[PATCH] eCryptfs: Generalize metadata read/write

Generalize the metadata reading and writing mechanisms, with two targets for
now: metadata in file header and metadata in the user.ecryptfs xattr of the
lower file.

[akpm@osdl.org: printk warning fix]
[bunk@stusta.de: make some needlessly global code static]
Signed-off-by: Michael Halcrow <mhalcrow@us.ibm.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>

1 files changed, 178 insertions, 56 deletions

diff --git a/fs/ecryptfs/crypto.c b/fs/ecryptfs/crypto.c
index 6d85aabb0179..96fa40a48b4f 100644
--- a/fs/ecryptfs/crypto.c
+++ b/fs/ecryptfs/crypto.c
@@ -3,7 +3,7 @@
  *
  * Copyright (C) 1997-2004 Erez Zadok
  * Copyright (C) 2001-2004 Stony Brook University
- * Copyright (C) 2004-2006 International Business Machines Corp.
+ * Copyright (C) 2004-2007 International Business Machines Corp.
  *   Author(s): Michael A. Halcrow <mahalcro@us.ibm.com>
  *              Michael C. Thompson <mcthomps@us.ibm.com>
  *
@@ -863,7 +863,10 @@ void ecryptfs_set_default_sizes(struct ecryptfs_crypt_stat *crypt_stat)
                         ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE;
         } else
                 crypt_stat->header_extent_size = PAGE_CACHE_SIZE;
-        crypt_stat->num_header_extents_at_front = 1;
+        if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
+                crypt_stat->num_header_extents_at_front = 0;
+        else
+                crypt_stat->num_header_extents_at_front = 1;
 }
 
 /**
@@ -1021,7 +1024,7 @@ int ecryptfs_new_file_context(struct dentry *ecryptfs_dentry)
  *
  * Returns one if marker found; zero if not found
  */
-int contains_ecryptfs_marker(char *data)
+static int contains_ecryptfs_marker(char *data)
 {
         u32 m_1, m_2;
 
@@ -1047,7 +1050,8 @@ struct ecryptfs_flag_map_elem {
 /* Add support for additional flags by adding elements here. */
 static struct ecryptfs_flag_map_elem ecryptfs_flag_map[] = {
         {0x00000001, ECRYPTFS_ENABLE_HMAC},
-        {0x00000002, ECRYPTFS_ENCRYPTED}
+        {0x00000002, ECRYPTFS_ENCRYPTED},
+        {0x00000004, ECRYPTFS_METADATA_IN_XATTR}
 };
 
 /**
@@ -1207,8 +1211,8 @@ int ecryptfs_cipher_code_to_string(char *str, u16 cipher_code)
  *
  * Returns zero on success; non-zero otherwise
  */
-int ecryptfs_read_header_region(char *data, struct dentry *dentry,
-                                struct vfsmount *mnt)
+static int ecryptfs_read_header_region(char *data, struct dentry *dentry,
+                                       struct vfsmount *mnt)
 {
         struct file *lower_file;
         mm_segment_t oldfs;
@@ -1237,6 +1241,21 @@ out:
         return rc;
 }
 
+int ecryptfs_read_and_validate_header_region(char *data, struct dentry *dentry,
+                                             struct vfsmount *mnt)
+{
+        int rc;
+
+        rc = ecryptfs_read_header_region(data, dentry, mnt);
+        if (rc)
+                goto out;
+        if (!contains_ecryptfs_marker(data + ECRYPTFS_FILE_SIZE_BYTES))
+                rc = -EINVAL;
+out:
+        return rc;
+}
+
+
 static void
 write_header_metadata(char *virt, struct ecryptfs_crypt_stat *crypt_stat,
                       size_t *written)
@@ -1288,9 +1307,9 @@ struct kmem_cache *ecryptfs_header_cache_2;
  *
  * Returns zero on success
  */
-int ecryptfs_write_headers_virt(char *page_virt,
-                                struct ecryptfs_crypt_stat *crypt_stat,
-                                struct dentry *ecryptfs_dentry)
+static int ecryptfs_write_headers_virt(char *page_virt, size_t *size,
+                                       struct ecryptfs_crypt_stat *crypt_stat,
+                                       struct dentry *ecryptfs_dentry)
 {
         int rc;
         size_t written;
@@ -1309,11 +1328,53 @@ int ecryptfs_write_headers_virt(char *page_virt,
         if (rc)
                 ecryptfs_printk(KERN_WARNING, "Error generating key packet "
                                 "set; rc = [%d]\n", rc);
+        if (size) {
+                offset += written;
+                *size = offset;
+        }
+        return rc;
+}
+
+static int ecryptfs_write_metadata_to_contents(struct ecryptfs_crypt_stat *crypt_stat,
+                                               struct file *lower_file,
+                                               char *page_virt)
+{
+        mm_segment_t oldfs;
+        int current_header_page;
+        int header_pages;
+
+        lower_file->f_pos = 0;
+        oldfs = get_fs();
+        set_fs(get_ds());
+        lower_file->f_op->write(lower_file, (char __user *)page_virt,
+                                PAGE_CACHE_SIZE, &lower_file->f_pos);
+        header_pages = ((crypt_stat->header_extent_size
+                         * crypt_stat->num_header_extents_at_front)
+                        / PAGE_CACHE_SIZE);
+        memset(page_virt, 0, PAGE_CACHE_SIZE);
+        current_header_page = 1;
+        while (current_header_page < header_pages) {
+                lower_file->f_op->write(lower_file, (char __user *)page_virt,
+                                        PAGE_CACHE_SIZE, &lower_file->f_pos);
+                current_header_page++;
+        }
+        set_fs(oldfs);
+        return 0;
+}
+
+static int ecryptfs_write_metadata_to_xattr(struct dentry *ecryptfs_dentry,
+                                            struct ecryptfs_crypt_stat *crypt_stat,
+                                            char *page_virt, size_t size)
+{
+        int rc;
+
+        rc = ecryptfs_setxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME, page_virt,
+                               size, 0);
         return rc;
 }
 
 /**
- * ecryptfs_write_headers
+ * ecryptfs_write_metadata
  * @lower_file: The lower file struct, which was returned from dentry_open
  *
  * Write the file headers out.  This will likely involve a userspace
@@ -1324,14 +1385,12 @@ int ecryptfs_write_headers_virt(char *page_virt,
  *
  * Returns zero on success; non-zero on error
  */
-int ecryptfs_write_headers(struct dentry *ecryptfs_dentry,
-                           struct file *lower_file)
+int ecryptfs_write_metadata(struct dentry *ecryptfs_dentry,
+                            struct file *lower_file)
 {
-        mm_segment_t oldfs;
         struct ecryptfs_crypt_stat *crypt_stat;
         char *page_virt;
-        int current_header_page;
-        int header_pages;
+        size_t size;
         int rc = 0;
 
         crypt_stat = &ecryptfs_inode_to_private(
@@ -1358,48 +1417,36 @@ int ecryptfs_write_headers(struct dentry *ecryptfs_dentry,
                 rc = -ENOMEM;
                 goto out;
         }
-
-        rc = ecryptfs_write_headers_virt(page_virt, crypt_stat,
-                                         ecryptfs_dentry);
+        rc = ecryptfs_write_headers_virt(page_virt, &size, crypt_stat,
+                                         ecryptfs_dentry);
         if (unlikely(rc)) {
                 ecryptfs_printk(KERN_ERR, "Error whilst writing headers\n");
                 memset(page_virt, 0, PAGE_CACHE_SIZE);
                 goto out_free;
         }
-        ecryptfs_printk(KERN_DEBUG,
-                        "Writing key packet set to underlying file\n");
-        lower_file->f_pos = 0;
-        oldfs = get_fs();
-        set_fs(get_ds());
-        ecryptfs_printk(KERN_DEBUG, "Calling lower_file->f_op->"
-                        "write() w/ header page; lower_file->f_pos = "
-                        "[0x%.16x]\n", lower_file->f_pos);
-        lower_file->f_op->write(lower_file, (char __user *)page_virt,
-                                PAGE_CACHE_SIZE, &lower_file->f_pos);
-        header_pages = ((crypt_stat->header_extent_size
-                         * crypt_stat->num_header_extents_at_front)
-                        / PAGE_CACHE_SIZE);
-        memset(page_virt, 0, PAGE_CACHE_SIZE);
-        current_header_page = 1;
-        while (current_header_page < header_pages) {
-                ecryptfs_printk(KERN_DEBUG, "Calling lower_file->f_op->"
-                                "write() w/ zero'd page; lower_file->f_pos = "
-                                "[0x%.16x]\n", lower_file->f_pos);
-                lower_file->f_op->write(lower_file, (char __user *)page_virt,
-                                        PAGE_CACHE_SIZE, &lower_file->f_pos);
-                current_header_page++;
+        if (crypt_stat->flags & ECRYPTFS_METADATA_IN_XATTR)
+                rc = ecryptfs_write_metadata_to_xattr(ecryptfs_dentry,
+                                                      crypt_stat, page_virt,
+                                                      size);
+        else
+                rc = ecryptfs_write_metadata_to_contents(crypt_stat, lower_file,
+                                                         page_virt);
+        if (rc) {
+                printk(KERN_ERR "Error writing metadata out to lower file; "
+                       "rc = [%d]\n", rc);
+                goto out_free;
         }
-        set_fs(oldfs);
-        ecryptfs_printk(KERN_DEBUG,
-                        "Done writing key packet set to underlying file.\n");
 out_free:
         kmem_cache_free(ecryptfs_header_cache_0, page_virt);
 out:
         return rc;
 }
 
+#define ECRYPTFS_DONT_VALIDATE_HEADER_SIZE 0
+#define ECRYPTFS_VALIDATE_HEADER_SIZE 1
 static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
-                                 char *virt, int *bytes_read)
+                                 char *virt, int *bytes_read,
+                                 int validate_header_size)
 {
         int rc = 0;
         u32 header_extent_size;
@@ -1414,9 +1461,10 @@ static int parse_header_metadata(struct ecryptfs_crypt_stat *crypt_stat,
         crypt_stat->num_header_extents_at_front =
                 (int)num_header_extents_at_front;
         (*bytes_read) = 6;
-        if ((crypt_stat->header_extent_size
-             * crypt_stat->num_header_extents_at_front)
-            < ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE) {
+        if ((validate_header_size == ECRYPTFS_VALIDATE_HEADER_SIZE)
+            && ((crypt_stat->header_extent_size
+                 * crypt_stat->num_header_extents_at_front)
+                < ECRYPTFS_MINIMUM_HEADER_EXTENT_SIZE)) {
                 rc = -EINVAL;
                 ecryptfs_printk(KERN_WARNING, "Invalid header extent size: "
                                 "[%d]\n", crypt_stat->header_extent_size);
@@ -1447,7 +1495,8 @@ static void set_default_header_data(struct ecryptfs_crypt_stat *crypt_stat)
  */
 static int ecryptfs_read_headers_virt(char *page_virt,
                                       struct ecryptfs_crypt_stat *crypt_stat,
-                                      struct dentry *ecryptfs_dentry)
+                                      struct dentry *ecryptfs_dentry,
+                                      int validate_header_size)
 {
         int rc = 0;
         int offset;
@@ -1481,7 +1530,7 @@ static int ecryptfs_read_headers_virt(char *page_virt,
         offset += bytes_read;
         if (crypt_stat->file_version >= 1) {
                 rc = parse_header_metadata(crypt_stat, (page_virt + offset),
-                                           &bytes_read);
+                                           &bytes_read, validate_header_size);
                 if (rc) {
                         ecryptfs_printk(KERN_WARNING, "Error reading header "
                                         "metadata; rc = [%d]\n", rc);
@@ -1496,12 +1545,60 @@ out:
 }
 
 /**
- * ecryptfs_read_headers
+ * ecryptfs_read_xattr_region
+ *
+ * Attempts to read the crypto metadata from the extended attribute
+ * region of the lower file.
+ */
+int ecryptfs_read_xattr_region(char *page_virt, struct dentry *ecryptfs_dentry)
+{
+        ssize_t size;
+        int rc = 0;
+
+        size = ecryptfs_getxattr(ecryptfs_dentry, ECRYPTFS_XATTR_NAME,
+                                 page_virt, ECRYPTFS_DEFAULT_EXTENT_SIZE);
+        if (size < 0) {
+                printk(KERN_DEBUG "Error attempting to read the [%s] "
+                       "xattr from the lower file; return value = [%zd]\n",
+                       ECRYPTFS_XATTR_NAME, size);
+                rc = -EINVAL;
+                goto out;
+        }
+out:
+        return rc;
+}
+
+int ecryptfs_read_and_validate_xattr_region(char *page_virt,
+                                            struct dentry *ecryptfs_dentry)
+{
+        int rc;
+
+        rc = ecryptfs_read_xattr_region(page_virt, ecryptfs_dentry);
+        if (rc)
+                goto out;
+        if (!contains_ecryptfs_marker(page_virt + ECRYPTFS_FILE_SIZE_BYTES)) {
+                printk(KERN_WARNING "Valid data found in [%s] xattr, but "
+                        "the marker is invalid\n", ECRYPTFS_XATTR_NAME);
+                rc = -EINVAL;
+        }
+out:
+        return rc;
+}
+
+/**
+ * ecryptfs_read_metadata
+ *
+ * Common entry point for reading file metadata. From here, we could
+ * retrieve the header information from the header region of the file,
+ * the xattr region of the file, or some other repostory that is
+ * stored separately from the file itself. The current implementation
+ * supports retrieving the metadata information from the file contents
+ * and from the xattr region.
  *
  * Returns zero if valid headers found and parsed; non-zero otherwise
  */
-int ecryptfs_read_headers(struct dentry *ecryptfs_dentry,
-                          struct file *lower_file)
+int ecryptfs_read_metadata(struct dentry *ecryptfs_dentry,
+                           struct file *lower_file)
 {
         int rc = 0;
         char *page_virt = NULL;
@@ -1530,11 +1627,36 @@ int ecryptfs_read_headers(struct dentry *ecryptfs_dentry,
                 goto out;
         }
         rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
-                                        ecryptfs_dentry);
+                                        ecryptfs_dentry,
+                                        ECRYPTFS_VALIDATE_HEADER_SIZE);
         if (rc) {
-                ecryptfs_printk(KERN_DEBUG, "Valid eCryptfs headers not "
-                                "found\n");
-                rc = -EINVAL;
+                rc = ecryptfs_read_xattr_region(page_virt,
+                                                ecryptfs_dentry);
+                if (rc) {
+                        printk(KERN_DEBUG "Valid eCryptfs headers not found in "
+                               "file header region or xattr region\n");
+                        rc = -EINVAL;
+                        goto out;
+                }
+                rc = ecryptfs_read_headers_virt(page_virt, crypt_stat,
+                                                ecryptfs_dentry,
+                                                ECRYPTFS_DONT_VALIDATE_HEADER_SIZE);
+                if (rc) {
+                        printk(KERN_DEBUG "Valid eCryptfs headers not found in "
+                               "file xattr region either\n");
+                        rc = -EINVAL;
+                }
+                if (crypt_stat->mount_crypt_stat->flags
+                    & ECRYPTFS_XATTR_METADATA_ENABLED) {
+                        crypt_stat->flags |= ECRYPTFS_METADATA_IN_XATTR;
+                } else {
+                        printk(KERN_WARNING "Attempt to access file with "
+                               "crypto metadata only in the extended attribute "
+                               "region, but eCryptfs was mounted without "
+                               "xattr support enabled. eCryptfs will not treat "
+                               "this like an encrypted file.\n");
+                        rc = -EINVAL;
+                }
         }
 out:
         if (page_virt) {