/*

 * Copyright (C) 2010 Martin Willi

 *

 * Copyright (C) secunet Security Networks AG

 *

 * This program is free software; you can redistribute it and/or modify it

 * under the terms of the GNU General Public License as published by the

 * Free Software Foundation; either version 2 of the License, or (at your

 * option) any later version.  See <http://www.fsf.org/copyleft/gpl.txt>.

 *

 * This program is distributed in the hope that it will be useful, but

 * WITHOUT ANY WARRANTY; without even the implied warranty of MERCHANTABILITY

 * or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License

 * for more details.

 */

#include "constraints_validator.h"

#include <utils/debug.h>

#include <asn1/asn1.h>

#include <collections/linked_list.h>

#include <credentials/certificates/x509.h>

typedef struct private_constraints_validator_t private_constraints_validator_t;

/**

 * Private data of an constraints_validator_t object.

 */

struct private_constraints_validator_t {

  /**

   * Public constraints_validator_t interface.

   */

  constraints_validator_t public;

};

/**

 * Check pathlen constraint of issuer certificate

 */

static bool check_pathlen(x509_t *issuer, int pathlen)

{

  u_int pathlen_constraint;

  pathlen_constraint = issuer->get_constraint(issuer, X509_PATH_LEN);

  if (pathlen_constraint != X509_NO_CONSTRAINT &&

    pathlen > pathlen_constraint)

  {

    DBG1(DBG_CFG, "path length of %d violates constraint of %d",

       pathlen, pathlen_constraint);

    return FALSE;

  }

  return TRUE;

}

/**

 * Check if a FQDN constraint matches

 */

static bool fqdn_matches(identification_t *constraint, identification_t *id)

{

  chunk_t c, i, diff;

  c = constraint->get_encoding(constraint);

  i = id->get_encoding(id);

  if (!c.len || i.len < c.len)

  {

    return FALSE;

  }

  diff = chunk_create(i.ptr, i.len - c.len);

  if (!chunk_equals(c, chunk_skip(i, diff.len)))

  {

    return FALSE;

  }

  if (!diff.len)

  {

    return TRUE;

  }

  if (c.ptr[0] == '.' || diff.ptr[diff.len - 1] == '.')

  {

    return TRUE;

  }

  return FALSE;

}

/**

 * Check if a RFC822 constraint matches

 */

static bool email_matches(identification_t *constraint, identification_t *id)

{

  chunk_t c, i, diff;

  c = constraint->get_encoding(constraint);

  i = id->get_encoding(id);

  if (!c.len || i.len < c.len)

  {

    return FALSE;

  }

  if (memchr(c.ptr, '@', c.len))

  { /* constraint is a full email address */

    return chunk_equals(c, i);

  }

  diff = chunk_create(i.ptr, i.len - c.len);

  if (!diff.len || !chunk_equals(c, chunk_skip(i, diff.len)))

  {

    return FALSE;

  }

  if (c.ptr[0] == '.')

  { /* constraint is domain, suffix match */

    return TRUE;

  }

  if (diff.ptr[diff.len - 1] == '@')

  { /* constraint is host specific, only username can be appended */

    return TRUE;

  }

  return FALSE;

}

/**

 * Check if a DN constraint matches (RDN prefix match)

 */

static bool dn_matches(identification_t *constraint, identification_t *id)

{

  enumerator_t *ec, *ei;

  id_part_t pc, pi;

  chunk_t cc, ci;

  bool match = TRUE;

  ec = constraint->create_part_enumerator(constraint);

  ei = id->create_part_enumerator(id);

  while (ec->enumerate(ec, &pc, &cc))

  {

    if (!ei->enumerate(ei, &pi, &ci) ||

      pi != pc || !chunk_equals(cc, ci))

    {

      match = FALSE;

      break;

    }

  }

  ec->destroy(ec);

  ei->destroy(ei);

  return match;

}

/**

 * Check if the given identity type matches the type of NameConstraint

 */

static bool type_matches(id_type_t constraint, id_type_t id)

{

  switch (constraint)

  {

    case ID_FQDN:

    case ID_RFC822_ADDR:

    case ID_DER_ASN1_DN:

      return constraint == id;

    case ID_IPV4_ADDR_SUBNET:

      return id == ID_IPV4_ADDR;

    case ID_IPV6_ADDR_SUBNET:

      return id == ID_IPV6_ADDR;

    default:

      return FALSE;

  }

}

/**

 * Check if a certificate matches to a NameConstraint

 */

static bool name_constraint_matches(identification_t *constraint,

                  certificate_t *cert, bool permitted)

{

  x509_t *x509 = (x509_t*)cert;

  enumerator_t *enumerator;

  identification_t *id;

  id_type_t type;

  bool matches = permitted;

  type = constraint->get_type(constraint);

  if (type == ID_DER_ASN1_DN)

  {

    matches = dn_matches(constraint, cert->get_subject(cert));

    if (matches != permitted)

    {

      return matches;

    }

  }

  enumerator = x509->create_subjectAltName_enumerator(x509);

  while (enumerator->enumerate(enumerator, &id))

  {

    if (type_matches(type, id->get_type(id)))

    {

      switch (type)

      {

        case ID_FQDN:

          matches = fqdn_matches(constraint, id);

          break;

        case ID_RFC822_ADDR:

          matches = email_matches(constraint, id);

          break;

        case ID_DER_ASN1_DN:

          matches = dn_matches(constraint, id);

          break;

        case ID_IPV4_ADDR_SUBNET:

        case ID_IPV6_ADDR_SUBNET:

          matches = id->matches(id, constraint);

          break;

        default:

          DBG1(DBG_CFG, "%N NameConstraint matching not implemented",

             id_type_names, type);

          matches = FALSE;

          break;

      }

    }

    if (matches != permitted)

    {

      break;

    }

  }

  enumerator->destroy(enumerator);

  return matches;

}

/**

 * Check if a permitted or excluded NameConstraint has been inherited to sub-CA

 */

static bool name_constraint_inherited(identification_t *constraint,

                    x509_t *x509, bool permitted)

{

  enumerator_t *enumerator;

  identification_t *id, *a, *b;

  bool inherited = FALSE;

  id_type_t type;

  if (!(x509->get_flags(x509) & X509_CA))

  { /* not a sub-CA, not required */

    return TRUE;

  }

  type = constraint->get_type(constraint);

  enumerator = x509->create_name_constraint_enumerator(x509, permitted);

  while (enumerator->enumerate(enumerator, &id))

  {

    if (id->get_type(id) == type)

    {

      if (permitted)

      { /* permitted constraint can be narrowed */

        a = constraint;

        b = id;

      }

      else

      { /* excluded constraint can be widened */

        a = id;

        b = constraint;

      }

      switch (type)

      {

        case ID_FQDN:

          inherited = fqdn_matches(a, b);

          break;

        case ID_RFC822_ADDR:

          inherited = email_matches(a, b);

          break;

        case ID_DER_ASN1_DN:

          inherited = dn_matches(a, b);

          break;

        default:

          DBG1(DBG_CFG, "%N NameConstraint matching not implemented",

             id_type_names, type);

          inherited = FALSE;

          break;

      }

    }

    if (inherited)

    {

      break;

    }

  }

  enumerator->destroy(enumerator);

  return inherited;

}

/**

 * Check name constraints

 */

static bool check_name_constraints(certificate_t *subject, x509_t *issuer)

{

  enumerator_t *enumerator;

  identification_t *constraint;

  enumerator = issuer->create_name_constraint_enumerator(issuer, TRUE);

  while (enumerator->enumerate(enumerator, &constraint))

  {

    if (!name_constraint_matches(constraint, subject, TRUE))

    {

      DBG1(DBG_CFG, "certificate '%Y' does not match permitted name "

         "constraint '%Y'", subject->get_subject(subject), constraint);

      enumerator->destroy(enumerator);

      return FALSE;

    }

    if (!name_constraint_inherited(constraint, (x509_t*)subject, TRUE))

    {

      DBG1(DBG_CFG, "intermediate CA '%Y' does not inherit permitted name "

         "constraint '%Y'", subject->get_subject(subject), constraint);

      enumerator->destroy(enumerator);

      return FALSE;

    }

  }

  enumerator->destroy(enumerator);

  enumerator = issuer->create_name_constraint_enumerator(issuer, FALSE);

  while (enumerator->enumerate(enumerator, &constraint))

  {

    if (name_constraint_matches(constraint, subject, FALSE))

    {

      DBG1(DBG_CFG, "certificate '%Y' matches excluded name "

         "constraint '%Y'", subject->get_subject(subject), constraint);

      enumerator->destroy(enumerator);

      return FALSE;

    }

    if (!name_constraint_inherited(constraint, (x509_t*)subject, FALSE))

    {

      DBG1(DBG_CFG, "intermediate CA '%Y' does not inherit excluded name "

         "constraint '%Y'", subject->get_subject(subject), constraint);

      enumerator->destroy(enumerator);

      return FALSE;

    }

  }

  enumerator->destroy(enumerator);

  return TRUE;

}

/**

 * Special OID for anyPolicy

 */

static chunk_t any_policy = chunk_from_chars(0x55,0x1d,0x20,0x00);

/**

 * Check if an issuer certificate has a given policy OID

 */

static bool has_policy(x509_t *issuer, chunk_t oid)

{

  x509_policy_mapping_t *mapping;

  x509_cert_policy_t *policy;

  enumerator_t *enumerator;

  enumerator = issuer->create_cert_policy_enumerator(issuer);

  while (enumerator->enumerate(enumerator, &policy))

  {

    if (chunk_equals(oid, policy->oid) ||

      chunk_equals(any_policy, policy->oid))

    {

      enumerator->destroy(enumerator);

      return TRUE;

    }

  }

  enumerator->destroy(enumerator);

  /* fall back to a mapped policy */

  enumerator = issuer->create_policy_mapping_enumerator(issuer);

  while (enumerator->enumerate(enumerator, &mapping))

  {

    if (chunk_equals(mapping->subject, oid))

    {

      enumerator->destroy(enumerator);

      return TRUE;

    }

  }

  enumerator->destroy(enumerator);

  return FALSE;

}

/**

 * Check certificatePolicies.

 */

static bool check_policy(x509_t *subject, x509_t *issuer)

{

  certificate_t *cert DBG_UNUSED = (certificate_t*)subject;

  x509_policy_mapping_t *mapping;

  x509_cert_policy_t *policy;

  enumerator_t *enumerator;

  char *oid;

  /* verify if policyMappings in subject are valid */

  enumerator = subject->create_policy_mapping_enumerator(subject);

  while (enumerator->enumerate(enumerator, &mapping))

  {

    if (!has_policy(issuer, mapping->issuer))

    {

      oid = asn1_oid_to_string(mapping->issuer);

      DBG1(DBG_CFG, "certificate '%Y' maps policy from %s, but issuer "

         "misses it", cert->get_subject(cert), oid);

      free(oid);

      enumerator->destroy(enumerator);

      return FALSE;

    }

  }

  enumerator->destroy(enumerator);

  enumerator = subject->create_cert_policy_enumerator(subject);

  while (enumerator->enumerate(enumerator, &policy))

  {

    if (!has_policy(issuer, policy->oid))

    {

      oid = asn1_oid_to_string(policy->oid);

      DBG1(DBG_CFG, "policy %s missing in issuing certificate '%Y'",

         oid, cert->get_issuer(cert));

      free(oid);

      enumerator->destroy(enumerator);

      return FALSE;

    }

  }

  enumerator->destroy(enumerator);

  return TRUE;

}

/**

 * Check if a given policy is valid under a trustchain

 */

static bool is_policy_valid(linked_list_t *chain, chunk_t oid)

{

  x509_policy_mapping_t *mapping;

  x509_cert_policy_t *policy;

  x509_t *issuer;

  enumerator_t *issuers, *policies, *mappings;

  bool found = TRUE;

  issuers = chain->create_enumerator(chain);

  while (issuers->enumerate(issuers, &issuer))

  {

    int maxmap = 8;

    while (found)

    {

      found = FALSE;

      policies = issuer->create_cert_policy_enumerator(issuer);

      while (policies->enumerate(policies, &policy))

      {

        if (chunk_equals(oid, policy->oid) ||

          chunk_equals(any_policy, policy->oid))

        {

          found = TRUE;

          break;

        }

      }

      policies->destroy(policies);

      if (found)

      {

        break;

      }

      /* fall back to a mapped policy */

      mappings = issuer->create_policy_mapping_enumerator(issuer);

      while (mappings->enumerate(mappings, &mapping))

      {

        if (chunk_equals(mapping->subject, oid))

        {

          oid = mapping->issuer;

          found = TRUE;

          break;

        }

      }

      mappings->destroy(mappings);

      if (--maxmap == 0)

      {

        found = FALSE;

        break;

      }

    }

    if (!found)

    {

      break;

    }

  }

  issuers->destroy(issuers);

  return found;

}

/**

 * Check len certificates in trustchain for inherited policies

 */

static bool has_policy_chain(linked_list_t *chain, x509_t *subject, int len)

{

  enumerator_t *enumerator;

  x509_t *issuer;

  bool valid = TRUE;

  enumerator = chain->create_enumerator(chain);

  while (len-- > 0 && enumerator->enumerate(enumerator, &issuer))

  {

    if (!check_policy(subject, issuer))

    {

      valid = FALSE;

      break;

    }

    subject = issuer;

  }

  enumerator->destroy(enumerator);

  return valid;

}

/**

 * Check len certificates in trustchain to have no policyMappings

 */

static bool has_no_policy_mapping(linked_list_t *chain, int len)

{

  enumerator_t *enumerator, *mappings;

  x509_policy_mapping_t *mapping;

  certificate_t *cert DBG_UNUSED;

  x509_t *x509;

  bool valid = TRUE;

  enumerator = chain->create_enumerator(chain);

  while (len-- > 0 && enumerator->enumerate(enumerator, &x509))

  {

    mappings = x509->create_policy_mapping_enumerator(x509);

    valid = !mappings->enumerate(mappings, &mapping);

    mappings->destroy(mappings);

    if (!valid)

    {

      cert = (certificate_t*)x509;

      DBG1(DBG_CFG, "found policyMapping in certificate '%Y', but "

         "inhibitPolicyMapping in effect", cert->get_subject(cert));

      break;

    }

  }

  enumerator->destroy(enumerator);

  return valid;

}

/**

 * Check len certificates in trustchain to have no anyPolicies

 */

static bool has_no_any_policy(linked_list_t *chain, int len)

{

  enumerator_t *enumerator, *policies;

  x509_cert_policy_t *policy;

  certificate_t *cert DBG_UNUSED;

  x509_t *x509;

  bool valid = TRUE;

  enumerator = chain->create_enumerator(chain);

  while (len-- > 0 && enumerator->enumerate(enumerator, &x509))

  {

    policies = x509->create_cert_policy_enumerator(x509);

    while (policies->enumerate(policies, &policy))

    {

      if (chunk_equals(policy->oid, any_policy))

      {

        cert = (certificate_t*)x509;

        DBG1(DBG_CFG, "found anyPolicy in certificate '%Y', but "

           "inhibitAnyPolicy in effect", cert->get_subject(cert));

        valid = FALSE;

        break;

      }

    }

    policies->destroy(policies);

  }

  enumerator->destroy(enumerator);

  return valid;

}

/**

 * Check requireExplicitPolicy and inhibitPolicyMapping constraints

 */

static bool check_policy_constraints(x509_t *issuer, u_int pathlen,

                   auth_cfg_t *auth)

{

  certificate_t *subject;

  bool valid = TRUE;

  subject = auth->get(auth, AUTH_RULE_SUBJECT_CERT);

  if (subject)

  {

    if (subject->get_type(subject) == CERT_X509)

    {

      x509_cert_policy_t *policy;

      enumerator_t *enumerator;

      linked_list_t *chain;

      certificate_t *cert;

      auth_rule_t rule;

      x509_t *x509;

      int len = 0;

      u_int expl, inh;

      char *oid;

      /* prepare trustchain to validate */

      chain = linked_list_create();

      enumerator = auth->create_enumerator(auth);

      while (enumerator->enumerate(enumerator, &rule, &cert))

      {

        if (rule == AUTH_RULE_IM_CERT &&

          cert->get_type(cert) == CERT_X509)

        {

          chain->insert_last(chain, cert);

        }

      }

      enumerator->destroy(enumerator);

      chain->insert_last(chain, issuer);

      /* search for requireExplicitPolicy constraints */

      enumerator = chain->create_enumerator(chain);

      while (enumerator->enumerate(enumerator, &x509))

      {

        expl = x509->get_constraint(x509, X509_REQUIRE_EXPLICIT_POLICY);

        if (expl != X509_NO_CONSTRAINT)

        {

          if (!has_policy_chain(chain, (x509_t*)subject, len - expl))

          {

            valid = FALSE;

            break;

          }

        }

        len++;

      }

      enumerator->destroy(enumerator);

      /* search for inhibitPolicyMapping/inhibitAnyPolicy constraints */

      len = 0;

      chain->insert_first(chain, subject);

      enumerator = chain->create_enumerator(chain);

      while (enumerator->enumerate(enumerator, &x509))

      {

        inh = x509->get_constraint(x509, X509_INHIBIT_POLICY_MAPPING);

        if (inh != X509_NO_CONSTRAINT)

        {

          if (!has_no_policy_mapping(chain, len - inh))

          {

            valid = FALSE;

            break;

          }

        }

        inh = x509->get_constraint(x509, X509_INHIBIT_ANY_POLICY);

        if (inh != X509_NO_CONSTRAINT)

        {

          if (!has_no_any_policy(chain, len - inh))

          {

            valid = FALSE;

            break;

          }

        }

        len++;

      }

      enumerator->destroy(enumerator);

      if (valid)

      {

        x509 = (x509_t*)subject;

        enumerator = x509->create_cert_policy_enumerator(x509);

        while (enumerator->enumerate(enumerator, &policy))

        {

          oid = asn1_oid_to_string(policy->oid);

          if (oid)

          {

            if (is_policy_valid(chain, policy->oid))

            {

              auth->add(auth, AUTH_RULE_CERT_POLICY, oid);

            }

            else

            {

              DBG1(DBG_CFG, "certificate policy %s for '%Y' "

                 "not allowed by trustchain, ignored",

                 oid, subject->get_subject(subject));

              free(oid);

            }

          }

        }

        enumerator->destroy(enumerator);

      }

      chain->destroy(chain);

    }

  }

  return valid;

}

METHOD(cert_validator_t, validate, bool,

  private_constraints_validator_t *this, certificate_t *subject,

  certificate_t *issuer, u_int pathlen, bool anchor, auth_cfg_t *auth)

{

  if (issuer->get_type(issuer) == CERT_X509 &&

    subject->get_type(subject) == CERT_X509)

  {

    if (!check_pathlen((x509_t*)issuer, pathlen))

    {

      lib->credmgr->call_hook(lib->credmgr, CRED_HOOK_EXCEEDED_PATH_LEN,

                  subject);

      return FALSE;

    }

    if (!check_name_constraints(subject, (x509_t*)issuer))

    {

      lib->credmgr->call_hook(lib->credmgr, CRED_HOOK_POLICY_VIOLATION,

                  subject);

      return FALSE;

    }

    if (anchor)

    {

      if (!check_policy_constraints((x509_t*)issuer, pathlen, auth))

      {

        lib->credmgr->call_hook(lib->credmgr,

                    CRED_HOOK_POLICY_VIOLATION, issuer);

        return FALSE;

      }

    }

  }

  return TRUE;

}

METHOD(constraints_validator_t, destroy, void,

  private_constraints_validator_t *this)

{

  free(this);

}

/**

 * See header

 */

constraints_validator_t *constraints_validator_create()

{

  private_constraints_validator_t *this;

  INIT(this,

    .public = {

      .validator.validate = _validate,

      .destroy = _destroy,

    },

  );

  return &this->public;

}