72 lines
2.1 KiB
Go
72 lines
2.1 KiB
Go
// Copyright 2014 ISRG. All rights reserved
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// This Source Code Form is subject to the terms of the Mozilla Public
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// License, v. 2.0. If a copy of the MPL was not distributed with this
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// file, You can obtain one at http://mozilla.org/MPL/2.0/.
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package core
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import (
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"crypto"
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"crypto/ecdsa"
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"crypto/rsa"
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"fmt"
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"reflect"
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blog "github.com/letsencrypt/boulder/log"
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)
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// GoodKey returns true iff the key is acceptable for both TLS use and account
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// key use (our requirements are the same for either one), according to basic
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// strength and algorithm checking.
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func GoodKey(key crypto.PublicKey) bool {
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log := blog.GetAuditLogger()
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switch t := key.(type) {
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case rsa.PublicKey:
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return GoodKeyRSA(t)
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case *rsa.PublicKey:
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return GoodKeyRSA(*t)
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case ecdsa.PublicKey:
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return GoodKeyECDSA(t)
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case *ecdsa.PublicKey:
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return GoodKeyECDSA(*t)
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default:
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log.Debug(fmt.Sprintf("Unknown key type %s", reflect.TypeOf(key)))
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return false
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}
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}
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func GoodKeyECDSA(key ecdsa.PublicKey) bool {
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log := blog.GetAuditLogger()
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log.Debug(fmt.Sprintf("ECDSA keys not yet supported."))
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return false
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}
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func GoodKeyRSA(key rsa.PublicKey) bool {
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log := blog.GetAuditLogger()
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// Baseline Requirements Appendix A
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// Modulus must be >= 2048 bits
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modulus := key.N
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if modulus.BitLen() < 2048 {
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log.Debug(fmt.Sprintf("Key too small: %d", modulus.BitLen()))
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return false
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}
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// The CA SHALL confirm that the value of the public exponent
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// is an odd number equal to 3 or more
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if key.E % 2 == 0 {
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log.Debug(fmt.Sprintf("Key exponent is an even number: %d", key.E))
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return false
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}
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// Additionally, the public exponent SHOULD be in the range between
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// 2^16 + 1 and 2^256-1.
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// NOTE: rsa.PublicKey cannot represent an exponent part greater than
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// 2^256 - 1, because it stores E as an integer. So we don't check the upper
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// bound.
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if key.E < ((1 << 6) + 1) {
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log.Debug(fmt.Sprintf("Key exponent is too small: %d", key.E))
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return false
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}
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// TODO: The modulus SHOULD also have the following
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// characteristics: an odd number, not the power of a prime,
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// and have no factors smaller than 752.
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return true
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}
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