GPG 仍然看到带有已撤销子项的好兆头仍然有效

Question

我创建了一个键，并创建了一个子键。使用子密钥，我签署了一个文件。验证工作。撤销密钥，验证不成立。这是预期的行为。

但是，如果我尝试使用相同的子密钥签名并验证它仍然有效。我究竟做错了什么？这是我正在做的全部内容：

$ gpg --gen-key
$ gpg -k
/Users/mustafa/.gnupg/pubring.kbx
---------------------------------
pub   rsa2048 2019-02-03 [SC] [expires: 2021-02-02]
      5DD923FBCF6392A5CB366167D4C0627A07510C6C
uid           [ultimate] Mustafa <mustafa91@gmail.com>
sub   rsa2048 2019-02-03 [E] [expires: 2021-02-02]

使用编辑键，添加一个子键。

$ gpg --edit-key 5DD923FBCF6392A5CB366167D4C0627A07510C6C

sec  rsa2048/D4C0627A07510C6C
     created: 2019-02-03  expires: 2021-02-02  usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa2048/E058B91696C43666
     created: 2019-02-03  expires: 2021-02-02  usage: E

gpg> addkey

sec  rsa2048/D4C0627A07510C6C
     created: 2019-02-03  expires: 2021-02-02  usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa2048/E058B91696C43666
     created: 2019-02-03  expires: 2021-02-02  usage: E
ssb  rsa2048/38616BDAE66E418C
     created: 2019-02-03  expires: 2019-02-13  usage: S
[ultimate] (1). Mustafa <mustafa91@gmail.com>

gpg> q
Save changes? (y/N) y

签署文件并验证它。

$ gpg --armor --detach-sign --default-key 38616BDAE66E418C  test.txt
gpg: using "38616BDAE66E418C" as default secret key for signing

$ gpg --verify test.txt.asc test.txt
gpg: Signature made Sun Feb  3 21:49:43 2019 +03
gpg:                using RSA key 485FC77FC73DA3B800C7F41538616BDAE66E418C
gpg: Good signature from "Mustafa <mustafa91@gmail.com>" [ultimate]

通过消息 "This key is now in the hands of the enemy."

撤销密钥

$ gpg --edit-key 5DD923FBCF6392A5CB366167D4C0627A07510C6C
gpg> key 2

sec  rsa2048/D4C0627A07510C6C
     created: 2019-02-03  expires: 2021-02-02  usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa2048/E058B91696C43666
     created: 2019-02-03  expires: 2021-02-02  usage: E
ssb* rsa2048/38616BDAE66E418C
     created: 2019-02-03  expires: 2019-02-13  usage: S

gpg> revkey
sec  rsa2048/D4C0627A07510C6C
     created: 2019-02-03  expires: 2021-02-02  usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa2048/E058B91696C43666
     created: 2019-02-03  expires: 2021-02-02  usage: E
The following key was revoked on 2019-02-03 by RSA key D4C0627A07510C6C Mustafa <mustafa91@gmail.com>
ssb  rsa2048/38616BDAE66E418C
     created: 2019-02-03  revoked: 2019-02-03  usage: S
[ultimate] (1). Mustafa <mustafa91@gmail.com>

尝试验证旧签名，发现失败。

$ gpg --verify test.txt.asc test.txt
gpg: Signature made Sun Feb  3 21:49:43 2019 +03
gpg:                using RSA key 485FC77FC73DA3B800C7F41538616BDAE66E418C
gpg: Good signature from "Mustafa <mustafa91@gmail.com>" [ultimate]
gpg: WARNING: This subkey has been revoked by its owner!
gpg: reason for revocation: Key has been compromised
gpg: revocation comment: This key is now in the hands of the enemy.

但是，尝试使用已撤销的密钥进行签名。

$ rm test.key.asc
$ gpg --armor --detach-sign --default-key 38616BDAE66E418C  test.txt
gpg: using "38616BDAE66E418C" as default secret key for signing

为什么不失败？如何验证？

$ gpg --verify test.txt.asc test.txt
gpg: Signature made Sun Feb  3 21:53:11 2019 +03
gpg:                using RSA key 5DD923FBCF6392A5CB366167D4C0627A07510C6C
gpg: Good signature from "Mustafa <mustafa91@gmail.com>" [ultimate]

Answer 1

看看你最后两段摘录。尽管您将默认签名密钥指定为 38616BDAE66E418C，但当您进行验证时，它会报告已使用 D4C0627A07510C6C.

签名

如果您使用 gpg 的 -v 详细选项，您将看到如果指定的默认密钥被撤销，它会回退到下一个可用的签名密钥。

为了说明这一点，我重新创建了您的场景：

sec  rsa2048/4E5CB15076F1318E
     created: 2019-02-09  expires: 2021-02-08  usage: SC
     trust: ultimate      validity: ultimate
ssb  rsa2048/3303CBB274AECA3B
     created: 2019-02-09  expires: 2021-02-08  usage: E
The following key was revoked on 2019-02-09 by RSA key 4E5CB15076F1318E Herp Derp <herp@derp.com>
ssb  rsa2048/8ABD3900E64E7972
     created: 2019-02-09  revoked: 2019-02-09  usage: S
[ultimate] (1). Herp Derp <herp@derp.com>

在撤销之前使用子密钥签名：

$ gpg -v --armor --detach-sign --default-key 8ABD3900E64E7972 test.txt
gpg: using pgp trust model
gpg: using "8ABD3900E64E7972" as default secret key for signing
gpg: using subkey 8ABD3900E64E7972 instead of primary key 4E5CB15076F1318E
gpg: writing to 'test.txt.asc'
gpg: RSA/SHA256 signature from: "8ABD3900E64E7972 Herp Derp <herp@derp.com>"

撤销后使用子密钥签名：

$ gpg -v --armor --detach-sign --default-key 8ABD3900E64E7972 test.txt
gpg: Note: signature key 8ABD3900E64E7972 has been revoked
gpg: using pgp trust model
gpg: using "8ABD3900E64E7972" as default secret key for signing
gpg: Note: signature key 8ABD3900E64E7972 has been revoked
gpg: writing to 'test.txt.asc'
gpg: RSA/SHA256 signature from: "4E5CB15076F1318E Herp Derp <herp@derp.com>"

你可以看到在第二个例子中，gpg 将子键识别为已撤销并回退到主键。

GPG 仍然看到带有已撤销子项的好兆头仍然有效

GPG Still sees good sign with revoked subkey still works

digital-signature

gnupg

verification

sign