cifs: implement CIFSParseMFSymlink()

Signed-off-by: Stefan Metzmacher <metze@samba.org>
Signed-off-by: Steve French <sfrench@us.ibm.com>

1 files changed, 62 insertions, 0 deletions

diff --git a/fs/cifs/link.c b/fs/cifs/link.c
index 473ca8033656..12eb491d4c52 100644
--- a/fs/cifs/link.c
+++ b/fs/cifs/link.c
@@ -28,6 +28,68 @@
 #include "cifsproto.h"
 #include "cifs_debug.h"
 #include "cifs_fs_sb.h"
+#include "md5.h"
+
+#define CIFS_MF_SYMLINK_LEN_OFFSET (4+1)
+#define CIFS_MF_SYMLINK_MD5_OFFSET (CIFS_MF_SYMLINK_LEN_OFFSET+(4+1))
+#define CIFS_MF_SYMLINK_LINK_OFFSET (CIFS_MF_SYMLINK_MD5_OFFSET+(32+1))
+#define CIFS_MF_SYMLINK_LINK_MAXLEN (1024)
+#define CIFS_MF_SYMLINK_FILE_SIZE \
+        (CIFS_MF_SYMLINK_LINK_OFFSET + CIFS_MF_SYMLINK_LINK_MAXLEN)
+
+#define CIFS_MF_SYMLINK_LEN_FORMAT "XSym\n%04u\n"
+#define CIFS_MF_SYMLINK_MD5_FORMAT \
+        "%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x%02x\n"
+#define CIFS_MF_SYMLINK_MD5_ARGS(md5_hash) \
+        md5_hash[0],  md5_hash[1],  md5_hash[2],  md5_hash[3], \
+        md5_hash[4],  md5_hash[5],  md5_hash[6],  md5_hash[7], \
+        md5_hash[8],  md5_hash[9],  md5_hash[10], md5_hash[11],\
+        md5_hash[12], md5_hash[13], md5_hash[14], md5_hash[15]
+
+static int
+CIFSParseMFSymlink(const u8 *buf,
+                   unsigned int buf_len,
+                   unsigned int *_link_len,
+                   char **_link_str)
+{
+        int rc;
+        unsigned int link_len;
+        const char *md5_str1;
+        const char *link_str;
+        struct MD5Context md5_ctx;
+        u8 md5_hash[16];
+        char md5_str2[34];
+
+        if (buf_len != CIFS_MF_SYMLINK_FILE_SIZE)
+                return -EINVAL;
+
+        md5_str1 = (const char *)&buf[CIFS_MF_SYMLINK_MD5_OFFSET];
+        link_str = (const char *)&buf[CIFS_MF_SYMLINK_LINK_OFFSET];
+
+        rc = sscanf(buf, CIFS_MF_SYMLINK_LEN_FORMAT, &link_len);
+        if (rc != 1)
+                return -EINVAL;
+
+        cifs_MD5_init(&md5_ctx);
+        cifs_MD5_update(&md5_ctx, (const u8 *)link_str, link_len);
+        cifs_MD5_final(md5_hash, &md5_ctx);
+
+        snprintf(md5_str2, sizeof(md5_str2),
+                 CIFS_MF_SYMLINK_MD5_FORMAT,
+                 CIFS_MF_SYMLINK_MD5_ARGS(md5_hash));
+
+        if (strncmp(md5_str1, md5_str2, 17) != 0)
+                return -EINVAL;
+
+        if (_link_str) {
+                *_link_str = kstrndup(link_str, link_len, GFP_KERNEL);
+                if (!*_link_str)
+                        return -ENOMEM;
+        }
+
+        *_link_len = link_len;
+        return 0;
+}
 
 int
 cifs_hardlink(struct dentry *old_file, struct inode *inode,