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Fix encoding of SSH certs with critical options (#9208)
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* Add tests for issue #9207

* Fix encoding of SSH certs with critical options

* Test unexpected additional values for crit opts/exts
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@lkubb
lkubb authored Jul 10, 2023
1 parent 50932e2 commit 1ca7adc
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4 changes: 4 additions & 0 deletions docs/development/test-vectors.rst
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Original file line number Diff line number Diff line change
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
18 changes: 16 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 +1063,10 @@ 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:
value, extra = _get_sshstr(value)
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 +1454,22 @@ 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
86 changes: 54 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 @@ -1131,26 +1131,28 @@ 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 @@ -1161,7 +1163,10 @@ 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 Down Expand Up @@ -1283,6 +1288,8 @@ 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 @@ -1709,6 +1716,11 @@ 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 @@ -1723,19 +1735,21 @@ 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 @@ -1761,6 +1775,11 @@ 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 @@ -1770,8 +1789,11 @@ 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 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
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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