Merge pull request #21 from fdistorted/issue-20

chore: add ec certificate support to pycert_bearssl

tools/pycert_bearssl/cert_util.py

@@ -32,6 +32,10 @@ DN_PRE = "TA_DN"
 RSA_N_PRE = "TA_RSA_N"
 # RSA public key exponent prefix
 RSA_E_PRE = "TA_RSA_E"
+# EC public key number prefix
+EC_CURVE_PRE = "TA_EC_CURVE"
+# EC curve type enum prefix
+EC_CURVE_NAME_PRE = "BR_EC_"
 
 
 # Template that defines the C header output format.
@@ -81,7 +85,7 @@ static const {ray_type} {ray_name}[] = {{
 {ray_data}
 }};"""
 
-# Template that defines a single root certificate entry in the BearSSL trust
+# Template that defines a single root RSA certificate entry in the BearSSL trust
 # anchor list
 # This takes in a few named parameters:
 #  - ta_dn_name: The name of the static byte array containing the distunguished
@@ -101,6 +105,25 @@ CROOTCA_TEMPLATE = """\
         }}
     }},"""
 
+# Template that defines a single root EC certificate entry in the BearSSL trust
+# anchor list
+# This takes in a few named parameters:
+#  - ta_dn_name: The name of the static byte array containing the distunguished
+#    name of the certificate.
+#  - ec_number_name: Varible name of the static array containing ec public key
+#  - ec_curve_name: Varible name of the enum that describes curve type
+CROOTCA_EC_TEMPLATE = """\
+    {{
+        {{ (unsigned char *){ta_dn_name}, sizeof {ta_dn_name} }},
+        BR_X509_TA_CA,
+        {{
+            BR_KEYTYPE_EC,
+            {{ .ec = {{{ec_curve_name}, (unsigned char *){ec_number_name}, sizeof {ec_number_name}}}
+        }}
+        }}
+    }},"""
+
+
 # Template that defines a description of the certificate, so that the header
 # file can be slightly more human readable
 # This takes in a few named parameters:
@@ -267,6 +290,8 @@ def x509_to_header(x509Certs, cert_var, cert_length_var, output_file, keep_dupes
         # next, the RSA public numbers
         pubkey = cert.get_pubkey()
         numbers = pubkey.to_cryptography_key().public_numbers()
+        numbers_typename = type(numbers).__name__
+        if 'RSA' in numbers_typename:
             # starting with the modulous
             n_bytes_str = bytes_to_c_data(numbers.n.to_bytes(pubkey.bits() // 8, byteorder="big"))
             static_arrays.append(CRAY_TEMPLATE.format(
@@ -284,6 +309,24 @@ def x509_to_header(x509Certs, cert_var, cert_length_var, output_file, keep_dupes
                 ta_dn_name=DN_PRE + str(cert_index), 
                 rsa_number_name=RSA_N_PRE + str(cert_index), 
                 rsa_exp_name=RSA_E_PRE + str(cert_index)))
+        elif 'Elliptic' in numbers_typename:
+            # starting with the modulous
+            curve_bytes = b'\x04' + numbers.x.to_bytes(pubkey.bits() // 8, byteorder="big") + numbers.y.to_bytes(
+                pubkey.bits() // 8, byteorder="big")
+            curve_str = bytes_to_c_data(curve_bytes)
+            curve_name = numbers.curve.name
+            static_arrays.append(CRAY_TEMPLATE.format(
+                ray_type="unsigned char",
+                ray_name=EC_CURVE_PRE + str(cert_index),
+                ray_data=curve_str))
+            # and then the exponent
+            CAs.append(CROOTCA_EC_TEMPLATE.format(
+                ta_dn_name=DN_PRE + str(cert_index),
+                ec_number_name=EC_CURVE_PRE + str(cert_index),
+                ec_curve_name=EC_CURVE_NAME_PRE + curve_name
+            ))
+        else:
+            raise Exception(f'Unknown public key type {numbers_typename}')
     # concatonate it all into the big header file template
     # cert descriptions
     cert_desc_out = '\n * \n'.join(cert_desc)

tools/pycert_bearssl/pycert_bearssl.py

@@ -86,7 +86,11 @@ def download(port, cert_var, cert_length_var, output, use_store, keep_dupes, dom
         # append cert to array
         down_certs.append(cert)
     # Combine PEMs and write output header.
+    try:
       cert_util.x509_to_header(down_certs, cert_var, cert_length_var, output, keep_dupes, domains=domain)
+    except Exception as E:
+      click.echo(f'Recieved error when converting certificate to header: {E}')
+      exit(1)
 
 
 @pycert_bearssl.command(short_help='Convert PEM certs into a C header.')
@@ -144,8 +148,11 @@ def convert(cert_var, cert_length_var, output, use_store, keep_dupes, no_search,
         else:
           root_certs.append(cert_dict[cn_hash])
     # Combine PEMs and write output header.
+    try:
       cert_util.x509_to_header(root_certs, cert_var, cert_length_var, output, keep_dupes)
-
+    except Exception as E:
+      click.echo(f'Recieved error when converting certificate to header: {E}')
+      exit(1)
 
 if __name__ == '__main__':
     pycert_bearssl()