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cmd/link/internal/ld: don't panic on short buildid

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When the linker was written in C, command line arguments were passed
around as null-terminated byte arrays which encouraged checking
characters one at a time. In Go, that can easily lead to
out-of-bounds panics.

Use the more idiomatic strings.HasPrefix when checking cmd/link's -B
argument to avoid the panic, and replace the manual hex decode with
use of the encoding/hex package.

Fixes #14636

Change-Id: I45f765bbd8cf796fee1a9a3496178bf76b117827
Reviewed-on: https://go-review.googlesource.com/20211
Run-TryBot: Brad Fitzpatrick <bradfitz@golang.org>
TryBot-Result: Gobot Gobot <gobot@golang.org>
Reviewed-by: Brad Fitzpatrick <bradfitz@golang.org>
This commit is contained in:
Rhys Hiltner 2016-03-03 22:37:14 -08:00 committed by Brad Fitzpatrick
parent b5481dd0a6
commit 3375974e0d
2 changed files with 60 additions and 31 deletions
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48
src/cmd/link/internal/ld/elf.go
View File

@ -8,6 +8,7 @@ import (
"cmd/internal/obj"
"crypto/sha1"
"encoding/binary"
"encoding/hex"
"fmt"
"path/filepath"
"sort"
@ -1196,45 +1197,30 @@ func elfwriteopenbsdsig() int {
}
func addbuildinfo(val string) {
var j int
if val[0] != '0' || val[1] != 'x' {
if !strings.HasPrefix(val, "0x") {
Exitf("-B argument must start with 0x: %s", val)
}
ov := val
val = val[2:]
i := 0
var b int
for val != "" {
if len(val) == 1 {
Exitf("-B argument must have even number of digits: %s", ov)
}
b = 0
for j = 0; j < 2; j, val = j+1, val[1:] {
b *= 16
if val[0] >= '0' && val[0] <= '9' {
b += int(val[0]) - '0'
} else if val[0] >= 'a' && val[0] <= 'f' {
b += int(val[0]) - 'a' + 10
} else if val[0] >= 'A' && val[0] <= 'F' {
b += int(val[0]) - 'A' + 10
} else {
Exitf("-B argument contains invalid hex digit %c: %s", val[0], ov)
}
}
const maxLen = 32
if i >= maxLen {
Exitf("-B option too long (max %d digits): %s", maxLen, ov)
}
buildinfo = append(buildinfo, uint8(b))
i++
const maxLen = 32
if hex.DecodedLen(len(val)) > maxLen {
Exitf("-B option too long (max %d digits): %s", maxLen, ov)
}
buildinfo = buildinfo[:i]
b, err := hex.DecodeString(val)
if err != nil {
if err == hex.ErrLength {
Exitf("-B argument must have even number of digits: %s", ov)
}
if inv, ok := err.(hex.InvalidByteError); ok {
Exitf("-B argument contains invalid hex digit %c: %s", byte(inv), ov)
}
Exitf("-B argument contains invalid hex: %s", ov)
}
buildinfo = b
}
// Build info note

43
test/fixedbugs/issue14636.go Normal file
View File

@ -0,0 +1,43 @@
// +build !nacl,!android,!darwin darwin,!arm
// run
// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.
package main
import (
"bytes"
"log"
"os/exec"
"strings"
)
func main() {
checkLinkOutput("", "-B argument must start with 0x")
checkLinkOutput("0", "-B argument must start with 0x")
checkLinkOutput("0x", "usage")
checkLinkOutput("0x0", "-B argument must have even number of digits")
checkLinkOutput("0x00", "usage")
checkLinkOutput("0xYZ", "-B argument contains invalid hex digit")
checkLinkOutput("0x"+strings.Repeat("00", 32), "usage")
checkLinkOutput("0x"+strings.Repeat("00", 33), "-B option too long (max 32 digits)")
}
func checkLinkOutput(buildid string, message string) {
cmd := exec.Command("go", "tool", "link", "-B", buildid)
out, err := cmd.CombinedOutput()
if err == nil {
log.Fatalf("expected cmd/link to fail")
}
firstLine := string(bytes.SplitN(out, []byte("\n"), 2)[0])
if strings.HasPrefix(firstLine, "panic") {
log.Fatalf("cmd/link panicked:\n%s", out)
}
if !strings.Contains(firstLine, message) {
log.Fatalf("cmd/link output did not include expected message %q: %s", message, firstLine)
}
}