x/crypto/openpgp: ReadMessage(): Panic on invalid input in packet.nextSubpacket() (slice bounds out of range)

[marete]

The following program panics:

package main

import (
    "bytes"
    "encoding/hex"
    "io"
    "log"
    "os"

    "golang.org/x/crypto/openpgp"
)

// An empty Keyring
type emptyKR struct {
}

func (kr emptyKR) KeysById(id uint64) []openpgp.Key {
    return nil
}

func (kr emptyKR) DecryptionKeys() []openpgp.Key {
    return nil
}

func (kr emptyKR) KeysByIdUsage(uint64, byte) []openpgp.Key {
    return nil
}

var data = "8c040402000aa430aa8228b9248b01fc899a91197130303030"

func main() {
    buf, err := hex.DecodeString(data)
    if err != nil {
        log.Fatalln(err)
    }

    md, err := openpgp.ReadMessage(bytes.NewBuffer(buf), emptyKR{},
        func([]openpgp.Key, bool) ([]byte, error) {
            return []byte("insecure"), nil
        }, nil)

    if err != nil {
        log.Fatalln(err)
    }

    _, err = io.Copy(os.Stdout, md.UnverifiedBody)
    if err != nil {
        log.Fatalln(err)
    }

    if md.SignatureError != nil {
        log.Fatalln("integrity check failed")
    }
}

with the trace:

panic: runtime error: slice bounds out of range

goroutine 1 [running]:
golang.org/x/crypto/openpgp/packet.nextSubpacket(0xc208068001, 0x4, 0x5ff, 0x2, 0xc2080202c0, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/packet/opaque.go:145 +0x1ff
golang.org/x/crypto/openpgp/packet.OpaqueSubpackets(0xc208068000, 0x5, 0x600, 0x0, 0x0, 0x0, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/packet/opaque.go:98 +0x93
golang.org/x/crypto/openpgp/packet.(*UserAttribute).parse(0xc2080202a0, 0x7eff58289bc0, 0xc208020280, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/packet/userattribute.go:63 +0xa6
golang.org/x/crypto/openpgp/packet.Read(0x7eff58289d38, 0xc20800a4b0, 0x7eff58289d60, 0xc2080202a0, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/packet/packet.go:375 +0x152
golang.org/x/crypto/openpgp/packet.(*Reader).Next(0xc20803c480, 0x0, 0x0, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/packet/reader.go:37 +0x10c
golang.org/x/crypto/openpgp.readSignedMessage(0xc20803c480, 0xc208060000, 0x7eff58289b88, 0x68c0a8, 0xc208060000, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/read.go:234 +0xc4
golang.org/x/crypto/openpgp.ReadMessage(0x7eff58289b60, 0xc2080120e0, 0x7eff58289b88, 0x68c0a8, 0x5f08c0, 0x0, 0xc208060000, 0x0, 0x0)
    /home/marebri/devel/go/src/golang.org/x/crypto/openpgp/read.go:217 +0xd90
main.main()
    /home/marebri/devel/lab/go/crypto/openpgp/issues/075301e76/main.go:40 +0x285

goroutine 2 [runnable]:
runtime.forcegchelper()
    /opt/go/src/runtime/proc.go:90
runtime.goexit()
    /opt/go/src/runtime/asm_amd64.s:2232 +0x1

goroutine 3 [runnable]:
runtime.bgsweep()
    /opt/go/src/runtime/mgc0.go:82
runtime.goexit()
    /opt/go/src/runtime/asm_amd64.s:2232 +0x1

goroutine 4 [runnable]:
runtime.runfinq()
    /opt/go/src/runtime/malloc.go:712
runtime.goexit()
    /opt/go/src/runtime/asm_amd64.s:2232 +0x1

Found using gofuzz. You may assign this issue to me.

[ianlancetaylor]

CC @agl

[marete]

Submitted CL https://go-review.googlesource.com/#/c/12634/ to fix this issue.

[gopherbot]

CL https://golang.org/cl/12634 mentions this issue.