From c538f6ec9f56996677c58cfd1f7f8108b0a944cb Mon Sep 17 00:00:00 2001 From: Ondrej Kozina Date: Mon, 21 Nov 2016 15:58:51 +0100 Subject: dm crypt: add ability to use keys from the kernel key retention service The kernel key service is a generic way to store keys for the use of other subsystems. Currently there is no way to use kernel keys in dm-crypt. This patch aims to fix that. Instead of key userspace may pass a key description with preceding ':'. So message that constructs encryption mapping now looks like this: [|:] [<#opt_params> ] where is in format: :: Currently we only support two elementary key types: 'user' and 'logon'. Keys may be loaded in dm-crypt either via or using classical method and pass the key in hex representation directly. dm-crypt device initialised with a key passed in hex representation may be replaced with key passed in key_string format and vice versa. (Based on original work by Andrey Ryabinin) Signed-off-by: Ondrej Kozina Reviewed-by: David Howells Signed-off-by: Mike Snitzer --- drivers/md/dm-crypt.c | 159 +++++++++++++++++++++++++++++++++++++++++++++----- 1 file changed, 146 insertions(+), 13 deletions(-) (limited to 'drivers/md') diff --git a/drivers/md/dm-crypt.c b/drivers/md/dm-crypt.c index 590d7c4e1083..da0b2e05fdf1 100644 --- a/drivers/md/dm-crypt.c +++ b/drivers/md/dm-crypt.c @@ -12,6 +12,7 @@ #include #include #include +#include #include #include #include @@ -29,6 +30,7 @@ #include #include #include +#include #include @@ -140,6 +142,7 @@ struct crypt_config { char *cipher; char *cipher_string; + char *key_string; const struct crypt_iv_operations *iv_gen_ops; union { @@ -1484,22 +1487,134 @@ static int crypt_setkey(struct crypt_config *cc) return err; } +#ifdef CONFIG_KEYS + +static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string) +{ + char *new_key_string, *key_desc; + int ret; + struct key *key; + const struct user_key_payload *ukp; + + /* look for next ':' separating key_type from key_description */ + key_desc = strpbrk(key_string, ":"); + if (!key_desc || key_desc == key_string || !strlen(key_desc + 1)) + return -EINVAL; + + if (strncmp(key_string, "logon:", key_desc - key_string + 1) && + strncmp(key_string, "user:", key_desc - key_string + 1)) + return -EINVAL; + + new_key_string = kstrdup(key_string, GFP_KERNEL); + if (!new_key_string) + return -ENOMEM; + + key = request_key(key_string[0] == 'l' ? &key_type_logon : &key_type_user, + key_desc + 1, NULL); + if (IS_ERR(key)) { + kzfree(new_key_string); + return PTR_ERR(key); + } + + rcu_read_lock(); + + ukp = user_key_payload(key); + if (!ukp) { + rcu_read_unlock(); + key_put(key); + kzfree(new_key_string); + return -EKEYREVOKED; + } + + if (cc->key_size != ukp->datalen) { + rcu_read_unlock(); + key_put(key); + kzfree(new_key_string); + return -EINVAL; + } + + memcpy(cc->key, ukp->data, cc->key_size); + + rcu_read_unlock(); + key_put(key); + + /* clear the flag since following operations may invalidate previously valid key */ + clear_bit(DM_CRYPT_KEY_VALID, &cc->flags); + + ret = crypt_setkey(cc); + + /* wipe the kernel key payload copy in each case */ + memset(cc->key, 0, cc->key_size * sizeof(u8)); + + if (!ret) { + set_bit(DM_CRYPT_KEY_VALID, &cc->flags); + kzfree(cc->key_string); + cc->key_string = new_key_string; + } else + kzfree(new_key_string); + + return ret; +} + +static int get_key_size(char **key_string) +{ + char *colon, dummy; + int ret; + + if (*key_string[0] != ':') + return strlen(*key_string) >> 1; + + /* look for next ':' in key string */ + colon = strpbrk(*key_string + 1, ":"); + if (!colon) + return -EINVAL; + + if (sscanf(*key_string + 1, "%u%c", &ret, &dummy) != 2 || dummy != ':') + return -EINVAL; + + *key_string = colon; + + /* remaining key string should be :: */ + + return ret; +} + +#else + +static int crypt_set_keyring_key(struct crypt_config *cc, const char *key_string) +{ + return -EINVAL; +} + +static int get_key_size(char **key_string) +{ + return (*key_string[0] == ':') ? -EINVAL : strlen(*key_string) >> 1; +} + +#endif + static int crypt_set_key(struct crypt_config *cc, char *key) { int r = -EINVAL; int key_string_len = strlen(key); - /* The key size may not be changed. */ - if (cc->key_size != (key_string_len >> 1)) - goto out; - /* Hyphen (which gives a key_size of zero) means there is no key. */ if (!cc->key_size && strcmp(key, "-")) goto out; + /* ':' means the key is in kernel keyring, short-circuit normal key processing */ + if (key[0] == ':') { + r = crypt_set_keyring_key(cc, key + 1); + goto out; + } + /* clear the flag since following operations may invalidate previously valid key */ clear_bit(DM_CRYPT_KEY_VALID, &cc->flags); + /* wipe references to any kernel keyring key */ + kzfree(cc->key_string); + cc->key_string = NULL; + if (cc->key_size && crypt_decode_key(cc->key, key, cc->key_size) < 0) goto out; @@ -1518,6 +1633,8 @@ static int crypt_wipe_key(struct crypt_config *cc) { clear_bit(DM_CRYPT_KEY_VALID, &cc->flags); memset(&cc->key, 0, cc->key_size * sizeof(u8)); + kzfree(cc->key_string); + cc->key_string = NULL; return crypt_setkey(cc); } @@ -1555,6 +1672,7 @@ static void crypt_dtr(struct dm_target *ti) kzfree(cc->cipher); kzfree(cc->cipher_string); + kzfree(cc->key_string); /* Must zero key material before freeing */ kzfree(cc); @@ -1723,12 +1841,13 @@ bad_mem: /* * Construct an encryption mapping: - * + * [|:::] */ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv) { struct crypt_config *cc; - unsigned int key_size, opt_params; + int key_size; + unsigned int opt_params; unsigned long long tmpll; int ret; size_t iv_size_padding; @@ -1745,7 +1864,11 @@ static int crypt_ctr(struct dm_target *ti, unsigned int argc, char **argv) return -EINVAL; } - key_size = strlen(argv[1]) >> 1; + key_size = get_key_size(&argv[1]); + if (key_size < 0) { + ti->error = "Cannot parse key size"; + return -EINVAL; + } cc = kzalloc(sizeof(*cc) + key_size * sizeof(u8), GFP_KERNEL); if (!cc) { @@ -1952,10 +2075,13 @@ static void crypt_status(struct dm_target *ti, status_type_t type, case STATUSTYPE_TABLE: DMEMIT("%s ", cc->cipher_string); - if (cc->key_size > 0) - for (i = 0; i < cc->key_size; i++) - DMEMIT("%02x", cc->key[i]); - else + if (cc->key_size > 0) { + if (cc->key_string) + DMEMIT(":%u:%s", cc->key_size, cc->key_string); + else + for (i = 0; i < cc->key_size; i++) + DMEMIT("%02x", cc->key[i]); + } else DMEMIT("-"); DMEMIT(" %llu %s %llu", (unsigned long long)cc->iv_offset, @@ -2011,7 +2137,7 @@ static void crypt_resume(struct dm_target *ti) static int crypt_message(struct dm_target *ti, unsigned argc, char **argv) { struct crypt_config *cc = ti->private; - int ret = -EINVAL; + int key_size, ret = -EINVAL; if (argc < 2) goto error; @@ -2022,6 +2148,13 @@ static int crypt_message(struct dm_target *ti, unsigned argc, char **argv) return -EINVAL; } if (argc == 3 && !strcasecmp(argv[1], "set")) { + /* The key size may not be changed. */ + key_size = get_key_size(&argv[2]); + if (key_size < 0 || cc->key_size != key_size) { + memset(argv[2], '0', strlen(argv[2])); + return -EINVAL; + } + ret = crypt_set_key(cc, argv[2]); if (ret) return ret; @@ -2065,7 +2198,7 @@ static void crypt_io_hints(struct dm_target *ti, struct queue_limits *limits) static struct target_type crypt_target = { .name = "crypt", - .version = {1, 14, 1}, + .version = {1, 15, 0}, .module = THIS_MODULE, .ctr = crypt_ctr, .dtr = crypt_dtr, -- cgit