unix_capture.c: support capturing extended attributes
authorEric Biggers <ebiggers3@gmail.com>
Tue, 27 Dec 2016 23:24:55 +0000 (17:24 -0600)
committerEric Biggers <ebiggers3@gmail.com>
Wed, 28 Dec 2016 04:30:51 +0000 (22:30 -0600)
src/unix_capture.c

index 1c207cb..d869f25 100644 (file)
 #include <fcntl.h>
 #include <limits.h> /* for PATH_MAX */
 #include <sys/stat.h>
+#include <sys/types.h>
+#ifdef HAVE_SYS_XATTR_H
+#  include <sys/xattr.h>
+#endif
 #include <unistd.h>
 
 #include "wimlib/blob_table.h"
@@ -39,6 +43,7 @@
 #include "wimlib/scan.h"
 #include "wimlib/timestamp.h"
 #include "wimlib/unix_data.h"
+#include "wimlib/xattr.h"
 
 #ifdef HAVE_FDOPENDIR
 #  define my_fdopendir(dirfd_p) fdopendir(*(dirfd_p))
@@ -99,6 +104,189 @@ my_fdopendir(int *dirfd_p)
 #  define AT_SYMLINK_NOFOLLOW  0x100
 #endif
 
+#ifdef HAVE_XATTR_SUPPORT
+/*
+ * Retrieves the values of the xattrs named by the null-terminated @names of the
+ * file at @path and serializes the xattr names and values into @entries.  If
+ * successful, returns the number of bytes used in @entries.  If unsuccessful,
+ * returns -1 and sets errno (ERANGE if @entries was too small).
+ */
+static ssize_t
+gather_xattr_entries(const char *path, const char *names, size_t names_size,
+                    void *entries, size_t entries_size)
+{
+       const char * const names_end = names + names_size;
+       void * const entries_end = entries + entries_size;
+       const char *name = names;
+       struct wimlib_xattr_entry *entry = entries;
+
+       wimlib_assert((uintptr_t)entries % 4 == 0 &&
+                     entries_size % 4 == 0 && names_size != 0);
+       do {
+               size_t name_len = strnlen(name, names_end - name);
+               void *value;
+               ssize_t value_len;
+
+               if (name_len == 0 || name_len >= names_end - name ||
+                   (u16)name_len != name_len) {
+                       ERROR("\"%s\": malformed extended attribute names list",
+                             path);
+                       errno = EINVAL;
+                       return -1;
+               }
+
+               /*
+                * Note: we take care to always call lgetxattr() with a nonzero
+                * size, since zero size means to return the value length only.
+                */
+               if (entries_end - (void *)entry <= sizeof(*entry) + name_len) {
+                       errno = ERANGE;
+                       return -1;
+               }
+
+               entry->name_len = cpu_to_le16(name_len);
+               entry->reserved = 0;
+               value = mempcpy(entry->name, name, name_len);
+
+               value_len = lgetxattr(path, name, value, entries_end - value);
+               if (value_len < 0) {
+                       if (errno != ERANGE) {
+                               ERROR_WITH_ERRNO("\"%s\": unable to read extended attribute \"%s\"",
+                                                path, name);
+                       }
+                       return -1;
+               }
+               if ((u32)value_len != value_len) {
+                       ERROR("\"%s\": value of extended attribute \"%s\" is too large",
+                             path, name);
+                       errno = EINVAL;
+                       return -1;
+               }
+               entry->value_len = cpu_to_le32(value_len);
+
+               /*
+                * Zero-pad the entry to the next 4-byte boundary.
+                * Note: because we've guaranteed that @entries_size is a
+                * multiple of 4, this cannot overflow the @entries buffer.
+                */
+               value += value_len;
+               while ((uintptr_t)value & 3) {
+                       *(u8 *)value = 0;
+                       value++;
+               }
+
+               entry = value;
+               name += name_len + 1;
+       } while (name < names_end);
+
+       return (void *)entry - entries;
+}
+
+static int
+create_xattr_item(const char *path, struct wim_inode *inode,
+                 const char *names, size_t names_size)
+{
+       char _entries[1024] _aligned_attribute(4);
+       char *entries = _entries;
+       size_t entries_avail = ARRAY_LEN(_entries);
+       ssize_t entries_size;
+       int ret;
+
+retry:
+       /* Serialize the xattrs into @entries */
+       entries_size = gather_xattr_entries(path, names, names_size,
+                                           entries, entries_avail);
+       if (entries_size < 0) {
+               ret = WIMLIB_ERR_STAT;
+               if (errno != ERANGE)
+                       goto out;
+               /* Not enough space in @entries.  Reallocate it. */
+               if (entries != _entries)
+                       FREE(entries);
+               ret = WIMLIB_ERR_NOMEM;
+               entries_avail *= 2;
+               entries = MALLOC(entries_avail);
+               if (!entries)
+                       goto out;
+               goto retry;
+       }
+
+       /* Copy @entries into an xattr item associated with @inode */
+       if ((u32)entries_size != entries_size) {
+               ERROR("\"%s\": too much xattr data!", path);
+               ret = WIMLIB_ERR_STAT;
+               goto out;
+       }
+       ret = WIMLIB_ERR_NOMEM;
+       if (!inode_set_linux_xattrs(inode, entries, entries_size))
+               goto out;
+
+       ret = 0;
+out:
+       if (entries != _entries)
+               FREE(entries);
+       return ret;
+}
+
+/*
+ * If the file at @path has Linux-style extended attributes, read them into
+ * memory and add them to @inode as a tagged item.
+ */
+static noinline_for_stack int
+scan_linux_xattrs(const char *path, struct wim_inode *inode)
+{
+       char _names[256];
+       char *names = _names;
+       ssize_t names_size = ARRAY_LEN(_names);
+       int ret = 0;
+
+retry:
+       /* Gather the names of the xattrs of the file at @path */
+       names_size = llistxattr(path, names, names_size);
+       if (names_size == 0) /* No xattrs? */
+               goto out;
+       if (names_size < 0) {
+               /* xattrs unsupported or disabled? */
+               if (errno == ENOTSUP || errno == ENOSYS)
+                       goto out;
+               if (errno == ERANGE) {
+                       /*
+                        * Not enough space in @names.  Ask for how much space
+                        * we need, then try again.
+                        */
+                       names_size = llistxattr(path, NULL, 0);
+                       if (names_size == 0)
+                               goto out;
+                       if (names_size > 0) {
+                               if (names != _names)
+                                       FREE(names);
+                               names = MALLOC(names_size);
+                               if (!names) {
+                                       ret = WIMLIB_ERR_NOMEM;
+                                       goto out;
+                               }
+                               goto retry;
+                       }
+               }
+               /* Some other error occurred. */
+               ERROR_WITH_ERRNO("\"%s\": unable to list extended attributes",
+                                path);
+               ret = WIMLIB_ERR_STAT;
+               goto out;
+       }
+
+       /*
+        * We have a nonempty list of xattr names.  Gather the xattr values and
+        * add them as a tagged item.
+        */
+       ret = create_xattr_item(path, inode, names, names_size);
+out:
+       if (names != _names)
+               FREE(names);
+       return ret;
+}
+#endif /* HAVE_XATTR_SUPPORT */
+
 static int
 unix_scan_regular_file(const char *path, u64 blocks, u64 size,
                       struct wim_inode *inode,
@@ -436,6 +624,11 @@ unix_build_dentry_tree_recursive(struct wim_dentry **tree_ret,
                        ret = WIMLIB_ERR_NOMEM;
                        goto out;
                }
+#ifdef HAVE_XATTR_SUPPORT
+               ret = scan_linux_xattrs(full_path, inode);
+               if (ret)
+                       goto out;
+#endif
        }
 
        if (params->add_flags & WIMLIB_ADD_FLAG_ROOT) {