[PATCH v2 3/5] eCryptfs: verify authentication tokens before their use

From: Roberto Sassu
Date: Mon Mar 21 2011 - 11:04:40 EST

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Authentication tokens content may change if another requestor calls the
update() method of the corresponding key. The new function
ecryptfs_verify_auth_tok_from_key() retrieves the authentication token from
the provided key and verifies if it is still valid before being used to
encrypt or decrypt an eCryptfs file.

Signed-off-by: Roberto Sassu <roberto.sassu@xxxxxxxxx>
---
fs/ecryptfs/ecryptfs_kernel.h | 1 -
fs/ecryptfs/keystore.c | 220 ++++++++++++++++++++++++++---------------
fs/ecryptfs/main.c | 4 +-
3 files changed, 144 insertions(+), 81 deletions(-)

diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index f39956a..43ab593 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -333,7 +333,6 @@ struct ecryptfs_global_auth_tok {
u32 flags;
struct list_head mount_crypt_stat_list;
struct key *global_auth_tok_key;
- struct ecryptfs_auth_tok *global_auth_tok;
unsigned char sig[ECRYPTFS_SIG_SIZE_HEX + 1];
};

diff --git a/fs/ecryptfs/keystore.c b/fs/ecryptfs/keystore.c
index bd139df..ff92b3c 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -65,6 +65,26 @@ static int process_request_key_err(long err_code)
return rc;
}

+static int process_find_global_auth_tok_for_sig_err(int err_code)
+{
+ int rc = err_code;
+
+ switch (err_code) {
+ case -ENOENT:
+ ecryptfs_printk(KERN_WARNING,
+ "Missing auth tok\n");
+ break;
+ case -EINVAL:
+ ecryptfs_printk(KERN_WARNING,
+ "Invalid auth tok\n");
+ break;
+ default:
+ rc = process_request_key_err(err_code);
+ break;
+ }
+ return rc;
+}
+
/**
* ecryptfs_parse_packet_length
* @data: Pointer to memory containing length at offset
@@ -403,27 +423,122 @@ out:
return rc;
}

+/**
+ * ecryptfs_verify_version
+ * @version: The version number to confirm
+ *
+ * Returns zero on good version; non-zero otherwise
+ */
+static int ecryptfs_verify_version(u16 version)
+{
+ int rc = 0;
+ unsigned char major;
+ unsigned char minor;
+
+ major = ((version >> 8) & 0xFF);
+ minor = (version & 0xFF);
+ if (major != ECRYPTFS_VERSION_MAJOR) {
+ ecryptfs_printk(KERN_ERR, "Major version number mismatch. "
+ "Expected [%d]; got [%d]\n",
+ ECRYPTFS_VERSION_MAJOR, major);
+ rc = -EINVAL;
+ goto out;
+ }
+ if (minor != ECRYPTFS_VERSION_MINOR) {
+ ecryptfs_printk(KERN_ERR, "Minor version number mismatch. "
+ "Expected [%d]; got [%d]\n",
+ ECRYPTFS_VERSION_MINOR, minor);
+ rc = -EINVAL;
+ goto out;
+ }
+out:
+ return rc;
+}
+
+/**
+ * ecryptfs_verify_auth_tok_from_key
+ * @auth_tok_key: key containing the authentication token
+ * @auth_tok: authentication token
+ *
+ * Returns zero on valid auth tok; -EINVAL otherwise
+ */
+static int
+ecryptfs_verify_auth_tok_from_key(struct key *auth_tok_key,
+ struct ecryptfs_auth_tok **auth_tok)
+{
+ int rc = 0;
+
+ (*auth_tok) = ecryptfs_get_key_payload_data(auth_tok_key);
+ if (ecryptfs_verify_version((*auth_tok)->version)) {
+ printk(KERN_ERR
+ "Data structure version mismatch. "
+ "Userspace tools must match eCryptfs "
+ "kernel module with major version [%d] "
+ "and minor version [%d]\n",
+ ECRYPTFS_VERSION_MAJOR,
+ ECRYPTFS_VERSION_MINOR);
+ rc = -EINVAL;
+ goto out;
+ }
+ if ((*auth_tok)->token_type != ECRYPTFS_PASSWORD
+ && (*auth_tok)->token_type != ECRYPTFS_PRIVATE_KEY) {
+ printk(KERN_ERR "Invalid auth_tok structure "
+ "returned from key query\n");
+ rc = -EINVAL;
+ goto out;
+ }
+out:
+ return rc;
+}
+
static int
ecryptfs_find_global_auth_tok_for_sig(
- struct ecryptfs_global_auth_tok **global_auth_tok,
+ struct key **auth_tok_key,
+ struct ecryptfs_auth_tok **auth_tok,
struct ecryptfs_mount_crypt_stat *mount_crypt_stat, char *sig)
{
struct ecryptfs_global_auth_tok *walker;
int rc = 0;

- (*global_auth_tok) = NULL;
+ (*auth_tok_key) = NULL;
+ (*auth_tok) = NULL;
mutex_lock(&mount_crypt_stat->global_auth_tok_list_mutex);
list_for_each_entry(walker,
&mount_crypt_stat->global_auth_tok_list,
mount_crypt_stat_list) {
- if (memcmp(walker->sig, sig, ECRYPTFS_SIG_SIZE_HEX) == 0) {
- rc = key_validate(walker->global_auth_tok_key);
- if (!rc)
- (*global_auth_tok) = walker;
+ if (memcmp(walker->sig, sig, ECRYPTFS_SIG_SIZE_HEX))
+ continue;
+
+ if (walker->flags & ECRYPTFS_AUTH_TOK_INVALID) {
+ rc = -EINVAL;
goto out;
}
+
+ rc = key_validate(walker->global_auth_tok_key);
+ if (rc) {
+ if (rc == -EKEYEXPIRED)
+ goto out;
+ else
+ goto out_invalid_auth_tok;
+ }
+
+ rc = ecryptfs_verify_auth_tok_from_key(
+ walker->global_auth_tok_key, auth_tok);
+ if (rc)
+ goto out_invalid_auth_tok;
+
+ (*auth_tok_key) = walker->global_auth_tok_key;
+ key_get(*auth_tok_key);
+ goto out;
}
- rc = -EINVAL;
+ rc = -ENOENT;
+ goto out;
+
+out_invalid_auth_tok:
+ printk(KERN_WARNING "Invalidating auth tok with sig = [%s]\n", sig);
+ walker->flags |= ECRYPTFS_AUTH_TOK_INVALID;
+ key_put(walker->global_auth_tok_key);
+ walker->global_auth_tok_key = NULL;
out:
mutex_unlock(&mount_crypt_stat->global_auth_tok_list_mutex);
return rc;
@@ -451,14 +566,11 @@ ecryptfs_find_auth_tok_for_sig(
struct ecryptfs_mount_crypt_stat *mount_crypt_stat,
char *sig)
{
- struct ecryptfs_global_auth_tok *global_auth_tok;
int rc = 0;

- (*auth_tok_key) = NULL;
- (*auth_tok) = NULL;
- if (ecryptfs_find_global_auth_tok_for_sig(&global_auth_tok,
- mount_crypt_stat, sig)) {
-
+ rc = ecryptfs_find_global_auth_tok_for_sig(auth_tok_key, auth_tok,
+ mount_crypt_stat, sig);
+ if (rc == -ENOENT) {
/* if the flag ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY is set in the
* mount_crypt_stat structure, we prevent to use auth toks that
* are not inserted through the ecryptfs_add_global_auth_tok
@@ -470,8 +582,8 @@ ecryptfs_find_auth_tok_for_sig(

rc = ecryptfs_keyring_auth_tok_for_sig(auth_tok_key, auth_tok,
sig);
- } else
- (*auth_tok) = global_auth_tok->global_auth_tok;
+ }
+
return rc;
}

@@ -1520,38 +1632,6 @@ out:
return rc;
}

-/**
- * ecryptfs_verify_version
- * @version: The version number to confirm
- *
- * Returns zero on good version; non-zero otherwise
- */
-static int ecryptfs_verify_version(u16 version)
-{
- int rc = 0;
- unsigned char major;
- unsigned char minor;
-
- major = ((version >> 8) & 0xFF);
- minor = (version & 0xFF);
- if (major != ECRYPTFS_VERSION_MAJOR) {
- ecryptfs_printk(KERN_ERR, "Major version number mismatch. "
- "Expected [%d]; got [%d]\n",
- ECRYPTFS_VERSION_MAJOR, major);
- rc = -EINVAL;
- goto out;
- }
- if (minor != ECRYPTFS_VERSION_MINOR) {
- ecryptfs_printk(KERN_ERR, "Minor version number mismatch. "
- "Expected [%d]; got [%d]\n",
- ECRYPTFS_VERSION_MINOR, minor);
- rc = -EINVAL;
- goto out;
- }
-out:
- return rc;
-}
-
int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
struct ecryptfs_auth_tok **auth_tok,
char *sig)
@@ -1566,29 +1646,12 @@ int ecryptfs_keyring_auth_tok_for_sig(struct key **auth_tok_key,
(*auth_tok_key) = NULL;
goto out;
}
- (*auth_tok) = ecryptfs_get_key_payload_data(*auth_tok_key);
- if (ecryptfs_verify_version((*auth_tok)->version)) {
- printk(KERN_ERR
- "Data structure version mismatch. "
- "Userspace tools must match eCryptfs "
- "kernel module with major version [%d] "
- "and minor version [%d]\n",
- ECRYPTFS_VERSION_MAJOR,
- ECRYPTFS_VERSION_MINOR);
- rc = -EINVAL;
- goto out_release_key;
- }
- if ((*auth_tok)->token_type != ECRYPTFS_PASSWORD
- && (*auth_tok)->token_type != ECRYPTFS_PRIVATE_KEY) {
- printk(KERN_ERR "Invalid auth_tok structure "
- "returned from key query\n");
- rc = -EINVAL;
- goto out_release_key;
- }
-out_release_key:
+
+ rc = ecryptfs_verify_auth_tok_from_key(*auth_tok_key, auth_tok);
if (rc) {
key_put(*auth_tok_key);
(*auth_tok_key) = NULL;
+ goto out;
}
out:
return rc;
@@ -2325,7 +2388,7 @@ ecryptfs_generate_key_packet_set(char *dest_base,
size_t max)
{
struct ecryptfs_auth_tok *auth_tok;
- struct ecryptfs_global_auth_tok *global_auth_tok;
+ struct key *auth_tok_key = NULL;
struct ecryptfs_mount_crypt_stat *mount_crypt_stat =
&ecryptfs_superblock_to_private(
ecryptfs_dentry->d_sb)->mount_crypt_stat;
@@ -2344,21 +2407,17 @@ ecryptfs_generate_key_packet_set(char *dest_base,
list_for_each_entry(key_sig, &crypt_stat->keysig_list,
crypt_stat_list) {
memset(key_rec, 0, sizeof(*key_rec));
- rc = ecryptfs_find_global_auth_tok_for_sig(&global_auth_tok,
+ rc = ecryptfs_find_global_auth_tok_for_sig(&auth_tok_key,
+ &auth_tok,
mount_crypt_stat,
key_sig->keysig);
if (rc) {
- printk(KERN_ERR "Error attempting to get the global "
- "auth_tok; rc = [%d]\n", rc);
- goto out_free;
- }
- if (global_auth_tok->flags & ECRYPTFS_AUTH_TOK_INVALID) {
printk(KERN_WARNING
- "Skipping invalid auth tok with sig = [%s]\n",
- global_auth_tok->sig);
- continue;
+ "Unable to retrieve auth tok with sig = [%s]\n",
+ key_sig->keysig);
+ rc = process_find_global_auth_tok_for_sig_err(rc);
+ goto out_free;
}
- auth_tok = global_auth_tok->global_auth_tok;
if (auth_tok->token_type == ECRYPTFS_PASSWORD) {
rc = write_tag_3_packet((dest_base + (*len)),
&max, auth_tok,
@@ -2396,6 +2455,8 @@ ecryptfs_generate_key_packet_set(char *dest_base,
rc = -EINVAL;
goto out_free;
}
+ key_put(auth_tok_key);
+ auth_tok_key = NULL;
}
if (likely(max > 0)) {
dest_base[(*len)] = 0x00;
@@ -2408,6 +2469,9 @@ out_free:
out:
if (rc)
(*len) = 0;
+ if (auth_tok_key)
+ key_put(auth_tok_key);
+
mutex_unlock(&crypt_stat->keysig_list_mutex);
return rc;
}
diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index 758323a..f079473 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -241,14 +241,14 @@ static int ecryptfs_init_global_auth_toks(
struct ecryptfs_mount_crypt_stat *mount_crypt_stat)
{
struct ecryptfs_global_auth_tok *global_auth_tok;
+ struct ecryptfs_auth_tok *auth_tok;
int rc = 0;

list_for_each_entry(global_auth_tok,
&mount_crypt_stat->global_auth_tok_list,
mount_crypt_stat_list) {
rc = ecryptfs_keyring_auth_tok_for_sig(
- &global_auth_tok->global_auth_tok_key,
- &global_auth_tok->global_auth_tok,
+ &global_auth_tok->global_auth_tok_key, &auth_tok,
global_auth_tok->sig);
if (rc) {
printk(KERN_ERR "Could not find valid key in user "
--
1.7.4

Attachment: smime.p7s
Description: S/MIME cryptographic signature

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