SSH serialization for public keys (#2957)

* SSH serialization for public keys

* name errors ahoy!

* id, ego, superego

* dsa support

* EC support

* Don't keyerror

* Documentation OpenSSH

* flake8

* fix

* bytes bytes bytes

* skip curve unsupported

* bytes!

* Move a function

* reorganize code for coverage

3 files changed, 87 insertions, 0 deletions

diff --git a/tests/hazmat/primitives/test_dsa.py b/tests/hazmat/primitives/test_dsa.py
index b02cadc8..6ad9762a 100644
--- a/tests/hazmat/primitives/test_dsa.py
+++ b/tests/hazmat/primitives/test_dsa.py
@@ -1018,6 +1018,29 @@ class TestDSAPEMPublicKeySerialization(object):
         )
         assert serialized == key_bytes
 
+    def test_public_bytes_openssh(self, backend):
+        key_bytes = load_vectors_from_file(
+            os.path.join("asymmetric", "PKCS8", "unenc-dsa-pkcs8.pub.pem"),
+            lambda pemfile: pemfile.read(), mode="rb"
+        )
+        key = serialization.load_pem_public_key(key_bytes, backend)
+
+        ssh_bytes = key.public_bytes(
+            serialization.Encoding.OpenSSH, serialization.PublicFormat.OpenSSH
+        )
+        assert ssh_bytes == (
+            b"ssh-dss AAAAB3NzaC1kc3MAAACBAKoJMMwUWCUiHK/6KKwolBlqJ4M95ewhJweR"
+            b"aJQgd3Si57I4sNNvGySZosJYUIPrAUMpJEGNhn+qIS3RBx1NzrJ4J5StOTzAik1K"
+            b"2n9o1ug5pfzTS05ALYLLioy0D+wxkRv5vTYLA0yqy0xelHmSVzyekAmcGw8FlAyr"
+            b"5dLeSaFnAAAAFQCtwOhps28KwBOmgf301ImdaYIEUQAAAIEAjGtFia+lOk0QSL/D"
+            b"RtHzhsp1UhzPct2qJRKGiA7hMgH/SIkLv8M9ebrK7HHnp3hQe9XxpmQi45QVvgPn"
+            b"EUG6Mk9bkxMZKRgsiKn6QGKDYGbOvnS1xmkMfRARBsJAq369VOTjMB/Qhs5q2ski"
+            b"+ycTorCIfLoTubxozlz/8kHNMkYAAACAKyYOqX3GoSrpMsZA5989j/BKigWgMk+N"
+            b"Xxsj8V+hcP8/QgYRJO/yWGyxG0moLc3BuQ/GqE+xAQnLZ9tdLalxrq8Xvl43KEVj"
+            b"5MZNnl/ISAJYsxnw3inVTYNQcNnih5FNd9+BSR9EI7YtqYTrP0XrKin86l2uUlrG"
+            b"q2vM4Ev99bY="
+        )
+
     def test_public_bytes_invalid_encoding(self, backend):
         key = DSA_KEY_2048.private_key(backend).public_key()
         with pytest.raises(TypeError):
diff --git a/tests/hazmat/primitives/test_ec.py b/tests/hazmat/primitives/test_ec.py
index 8747ea4f..8705f79c 100644
--- a/tests/hazmat/primitives/test_ec.py
+++ b/tests/hazmat/primitives/test_ec.py
@@ -815,6 +815,34 @@ class TestEllipticCurvePEMPublicKeySerialization(object):
         )
         assert serialized == key_bytes
 
+    def test_public_bytes_openssh(self, backend):
+        _skip_curve_unsupported(backend, ec.SECP192R1())
+        _skip_curve_unsupported(backend, ec.SECP256R1())
+
+        key_bytes = load_vectors_from_file(
+            os.path.join(
+                "asymmetric", "PEM_Serialization", "ec_public_key.pem"
+            ),
+            lambda pemfile: pemfile.read(), mode="rb"
+        )
+        key = serialization.load_pem_public_key(key_bytes, backend)
+
+        ssh_bytes = key.public_bytes(
+            serialization.Encoding.OpenSSH, serialization.PublicFormat.OpenSSH
+        )
+        assert ssh_bytes == (
+            b"ecdsa-sha2-nistp256 AAAAE2VjZHNhLXNoYTItbmlzdHAyNTYAAAAIbmlzdHAy"
+            b"NTYAAABBBCS8827s9rUZyxZTi/um01+oIlWrwLHOjQxRU9CDAndom00zVAw5BRrI"
+            b"KtHB+SWD4P+sVJTARSq1mHt8kOIWrPc="
+        )
+
+        key = ec.generate_private_key(ec.SECP192R1(), backend).public_key()
+        with pytest.raises(ValueError):
+            key.public_bytes(
+                serialization.Encoding.OpenSSH,
+                serialization.PublicFormat.OpenSSH
+            )
+
     def test_public_bytes_invalid_encoding(self, backend):
         _skip_curve_unsupported(backend, ec.SECP256R1())
         key = load_vectors_from_file(
diff --git a/tests/hazmat/primitives/test_rsa.py b/tests/hazmat/primitives/test_rsa.py
index 6a8bb95d..320a96e5 100644
--- a/tests/hazmat/primitives/test_rsa.py
+++ b/tests/hazmat/primitives/test_rsa.py
@@ -2066,6 +2066,42 @@ class TestRSAPEMPublicKeySerialization(object):
         serialized = key.public_bytes(encoding, format)
         assert serialized == key_bytes
 
+    def test_public_bytes_openssh(self, backend):
+        key_bytes = load_vectors_from_file(
+            os.path.join("asymmetric", "public", "PKCS1", "rsa.pub.pem"),
+            lambda pemfile: pemfile.read(), mode="rb"
+        )
+        key = serialization.load_pem_public_key(key_bytes, backend)
+
+        ssh_bytes = key.public_bytes(
+            serialization.Encoding.OpenSSH, serialization.PublicFormat.OpenSSH
+        )
+        assert ssh_bytes == (
+            b"ssh-rsa AAAAB3NzaC1yc2EAAAADAQABAAAAgQC7JHoJfg6yNzLMOWet8Z49a4KD"
+            b"0dCspMAYvo2YAMB7/wdEycocujbhJ2n/seONi+5XqTqqFkM5VBl8rmkkFPZk/7x0"
+            b"xmdsTPECSWnHK+HhoaNDFPR3j8jQhVo1laxiqcEhAHegi5cwtFosuJAvSKAFKEvy"
+            b"D43si00DQnXWrYHAEQ=="
+        )
+
+        with pytest.raises(ValueError):
+            key.public_bytes(
+                serialization.Encoding.PEM, serialization.PublicFormat.OpenSSH
+            )
+        with pytest.raises(ValueError):
+            key.public_bytes(
+                serialization.Encoding.DER, serialization.PublicFormat.OpenSSH
+            )
+        with pytest.raises(ValueError):
+            key.public_bytes(
+                serialization.Encoding.OpenSSH,
+                serialization.PublicFormat.PKCS1,
+            )
+        with pytest.raises(ValueError):
+            key.public_bytes(
+                serialization.Encoding.OpenSSH,
+                serialization.PublicFormat.SubjectPublicKeyInfo,
+            )
+
     def test_public_bytes_invalid_encoding(self, backend):
         key = RSA_KEY_2048.private_key(backend).public_key()
         with pytest.raises(TypeError):