From 348b23830d82aece5775eb9f7f3b3587cf5300c6 Mon Sep 17 00:00:00 2001 From: Roland Shoemaker Date: Thu, 25 Apr 2024 13:09:54 -0700 Subject: [PATCH] cmd/go: disallow -lto_library in LDFLAGS MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit The darwin linker allows setting the LTO library with the -lto_library flag. This wasn't caught by our "safe linker flags" check because it was covered by the -lx flag used for linking libraries. This change adds a specific check for excluded flags which otherwise satisfy our existing checks. Loading a mallicious LTO library would allow an attacker to cause the linker to execute abritrary code when "go build" was called. Thanks to Juho Forsén of Mattermost for reporting this issue. Fixes #67119 Fixes CVE-2024-24787 Change-Id: I77ac8585efbdbdfd5f39c39ed623b9408a0f9eaf Reviewed-on: https://go-internal-review.googlesource.com/c/go/+/1380 Reviewed-by: Russ Cox Reviewed-by: Damien Neil Reviewed-on: https://go-review.googlesource.com/c/go/+/583815 Reviewed-by: David Chase LUCI-TryBot-Result: Go LUCI --- src/cmd/go/internal/work/security.go | 19 +++++++++++++++---- .../script/darwin_lto_library_ldflag.txt | 17 +++++++++++++++++ 2 files changed, 32 insertions(+), 4 deletions(-) create mode 100644 src/cmd/go/testdata/script/darwin_lto_library_ldflag.txt diff --git a/src/cmd/go/internal/work/security.go b/src/cmd/go/internal/work/security.go index 3289276e77..8e788b0425 100644 --- a/src/cmd/go/internal/work/security.go +++ b/src/cmd/go/internal/work/security.go @@ -145,6 +145,12 @@ var validCompilerFlagsWithNextArg = []string{ "-x", } +var invalidLinkerFlags = []*lazyregexp.Regexp{ + // On macOS this means the linker loads and executes the next argument. + // Have to exclude separately because -lfoo is allowed in general. + re(`-lto_library`), +} + var validLinkerFlags = []*lazyregexp.Regexp{ re(`-F([^@\-].*)`), re(`-l([^@\-].*)`), @@ -234,12 +240,12 @@ var validLinkerFlagsWithNextArg = []string{ func checkCompilerFlags(name, source string, list []string) error { checkOverrides := true - return checkFlags(name, source, list, validCompilerFlags, validCompilerFlagsWithNextArg, checkOverrides) + return checkFlags(name, source, list, nil, validCompilerFlags, validCompilerFlagsWithNextArg, checkOverrides) } func checkLinkerFlags(name, source string, list []string) error { checkOverrides := true - return checkFlags(name, source, list, validLinkerFlags, validLinkerFlagsWithNextArg, checkOverrides) + return checkFlags(name, source, list, invalidLinkerFlags, validLinkerFlags, validLinkerFlagsWithNextArg, checkOverrides) } // checkCompilerFlagsForInternalLink returns an error if 'list' @@ -248,7 +254,7 @@ func checkLinkerFlags(name, source string, list []string) error { // external linker). func checkCompilerFlagsForInternalLink(name, source string, list []string) error { checkOverrides := false - if err := checkFlags(name, source, list, validCompilerFlags, validCompilerFlagsWithNextArg, checkOverrides); err != nil { + if err := checkFlags(name, source, list, nil, validCompilerFlags, validCompilerFlagsWithNextArg, checkOverrides); err != nil { return err } // Currently the only flag on the allow list that causes problems @@ -261,7 +267,7 @@ func checkCompilerFlagsForInternalLink(name, source string, list []string) error return nil } -func checkFlags(name, source string, list []string, valid []*lazyregexp.Regexp, validNext []string, checkOverrides bool) error { +func checkFlags(name, source string, list []string, invalid, valid []*lazyregexp.Regexp, validNext []string, checkOverrides bool) error { // Let users override rules with $CGO_CFLAGS_ALLOW, $CGO_CFLAGS_DISALLOW, etc. var ( allow *regexp.Regexp @@ -293,6 +299,11 @@ Args: if allow != nil && allow.FindString(arg) == arg { continue Args } + for _, re := range invalid { + if re.FindString(arg) == arg { // must be complete match + goto Bad + } + } for _, re := range valid { if re.FindString(arg) == arg { // must be complete match continue Args diff --git a/src/cmd/go/testdata/script/darwin_lto_library_ldflag.txt b/src/cmd/go/testdata/script/darwin_lto_library_ldflag.txt new file mode 100644 index 0000000000..d7acefdbad --- /dev/null +++ b/src/cmd/go/testdata/script/darwin_lto_library_ldflag.txt @@ -0,0 +1,17 @@ +[!GOOS:darwin] skip +[!cgo] skip + +! go build +stderr 'invalid flag in #cgo LDFLAGS: -lto_library' + +-- go.mod -- +module ldflag + +-- main.go -- +package main + +// #cgo CFLAGS: -flto +// #cgo LDFLAGS: -lto_library bad.dylib +import "C" + +func main() {} \ No newline at end of file