Adds CSR builder.

5 files changed, 377 insertions, 1 deletions

diff --git a/CHANGELOG.rst b/CHANGELOG.rst
index 5c9d08ea..bc95cf74 100644
--- a/CHANGELOG.rst
+++ b/CHANGELOG.rst
@@ -24,6 +24,8 @@ Changelog
   and :class:`~cryptography.hazmat.primitives.kdf.concatkdf.ConcatKDFHMAC`.
 * Raise a ``TypeError`` when passing objects that are not text as the value to
   :class:`~cryptography.x509.NameAttribute`.
+* Add support for creating certificate signing requests with
+  :class:`~cryptography.x509.CertificateSigningRequestBuilder`.
 
 0.9.1 - 2015-06-06
 ~~~~~~~~~~~~~~~~~~
diff --git a/docs/x509.rst b/docs/x509.rst
index b8e3c8ee..8507edc1 100644
--- a/docs/x509.rst
+++ b/docs/x509.rst
@@ -468,6 +468,47 @@ X.509 Revoked Certificate Object
 
         The extensions encoded in the revoked certificate.
 
+X.509 CSR (Certificate Signing Request) Builder Object
+~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
+
+.. class:: CertificateSigningRequestBuilder
+
+    .. method:: __init__()
+
+        Creates an empty certificate signing request.
+
+    .. method:: set_version(version)
+
+       :param version: The :class:`Version` of the X.509 protocol.
+
+    .. method:: set_subject_name(name)
+
+        :param name: The :class:`Name` of the certificate subject.
+
+    .. method:: add_extension(extension)
+
+        :param extension: The :class:`Extension` to add to the request.
+
+    .. method:: sign(backend, private_key, algorithm)
+
+        :param backend: Backend that will be used to sign the request.
+            Must support the
+            :class:`~cryptography.hazmat.backends.interfaces.X509Backend`
+            interface.
+
+        :param private_key: The
+            :class:`~cryptography.hazmat.primitives.asymmetric.rsa.RSAPrivateKey`
+            that will be used to sign the request.  When the request is
+            signed by a certificate authority, the private key's associated
+            public key will be stored in the resulting certificate.
+
+        :param algorithm: The
+            :class:`~cryptography.hazmat.primitives.hashes.HashAlgorithm`
+            that will be used to generate the request signature.
+
+        :type: :class:`CertificateSigningRequest`
+
+
 .. class:: Name
 
     .. versionadded:: 0.8
diff --git a/src/cryptography/hazmat/backends/openssl/backend.py b/src/cryptography/hazmat/backends/openssl/backend.py
index 4d469c40..f03ca077 100644
--- a/src/cryptography/hazmat/backends/openssl/backend.py
+++ b/src/cryptography/hazmat/backends/openssl/backend.py
@@ -10,7 +10,7 @@ from contextlib import contextmanager
 
 import six
 
-from cryptography import utils
+from cryptography import utils, x509
 from cryptography.exceptions import (
     InternalError, UnsupportedAlgorithm, _Reasons
 )
@@ -56,6 +56,88 @@ _OpenSSLError = collections.namedtuple("_OpenSSLError",
                                        ["code", "lib", "func", "reason"])
 
 
+def _encode_asn1_int(backend, x):
+    i = backend._lib.ASN1_INTEGER_new()
+    # i = backend._ffi.gc(i, backend._lib.ASN1_INTEGER_free)
+    backend._lib.ASN1_INTEGER_set(i, x)
+    return i
+
+
+def _encode_asn1_str(backend, x, n):
+    s = backend._lib.ASN1_OCTET_STRING_new()
+    # s = backend._ffi.gc(s, backend._lib.ASN1_OCTET_STRING_free)
+    backend._lib.ASN1_OCTET_STRING_set(s, x, n)
+    return s
+
+
+def _encode_name(backend, attributes):
+    resolve = {
+        x509.OID_COMMON_NAME: b'CN',
+        x509.OID_COUNTRY_NAME: b'C',
+        x509.OID_STATE_OR_PROVINCE_NAME: b'ST',
+        x509.OID_LOCALITY_NAME: b'L',
+        x509.OID_ORGANIZATION_NAME: b'O',
+        x509.OID_ORGANIZATIONAL_UNIT_NAME: b'OU',
+    }
+    subject = backend._lib.X509_NAME_new()
+    subject = backend._ffi.gc(subject, backend._lib.X509_NAME_free)
+    for attribute in attributes:
+        value = attribute.value
+        if isinstance(value, six.text_type):
+            value = value.encode('ascii')
+        res = backend._lib.X509_NAME_add_entry_by_txt(
+            subject,
+            resolve[attribute.oid],
+            backend._lib.MBSTRING_ASC,
+            value,
+            -1, -1, 0,
+        )
+        assert res == 1
+    return subject
+
+
+def _txt2obj(backend, name):
+    if isinstance(name, six.text_type):
+        name = name.encode('ascii')
+    obj = backend._lib.OBJ_txt2obj(name, 1)
+    assert obj != backend._ffi.NULL
+    # NOTE: not sure if we should GC...
+    return obj
+
+
+def _encode_basic_constraints(backend, ca=False, pathlen=0, critical=False):
+    obj = _txt2obj(backend, x509.OID_BASIC_CONSTRAINTS.dotted_string)
+    assert obj is not None
+    constraints = backend._lib.BASIC_CONSTRAINTS_new()
+    constraints.ca = 255 if ca else 0
+    if ca:
+        constraints.pathlen = _encode_asn1_int(backend, pathlen)
+
+    # Allocate a buffer for encoded payload.
+    cdata = backend._ffi.new(
+        'unsigned char[]',
+        2048,  # TODO: shrink to fit!
+    )
+    assert cdata != backend._ffi.NULL
+
+    # Fetch the encoded payload.
+    p = backend._ffi.new('unsigned char*[1]')
+    assert p != backend._ffi.NULL
+    p[0] = cdata
+    r = backend._lib.i2d_BASIC_CONSTRAINTS(constraints, p)
+    assert r > 0
+
+    # Wrap that in an X509 extension object.
+    extension = backend._lib.X509_EXTENSION_create_by_OBJ(
+        backend._ffi.NULL,
+        obj,
+        1 if critical else 0,
+        _encode_asn1_str(backend, cdata, r),
+    )
+    assert extension != backend._ffi.NULL
+    return extension
+
+
 @utils.register_interface(CipherBackend)
 @utils.register_interface(CMACBackend)
 @utils.register_interface(DERSerializationBackend)
@@ -710,6 +792,67 @@ class Backend(object):
     def create_cmac_ctx(self, algorithm):
         return _CMACContext(self, algorithm)
 
+    def sign_x509_request(self, builder, private_key, algorithm):
+        # TODO: check type of private key parameter.
+        if not isinstance(algorithm, hashes.HashAlgorithm):
+            raise TypeError('Algorithm must be a registered hash algorithm.')
+
+        # Resolve the signature algorithm.
+        evp_md = self._lib.EVP_get_digestbyname(
+            algorithm.name.encode('ascii')
+        )
+        assert evp_md != self._ffi.NULL
+
+        # Create an empty request.
+        x509_req = self._lib.X509_REQ_new()
+        assert x509_req != self._ffi.NULL
+
+        # Set x509 version.
+        res = self._lib.X509_REQ_set_version(x509_req, builder._version.value)
+        assert res == 1
+
+        # Set subject name.
+        res = self._lib.X509_REQ_set_subject_name(
+            x509_req, _encode_name(self, list(builder._subject_name))
+        )
+        assert res == 1
+
+        # Set subject public key.
+        public_key = private_key.public_key()
+        res = self._lib.X509_REQ_set_pubkey(
+            x509_req, public_key._evp_pkey
+        )
+        assert res == 1
+
+        # Add extensions.
+        extensions = self._lib.sk_X509_EXTENSION_new_null()
+        extensions = self._ffi.gc(
+            extensions,
+            self._lib.sk_X509_EXTENSION_free,
+        )
+        for extension in builder._extensions:
+            if isinstance(extension.value, x509.BasicConstraints):
+                extension = _encode_basic_constraints(
+                    self,
+                    extension.value.ca,
+                    extension.value.path_length,
+                    extension.critical
+                )
+            else:
+                raise ValueError('Extension not yet supported.')
+            res = self._lib.sk_X509_EXTENSION_push(extensions, extension)
+            assert res == 1
+        res = self._lib.X509_REQ_add_extensions(x509_req, extensions)
+        assert res == 1
+
+        # Sign the request using the requester's private key.
+        res = self._lib.X509_REQ_sign(
+            x509_req, private_key._evp_pkey, evp_md
+        )
+        assert res > 0
+
+        return _CertificateSigningRequest(self, x509_req)
+
     def load_pem_private_key(self, data, password):
         return self._load_key(
             self._lib.PEM_read_bio_PrivateKey,
diff --git a/src/cryptography/x509.py b/src/cryptography/x509.py
index 4b030ca9..012c13ba 100644
--- a/src/cryptography/x509.py
+++ b/src/cryptography/x509.py
@@ -1442,3 +1442,46 @@ class RevokedCertificate(object):
         """
         Returns an Extensions object containing a list of Revoked extensions.
         """
+
+
+class CertificateSigningRequestBuilder(object):
+    def __init__(self):
+        """
+        Creates an empty X.509 certificate request (v1).
+        """
+        self._version = Version.v1
+        self._subject_name = None
+        self._extensions = []
+
+    def set_version(self, version):
+        """
+        Sets the X.509 version.
+        """
+        if not isinstance(version, Version):
+            raise TypeError('Expecting x509.Version object.')
+        self._version = version
+
+    def set_subject_name(self, name):
+        """
+        Sets the certificate requestor's distinguished name.
+        """
+        if not isinstance(name, Name):
+            raise TypeError('Expecting x509.Name object.')
+        self._subject_name = name
+
+    def add_extension(self, extension):
+        """
+        Adds an X.509 extension to the certificate request.
+        """
+        if not isinstance(extension, Extension):
+            raise TypeError('Expecting x509.Extension object.')
+        for e in self._extensions:
+            if e.oid == extension.oid:
+                raise ValueError('This extension has already been set.')
+        self._extensions.append(extension)
+
+    def sign(self, backend, private_key, algorithm):
+        """
+        Signs the request using the requestor's private key.
+        """
+        return backend.sign_x509_request(self, private_key, algorithm)
diff --git a/tests/test_x509.py b/tests/test_x509.py
index cf3499bf..85ef4b5c 100644
--- a/tests/test_x509.py
+++ b/tests/test_x509.py
@@ -679,6 +679,153 @@ class TestRSACertificateRequest(object):
         assert serialized == request_bytes
 
 
+@pytest.mark.requires_backend_interface(interface=RSABackend)
+@pytest.mark.requires_backend_interface(interface=X509Backend)
+class TestCertificateSigningRequestBuilder(object):
+    def test_sign_invalid_hash_algorithm(self, backend):
+        private_key = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=2048,
+            backend=backend,
+        )
+        builder = x509.CertificateSigningRequestBuilder()
+        with pytest.raises(TypeError):
+            builder.sign(backend, private_key, 'NotAHash')
+
+    def test_build_ca_request(self, backend):
+        private_key = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=2048,
+            backend=backend,
+        )
+
+        builder = x509.CertificateSigningRequestBuilder()
+        builder.set_version(x509.Version.v3)
+        builder.set_subject_name(x509.Name([
+            x509.NameAttribute(x509.OID_COUNTRY_NAME, 'US'),
+            x509.NameAttribute(x509.OID_STATE_OR_PROVINCE_NAME, 'Texas'),
+            x509.NameAttribute(x509.OID_LOCALITY_NAME, 'Austin'),
+            x509.NameAttribute(x509.OID_ORGANIZATION_NAME, 'PyCA'),
+            x509.NameAttribute(x509.OID_COMMON_NAME, 'cryptography.io'),
+        ]))
+        builder.add_extension(x509.Extension(
+            x509.OID_BASIC_CONSTRAINTS,
+            True,
+            x509.BasicConstraints(True, 2),
+        ))
+        request = builder.sign(backend, private_key, hashes.SHA1())
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(x509.OID_COUNTRY_NAME, 'US'),
+            x509.NameAttribute(x509.OID_STATE_OR_PROVINCE_NAME, 'Texas'),
+            x509.NameAttribute(x509.OID_LOCALITY_NAME, 'Austin'),
+            x509.NameAttribute(x509.OID_ORGANIZATION_NAME, 'PyCA'),
+            x509.NameAttribute(x509.OID_COMMON_NAME, 'cryptography.io'),
+        ]
+        basic_constraints = request.extensions.get_extension_for_oid(
+            x509.OID_BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is True
+        assert basic_constraints.value.path_length == 2
+
+    def test_build_nonca_request(self, backend):
+        private_key = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=2048,
+            backend=backend,
+        )
+
+        builder = x509.CertificateSigningRequestBuilder()
+        builder.set_version(x509.Version.v3)
+        builder.set_subject_name(x509.Name([
+            x509.NameAttribute(x509.OID_COUNTRY_NAME, 'US'),
+            x509.NameAttribute(x509.OID_STATE_OR_PROVINCE_NAME, 'Texas'),
+            x509.NameAttribute(x509.OID_LOCALITY_NAME, 'Austin'),
+            x509.NameAttribute(x509.OID_ORGANIZATION_NAME, 'PyCA'),
+            x509.NameAttribute(x509.OID_COMMON_NAME, 'cryptography.io'),
+        ]))
+        builder.add_extension(x509.Extension(
+            x509.OID_BASIC_CONSTRAINTS,
+            True,
+            x509.BasicConstraints(False, None),
+        ))
+        request = builder.sign(backend, private_key, hashes.SHA1())
+
+        assert isinstance(request.signature_hash_algorithm, hashes.SHA1)
+        public_key = request.public_key()
+        assert isinstance(public_key, rsa.RSAPublicKey)
+        subject = request.subject
+        assert isinstance(subject, x509.Name)
+        assert list(subject) == [
+            x509.NameAttribute(x509.OID_COUNTRY_NAME, 'US'),
+            x509.NameAttribute(x509.OID_STATE_OR_PROVINCE_NAME, 'Texas'),
+            x509.NameAttribute(x509.OID_LOCALITY_NAME, 'Austin'),
+            x509.NameAttribute(x509.OID_ORGANIZATION_NAME, 'PyCA'),
+            x509.NameAttribute(x509.OID_COMMON_NAME, 'cryptography.io'),
+        ]
+        basic_constraints = request.extensions.get_extension_for_oid(
+            x509.OID_BASIC_CONSTRAINTS
+        )
+        assert basic_constraints.value.ca is False
+        assert basic_constraints.value.path_length is None
+
+    def test_add_duplicate_extension(self, backend):
+        builder = x509.CertificateSigningRequestBuilder()
+        builder.add_extension(x509.Extension(
+            x509.OID_BASIC_CONSTRAINTS,
+            True,
+            x509.BasicConstraints(True, 2),
+        ))
+        with pytest.raises(ValueError):
+            builder.add_extension(x509.Extension(
+                x509.OID_BASIC_CONSTRAINTS,
+                True,
+                x509.BasicConstraints(True, 2),
+            ))
+
+    def test_add_invalid_extension(self, backend):
+        builder = x509.CertificateSigningRequestBuilder()
+        with pytest.raises(TypeError):
+            builder.add_extension('NotAnExtension')
+
+    def test_set_invalid_subject(self, backend):
+        builder = x509.CertificateSigningRequestBuilder()
+        with pytest.raises(TypeError):
+            builder.set_subject_name('NotAName')
+
+    def test_set_invalid_version(self, backend):
+        builder = x509.CertificateSigningRequestBuilder()
+        with pytest.raises(TypeError):
+            builder.set_version('NotAVersion')
+
+    def test_add_unsupported_extension(self, backend):
+        private_key = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=2048,
+            backend=backend,
+        )
+        builder = x509.CertificateSigningRequestBuilder()
+        builder.set_subject_name(x509.Name([
+            x509.NameAttribute(x509.OID_COUNTRY_NAME, u'US'),
+            x509.NameAttribute(x509.OID_STATE_OR_PROVINCE_NAME, u'Texas'),
+            x509.NameAttribute(x509.OID_LOCALITY_NAME, u'Austin'),
+            x509.NameAttribute(x509.OID_ORGANIZATION_NAME, u'PyCA'),
+            x509.NameAttribute(x509.OID_COMMON_NAME, u'cryptography.io'),
+        ]))
+        builder.add_extension(x509.Extension(
+            x509.ObjectIdentifier('1.2.3.4'),
+            False,
+            'value',
+        ))
+        with pytest.raises(ValueError):
+            builder.sign(backend, private_key, hashes.SHA1())
+
+
 @pytest.mark.requires_backend_interface(interface=DSABackend)
 @pytest.mark.requires_backend_interface(interface=X509Backend)
 class TestDSACertificate(object):