[apparmor] [RFC][PATCH 3/4] eCryptfs: override prepared credentials

[Roberto Sassu]

The new mount parameter 'ecryptfs_security_ctx' allows to override the
security label of the filesystem's credentials. This feature can be used to
identify or restrict actions performed by a specific eCryptfs filesystem.

Signed-off-by: Roberto Sassu <roberto.sassu at polito.it>
---
 fs/ecryptfs/main.c |   16 +++++++++++++++-
 1 files changed, 15 insertions(+), 1 deletions(-)

diff --git a/fs/ecryptfs/main.c b/fs/ecryptfs/main.c
index d53f834..075634b 100644
--- a/fs/ecryptfs/main.c
+++ b/fs/ecryptfs/main.c
@@ -254,7 +254,7 @@ enum { ecryptfs_opt_sig, ecryptfs_opt_ecryptfs_sig,
        ecryptfs_opt_encrypted_view, ecryptfs_opt_fnek_sig,
        ecryptfs_opt_fn_cipher, ecryptfs_opt_fn_cipher_key_bytes,
        ecryptfs_opt_unlink_sigs, ecryptfs_opt_mount_auth_tok_only,
-       ecryptfs_opt_err };
+       ecryptfs_opt_security_ctx, ecryptfs_opt_err };
 
 static const match_table_t tokens = {
 	{ecryptfs_opt_sig, "sig=%s"},
@@ -270,6 +270,7 @@ static const match_table_t tokens = {
 	{ecryptfs_opt_fn_cipher_key_bytes, "ecryptfs_fn_key_bytes=%u"},
 	{ecryptfs_opt_unlink_sigs, "ecryptfs_unlink_sigs"},
 	{ecryptfs_opt_mount_auth_tok_only, "ecryptfs_mount_auth_tok_only"},
+	{ecryptfs_opt_security_ctx, "ecryptfs_security_ctx=%s"},
 	{ecryptfs_opt_err, NULL}
 };
 
@@ -365,6 +366,7 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options)
 	char *fnek_src;
 	char *cipher_key_bytes_src;
 	char *fn_cipher_key_bytes_src;
+	char *security_ctx = NULL;
 
 	if (!options) {
 		rc = -EINVAL;
@@ -474,6 +476,9 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options)
 			mount_crypt_stat->flags |=
 				ECRYPTFS_GLOBAL_MOUNT_AUTH_TOK_ONLY;
 			break;
+		case ecryptfs_opt_security_ctx:
+			security_ctx = args[0].from;
+			break;
 		case ecryptfs_opt_err:
 		default:
 			printk(KERN_WARNING
@@ -505,6 +510,15 @@ static int ecryptfs_parse_options(struct ecryptfs_sb_info *sbi, char *options)
 	    && !fn_cipher_key_bytes_set)
 		mount_crypt_stat->global_default_fn_cipher_key_bytes =
 			mount_crypt_stat->global_default_cipher_key_size;
+	if (security_ctx) {
+		rc = set_security_override_from_ctx(
+			mount_crypt_stat->subject_cred, security_ctx);
+		if (rc) {
+			printk(KERN_ERR "%s: set_security_override_from_ctx "
+					"failed: rc = [%d]\n", __func__, rc);
+			goto out;
+		}
+	}
 	mutex_lock(&key_tfm_list_mutex);
 	if (!ecryptfs_tfm_exists(mount_crypt_stat->global_default_cipher_name,
 				 NULL)) {
-- 
1.7.4.4

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