[release-branch.go1.20] mime/multipart: limit memory/inode consumption of ReadForm

Reader.ReadForm is documented as storing "up to maxMemory bytes + 10MB"
in memory. Parsed forms can consume substantially more memory than
this limit, since ReadForm does not account for map entry overhead
and MIME headers.

In addition, while the amount of disk memory consumed by ReadForm can
be constrained by limiting the size of the parsed input, ReadForm will
create one temporary file per form part stored on disk, potentially
consuming a large number of inodes.

Update ReadForm's memory accounting to include part names,
MIME headers, and map entry overhead.

Update ReadForm to store all on-disk file parts in a single
temporary file.

Files returned by FileHeader.Open are documented as having a concrete
type of *os.File when a file is stored on disk. The change to use a
single temporary file for all parts means that this is no longer the
case when a form contains more than a single file part stored on disk.

The previous behavior of storing each file part in a separate disk
file may be reenabled with GODEBUG=multipartfiles=distinct.

Update Reader.NextPart and Reader.NextRawPart to set a 10MiB cap
on the size of MIME headers.

Thanks to Jakob Ackermann (@das7pad) for reporting this issue.

Updates #58006
Fixes #58363
Fixes CVE-2022-41725

Change-Id: Ibd780a6c4c83ac8bcfd3cbe344f042e9940f2eab
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1714276
Reviewed-by: Julie Qiu <julieqiu@google.com>
TryBot-Result: Security TryBots <security-trybots@go-security-trybots.iam.gserviceaccount.com>
Reviewed-by: Roland Shoemaker <bracewell@google.com>
Run-TryBot: Damien Neil <dneil@google.com>
(cherry picked from commit 7d0da0029bfbe3228cc5216ced8c7b3184eb517d)
Reviewed-on: https://team-review.git.corp.google.com/c/golang/go-private/+/1728950
Reviewed-by: Damien Neil <dneil@google.com>
Run-TryBot: Roland Shoemaker <bracewell@google.com>
Reviewed-by: Tatiana Bradley <tatianabradley@google.com>
Reviewed-on: https://go-review.googlesource.com/c/go/+/468120
Auto-Submit: Michael Pratt <mpratt@google.com>
Run-TryBot: Michael Pratt <mpratt@google.com>
Reviewed-by: Than McIntosh <thanm@google.com>
TryBot-Result: Gopher Robot <gobot@golang.org>
6 files changed
tree: b3043bdc23df931cbdab963243b94b450cd4e1e0
  1. .github/
  2. api/
  3. doc/
  4. lib/
  5. misc/
  6. src/
  7. test/
  8. .gitattributes
  9. .gitignore
  10. codereview.cfg
  11. CONTRIBUTING.md
  12. LICENSE
  13. PATENTS
  14. README.md
  15. SECURITY.md
  16. VERSION
README.md

The Go Programming Language

Go is an open source programming language that makes it easy to build simple, reliable, and efficient software.

Gopher image Gopher image by Renee French, licensed under Creative Commons 4.0 Attributions license.

Our canonical Git repository is located at https://go.googlesource.com/go. There is a mirror of the repository at https://github.com/golang/go.

Unless otherwise noted, the Go source files are distributed under the BSD-style license found in the LICENSE file.

Download and Install

Binary Distributions

Official binary distributions are available at https://go.dev/dl/.

After downloading a binary release, visit https://go.dev/doc/install for installation instructions.

Install From Source

If a binary distribution is not available for your combination of operating system and architecture, visit https://go.dev/doc/install/source for source installation instructions.

Contributing

Go is the work of thousands of contributors. We appreciate your help!

To contribute, please read the contribution guidelines at https://go.dev/doc/contribute.

Note that the Go project uses the issue tracker for bug reports and proposals only. See https://go.dev/wiki/Questions for a list of places to ask questions about the Go language.