ -184,7 +185,7 @@ static struct crypt_cpu *this_crypt_config(struct crypt_config *cc)
  */
 static struct crypto_ablkcipher *any_tfm(struct crypt_config *cc)
 {
-        return __this_cpu_ptr(cc->cpu)->tfm;
+        return __this_cpu_ptr(cc->cpu)->tfms[0];
 }
 
 /*
@@ -567,11 +568,12 @@ static void crypt_alloc_req(struct crypt_config *cc,
                             struct convert_context *ctx)
 {
         struct crypt_cpu *this_cc = this_crypt_config(cc);
+        unsigned key_index = ctx->sector & (cc->tfms_count - 1);
 
         if (!this_cc->req)
                 this_cc->req = mempool_alloc(cc->req_pool, GFP_NOIO);
 
-        ablkcipher_request_set_tfm(this_cc->req, this_cc->tfm);
+        ablkcipher_request_set_tfm(this_cc->req, this_cc->tfms[key_index]);
         ablkcipher_request_set_callback(this_cc->req,
             CRYPTO_TFM_REQ_MAY_BACKLOG | CRYPTO_TFM_REQ_MAY_SLEEP,
             kcryptd_async_done, dmreq_of_req(cc, this_cc->req));
@@ -1097,15 +1099,48 @@ static void crypt_encode_key(char *hex, u8 *key, unsigned int size)
         }
 }
 
+static void crypt_free_tfms(struct crypt_config *cc, int cpu)
+{
+        struct crypt_cpu *cpu_cc = per_cpu_ptr(cc->cpu, cpu);
+        unsigned i;
+
+        for (i = 0; i < cc->tfms_count; i++)
+                if (cpu_cc->tfms[i] && !IS_ERR(cpu_cc->tfms[i])) {
+                        crypto_free_ablkcipher(cpu_cc->tfms[i]);
+                        cpu_cc->tfms[i] = NULL;
+                }
+}
+
+static int crypt_alloc_tfms(struct crypt_config *cc, int cpu, char *ciphermode)
+{
+        struct crypt_cpu *cpu_cc = per_cpu_ptr(cc->cpu, cpu);
+        unsigned i;
+        int err;
+
+        for (i = 0; i < cc->tfms_count; i++) {
+                cpu_cc->tfms[i] = crypto_alloc_ablkcipher(ciphermode, 0, 0);
+                if (IS_ERR(cpu_cc->tfms[i])) {
+                        err = PTR_ERR(cpu_cc->tfms[i]);
+                        crypt_free_tfms(cc, cpu);
+                        return err;
+                }
+        }
+
+        return 0;
+}
+
 static int crypt_setkey_allcpus(struct crypt_config *cc)
 {
-        int cpu, err = 0, r;
+        unsigned subkey_size = cc->key_size >> ilog2(cc->tfms_count);
+        int cpu, err = 0, i, r;
 
         for_each_possible_cpu(cpu) {
-                r = crypto_ablkcipher_setkey(per_cpu_ptr(cc->cpu, cpu)->tfm,
-                                               cc->key, cc->key_size);
-                if (r)
-                        err = r;
+                for (i = 0; i < cc->tfms_count; i++) {
+                        r = crypto_ablkcipher_setkey(per_cpu_ptr(cc->cpu, cpu)->tfms[i],
+                                                     cc->key + (i * subkey_size), subkey_size);
+                        if (r)
+                                err = r;
+                }
         }
 
         return err;
@@ -1158,8 +1193,7 @@ static void crypt_dtr(struct dm_target *ti)
                         cpu_cc = per_cpu_ptr(cc->cpu, cpu);
                         if (cpu_cc->req)
                                 mempool_free(cpu_cc->req, cc->req_pool);
-                        if (cpu_cc->tfm)
-                                crypto_free_ablkcipher(cpu_cc->tfm);
+                        crypt_free_tfms(cc, cpu);
                 }
 
         if (cc->bs)
@@ -1192,8 +1226,7 @@ static int crypt_ctr_cipher(struct dm_target *ti,
                             char *cipher_in, char *key)
 {
         struct crypt_config *cc = ti->private;
-        struct crypto_ablkcipher *tfm;
-        char *tmp, *cipher, *chainmode, *ivmode, *ivopts;
+        char *tmp, *cipher, *chainmode, *ivmode, *ivopts, *keycount;
         char *cipher_api = NULL;
         int cpu, ret = -EINVAL;
 
@@ -1209,10 +1242,20 @@ static int crypt_ctr_cipher(struct dm_target *ti,
 
         /*
          * Legacy dm-crypt cipher specification
-         * cipher-mode-iv:ivopts
+         * cipher[:keycount]-mode-iv:ivopts
          */
         tmp = cipher_in;
-        cipher = strsep(&tmp, "-");
+        keycount = strsep(&tmp, "-");
+        cipher = strsep(&keycount, ":");
+
+        if (!keycount)
+                cc->tfms_count = 1;
+        else if (sscanf(keycount, "%u", &cc->tfms_count) != 1 ||
+                 !is_power_of_2(cc->tfms_count)) {
+                ti->error = "Bad cipher key count specification";
+                return -EINVAL;
+        }
+        cc->key_parts = cc->tfms_count;
 
         cc->cipher = kstrdup(cipher, GFP_KERNEL);
         if (!cc->cipher)
@@ -1225,7 +1268,9 @@ static int crypt_ctr_cipher(struct dm_target *ti,
         if (tmp)
                 DMWARN("Ignoring unexpected additional cipher options");
 
-        cc->cpu = alloc_percpu(struct crypt_cpu);
+        cc->cpu = __alloc_percpu(sizeof(*(cc->cpu)) +
+                                 cc->tfms_count * sizeof(*(cc->cpu->tfms)),
+                                 __alignof__(struct crypt_cpu));
         if (!cc->cpu) {
                 ti->error = "Cannot allocate per cpu state";
                 goto bad_mem;
@@ -1258,13 +1303,11 @@ static int crypt_ctr_cipher(struct dm_target *ti,
 
         /* Allocate cipher */
         for_each_possible_cpu(cpu) {
-                tfm = crypto_alloc_ablkcipher(cipher_api, 0, 0);
-                if (IS_ERR(tfm)) {
-                        ret = PTR_ERR(tfm);
+                ret = crypt_alloc_tfms(cc, cpu, cipher_api);
+                if (ret < 0) {
                         ti->error = "Error allocating crypto tfm";
                         goto bad;
                 }
-                per_cpu_ptr(cc->cpu, cpu)->tfm = tfm;
         }
 
         /* Initialize and set key */
@@ -1587,7 +1630,7 @@ static int crypt_iterate_devices(struct dm_target *ti,
 
 static struct target_type crypt_target = {
         .name   = "crypt",
-        .version = {1, 9, 0},
+        .version = {1, 10, 0},
         .module = THIS_MODULE,
         .ctr    = crypt_ctr,
         .dtr    = crypt_dtr,