csrgen: fix when attribute shortname is lower case

OpenSSL requires attribute short names ("CN", "O", etc) to be in
upper case, otherwise it fails to add the attribute.  This can be
triggered when FreeIPA has been installed with --subject-base
containing a lower-case attribute shortname (e.g.
--subject-base="o=Red Hat").

Explicitly convert the attribute type string to an OID
(ASN1_OBJECT *).  If that fails, upper-case the type string and try
again.

Add some tests for the required behaviour.

Fixes: https://pagure.io/freeipa/issue/7496
Reviewed-By: Christian Heimes <cheimes@redhat.com>

2 files changed, 93 insertions, 7 deletions

diff --git a/ipaclient/csrgen_ffi.py b/ipaclient/csrgen_ffi.py
index a005bcd41..c5428cfd4 100644
--- a/ipaclient/csrgen_ffi.py
+++ b/ipaclient/csrgen_ffi.py
@@ -59,6 +59,7 @@ void EVP_PKEY_free(EVP_PKEY *pkey);
 /* openssl/x509.h */
 typedef ... ASN1_INTEGER;
 typedef ... ASN1_BIT_STRING;
+typedef ... ASN1_OBJECT;
 typedef ... X509;
 typedef ... X509_ALGOR;
 typedef ... X509_CRL;
@@ -86,11 +87,14 @@ X509_REQ *X509_REQ_new(void);
 void X509_REQ_free(X509_REQ *);
 EVP_PKEY *d2i_PUBKEY_bio(BIO *bp, EVP_PKEY **a);
 int X509_REQ_set_pubkey(X509_REQ *x, EVP_PKEY *pkey);
-int X509_NAME_add_entry_by_txt(X509_NAME *name, const char *field, int type,
+int X509_NAME_add_entry_by_OBJ(X509_NAME *name, const ASN1_OBJECT *obj, int type,
                                const unsigned char *bytes, int len, int loc,
                                int set);
 int X509_NAME_entry_count(X509_NAME *name);
-int i2d_X509_REQ_INFO(X509_REQ_INFO *a, unsigned char **out); \
+int i2d_X509_REQ_INFO(X509_REQ_INFO *a, unsigned char **out);
+
+/* openssl/objects.h */
+ASN1_OBJECT *OBJ_txt2obj(const char *s, int no_name);
 
 /* openssl/x509v3.h */
 typedef ... X509V3_CONF_METHOD;
@@ -114,7 +118,7 @@ int X509V3_EXT_REQ_add_nconf(CONF *conf, X509V3_CTX *ctx, char *section,
 /* openssl/x509v3.h */
 unsigned long ERR_get_error(void);
 char *ERR_error_string(unsigned long e, char *buf);
-''')
+''')  # noqa: E501
 
 _libcrypto = _ffi.dlopen(ctypes.util.find_library('crypto'))
 
@@ -154,13 +158,17 @@ X509_REQ_free = _libcrypto.X509_REQ_free
 X509_REQ_set_pubkey = _libcrypto.X509_REQ_set_pubkey
 d2i_PUBKEY_bio = _libcrypto.d2i_PUBKEY_bio
 i2d_X509_REQ_INFO = _libcrypto.i2d_X509_REQ_INFO
-X509_NAME_add_entry_by_txt = _libcrypto.X509_NAME_add_entry_by_txt
+X509_NAME_add_entry_by_OBJ = _libcrypto.X509_NAME_add_entry_by_OBJ
 X509_NAME_entry_count = _libcrypto.X509_NAME_entry_count
 
 
 def X509_REQ_get_subject_name(req):
     return req.req_info.subject
 
+
+# openssl/objects.h
+OBJ_txt2obj = _libcrypto.OBJ_txt2obj
+
 # openssl/evp.h
 EVP_PKEY_free = _libcrypto.EVP_PKEY_free
 
@@ -209,8 +217,24 @@ def _parse_dn_section(subj, dn_sk):
             mval = -1
         else:
             mval = 0
-        if not X509_NAME_add_entry_by_txt(
-                subj, rdn_type, MBSTRING_UTF8,
+
+        # convert rdn_type to an OID
+        #
+        # OpenSSL is fussy about the case of the string.  For example,
+        # lower-case 'o' (for "organization name") is not recognised.
+        # Therefore, try to convert the given string into an OID.  If
+        # that fails, convert it upper case and try again.
+        #
+        oid = OBJ_txt2obj(rdn_type, 0)
+        if oid == NULL:
+            oid = OBJ_txt2obj(rdn_type.upper(), 0)
+        if oid == NULL:
+            raise errors.CSRTemplateError(
+                reason='unrecognised attribute type: {}'
+                .format(rdn_type.decode('utf-8')))
+
+        if not X509_NAME_add_entry_by_OBJ(
+                subj, oid, MBSTRING_UTF8,
                 _ffi.cast("unsigned char *", v.value), -1, -1, mval):
             _raise_openssl_errors()
 
diff --git a/ipatests/test_ipaclient/test_csrgen.py b/ipatests/test_ipaclient/test_csrgen.py
index d0798f836..b58596b86 100644
--- a/ipatests/test_ipaclient/test_csrgen.py
+++ b/ipatests/test_ipaclient/test_csrgen.py
@@ -5,7 +5,11 @@
 import os
 import pytest
 
-from ipaclient import csrgen
+from cryptography.hazmat.backends import default_backend
+from cryptography.hazmat.primitives.asymmetric import rsa
+from cryptography import x509
+
+from ipaclient import csrgen, csrgen_ffi
 from ipalib import errors
 
 BASE_DIR = os.path.dirname(__file__)
@@ -201,6 +205,64 @@ class test_CSRGenerator(object):
             expected_script = f.read()
         assert script == expected_script
 
+    def test_works_with_lowercase_attr_type_shortname(self, generator):
+        principal = {
+            'uid': ['testuser'],
+            'mail': ['testuser@example.com'],
+        }
+        template_env = {
+            'ipacertificatesubjectbase': [
+                'o=DOMAIN.EXAMPLE.COM'  # lower-case attr type shortname
+            ],
+        }
+        config = generator.csr_config(principal, template_env, 'userCert')
+
+        key = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=2048,
+            backend=default_backend(),
+        )
+        adaptor = csrgen.OpenSSLAdaptor(key=key)
+
+        reqinfo = bytes(csrgen_ffi.build_requestinfo(
+            config.encode('utf-8'), adaptor.get_subject_public_key_info()))
+        csr_der = adaptor.sign_csr(reqinfo)
+        csr = x509.load_der_x509_csr(csr_der, default_backend())
+        assert (
+            csr.subject.get_attributes_for_oid(x509.NameOID.COMMON_NAME)
+            == [x509.NameAttribute(x509.NameOID.COMMON_NAME, u'testuser')]
+        )
+        assert (
+            csr.subject.get_attributes_for_oid(x509.NameOID.ORGANIZATION_NAME)
+            == [x509.NameAttribute(
+                x509.NameOID.ORGANIZATION_NAME, u'DOMAIN.EXAMPLE.COM')]
+        )
+
+    def test_unrecognised_attr_type_raises(self, generator):
+        principal = {
+            'uid': ['testuser'],
+            'mail': ['testuser@example.com'],
+        }
+        template_env = {
+            'ipacertificatesubjectbase': [
+                'X=DOMAIN.EXAMPLE.COM'  # unrecognised attr type
+            ],
+        }
+        config = generator.csr_config(principal, template_env, 'userCert')
+
+        key = rsa.generate_private_key(
+            public_exponent=65537,
+            key_size=2048,
+            backend=default_backend(),
+        )
+        adaptor = csrgen.OpenSSLAdaptor(key=key)
+
+        with pytest.raises(
+                errors.CSRTemplateError,
+                message='unrecognised attribute type: X'):
+            csrgen_ffi.build_requestinfo(
+                config.encode('utf-8'), adaptor.get_subject_public_key_info())
+
 
 class test_rule_handling(object):
     def test_optionalAttributeMissing(self, generator):