Add preliminary PAM authentication backend

certidude/auth.py

@@ -7,6 +7,7 @@ import logging
 import os
 import re
 import socket
+from certidude import config
 
 logger = logging.getLogger("api")
 
@@ -20,20 +21,47 @@ logger = logging.getLogger("api")
 
 FQDN = socket.getaddrinfo(socket.gethostname(), 0, socket.AF_INET, 0, 0, socket.AI_CANONNAME)[0][3]
 
-if not os.getenv("KRB5_KTNAME"):
+if config.AUTHENTICATION_BACKEND == "kerberos":
+    if not os.getenv("KRB5_KTNAME"):
         click.echo("Kerberos keytab not specified, set environment variable 'KRB5_KTNAME'", err=True)
         exit(250)
 
-try:
+    try:
         principal = kerberos.getServerPrincipalDetails("HTTP", FQDN)
-except kerberos.KrbError as exc:
+    except kerberos.KrbError as exc:
         click.echo("Failed to initialize Kerberos, reason: %s" % exc, err=True)
         exit(249)
-else:
+    else:
         click.echo("Kerberos enabled, service principal is HTTP/%s" % FQDN)
+else:
+    NotImplemented
 
 def login_required(func):
-    def authenticate(resource, req, resp, *args, **kwargs):
+    def pam_authenticate(resource, req, resp, *args, **kwargs):
+        """
+        Authenticate against PAM with WWW Basic Auth credentials
+        """
+        authorization = req.get_header("Authorization")
+        if not authorization:
+            resp.append_header("WWW-Authenticate", "Basic")
+            raise falcon.HTTPUnauthorized("Forbidden", "Please authenticate")
+
+        if not authorization.startswith("Basic "):
+            raise falcon.HTTPForbidden("Forbidden", "Bad header: %s" % authorization)
+
+        from base64 import b64decode
+        basic, token = authorization.split(" ", 1)
+        user, passwd = b64decode(token).split(":", 1)
+
+        import simplepam
+        if not simplepam.authenticate(user, passwd, "sshd"):
+            raise falcon.HTTPForbidden("Forbidden", "Invalid password")
+
+        req.context["user"] = user
+        return func(resource, req, resp, *args, **kwargs)
+
+
+    def kerberos_authenticate(resource, req, resp, *args, **kwargs):
         authorization = req.get_header("Authorization")
 
         if not authorization:
@@ -82,7 +110,12 @@ def login_required(func):
             # TODO: logger.error
             raise falcon.HTTPForbidden("Forbidden", "Tried GSSAPI")
 
-    return authenticate
+    if config.AUTHENTICATION_BACKEND == "kerberos":
+        return kerberos_authenticate
+    elif config.AUTHENTICATION_BACKEND == "pam":
+        return pam_authenticate
+    else:
+        NotImplemented
 
 
 def authorize_admin(func):

certidude/cli.py

@@ -1006,6 +1006,7 @@ def certidude_serve(user, port, listen, enable_signature):
     from wsgiref.simple_server import make_server, WSGIServer
     from socketserver import ThreadingMixIn
     from certidude.api import certidude_app, StaticResource
+    from certidude import config
 
     class ThreadingWSGIServer(ThreadingMixIn, WSGIServer):
         pass
@@ -1024,13 +1025,26 @@ def certidude_serve(user, port, listen, enable_signature):
         from jinja2.debug import make_traceback as _make_traceback
         "".encode("charmap")
 
+        if config.AUTHENTICATION_BACKEND == "pam":
+            # PAM needs access to /etc/shadow
+            import grp
+            name, passwd, gid, mem = grp.getgrnam("shadow")
+            click.echo("Adding current user to shadow group due to PAM authentication backend")
+            os.setgroups([gid])
+        else:
+            os.setgroups([])
+
         _, _, uid, gid, gecos, root, shell = pwd.getpwnam(user)
         if uid == 0:
             click.echo("Please specify unprivileged user")
             exit(254)
-        click.echo("Switching to user %s (uid=%d, gid=%d)" % (user, uid, gid))
+
         os.setgid(gid)
         os.setuid(uid)
+
+        click.echo("Switched to user %s (uid=%d, gid=%d); member of groups %s" %
+            (user, uid, gid, ", ".join([str(j) for j in os.getgroups()])))
+
         os.umask(0o007)
     elif os.getuid() == 0:
         click.echo("Warning: running as root, this is not recommended!")

certidude/config.py

@@ -14,6 +14,9 @@ FQDN = socket.getaddrinfo(socket.gethostname(), 0, socket.AF_INET, 0, 0, socket.
 cp = configparser.ConfigParser()
 cp.readfp(codecs.open("/etc/certidude/server.conf", "r", "utf8"))
 
+AUTHENTICATION_BACKEND = cp.get("authentication", "backend") # kerberos, pam
+AUTHORIZATION_BACKEND = cp.get("authorization", "backend") # whitelist, ldap, pam
+
 ADMIN_USERS = set([j for j in  cp.get("authorization", "admin_users").split(" ") if j])
 ADMIN_SUBNETS = set([ipaddress.ip_network(j) for j in cp.get("authorization", "admin_subnets").split(" ") if j])
 AUTOSIGN_SUBNETS = set([ipaddress.ip_network(j) for j in cp.get("authorization", "autosign_subnets").split(" ") if j])

requirements.txt

@@ -18,4 +18,5 @@ pyOpenSSL==0.15.1
 python-mimeparse==0.1.4
 requests==2.2.1
 setproctitle==1.1.9
+simplepam==0.1.5
 six==1.9.0