Add support for Windows shortcuts (*.lnk files)

Supports only relative links across the same volume.

Change-Id: I4f61bb9d5f2385d5b15d2b9d9a3f814a7ac85b54

3 files changed, 346 insertions, 0 deletions

diff --git a/apps/plugins/SOURCES b/apps/plugins/SOURCES
index 6551df71a9..9e153a3c96 100644
--- a/apps/plugins/SOURCES
+++ b/apps/plugins/SOURCES
@@ -34,6 +34,7 @@ flipit.c
 shopper.c
 resistor.c
 otp.c
+windows_lnk.c
 
 #ifdef USB_ENABLE_HID
 remote_control.c
diff --git a/apps/plugins/viewers.config b/apps/plugins/viewers.config
index c938eeb275..96228085c9 100644
--- a/apps/plugins/viewers.config
+++ b/apps/plugins/viewers.config
@@ -100,3 +100,4 @@ z6,viewers/frotz,-
 z7,viewers/frotz,-
 z8,viewers/frotz,-
 shopper,viewers/shopper,1
+lnk,viewers/windows_lnk,-
diff --git a/apps/plugins/windows_lnk.c b/apps/plugins/windows_lnk.c
new file mode 100644
index 0000000000..6ef1a6a3ac
--- /dev/null
+++ b/apps/plugins/windows_lnk.c
@@ -0,0 +1,344 @@
+/***************************************************************************
+ *             __________               __   ___.
+ *   Open      \______   \ ____   ____ |  | _\_ |__   _______  ___
+ *   Source     |       _//  _ \_/ ___\|  |/ /| __ \ /  _ \  \/  /
+ *   Jukebox    |    |   (  <_> )  \___|    < | \_\ (  <_> > <  <
+ *   Firmware   |____|_  /\____/ \___  >__|_ \|___  /\____/__/\_ \
+ *                     \/            \/     \/    \/            \/
+ * $Id$
+ *
+ * Copyright (C) 2017 Sebastian Leonhardt
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
+ * KIND, either express or implied.
+ *
+ ****************************************************************************/
+
+#include "plugin.h"
+
+/**
+ *  Follow Windows shortcuts (*.lnk files) in Rockbox.
+ *  If the destination is a file, it will be selected in the file browser,
+ *  a directory will be entered.
+ *  For now, only relative links are supported.
+ */
+
+/* a selection of link flags */
+#define HAS_LINK_TARGET_ID_LIST     0x01
+#define HAS_LINK_INFO               0x02
+#define HAS_NAME                    0x04
+#define HAS_RELATIVE_PATH           0x08
+#define HAS_WORKING_DIR             0x10
+#define HAS_ARGUMENTS               0x20
+#define HAS_ICON_LOCATION           0x40
+#define IS_UNICODE                  0x80
+#define FORCE_NO_LINK_INFO         0x100
+/* a selection of file attributes flags */
+#define FILE_ATTRIBUTE_DIRECTORY    0x10
+#define FILE_ATTRIBUTE_NORMAL       0x80
+
+
+/**
+ *  Read one byte from file
+ *  \param  fd  file descriptor
+ *  \param  *a  where the data should go
+ *  \return     false if an error occured, true on success
+ */
+static bool read_byte(const int fd, unsigned char *a)
+{
+    if (!rb->read(fd, a, 1))
+        return false;
+    return true;
+}
+
+/**
+ *  Read 16-bit word from file, respecting windows endianness (little endian)
+ *  \param  fd  file descriptor
+ *  \param  *a  where the data should go
+ *  \return     false if an error occured, true on success
+ */
+static bool read_word(const int fd, int *a)
+{
+    unsigned char a1,a2;
+    int r;
+
+    r = read_byte(fd, &a1);
+    if (!r)
+        return false;
+    r = read_byte(fd, &a2);
+    if (!r)
+        return false;
+    *a = (a2<<8) + a1;
+    return true;
+}
+
+/**
+ *  Read 32-bit word from file, respecting windows endianness (little endian)
+ *  \param  fd  file descriptor
+ *  \param  *a  where the data should go
+ *  \return     false if an error occured, true on success
+ */
+static bool read_lword(const int fd, uint32_t *a)
+{
+    int a1,a2;
+    int r;
+
+    r = read_word(fd, &a1);
+    if (!r)
+        return false;
+    r = read_word(fd, &a2);
+    if (!r)
+        return false;
+    *a = (a2<<16) + a1;
+    return true;
+}
+
+
+/**
+ *  Scan *.lnk file for relative link target
+ *  \param  fd          file descriptor
+ *  \param  link_target the extracted link destination
+ *  \param  target_size available space for the extracted link (in bytes)
+ *  \param  link_flags  the link flags are stored here
+ *  \param  file_atts   file attributes are stored here
+ *  \return             returns false if extraction failed.
+ */
+static bool extract_link_destination(const int fd,
+            char *link_target, const int target_size,
+            uint32_t *link_flags, uint32_t *file_atts)
+{
+    int r;
+
+    /* Read ShellLinkHeader */
+    uint32_t size;
+    r = read_lword(fd, &size);
+    if (!r) return false;
+    if (size!=0x4c) {       /* header size MUST be 76 bytes */
+        DEBUGF("unexpected header size 0x%08lx (must be 0x0000004c)\n", size);
+        return false;
+    }
+
+    /* Skip LinkCLSID (class identifier) */
+    rb->lseek(fd, 0x10, SEEK_CUR);
+    /* We need the LinkFlags and File attribute (to see if target is a directory) */
+    r = read_lword(fd, link_flags);
+    if (!r) return false;
+    r = read_lword(fd, file_atts);
+    if (!r) return false;
+    rb->lseek(fd, size, SEEK_SET);    /* Skip to end of header */
+
+    /* For now we only support relative links, so we can exit right away
+       if no relative link structure is present */
+    if (!(*link_flags & HAS_RELATIVE_PATH)) {
+        DEBUGF("Link doesn't have relative path information\n");
+        return false;
+    }
+
+    /* Read (skip) LinkTargetIDList structure if present */
+    if (*link_flags & HAS_LINK_TARGET_ID_LIST) {
+        int size;
+        if (!read_word(fd, &size))
+            return false;
+        rb->lseek(fd, size, SEEK_CUR);
+    }
+
+    /* Read (skip) LinkInfo structure if present */
+    if (*link_flags & HAS_LINK_INFO) {
+        uint32_t size;
+        r = read_lword(fd, &size);
+        if (!r) return false;
+        rb->lseek(fd, size-4, SEEK_CUR);
+    }
+
+    /* String Data section */
+
+    /* Read (skip) NAME_STRING StringData structure if present */
+    if (*link_flags & HAS_NAME) {
+        int ccount;
+        if (!read_word(fd, &ccount))
+            return false;
+        if (*link_flags & IS_UNICODE)
+            rb->lseek(fd, ccount*2, SEEK_CUR);
+        else
+            rb->lseek(fd, ccount, SEEK_CUR);
+    }
+
+    /* Read RELATIVE_PATH StringData structure if present */
+    /* This is finally the data we are searching for! */
+    if (*link_flags & HAS_RELATIVE_PATH) {
+        int ccount;
+        r = read_word(fd, &ccount);
+        if (*link_flags & IS_UNICODE) {
+            unsigned char utf16[4], utf8[10];
+            link_target[0] = '\0';
+            for (int i=0; i<ccount; ++i) {
+                r = read_byte(fd, &utf16[0]);
+                if (!r) return false;
+                r = read_byte(fd, &utf16[1]);
+                if (!r) return false;
+                /* check for surrogate pair and read the second char */
+                if (utf16[1] >= 0xD8 && utf16[1] < 0xE0) {
+                    r = read_byte(fd, &utf16[2]);
+                    if (!r) return false;
+                    r = read_byte(fd, &utf16[3]);
+                    if (!r) return false;
+                    ++i;
+                }
+                char *ptr = rb->utf16LEdecode(utf16, utf8, 1);
+                *ptr = '\0';
+                rb->strlcat(link_target, utf8, target_size);
+            }
+        }
+        else { /* non-unicode */
+            if (ccount >= target_size) {
+                DEBUGF("ERROR: link target filename exceeds size!");
+                return false;
+            }
+            rb->read(fd, link_target, ccount);
+            link_target[ccount] = '\0';
+        }
+    }
+
+    /* convert from windows to unix subdir separators */
+    for (int i=0; link_target[i] != '\0'; ++i) {
+        if (link_target[i]=='\\')
+            link_target[i] = '/';
+    }
+
+    return true;
+}
+
+
+/**
+ * strip rightmost part of file/pathname to next '/', i.e. remove filename
+ * or last subdirectory. Leaves a trailing '/' character.
+ * \param   pathname    full path or filename
+*/
+static void strip_rightmost_part(char *pathname)
+{
+    for (int i = rb->strlen(pathname)-2; i >= 0; --i) {
+        if (pathname[i] == '/') {
+            pathname[i+1] = '\0'; /* cut off */
+            return;
+        }
+    }
+    pathname[0] = '\0';
+}
+
+
+/**
+ * Combine link file's absolute path with relative link target to form
+ * (absolute) link destination
+ * \param   abs_path    full shortcut filename (including path)
+ * \param   rel_path    the extracted relative link target
+ * \param   max_len     maximum lengt of combined filename
+ */
+static void assemble_link_dest(char *const abs_path, char const *rel_path,
+                                const size_t max_len)
+{
+    strip_rightmost_part(abs_path); /* cut off link filename */
+
+    for (;;) {
+        if (rb->strncmp(rel_path, "../", 3)==0) {
+            rel_path += 3;
+            strip_rightmost_part(abs_path);
+        }
+        else if (rb->strncmp(rel_path, "./", 2)==0) {
+            rel_path += 2;
+        }
+        else
+            break;
+    }
+
+    if (*rel_path=='/')
+        ++rel_path;      /* avoid double '/' chars when concatenating */
+    rb->strlcat(abs_path, rel_path, max_len);
+}
+
+
+/**
+ *  Select the chosen file in the file browser. A directory (filename ending
+ *  with '/') will be entered.
+ *  \param  link_target link target to be selected in the browser
+ *  \return             returns false if the target doesn't exist
+ */
+static bool goto_entry(char *link_target)
+{
+    DEBUGF("Trying to go to '%s'...\n", link_target);
+    if (!rb->file_exists(link_target))
+        return false;
+
+    /* Set the browsers dirfilter to the global setting.
+     * This is required in case the plugin was launched
+     * from the plugins browser, in which case the
+     * dirfilter is set to only display .rock files */
+    rb->set_dirfilter(rb->global_settings->dirfilter);
+
+    /* Change directory to the entry selected by the user */
+    rb->set_current_file(link_target);
+    return true;
+}
+
+
+enum plugin_status plugin_start(const void* void_parameter)
+{
+    char *link_filename;
+    char extracted_link[MAX_PATH];
+    char link_target[MAX_PATH];
+    uint32_t lnk_flags;
+    uint32_t file_atts;
+
+    /* This is a viewer, so a parameter must have been specified */
+    if (void_parameter == NULL) {
+        rb->splash(HZ*3, "No *.lnk file selected");
+        return PLUGIN_OK;
+    }
+
+    link_filename = (char*)void_parameter;
+    DEBUGF("Shortcut filename: \"%s\"\n", link_filename);
+
+    int fd = rb->open(link_filename, O_RDONLY);
+    if (fd < 0) {
+        DEBUGF("Can't open link file\n");
+        rb->splashf(HZ*3, "Can't open link file!");
+        return PLUGIN_OK;
+    }
+
+    if (!extract_link_destination(fd, extracted_link, sizeof(extracted_link),
+                                   &lnk_flags, &file_atts)) {
+        rb->close(fd);
+        DEBUGF("Error in extract_link_destination()\n");
+        rb->splashf(HZ*3, "Unsupported or erroneous link file format");
+        return PLUGIN_OK;
+    }
+    rb->close(fd);
+    DEBUGF("Shortcut destination: \"%s\"\n", extracted_link);
+
+    rb->strcpy(link_target, link_filename);
+    assemble_link_dest(link_target, extracted_link, sizeof(link_target));
+    DEBUGF("Link absolute path: \"%s\"\n", link_target);
+
+    /* if target is a directory, add '/' to the dir name,
+       so that the directory gets entered instead of just highlighted */
+    if (file_atts & FILE_ATTRIBUTE_DIRECTORY)
+        if (link_target[rb->strlen(link_target)-1] != '/')
+            rb->strlcat(link_target, "/", sizeof(link_target));
+
+    if (!goto_entry(link_target)) {
+        char *what;
+        if (file_atts & FILE_ATTRIBUTE_DIRECTORY)
+            what = "directory";
+        else
+            what = "file";
+        rb->splashf(HZ*3, "Can't find %s %s", what, link_target);
+        DEBUGF("Can't find %s %s", what, link_target);
+        return PLUGIN_OK;
+    }
+
+    return PLUGIN_OK;
+}