HackMD
  • Prime
    Prime  Full-text search on all paid plans
    Search anywhere and reach everything in a Workspace with Prime plan.
    Got it
    • Prime  Full-text search on all paid plans
      Prime  Full-text search on all paid plans
      Search anywhere and reach everything in a Workspace with Prime plan.
      Got it
      • Options
      • Versions and GitHub Sync
      • Transfer ownership
      • Delete this note
      • Template
      • Insert from template
      • Export
      • Dropbox
      • Google Drive
      • Gist
      • Import
      • Dropbox
      • Google Drive
      • Gist
      • Clipboard
      • Download
      • Markdown
      • HTML
      • Raw HTML
      • Sharing Link copied
      • /edit
      • View mode
        • Edit mode
        • View mode
        • Book mode
        • Slide mode
        Edit mode View mode Book mode Slide mode
      • Note Permission
      • Read
        • Owners
        • Signed-in users
        • Everyone
        Owners Signed-in users Everyone
      • Write
        • Owners
        • Signed-in users
        • Everyone
        Owners Signed-in users Everyone
      • More (Comment, Invitee)
      • Publishing
        Everyone on the web can find and read all notes of this public team.
        After the note is published, everyone on the web can find and read this note.
        See all published notes on profile page.
      • Commenting Enable
        Disabled Forbidden Owners Signed-in users Everyone
      • Permission
        • Forbidden
        • Owners
        • Signed-in users
        • Everyone
      • Invitee
      • No invitee
    Menu Sharing Help
    Menu
    Options
    Versions and GitHub Sync Transfer ownership Delete this note
    Export
    Dropbox Google Drive Gist
    Import
    Dropbox Google Drive Gist Clipboard
    Download
    Markdown HTML Raw HTML
    Back
    Sharing
    Sharing Link copied
    /edit
    View mode
    • Edit mode
    • View mode
    • Book mode
    • Slide mode
    Edit mode View mode Book mode Slide mode
    Note Permission
    Read
    Owners
    • Owners
    • Signed-in users
    • Everyone
    Owners Signed-in users Everyone
    Write
    Owners
    • Owners
    • Signed-in users
    • Everyone
    Owners Signed-in users Everyone
    More (Comment, Invitee)
    Publishing
    Everyone on the web can find and read all notes of this public team.
    After the note is published, everyone on the web can find and read this note.
    See all published notes on profile page.
    More (Comment, Invitee)
    Commenting Enable
    Disabled Forbidden Owners Signed-in users Everyone
    Permission
    Owners
    • Forbidden
    • Owners
    • Signed-in users
    • Everyone
    Invitee
    No invitee
       owned this note    owned this note      
    Published Linked with GitHub
    Like BookmarkBookmarked
    Subscribed
    • Any changes
      Be notified of any changes
    • Mention me
      Be notified of mention me
    • Unsubscribe
    Subscribe
    # Slic3r libslic3r STL File GCode::extrude() out-of-bounds read vulnerability ### CVE Number CVE-2021-44962 ### Summary An out-of-bounds read vulnerability exists in the GCode::extrude() functionality of Slic3r libslic3r 1.3.0 and Master Commit b1a5500. A specially crafted stl file could lead to information disclosure. An attacker can provide a malicious file to trigger this vulnerability. ### Tested Versions Slic3r libslic3r 1.3.0 Slic3r libslic3r Master Commit b1a5500 ### Tested Environment Ubuntu 16.04.7 LTS (GNU/Linux 4.15.0-142-generic x86_64) ### Product URLs https://slic3r.org/ ### Details When reading in an `.stl` file with the `--export-gcode` argument, the `GCode::extrude()` function tries to access the second to last element of `paths.back().polyline.points` on line 430 in the file `GCode.cpp`. ```cpp=425 // make a little move inwards before leaving loop if (paths.back().role == erExternalPerimeter && this->layer != NULL && this->config.perimeters > 1) { // detect angle between last and first segment // the side depends on the original winding order of the polygon (left for contours, right for holes) Point a = paths.front().polyline.points[1]; // second point Point b = *(paths.back().polyline.points.end()-3); // second to last point if (was_clockwise) { // swap points Point c = a; a = b; b = c; } double angle = paths.front().first_point().ccw_angle(a, b) / 3; // turn left if contour, turn right if hole if (was_clockwise) angle *= -1; [...] ``` Following the chain of member and element accesses, we find that `paths` is a vector of `class ExtrusionPath`, namely `std::vector<ExtrusionPath>`. Each of the vector elements has a public member `Polyline polyline`, which in turn stores a vector of `class Point`, `std::vector<Point>`. ```cpp=62 class ExtrusionPath : public ExtrusionEntity { public: Polyline polyline; ExtrusionRole role; /// Volumetric velocity. mm^3 of plastic per mm of linear head motion double mm3_per_mm; /// Width of the extrusion. float width; /// Height of the extrusion. float height; [...] ``` Though by definition, a polyline should consist of more than 2 points, the vlnerability is triggered because for some input `.stl` files, the length of `std::vector<Point>` may be equal to or less than 2. Therefore, this vulnerability can cause an unexpected access on heap, leading to potential information leakage. ### Crash Information ```sh ==87315==ERROR: AddressSanitizer: heap-buffer-overflow on address 0x60300089e0b0 at pc 0x00000052b879 bp 0x7ffc8ed1b0d0 sp 0x7ffc8ed1a880 READ of size 16 at 0x60300089e0b0 thread T0 #0 0x52b878 in __asan_memcpy (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x52b878) #1 0xf08e45 in Slic3r::GCode::extrude(Slic3r::ExtrusionLoop, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, double) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/GCode.cpp:430:19 #2 0xf0fd1b in Slic3r::GCode::extrude(Slic3r::ExtrusionEntity const&, std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, double) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/GCode.cpp:468:22 #3 0xf475a4 in Slic3r::PrintGCode::_extrude_perimeters[abi:cxx11](std::map<unsigned long, Slic3r::ExtrusionEntityCollection, std::less<unsigned long>, std::allocator<std::pair<unsigned long const, Slic3r::ExtrusionEntityCollection> > >&) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/PrintGCode.cpp:742:38 #4 0xf3c0a1 in Slic3r::PrintGCode::process_layer(unsigned long, Slic3r::Layer const*, std::vector<Slic3r::Point, std::allocator<Slic3r::Point> > const&) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/PrintGCode.cpp:696:36 #5 0xf2956a in Slic3r::PrintGCode::output() /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/PrintGCode.cpp:295:27 #6 0x9b5aec in Slic3r::Print::export_gcode(std::ostream&, bool) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/Print.cpp:692:39 #7 0x9b611f in Slic3r::Print::export_gcode(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >, bool) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/Print.cpp:704:11 #8 0xb0d7cd in Slic3r::SimplePrint::export_gcode(std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >) /home/bug/LabSpace/Slic3rFuzzer/xs/src/libslic3r/SimplePrint.cpp:40:18 #9 0x56dc91 in Slic3r::CLI::run(int, char**) /home/bug/LabSpace/Slic3rFuzzer/src/slic3r.cpp:362:27 #10 0x57a4e8 in LLVMFuzzerTestOneInput /home/bug/LabSpace/Slic3rFuzzer/src/slic3r.cpp:546:11 #11 0x46443a in fuzzer::Fuzzer::ExecuteCallback(unsigned char const*, unsigned long) (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x46443a) #12 0x454e07 in fuzzer::RunOneTest(fuzzer::Fuzzer*, char const*, unsigned long) (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x454e07) #13 0x45a801 in fuzzer::FuzzerDriver(int*, char***, int (*)(unsigned char const*, unsigned long)) (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x45a801) #14 0x480912 in main (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x480912) #15 0x7fa614e4383f in __libc_start_main /build/glibc-S7Ft5T/glibc-2.23/csu/../csu/libc-start.c:291 #16 0x4536e8 in _start (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x4536e8) 0x60300089e0b0 is located 1 bytes to the right of 31-byte region [0x60300089e090,0x60300089e0af) allocated by thread T0 here: #0 0x55dca2 in operator new(unsigned long) (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x55dca2) #1 0x7fa615e54498 in std::__cxx11::basic_string<char, std::char_traits<char>, std::allocator<char> >::_M_mutate(unsigned long, unsigned long, char const*, unsigned long) (/usr/lib/x86_64-linux-gnu/libstdc++.so.6+0x11f498) SUMMARY: AddressSanitizer: heap-buffer-overflow (/home/bug/LabSpace/FuzzerRun/Slic3rFuzzer/build/slic3r+0x52b878) in __asan_memcpy Shadow bytes around the buggy address: 0x0c068010bbc0: fd fd fa fa fd fd fd fd fa fa fd fd fd fa fa fa 0x0c068010bbd0: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fd 0x0c068010bbe0: fa fa fd fd fd fd fa fa fd fd fd fd fa fa fd fd 0x0c068010bbf0: fd fa fa fa fd fd fd fa fa fa fd fd fd fa fa fa 0x0c068010bc00: fd fd fd fd fa fa 00 00 00 00 fa fa fd fd fd fd =>0x0c068010bc10: fa fa 00 00 00 07[fa]fa 00 00 00 00 fa fa fd fd 0x0c068010bc20: fd fd fa fa fd fd fd fd fa fa fd fd fd fa fa fa 0x0c068010bc30: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fa 0x0c068010bc40: fa fa fd fd fd fa fa fa fd fd fd fd fa fa fd fd 0x0c068010bc50: fd fa fa fa fd fd fd fd fa fa fd fd fd fd fa fa 0x0c068010bc60: fd fd fd fd fa fa fd fd fd fd fa fa fd fd fd fa Shadow byte legend (one shadow byte represents 8 application bytes): Addressable: 00 Partially addressable: 01 02 03 04 05 06 07 Heap left redzone: fa Freed heap region: fd Stack left redzone: f1 Stack mid redzone: f2 Stack right redzone: f3 Stack after return: f5 Stack use after scope: f8 Global redzone: f9 Global init order: f6 Poisoned by user: f7 Container overflow: fc Array cookie: ac Intra object redzone: bb ASan internal: fe Left alloca redzone: ca Right alloca redzone: cb Shadow gap: cc ==87315==ABORTING ``` ### GDB Trace ```sh bug@ubuntu:~/LabSpace/gdb_NormalRun/Slic3r/build$ gdb ./slic3r GNU gdb (Ubuntu 7.11.1-0ubuntu1~16.5) 7.11.1 Copyright (C) 2016 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html> This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. Type "show copying" and "show warranty" for details. This GDB was configured as "x86_64-linux-gnu". Type "show configuration" for configuration details. For bug reporting instructions, please see: <http://www.gnu.org/software/gdb/bugs/>. Find the GDB manual and other documentation resources online at: <http://www.gnu.org/software/gdb/documentation/>. For help, type "help". Type "apropos word" to search for commands related to "word"... Reading symbols from ./slic3r...done. (gdb) b GCode.cpp:430 Breakpoint 1 at 0x662fa2: file /home/bug/LabSpace/gdb_NormalRun/Slic3r/xs/src/libslic3r/GCode.cpp, line 430. (gdb) r --export-gcode ../../input.stl --output ../../output.gcode Starting program: /home/bug/LabSpace/gdb_NormalRun/Slic3r/build/slic3r --export-gcode ../../input.stl --output ../../output.gcode [Thread debugging using libthread_db enabled] Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1". CLI ERR: Arrange: 1, center: 1 Infilling layers Processing triangulated mesh [New Thread 0x7ffff6f4e700 (LWP 88895)] [New Thread 0x7ffff6f4e700 (LWP 88896)] [Thread 0x7ffff6f4e700 (LWP 88895) exited] [Thread 0x7ffff6f4e700 (LWP 88896) exited] [New Thread 0x7ffff6f4e700 (LWP 88897)] [Thread 0x7ffff6f4e700 (LWP 88897) exited] [New Thread 0x7ffff6f4e700 (LWP 88898)] [New Thread 0x7ffff6f4e700 (LWP 88899)] [Thread 0x7ffff6f4e700 (LWP 88898) exited] Preparing infill [New Thread 0x7ffff6f4e700 (LWP 88900)] [Thread 0x7ffff6f4e700 (LWP 88899) exited] [Thread 0x7ffff6f4e700 (LWP 88900) exited] [New Thread 0x7ffff6f4e700 (LWP 88901)] Generating skirt Generating brim Exporting G-Code... [Thread 0x7ffff6f4e700 (LWP 88901) exited] Thread 1 "slic3r" hit Breakpoint 1, Slic3r::GCode::extrude ( this=0x7fffffff9490, loop=..., description="external small perimeter", speed=15) at /home/bug/LabSpace/gdb_NormalRun/Slic3r/xs/src/libslic3r/GCode.cpp:430 430 Point b = *(paths.back().polyline.points.end()-3); // second to last point (gdb) c 10 Will ignore next 9 crossings of breakpoint 1. Continuing. Thread 1 "slic3r" hit Breakpoint 1, Slic3r::GCode::extrude ( this=0x7fffffff9490, loop=..., description="external perimeter", speed=-1) at /home/bug/LabSpace/gdb_NormalRun/Slic3r/xs/src/libslic3r/GCode.cpp:430 430 Point b = *(paths.back().polyline.points.end()-3); // second to last point (gdb) p paths.back().polyline.points.size() $1 = 2 ``` ### Timeline 2021-11-19 - Vendor Disclosure 2022-01-16 - Public Release ### Credit Discovered by Yuanhaur Chang, Yujie Wang, Ning Zhang

    Import from clipboard

    Advanced permission required

    Your current role can only read. Ask the system administrator to acquire write and comment permission.

    This team is disabled

    Sorry, this team is disabled. You can't edit this note.

    This note is locked

    Sorry, only owner can edit this note.

    Reach the limit

    Sorry, you've reached the max length this note can be.
    Please reduce the content or divide it to more notes, thank you!

    Import from Gist

    Import from Snippet

    or

    Export to Snippet

    Are you sure?

    Do you really want to delete this note?
    All users will lost their connection.

    Create a note from template

    Create a note from template

    Oops...
    This template is not available.


    Upgrade

    All
    • All
    • Team
    No template found.

    Create custom template


    Upgrade

    Delete template

    Do you really want to delete this template?

    This page need refresh

    You have an incompatible client version.
    Refresh to update.
    New version available!
    See releases notes here
    Refresh to enjoy new features.
    Your user state has changed.
    Refresh to load new user state.

    Sign in

    Forgot password

    or

    By clicking below, you agree to our terms of service.

    Sign in via Facebook Sign in via Twitter Sign in via GitHub Sign in via Dropbox Sign in via Google

    New to HackMD? Sign up

    Help

    • English
    • 中文
    • Français
    • Deutsch
    • 日本語
    • Español
    • Català
    • Ελληνικά
    • Português
    • italiano
    • Türkçe
    • Русский
    • Nederlands
    • hrvatski jezik
    • język polski
    • Українська
    • हिन्दी
    • svenska
    • Esperanto
    • dansk

    Documents

    Tutorials

    Book Mode Tutorial

    Slide Mode Tutorial

    YAML Metadata

    Contacts

    Facebook

    Twitter

    Feedback

    Send us email

    Resources

    Releases

    Pricing

    Blog

    Policy

    Terms

    Privacy

    Cheatsheet

    Syntax Example Reference
    # Header Header 基本排版
    - Unordered List
    • Unordered List
    1. Ordered List
    1. Ordered List
    - [ ] Todo List
    • Todo List
    > Blockquote
    Blockquote
    **Bold font** Bold font
    *Italics font* Italics font
    ~~Strikethrough~~ Strikethrough
    19^th^ 19th
    H~2~O H2O
    ++Inserted text++ Inserted text
    ==Marked text== Marked text
    [link text](https:// "title") Link
    ![image alt](https:// "title") Image
    `Code` Code 在筆記中貼入程式碼
    ```javascript
    var i = 0;
    ```
    var i = 0;
    :smile: :smile: Emoji list
    {%youtube youtube_id %} Externals
    $L^aT_eX$ LaTeX
    :::info
    This is a alert area.
    :::

    This is a alert area.

    Versions

    Versions and GitHub Sync

    Sign in to link this note to GitHub Learn more
    This note is not linked with GitHub Learn more
     
    Add badge Pull Push GitHub Link Settings
    Upgrade now

    Version named by    

    More Less
    • Edit
    • Delete

    Note content is identical to the latest version.
    Compare with
      Choose a version
      No search result
      Version not found

    Feedback

    Submission failed, please try again

    Thanks for your support.

    On a scale of 0-10, how likely is it that you would recommend HackMD to your friends, family or business associates?

    Please give us some advice and help us improve HackMD.

     

    Thanks for your feedback

    Remove version name

    Do you want to remove this version name and description?

    Transfer ownership

    Transfer to
      Warning: is a public team. If you transfer note to this team, everyone on the web can find and read this note.

        Link with GitHub

        Please authorize HackMD on GitHub

        Please sign in to GitHub and install the HackMD app on your GitHub repo. Learn more

         Sign in to GitHub

        HackMD links with GitHub through a GitHub App. You can choose which repo to install our App.

        Push the note to GitHub Push to GitHub Pull a file from GitHub

          Authorize again
         

        Choose which file to push to

        Select repo
        Refresh Authorize more repos
        Select branch
        Select file
        Select branch
        Choose version(s) to push
        • Save a new version and push
        • Choose from existing versions
        Available push count

        Upgrade

        Pull from GitHub

         
        File from GitHub
        File from HackMD

        GitHub Link Settings

        File linked

        Linked by
        File path
        Last synced branch
        Available push count

        Upgrade

        Danger Zone

        Unlink
        You will no longer receive notification when GitHub file changes after unlink.

        Syncing

        Push failed

        Push successfully