github.com/zmap/zlint@v1.1.0/lints/lint_dsa_correct_order_in_subgroup.go (about)

     1  package lints
     2  
     3  /*
     4   * ZLint Copyright 2018 Regents of the University of Michigan
     5   *
     6   * Licensed under the Apache License, Version 2.0 (the "License"); you may not
     7   * use this file except in compliance with the License. You may obtain a copy
     8   * of the License at http://www.apache.org/licenses/LICENSE-2.0
     9   *
    10   * Unless required by applicable law or agreed to in writing, software
    11   * distributed under the License is distributed on an "AS IS" BASIS,
    12   * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or
    13   * implied. See the License for the specific language governing
    14   * permissions and limitations under the License.
    15   */
    16  
    17  import (
    18  	"crypto/dsa"
    19  	"math/big"
    20  
    21  	"github.com/zmap/zcrypto/x509"
    22  	"github.com/zmap/zlint/util"
    23  )
    24  
    25  type dsaSubgroup struct{}
    26  
    27  func (l *dsaSubgroup) Initialize() error {
    28  	return nil
    29  }
    30  
    31  func (l *dsaSubgroup) CheckApplies(c *x509.Certificate) bool {
    32  	if c.PublicKeyAlgorithm != x509.DSA {
    33  		return false
    34  	}
    35  	if _, ok := c.PublicKey.(*dsa.PublicKey); !ok {
    36  		return false
    37  	}
    38  	return true
    39  }
    40  
    41  func (l *dsaSubgroup) Execute(c *x509.Certificate) *LintResult {
    42  	dsaKey, ok := c.PublicKey.(*dsa.PublicKey)
    43  	if !ok {
    44  		return &LintResult{Status: NA}
    45  	}
    46  	output := big.Int{}
    47  
    48  	// Enforce that Y^Q == 1 mod P, e.g. that Order(Y) == Q mod P.
    49  	output.Exp(dsaKey.Y, dsaKey.Q, dsaKey.P)
    50  	if output.Cmp(big.NewInt(1)) == 0 {
    51  		return &LintResult{Status: Pass}
    52  	}
    53  	return &LintResult{Status: Error}
    54  }
    55  
    56  func init() {
    57  	RegisterLint(&Lint{
    58  		Name:          "e_dsa_correct_order_in_subgroup",
    59  		Description:   "DSA: Public key value has the unique correct representation in the field, and that the key has the correct order in the subgroup",
    60  		Citation:      "BRs: 6.1.6",
    61  		Source:        CABFBaselineRequirements,
    62  		EffectiveDate: util.CABEffectiveDate,
    63  		Lint:          &dsaSubgroup{},
    64  	})
    65  }