x/crypto/openpgp: handle "gnu-dummy" S2K #13605
Description
GPG added a "gnu-dummy" S2K type for keyrings that contain only subkey secret data (like in this guide). openpgp.ReadKeyRing returns an unsupported feature: S2K function error. Value 101 for a "gnu-dummy" S2K which x/crypto/openpgp/s2k.Parse doesn't recognize. Although RFC 4880 does not include this S2K, it does reserve 100 through 110 for extensions like this. These keys could be handled by adding Dummy bool field to encrypted keys and updating the S2K parser to recognize "gnu-dummy" type.
package main
import (
"bytes"
"encoding/base64"
"golang.org/x/crypto/openpgp"
)
func main() {
data, err := base64.StdEncoding.DecodeString(secring)
if err != nil {
panic(err)
}
if _, err = openpgp.ReadKeyRing(bytes.NewBuffer(data)); err != nil {
panic(err)
}
}
var secring = `lQCVBFZuSwwBBAC04VdUUq2REb7+IF/x21yOV3kIn798XRl7A7RiGcE9VpBjT5xMxtghWhH1mxyT+nrS36OJxdvtgJb3NB6hhh3qBQC6DmCGbWe61tT6TfyFbN6OvzZKMEa6RMunyd+2ErX4RLOcO+9X7a0weVASH5wRYjjqQtvPvt1/k25sloPnZQARAQAB/gNlAkdOVQG0EyA8dGVzdEBleGFtcGxlLmNvbT6IuAQTAQIAIgUCVm5LDAIbLwYLCQgHAwIGFQgCCQoLBBYCAwECHgECF4AACgkQwaXYFkPfLEVROQP/RF4GXi/yGm6yQoDNXFkFiwNhJndayfZxf5Qa+JWz1ltLyal7Dm1c+U6/R/7D25gmEslI+5YrHpbExWXyfG8DbX/5Ef9Be04e9IvjoZboeRpxmyb8IflEw90tJGL8YAK2xWohvayigPnjjhycZQPMuMK9X35o89oJs+p1MxcC9EOwAgAAnQH9BFZuSwwBBADBDfq8oUK8Jr8IVkQEEEZzQ7AWh03oTVodROebMz4vAk34HkrebZuxT4U/8yFIP+kJ3Yie3T8V6F8jF3a3ZUHNj2ghgxMbPH+kRKwBphvX8Fb5GtoFVbJq1tNMDaLhVRIkDLBTqQp/20spcuU5+OMzQRUt+Z6GxMaUwt5zLHPUgwARAQAB/gMDAvozhXZdexxPYMKrp7yC2FNNpVAC61hD0VQKvFeeeXZIGOBx57F1wVBNjuPyglji0kaX0m9yYI+I1V546END4aV/hXlZve3r6qYVE9W+T1imwx1NXPSb0j/nMmdiFYFXuyz70yEO+cDwHONzmRLdBZlP1DKYBcjF7rwF0gWuIoWgDYdfECo/aANSRQtKw5Q6UowQLzpHTV+X6iL/CbjIL5f81KXPMO1AubxzAW+iatzI7jfL0MvA1FxRpMjpHc1uyT8oIfic17PklbjcnLe5GH782AEGhXwn4bY1H+ss0bxmkJV9HkcMokJUVMQxKw+a6+/IuLXdFtcA5z4CDeIbt9rv+b8s0bfq9aW4kDxG3PDcyoMTrTuJLBd6/XwJgdtrmLSCtlU4fLzZEoAd2FVyWbS6Nys3eXgIBkRRokzKANknne78LpvIiamzinb0iJk2X+AYnRKoy1pUsC+unqaXm9YHfdpxv/OXLe13zhSJAT0EGAECAAkFAlZuSwwCGy4AqAkQwaXYFkPfLEWdIAQZAQIABgUCVm5LDAAKCRBv1XiTGF5T/qsmA/9LOUNetM1QtsJ71OVdXE3dutUZULE/27DTrA/vvSfhzSFj3U3FnyI7AVsiiiwmnJnthf0zaa2HYBL844Bm7drtzGBNVvddgIJZKBE0x2vUlTVc661e2FBhtLh6xX2nhEy9owc+C7PR9OXvGiET8tTRnUDUO3PgPkyALkHfQMWMR11sA/0YQl4wf3knjk83DVVhFK5fT2lW4hmSO74tuCAA4V71C8B5rJzVq2vy1L2bGHAroe+LtX30LtZM5qWKzZzK7jjo1/eaXimOkJcnnpg6jmUP7TMkWpU7hlOQ3ZHjS2K5xJYJqBwP86TWPtDLxYD3mTlYtp2dDT8ogV/sEPPd44yWlrACAAA=`The base64 encoded secring in the above contains a gnu-dummy S2K (notice the gnu-dummy S2K in the output):
$ gpg --list-packets secring.gpg
:secret key packet:
version 4, algo 1, created 1450068748, expires 0
skey[0]: [1024 bits]
skey[1]: [17 bits]
gnu-dummy S2K, algo: 3, SHA1 protection, hash: 2
protect IV:
keyid: C1A5D81643DF2C45
:user ID packet: " <test@example.com>"
:signature packet: algo 1, keyid C1A5D81643DF2C45
version 4, created 1450068748, md5len 0, sigclass 0x13
digest algo 2, begin of digest 51 39
hashed subpkt 2 len 4 (sig created 2015-12-14)
hashed subpkt 27 len 1 (key flags: 2F)
hashed subpkt 11 len 5 (pref-sym-algos: 9 8 7 3 2)
hashed subpkt 21 len 5 (pref-hash-algos: 8 2 9 10 11)
hashed subpkt 22 len 3 (pref-zip-algos: 2 3 1)
hashed subpkt 30 len 1 (features: 01)
hashed subpkt 23 len 1 (key server preferences: 80)
subpkt 16 len 8 (issuer key ID C1A5D81643DF2C45)
data: [1023 bits]
:trust packet: flag=00 sigcache=00
:secret sub key packet:
version 4, algo 1, created 1450068748, expires 0
skey[0]: [1024 bits]
skey[1]: [17 bits]
iter+salt S2K, algo: 3, SHA1 protection, hash: 2, salt: fa3385765d7b1c4f
protect count: 65536 (96)
protect IV: c2 ab a7 bc 82 d8 53 4d
encrypted stuff follows
keyid: 6FD57893185E53FE
:signature packet: algo 1, keyid C1A5D81643DF2C45
version 4, created 1450068748, md5len 0, sigclass 0x18
digest algo 2, begin of digest 5d 6c
hashed subpkt 2 len 4 (sig created 2015-12-14)
hashed subpkt 27 len 1 (key flags: 2E)
subpkt 16 len 8 (issuer key ID C1A5D81643DF2C45)
subpkt 32 len 156 (signature: v4, class 0x19, algo 1, digest algo 2)
data: [1021 bits]
:trust packet: flag=00 sigcache=00