eCryptfs: verify authentication tokens before their use

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@polito.it>
[tyhicks: Minor formatting changes]
Signed-off-by: Tyler Hicks <tyhicks@linux.vnet.ibm.com>

3 files changed, 135 insertions, 81 deletions

diff --git a/fs/ecryptfs/ecryptfs_kernel.h b/fs/ecryptfs/ecryptfs_kernel.h
index 40c93fe41cc3..bd3cafd0949d 100644
--- a/fs/ecryptfs/ecryptfs_kernel.h
+++ b/fs/ecryptfs/ecryptfs_kernel.h
@@ -331,7 +331,6 @@ 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 bd139dfad8e7..3c4039cc18d1 100644
--- a/fs/ecryptfs/keystore.c
+++ b/fs/ecryptfs/keystore.c
@@ -65,6 +65,24 @@ 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 +421,117 @@ 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;
+                        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 +559,11 @@ 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 +575,7 @@ 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 +1624,6 @@ 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 +1638,12 @@ 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 +2380,7 @@ 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 +2399,16 @@ 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);
+                        printk(KERN_WARNING "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;
                 }
-                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;
-                }
-                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 +2446,8 @@ 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 +2460,9 @@ 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 63e412cf0fa1..520d05f5ad01 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -239,14 +239,14 @@ 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 "