package rfc

/*
 * ZLint Copyright 2020 Regents of the University of Michigan
 *
 * Licensed under the Apache License, Version 2.0 (the "License"); you may not
 * use this file except in compliance with the License. You may obtain a copy
 * of the License at http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
 * implied. See the License for the specific language governing
 * permissions and limitations under the License.
 */

/********************************************************************
4.1.2.5.2.  GeneralizedTime
The generalized time type, GeneralizedTime, is a standard ASN.1 type
for variable precision representation of time.  Optionally, the
GeneralizedTime field can include a representation of the time
differential between local and Greenwich Mean Time.

For the purposes of this profile, GeneralizedTime values MUST be
expressed in Greenwich Mean Time (Zulu) and MUST include seconds
(i.e., times are YYYYMMDDHHMMSSZ), even where the number of seconds
is zero.  GeneralizedTime values MUST NOT include fractional seconds.
********************************************************************/

import (
	"encoding/asn1"

	"github.com/zmap/zcrypto/x509"
	"github.com/zmap/zlint/v3/lint"
	"github.com/zmap/zlint/v3/util"
)

type generalizedTimeFraction struct {
}

func (l *generalizedTimeFraction) Initialize() error {
	return nil
}

func (l *generalizedTimeFraction) CheckApplies(c *x509.Certificate) bool {
	firstDate, secondDate := util.GetTimes(c)
	beforeTag, afterTag := util.FindTimeType(firstDate, secondDate)
	date1Gen := beforeTag == 24
	date2Gen := afterTag == 24
	return date1Gen || date2Gen
}

func (l *generalizedTimeFraction) Execute(c *x509.Certificate) *lint.LintResult {
	r := lint.Pass
	date1, date2 := util.GetTimes(c)
	beforeTag, afterTag := util.FindTimeType(date1, date2)
	date1Gen := beforeTag == 24
	date2Gen := afterTag == 24
	if date1Gen {
		// UTC Tests on notBefore
		checkFraction(&r, date1)
		if r == lint.Error {
			return &lint.LintResult{Status: r}
		}
	}
	if date2Gen {
		checkFraction(&r, date2)
	}
	return &lint.LintResult{Status: r}
}

//nolint:nestif
func checkFraction(r *lint.LintStatus, t asn1.RawValue) {
	if t.Bytes[len(t.Bytes)-1] == 'Z' {
		if len(t.Bytes) > 15 {
			*r = lint.Error
		}
	} else if t.Bytes[len(t.Bytes)-5] == '-' || t.Bytes[len(t.Bytes)-1] == '+' {
		if len(t.Bytes) > 19 {
			*r = lint.Error
		}
	} else {
		if len(t.Bytes) > 14 {
			*r = lint.Error
		}
	}
}

func init() {
	lint.RegisterLint(&lint.Lint{
		Name:          "e_generalized_time_includes_fraction_seconds",
		Description:   "Generalized time values MUST NOT include fractional seconds",
		Citation:      "RFC 5280: 4.1.2.5.2",
		Source:        lint.RFC5280,
		EffectiveDate: util.RFC2459Date,
		Lint:          &generalizedTimeFraction{},
	})
}
