github.com/zmap/zlint@v1.1.0/lints/lint_rsa_public_exponent_not_in_range.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  /*******************************************************************************************************
    18  "BRs: 6.1.6"
    19  RSA: The CA SHALL confirm that the value of the public exponent is an odd number equal to 3 or more. Additionally, the public exponent SHOULD be in the range between 2^16+1 and 2^256-1. The modulus SHOULD also have the following characteristics: an odd number, not the power of a prime, and have no factors smaller than 752. [Citation: Section 5.3.3, NIST SP 800-89].
    20  *******************************************************************************************************/
    21  
    22  import (
    23  	"crypto/rsa"
    24  	"math/big"
    25  
    26  	"github.com/zmap/zcrypto/x509"
    27  	"github.com/zmap/zlint/util"
    28  )
    29  
    30  type rsaParsedTestsExpInRange struct {
    31  	upperBound *big.Int
    32  }
    33  
    34  func (l *rsaParsedTestsExpInRange) Initialize() error {
    35  	l.upperBound = &big.Int{}
    36  	l.upperBound.Exp(big.NewInt(2), big.NewInt(256), nil)
    37  	return nil
    38  }
    39  
    40  func (l *rsaParsedTestsExpInRange) CheckApplies(c *x509.Certificate) bool {
    41  	_, ok := c.PublicKey.(*rsa.PublicKey)
    42  	return ok && c.PublicKeyAlgorithm == x509.RSA
    43  }
    44  
    45  func (l *rsaParsedTestsExpInRange) Execute(c *x509.Certificate) *LintResult {
    46  	key := c.PublicKey.(*rsa.PublicKey)
    47  	exponent := key.E
    48  	const lowerBound = 65536 // 2^16 + 1
    49  	if exponent > lowerBound && l.upperBound.Cmp(big.NewInt(int64(exponent))) == 1 {
    50  		return &LintResult{Status: Pass}
    51  	}
    52  	return &LintResult{Status: Warn}
    53  }
    54  
    55  func init() {
    56  	RegisterLint(&Lint{
    57  		Name:          "w_rsa_public_exponent_not_in_range",
    58  		Description:   "RSA: Public exponent SHOULD be in the range between 2^16 + 1 and 2^256 - 1",
    59  		Citation:      "BRs: 6.1.6",
    60  		Source:        CABFBaselineRequirements,
    61  		EffectiveDate: util.CABV113Date,
    62  		Lint:          &rsaParsedTestsExpInRange{},
    63  	})
    64  }