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Backport ssh cert fix (#9211)
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* Fix encoding of SSH certs with critical options (#9208)

* Add tests for issue #9207

* Fix encoding of SSH certs with critical options

* Test unexpected additional values for crit opts/exts

* temporarily allow invalid ssh cert encoding

---------

Co-authored-by: jeanluc <2163936+lkubb@users.noreply.github.com>
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@reaperhulk @lkubb
reaperhulk and lkubb authored Jul 11, 2023
1 parent bb204c8 commit e190ef1
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11 changes: 11 additions & 0 deletions CHANGELOG.rst
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@@ -1,6 +1,17 @@
Changelog
=========

.. _v41-0-2:

41.0.2 - 2023-07-10
~~~~~~~~~~~~~~~~~~~

* Fixed bugs in creating and parsing SSH certificates where critical options
with values were handled incorrectly. Certificates are now created correctly
and parsing accepts correct values as well as the previously generated
invalid forms with a warning. In the next release, support for parsing these
invalid forms will be removed.

.. _v41-0-1:

41.0.1 - 2023-06-01
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4 changes: 4 additions & 0 deletions docs/development/test-vectors.rst
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Expand Up @@ -866,6 +866,10 @@ Custom OpenSSH Certificate Test Vectors
critical option.
* ``p256-p256-non-lexical-crit-opts.pub`` - A certificate with critical
options in non-lexical order.
* ``p256-ed25519-non-singular-crit-opt-val.pub`` - A certificate with
a critical option that contains more than one value.
* ``p256-ed25519-non-singular-ext-val.pub`` - A certificate with
an extension that contains more than one value.
* ``dsa-p256.pub`` - A certificate with a DSA public key signed by a P256
CA.
* ``p256-dsa.pub`` - A certificate with a P256 public key signed by a DSA
Expand Down
28 changes: 26 additions & 2 deletions src/cryptography/hazmat/primitives/serialization/ssh.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1063,6 +1063,20 @@ def _parse_exts_opts(exts_opts: memoryview) -> typing.Dict[bytes, bytes]:
if last_name is not None and bname < last_name:
raise ValueError("Fields not lexically sorted")
value, exts_opts = _get_sshstr(exts_opts)
if len(value) > 0:
try:
value, extra = _get_sshstr(value)
except ValueError:
warnings.warn(
"This certificate has an incorrect encoding for critical "
"options or extensions. This will be an exception in "
"cryptography 42",
utils.DeprecatedIn41,
stacklevel=4,
)
else:
if len(extra) > 0:
raise ValueError("Unexpected extra data after value")
result[bname] = bytes(value)
last_name = bname
return result
Expand Down Expand Up @@ -1450,12 +1464,22 @@ def sign(self, private_key: SSHCertPrivateKeyTypes) -> SSHCertificate:
fcrit = _FragList()
for name, value in self._critical_options:
fcrit.put_sshstr(name)
fcrit.put_sshstr(value)
if len(value) > 0:
foptval = _FragList()
foptval.put_sshstr(value)
fcrit.put_sshstr(foptval.tobytes())
else:
fcrit.put_sshstr(value)
f.put_sshstr(fcrit.tobytes())
fext = _FragList()
for name, value in self._extensions:
fext.put_sshstr(name)
fext.put_sshstr(value)
if len(value) > 0:
fextval = _FragList()
fextval.put_sshstr(value)
fext.put_sshstr(fextval.tobytes())
else:
fext.put_sshstr(value)
f.put_sshstr(fext.tobytes())
f.put_sshstr(b"") # RESERVED FIELD
# encode CA public key
Expand Down
111 changes: 79 additions & 32 deletions tests/hazmat/primitives/test_ssh.py
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Original file line number Diff line number Diff line change
Expand Up @@ -1115,26 +1115,28 @@ def test_loads_ssh_cert(self, backend):
# secp256r1 public key, ed25519 signing key
cert = load_ssh_public_identity(
b"ecdsa-sha2-nistp256-cert-v01@openssh.com AAAAKGVjZHNhLXNoYTItbm"
b"lzdHAyNTYtY2VydC12MDFAb3BlbnNzaC5jb20AAAAgtdU+dl9vD4xPi8afxERYo"
b"s0c0d9/3m7XGY6fGeSkqn0AAAAIbmlzdHAyNTYAAABBBAsuVFNNj/mMyFm2xB99"
b"G4xiaUJE1lZNjcp+S2tXYW5KorcHpusSlSqOkUPZ2l0644dgiNPDKR/R+BtYENC"
b"8aq8AAAAAAAAAAAAAAAEAAAAUdGVzdEBjcnlwdG9ncmFwaHkuaW8AAAAaAAAACm"
b"NyeXB0b3VzZXIAAAAIdGVzdHVzZXIAAAAAY7KyZAAAAAB2frXAAAAAAAAAAIIAA"
b"AAVcGVybWl0LVgxMS1mb3J3YXJkaW5nAAAAAAAAABdwZXJtaXQtYWdlbnQtZm9y"
b"d2FyZGluZwAAAAAAAAAWcGVybWl0LXBvcnQtZm9yd2FyZGluZwAAAAAAAAAKcGV"
b"ybWl0LXB0eQAAAAAAAAAOcGVybWl0LXVzZXItcmMAAAAAAAAAAAAAADMAAAALc3"
b"NoLWVkMjU1MTkAAAAg3P0eyGf2crKGwSlnChbLzTVOFKwQELE1Ve+EZ6rXF18AA"
b"ABTAAAAC3NzaC1lZDI1NTE5AAAAQKoij8BsPj/XLb45+wHmRWKNqXeZYXyDIj8J"
b"IE6dIymjEqq0TP6ntu5t59hTmWlDO85GnMXAVGBjFbeikBMfAQc= reaperhulk"
b"@despoina.local"
b"lzdHAyNTYtY2VydC12MDFAb3BlbnNzaC5jb20AAAAgLfsFv9Gbc6LZSiJFWdYQl"
b"IMNI50GExXW0fBpgGVf+Y4AAAAIbmlzdHAyNTYAAABBBIzVyRgVLR4F38bIOLBN"
b"8CNm8Nf+eBHCVkKDKb9WDyLLD61CEmzjK/ORwFuSE4N60eIGbFidBf0D0xh7G6o"
b"TNxsAAAAAAAAAAAAAAAEAAAAUdGVzdEBjcnlwdG9ncmFwaHkuaW8AAAAaAAAACm"
b"NyeXB0b3VzZXIAAAAIdGVzdHVzZXIAAAAAY7KyZAAAAAB2frXAAAAAWAAAAA1mb"
b"3JjZS1jb21tYW5kAAAALAAAAChlY2hvIGFhYWFhYWFhYWFhYWFhYWFhYWFhYWFh"
b"YWFhYWFhYWFhYWFhAAAAD3ZlcmlmeS1yZXF1aXJlZAAAAAAAAACCAAAAFXBlcm1"
b"pdC1YMTEtZm9yd2FyZGluZwAAAAAAAAAXcGVybWl0LWFnZW50LWZvcndhcmRpbm"
b"cAAAAAAAAAFnBlcm1pdC1wb3J0LWZvcndhcmRpbmcAAAAAAAAACnBlcm1pdC1wd"
b"HkAAAAAAAAADnBlcm1pdC11c2VyLXJjAAAAAAAAAAAAAAAzAAAAC3NzaC1lZDI1"
b"NTE5AAAAICH6csEOmGbOfT2B/S/FJg3uyPsaPSZUZk2SVYlfs0KLAAAAUwAAAAt"
b"zc2gtZWQyNTUxOQAAAEDz2u7X5/TFbN7Ms7DP4yArhz1oWWYKkdAk7FGFkHfjtY"
b"/YfNQ8Oky3dCZRi7PnSzScEEjos7723dhF8/y99WwH reaperhulk@despoina."
b"local"
)
assert isinstance(cert, SSHCertificate)
cert.verify_cert_signature()
signature_key = cert.signature_key()
assert isinstance(signature_key, ed25519.Ed25519PublicKey)
assert cert.nonce == (
b"\xb5\xd5>v_o\x0f\x8cO\x8b\xc6\x9f\xc4DX\xa2\xcd\x1c\xd1\xdf"
b"\x7f\xden\xd7\x19\x8e\x9f\x19\xe4\xa4\xaa}"
b'-\xfb\x05\xbf\xd1\x9bs\xa2\xd9J"EY\xd6\x10\x94\x83\r#\x9d'
b"\x06\x13\x15\xd6\xd1\xf0i\x80e_\xf9\x8e"
)
public_key = cert.public_key()
assert isinstance(public_key, ec.EllipticCurvePublicKey)
Expand All @@ -1145,7 +1147,10 @@ def test_loads_ssh_cert(self, backend):
assert cert.valid_principals == [b"cryptouser", b"testuser"]
assert cert.valid_before == 1988015552
assert cert.valid_after == 1672655460
assert cert.critical_options == {}
assert cert.critical_options == {
b"force-command": b"echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
b"verify-required": b"",
}
assert cert.extensions == {
b"permit-X11-forwarding": b"",
b"permit-agent-forwarding": b"",
Expand All @@ -1154,6 +1159,31 @@ def test_loads_ssh_cert(self, backend):
b"permit-user-rc": b"",
}

def test_loads_deprecated_invalid_encoding_cert(self, backend):
with pytest.warns(utils.DeprecatedIn41):
cert = load_ssh_public_identity(
b"ecdsa-sha2-nistp256-cert-v01@openssh.com AAAAKGVjZHNhLXNoYT"
b"ItbmlzdHAyNTYtY2VydC12MDFAb3BlbnNzaC5jb20AAAAgXE7sJ+xDVVNCO"
b"cEvpZS+SXIbc0nJdny/KqVbnwHslMIAAAAIbmlzdHAyNTYAAABBBI/qcLq8"
b"iiErpAhOWRqdMkpFSCNv7TVUcXCIfAl01JXbe2MvS4V7lFtiyrBjLSV7Iyw"
b"3TrulrWLibjPzZvLwmQcAAAAAAAAAAAAAAAEAAAAAAAAAAAAAAAAAAAAA//"
b"////////8AAABUAAAADWZvcmNlLWNvbW1hbmQAAAAoZWNobyBhYWFhYWFhY"
b"WFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYQAAAA92ZXJpZnktcmVxdWly"
b"ZWQAAAAAAAAAEgAAAApwZXJtaXQtcHR5AAAAAAAAAAAAAABoAAAAE2VjZHN"
b"hLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAyNTYAAABBBI/qcLq8iiErpAhOWR"
b"qdMkpFSCNv7TVUcXCIfAl01JXbe2MvS4V7lFtiyrBjLSV7Iyw3TrulrWLib"
b"jPzZvLwmQcAAABlAAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAABKAAAAIQCi"
b"eCsIhGKrZdkE1+zY5EBucrLzxFpwnm/onIT/6rapvQAAACEAuVQ1yQjlPKr"
b"kfsGfjeG+2umZrOS5Ycx85BQhYf0RgsA="
)
assert isinstance(cert, SSHCertificate)
cert.verify_cert_signature()
assert cert.extensions == {b"permit-pty": b""}
assert cert.critical_options == {
b"force-command": b"echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa",
b"verify-required": b"",
}

@pytest.mark.parametrize(
"filename",
[
Expand Down Expand Up @@ -1267,6 +1297,8 @@ def test_invalid_cert_type(self):
"p256-p256-non-lexical-extensions.pub",
"p256-p256-duplicate-crit-opts.pub",
"p256-p256-non-lexical-crit-opts.pub",
"p256-ed25519-non-singular-crit-opt-val.pub",
"p256-ed25519-non-singular-ext-val.pub",
],
)
def test_invalid_encodings(self, filename):
Expand Down Expand Up @@ -1693,6 +1725,11 @@ def test_sign_and_byte_compare_rsa(self, monkeypatch):
.valid_after(1672531200)
.valid_before(1672617600)
.type(SSHCertificateType.USER)
.add_extension(b"permit-pty", b"")
.add_critical_option(
b"force-command", b"echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
)
.add_critical_option(b"verify-required", b"")
)
cert = builder.sign(private_key)
sig_key = cert.signature_key()
Expand All @@ -1707,19 +1744,21 @@ def test_sign_and_byte_compare_rsa(self, monkeypatch):
b"4kyHpbLEIVloBjzetoqXK6u8Hjz/APuagONypNDCySDR6M7jM85HDcLoFFrbBb8"
b"pruHSTxQejMeEmJxYf8b7rNl58/IWPB1ymbNlvHL/4oSOlnrtHkjcxRWzpQ7U3g"
b"T9BThGyhCiI7EMyEHMgP3r7kTzEUwT6IavWDAAAAAAAAAAAAAAABAAAAAAAAAAA"
b"AAAAAY7DNAAAAAABjsh6AAAAAAAAAAAAAAAAAAAABFwAAAAdzc2gtcnNhAAAAAw"
b"EAAQAAAQEAwXr8fndHTKpaqDA2FYo/+/e1IWhRuiIw5dar/MHGz+9Z6SPqEzC8W"
b"TtzgCq2CKbkozBlI6MRa6WqOWYUUXThO2xJ6beAYuRJ1y77EP1J6R+gi5bQUeeC"
b"6fWrxbWm95hIJ6245z2gDyKy79zbduq0btrZjtZWYnQ/3GwOM2pdDNuqfcKeU2N"
b"eJMh6WyxCFZaAY83raKlyurvB48/wD7moDjcqTQwskg0ejO4zPORw3C6BRa2wW/"
b"Ka7h0k8UHozHhJicWH/G+6zZefPyFjwdcpmzZbxy/+KEjpZ67R5I3MUVs6UO1N4"
b"E/QU4RsoQoiOxDMhBzID96+5E8xFME+iGr1gwAAARQAAAAMcnNhLXNoYTItNTEy"
b"AAABAKCRnfhn6MZs3jRgIDICUpUyWrDCbpStEbdzhmoxF8w2m8klR7owRH/rxOf"
b"nWhKMGnXnoERS+az3Zh9ckiQPujkuEToORKpzu6CEWlzHSzyK1o2X548KkW76HJ"
b"gqzwMas94HY7UOJUgKSFUI0S3jAgqXAKSa1DxvJBu5/n57aUqPq+BmAtoI8uNBo"
b"x4F1pNEop38+oD7rUt8bZ8K0VcrubJZz806K8UNiK0mOahaEIkvZXBfzPGvSNRj"
b"0OjDl1dLUZaP8C1o5lVRomEm7pLcgE9i+ZDq5iz+mvQrSBStlpQ5hPGuUOrZ/oY"
b"ZLZ1G30R5tWj212MHoNZjxFxM8+f2OT4="
b"AAAAAY7DNAAAAAABjsh6AAAAAWAAAAA1mb3JjZS1jb21tYW5kAAAALAAAAChlY2"
b"hvIGFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhAAAAD3Zlcmlme"
b"S1yZXF1aXJlZAAAAAAAAAASAAAACnBlcm1pdC1wdHkAAAAAAAAAAAAAARcAAAAH"
b"c3NoLXJzYQAAAAMBAAEAAAEBAMF6/H53R0yqWqgwNhWKP/v3tSFoUboiMOXWq/z"
b"Bxs/vWekj6hMwvFk7c4Aqtgim5KMwZSOjEWulqjlmFFF04TtsSem3gGLkSdcu+x"
b"D9SekfoIuW0FHngun1q8W1pveYSCetuOc9oA8isu/c23bqtG7a2Y7WVmJ0P9xsD"
b"jNqXQzbqn3CnlNjXiTIelssQhWWgGPN62ipcrq7wePP8A+5qA43Kk0MLJINHozu"
b"MzzkcNwugUWtsFvymu4dJPFB6Mx4SYnFh/xvus2Xnz8hY8HXKZs2W8cv/ihI6We"
b"u0eSNzFFbOlDtTeBP0FOEbKEKIjsQzIQcyA/evuRPMRTBPohq9YMAAAEUAAAADH"
b"JzYS1zaGEyLTUxMgAAAQCYbbNzhflDqZAxyBpdLIX0nLAdnTeFNBudMqgo3KGND"
b"WlU9N17hqBEmcvIOrtNi+JKuKZW89zZrbORHvdjv6NjGSKzJD/XA25YrX1KgMEO"
b"wt5pzMZX+100drwrjQo+vZqeIN3FJNmT3wssge73v+JsxQrdIAz7YM2OZrFr5HM"
b"qZEZ5tMvAf/s5YEMDttEU4zMtmjubQyDM5KyYnZdoDT4sKi2rB8gfaigc4IdI/K"
b"8oXL/3Y7rHuOtejl3lUK4v6DxeRl4aqGYWmhUJc++Rh0cbDgC2S6Cq7gAfG2tND"
b"zbwL217Q93R08bJn1hDWuiTiaHGauSy2gPUI+cnkvlEocHM"
)

@pytest.mark.supported(
Expand All @@ -1745,6 +1784,11 @@ def test_sign_and_byte_compare_ed25519(self, monkeypatch, backend):
.valid_after(1672531200)
.valid_before(1672617600)
.type(SSHCertificateType.USER)
.add_extension(b"permit-pty", b"")
.add_critical_option(
b"force-command", b"echo aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa"
)
.add_critical_option(b"verify-required", b"")
)
cert = builder.sign(private_key)
sig_key = cert.signature_key()
Expand All @@ -1754,8 +1798,11 @@ def test_sign_and_byte_compare_ed25519(self, monkeypatch, backend):
b"ssh-ed25519-cert-v01@openssh.com AAAAIHNzaC1lZDI1NTE5LWNlcnQtdj"
b"AxQG9wZW5zc2guY29tAAAAIAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAA"
b"AAAAAAAINdamAGCsQq31Uv+08lkBzoO4XLz2qYjJa8CGmj3B1EaAAAAAAAAAAAA"
b"AAABAAAAAAAAAAAAAAAAY7DNAAAAAABjsh6AAAAAAAAAAAAAAAAAAAAAMwAAAAt"
b"zc2gtZWQyNTUxOQAAACDXWpgBgrEKt9VL/tPJZAc6DuFy89qmIyWvAhpo9wdRGg"
b"AAAFMAAAALc3NoLWVkMjU1MTkAAABAAlF6Lxabxs+8fkOr7KjKYei9konIG13cQ"
b"gJ2tWf3yFcg3OuV5s/AkRmKdwHlQfTUrhRdOmDnGxeLEB0mvkVFCw=="
b"AAABAAAAAAAAAAAAAAAAY7DNAAAAAABjsh6AAAAAWAAAAA1mb3JjZS1jb21tYW5"
b"kAAAALAAAAChlY2hvIGFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYW"
b"FhAAAAD3ZlcmlmeS1yZXF1aXJlZAAAAAAAAAASAAAACnBlcm1pdC1wdHkAAAAAA"
b"AAAAAAAADMAAAALc3NoLWVkMjU1MTkAAAAg11qYAYKxCrfVS/7TyWQHOg7hcvPa"
b"piMlrwIaaPcHURoAAABTAAAAC3NzaC1lZDI1NTE5AAAAQL2aUjeD60C2FrbgHcN"
b"t8yRa8IRbxvOyA9TZYDGG1dRE3DiR0fuudU20v6vqfTd1gx0S5QyEdECXLl9ZI3"
b"AwZgc="
)
1 change: 1 addition & 0 deletions .../cryptography_vectors/asymmetric/OpenSSH/certs/p256-ed25519-non-singular-crit-opt-val.pub
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@@ -0,0 +1 @@
ecdsa-sha2-nistp256-cert-v01@openssh.com AAAAKGVjZHNhLXNoYTItbmlzdHAyNTYtY2VydC12MDFAb3BlbnNzaC5jb20AAAAgAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAAIbmlzdHAyNTYAAABBBCZWRs4GYIHGJpyXuqvfFGWN49dnJRkZJLDkFrHf6mNHhIMI3vtrLfCZwxPSfnCYWK6YofssZ1FYA6TkVJq8Xi8AAAAAAAAAAAAAAAEAAAAAAAAAAAAAAABjsM0AAAAAAGOyHoAAAABtAAAADWZvcmNlLWNvbW1hbmQAAABBAAAAKGVjaG8gYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWFhYWEAAAARaW52YWxpZF9taXNjX2RhdGEAAAAPdmVyaWZ5LXJlcXVpcmVkAAAAAAAAABIAAAAKcGVybWl0LXB0eQAAAAAAAAAAAAAAMwAAAAtzc2gtZWQyNTUxOQAAACDdZgztgAFFC7T5PifrUy/kMu0Pnwq1au3vStKHe7FFMAAAAFMAAAALc3NoLWVkMjU1MTkAAABAt/0pBSDBFy1crBPHOBoKFoxRjKd1tKVdOrD3QVgbBfpaHfxi4vrgYe6JfQ54+vu5P+8yrMyACekT8H6hhvxHDw==
1 change: 1 addition & 0 deletions vectors/cryptography_vectors/asymmetric/OpenSSH/certs/p256-ed25519-non-singular-ext-val.pub
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Original file line number Diff line number Diff line change
@@ -0,0 +1 @@
ecdsa-sha2-nistp256-cert-v01@openssh.com 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