665 lines
16 KiB
Go
665 lines
16 KiB
Go
package dns
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import (
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"bytes"
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"crypto"
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"crypto/dsa"
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"crypto/ecdsa"
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"crypto/elliptic"
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_ "crypto/md5"
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"crypto/rand"
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"crypto/rsa"
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_ "crypto/sha1"
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_ "crypto/sha256"
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_ "crypto/sha512"
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"encoding/asn1"
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"encoding/hex"
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"math/big"
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"sort"
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"strings"
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"time"
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)
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// DNSSEC encryption algorithm codes.
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const (
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_ uint8 = iota
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RSAMD5
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DH
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DSA
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_ // Skip 4, RFC 6725, section 2.1
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RSASHA1
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DSANSEC3SHA1
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RSASHA1NSEC3SHA1
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RSASHA256
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_ // Skip 9, RFC 6725, section 2.1
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RSASHA512
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_ // Skip 11, RFC 6725, section 2.1
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ECCGOST
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ECDSAP256SHA256
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ECDSAP384SHA384
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INDIRECT uint8 = 252
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PRIVATEDNS uint8 = 253 // Private (experimental keys)
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PRIVATEOID uint8 = 254
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)
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// Map for algorithm names.
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var AlgorithmToString = map[uint8]string{
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RSAMD5: "RSAMD5",
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DH: "DH",
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DSA: "DSA",
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RSASHA1: "RSASHA1",
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DSANSEC3SHA1: "DSA-NSEC3-SHA1",
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RSASHA1NSEC3SHA1: "RSASHA1-NSEC3-SHA1",
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RSASHA256: "RSASHA256",
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RSASHA512: "RSASHA512",
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ECCGOST: "ECC-GOST",
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ECDSAP256SHA256: "ECDSAP256SHA256",
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ECDSAP384SHA384: "ECDSAP384SHA384",
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INDIRECT: "INDIRECT",
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PRIVATEDNS: "PRIVATEDNS",
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PRIVATEOID: "PRIVATEOID",
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}
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// Map of algorithm strings.
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var StringToAlgorithm = reverseInt8(AlgorithmToString)
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// Map of algorithm crypto hashes.
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var AlgorithmToHash = map[uint8]crypto.Hash{
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RSAMD5: crypto.MD5, // Deprecated in RFC 6725
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RSASHA1: crypto.SHA1,
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RSASHA1NSEC3SHA1: crypto.SHA1,
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RSASHA256: crypto.SHA256,
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ECDSAP256SHA256: crypto.SHA256,
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ECDSAP384SHA384: crypto.SHA384,
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RSASHA512: crypto.SHA512,
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}
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// DNSSEC hashing algorithm codes.
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const (
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_ uint8 = iota
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SHA1 // RFC 4034
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SHA256 // RFC 4509
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GOST94 // RFC 5933
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SHA384 // Experimental
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SHA512 // Experimental
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)
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// Map for hash names.
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var HashToString = map[uint8]string{
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SHA1: "SHA1",
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SHA256: "SHA256",
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GOST94: "GOST94",
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SHA384: "SHA384",
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SHA512: "SHA512",
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}
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// Map of hash strings.
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var StringToHash = reverseInt8(HashToString)
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// DNSKEY flag values.
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const (
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SEP = 1
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REVOKE = 1 << 7
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ZONE = 1 << 8
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)
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// The RRSIG needs to be converted to wireformat with some of
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// the rdata (the signature) missing. Use this struct to ease
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// the conversion (and re-use the pack/unpack functions).
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type rrsigWireFmt struct {
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TypeCovered uint16
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Algorithm uint8
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Labels uint8
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OrigTtl uint32
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Expiration uint32
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Inception uint32
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KeyTag uint16
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SignerName string `dns:"domain-name"`
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/* No Signature */
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}
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// Used for converting DNSKEY's rdata to wirefmt.
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type dnskeyWireFmt struct {
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Flags uint16
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Protocol uint8
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Algorithm uint8
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PublicKey string `dns:"base64"`
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/* Nothing is left out */
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}
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func divRoundUp(a, b int) int {
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return (a + b - 1) / b
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}
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// KeyTag calculates the keytag (or key-id) of the DNSKEY.
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func (k *DNSKEY) KeyTag() uint16 {
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if k == nil {
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return 0
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}
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var keytag int
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switch k.Algorithm {
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case RSAMD5:
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// Look at the bottom two bytes of the modules, which the last
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// item in the pubkey. We could do this faster by looking directly
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// at the base64 values. But I'm lazy.
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modulus, _ := fromBase64([]byte(k.PublicKey))
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if len(modulus) > 1 {
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x, _ := unpackUint16(modulus, len(modulus)-2)
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keytag = int(x)
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}
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default:
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keywire := new(dnskeyWireFmt)
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keywire.Flags = k.Flags
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keywire.Protocol = k.Protocol
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keywire.Algorithm = k.Algorithm
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keywire.PublicKey = k.PublicKey
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wire := make([]byte, DefaultMsgSize)
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n, err := PackStruct(keywire, wire, 0)
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if err != nil {
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return 0
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}
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wire = wire[:n]
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for i, v := range wire {
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if i&1 != 0 {
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keytag += int(v) // must be larger than uint32
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} else {
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keytag += int(v) << 8
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}
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}
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keytag += (keytag >> 16) & 0xFFFF
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keytag &= 0xFFFF
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}
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return uint16(keytag)
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}
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// ToDS converts a DNSKEY record to a DS record.
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func (k *DNSKEY) ToDS(h uint8) *DS {
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if k == nil {
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return nil
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}
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ds := new(DS)
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ds.Hdr.Name = k.Hdr.Name
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ds.Hdr.Class = k.Hdr.Class
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ds.Hdr.Rrtype = TypeDS
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ds.Hdr.Ttl = k.Hdr.Ttl
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ds.Algorithm = k.Algorithm
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ds.DigestType = h
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ds.KeyTag = k.KeyTag()
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keywire := new(dnskeyWireFmt)
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keywire.Flags = k.Flags
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keywire.Protocol = k.Protocol
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keywire.Algorithm = k.Algorithm
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keywire.PublicKey = k.PublicKey
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wire := make([]byte, DefaultMsgSize)
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n, err := PackStruct(keywire, wire, 0)
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if err != nil {
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return nil
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}
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wire = wire[:n]
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owner := make([]byte, 255)
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off, err1 := PackDomainName(strings.ToLower(k.Hdr.Name), owner, 0, nil, false)
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if err1 != nil {
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return nil
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}
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owner = owner[:off]
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// RFC4034:
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// digest = digest_algorithm( DNSKEY owner name | DNSKEY RDATA);
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// "|" denotes concatenation
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// DNSKEY RDATA = Flags | Protocol | Algorithm | Public Key.
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// digest buffer
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digest := append(owner, wire...) // another copy
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var hash crypto.Hash
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switch h {
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case SHA1:
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hash = crypto.SHA1
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case SHA256:
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hash = crypto.SHA256
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case SHA384:
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hash = crypto.SHA384
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case SHA512:
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hash = crypto.SHA512
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default:
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return nil
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}
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s := hash.New()
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s.Write(digest)
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ds.Digest = hex.EncodeToString(s.Sum(nil))
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return ds
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}
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// ToCDNSKEY converts a DNSKEY record to a CDNSKEY record.
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func (k *DNSKEY) ToCDNSKEY() *CDNSKEY {
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c := &CDNSKEY{DNSKEY: *k}
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c.Hdr = *k.Hdr.copyHeader()
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c.Hdr.Rrtype = TypeCDNSKEY
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return c
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}
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// ToCDS converts a DS record to a CDS record.
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func (d *DS) ToCDS() *CDS {
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c := &CDS{DS: *d}
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c.Hdr = *d.Hdr.copyHeader()
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c.Hdr.Rrtype = TypeCDS
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return c
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}
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// Sign signs an RRSet. The signature needs to be filled in with the values:
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// Inception, Expiration, KeyTag, SignerName and Algorithm. The rest is copied
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// from the RRset. Sign returns a non-nill error when the signing went OK.
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// There is no check if RRSet is a proper (RFC 2181) RRSet. If OrigTTL is non
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// zero, it is used as-is, otherwise the TTL of the RRset is used as the
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// OrigTTL.
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func (rr *RRSIG) Sign(k crypto.Signer, rrset []RR) error {
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if k == nil {
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return ErrPrivKey
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}
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// s.Inception and s.Expiration may be 0 (rollover etc.), the rest must be set
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if rr.KeyTag == 0 || len(rr.SignerName) == 0 || rr.Algorithm == 0 {
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return ErrKey
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}
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rr.Hdr.Rrtype = TypeRRSIG
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rr.Hdr.Name = rrset[0].Header().Name
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rr.Hdr.Class = rrset[0].Header().Class
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if rr.OrigTtl == 0 { // If set don't override
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rr.OrigTtl = rrset[0].Header().Ttl
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}
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rr.TypeCovered = rrset[0].Header().Rrtype
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rr.Labels = uint8(CountLabel(rrset[0].Header().Name))
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if strings.HasPrefix(rrset[0].Header().Name, "*") {
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rr.Labels-- // wildcard, remove from label count
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}
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sigwire := new(rrsigWireFmt)
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sigwire.TypeCovered = rr.TypeCovered
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sigwire.Algorithm = rr.Algorithm
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sigwire.Labels = rr.Labels
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sigwire.OrigTtl = rr.OrigTtl
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sigwire.Expiration = rr.Expiration
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sigwire.Inception = rr.Inception
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sigwire.KeyTag = rr.KeyTag
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// For signing, lowercase this name
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sigwire.SignerName = strings.ToLower(rr.SignerName)
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// Create the desired binary blob
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signdata := make([]byte, DefaultMsgSize)
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n, err := PackStruct(sigwire, signdata, 0)
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if err != nil {
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return err
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}
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signdata = signdata[:n]
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wire, err := rawSignatureData(rrset, rr)
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if err != nil {
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return err
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}
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signdata = append(signdata, wire...)
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hash, ok := AlgorithmToHash[rr.Algorithm]
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if !ok {
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return ErrAlg
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}
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h := hash.New()
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h.Write(signdata)
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signature, err := sign(k, h.Sum(nil), hash, rr.Algorithm)
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if err != nil {
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return err
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}
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rr.Signature = toBase64(signature)
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return nil
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}
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func sign(k crypto.Signer, hashed []byte, hash crypto.Hash, alg uint8) ([]byte, error) {
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signature, err := k.Sign(rand.Reader, hashed, hash)
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if err != nil {
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return nil, err
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}
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switch alg {
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case RSASHA1, RSASHA1NSEC3SHA1, RSASHA256, RSASHA512:
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return signature, nil
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case ECDSAP256SHA256, ECDSAP384SHA384:
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ecdsaSignature := &struct {
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R, S *big.Int
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}{}
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if _, err := asn1.Unmarshal(signature, ecdsaSignature); err != nil {
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return nil, err
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}
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var intlen int
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switch alg {
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case ECDSAP256SHA256:
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intlen = 32
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case ECDSAP384SHA384:
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intlen = 48
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}
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signature := intToBytes(ecdsaSignature.R, intlen)
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signature = append(signature, intToBytes(ecdsaSignature.S, intlen)...)
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return signature, nil
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// There is no defined interface for what a DSA backed crypto.Signer returns
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case DSA, DSANSEC3SHA1:
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// t := divRoundUp(divRoundUp(p.PublicKey.Y.BitLen(), 8)-64, 8)
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// signature := []byte{byte(t)}
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// signature = append(signature, intToBytes(r1, 20)...)
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// signature = append(signature, intToBytes(s1, 20)...)
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// rr.Signature = signature
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}
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return nil, ErrAlg
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}
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// Verify validates an RRSet with the signature and key. This is only the
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// cryptographic test, the signature validity period must be checked separately.
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// This function copies the rdata of some RRs (to lowercase domain names) for the validation to work.
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func (rr *RRSIG) Verify(k *DNSKEY, rrset []RR) error {
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// First the easy checks
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if !IsRRset(rrset) {
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return ErrRRset
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}
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if rr.KeyTag != k.KeyTag() {
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return ErrKey
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}
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if rr.Hdr.Class != k.Hdr.Class {
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return ErrKey
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}
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if rr.Algorithm != k.Algorithm {
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return ErrKey
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}
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if strings.ToLower(rr.SignerName) != strings.ToLower(k.Hdr.Name) {
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return ErrKey
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}
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if k.Protocol != 3 {
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return ErrKey
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}
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// IsRRset checked that we have at least one RR and that the RRs in
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// the set have consistent type, class, and name. Also check that type and
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// class matches the RRSIG record.
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if rrset[0].Header().Class != rr.Hdr.Class {
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return ErrRRset
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}
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if rrset[0].Header().Rrtype != rr.TypeCovered {
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return ErrRRset
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}
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// RFC 4035 5.3.2. Reconstructing the Signed Data
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// Copy the sig, except the rrsig data
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sigwire := new(rrsigWireFmt)
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sigwire.TypeCovered = rr.TypeCovered
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sigwire.Algorithm = rr.Algorithm
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sigwire.Labels = rr.Labels
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sigwire.OrigTtl = rr.OrigTtl
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sigwire.Expiration = rr.Expiration
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sigwire.Inception = rr.Inception
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sigwire.KeyTag = rr.KeyTag
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sigwire.SignerName = strings.ToLower(rr.SignerName)
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// Create the desired binary blob
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signeddata := make([]byte, DefaultMsgSize)
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n, err := PackStruct(sigwire, signeddata, 0)
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if err != nil {
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return err
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}
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signeddata = signeddata[:n]
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wire, err := rawSignatureData(rrset, rr)
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if err != nil {
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return err
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}
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signeddata = append(signeddata, wire...)
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sigbuf := rr.sigBuf() // Get the binary signature data
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if rr.Algorithm == PRIVATEDNS { // PRIVATEOID
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// TODO(miek)
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// remove the domain name and assume its ours?
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}
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hash, ok := AlgorithmToHash[rr.Algorithm]
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if !ok {
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return ErrAlg
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}
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switch rr.Algorithm {
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case RSASHA1, RSASHA1NSEC3SHA1, RSASHA256, RSASHA512, RSAMD5:
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// TODO(mg): this can be done quicker, ie. cache the pubkey data somewhere??
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pubkey := k.publicKeyRSA() // Get the key
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if pubkey == nil {
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return ErrKey
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}
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h := hash.New()
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h.Write(signeddata)
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return rsa.VerifyPKCS1v15(pubkey, hash, h.Sum(nil), sigbuf)
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case ECDSAP256SHA256, ECDSAP384SHA384:
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pubkey := k.publicKeyECDSA()
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if pubkey == nil {
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return ErrKey
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}
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// Split sigbuf into the r and s coordinates
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r := new(big.Int).SetBytes(sigbuf[:len(sigbuf)/2])
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s := new(big.Int).SetBytes(sigbuf[len(sigbuf)/2:])
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h := hash.New()
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h.Write(signeddata)
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if ecdsa.Verify(pubkey, h.Sum(nil), r, s) {
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return nil
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}
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return ErrSig
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default:
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return ErrAlg
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}
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}
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// ValidityPeriod uses RFC1982 serial arithmetic to calculate
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// if a signature period is valid. If t is the zero time, the
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// current time is taken other t is. Returns true if the signature
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// is valid at the given time, otherwise returns false.
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func (rr *RRSIG) ValidityPeriod(t time.Time) bool {
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var utc int64
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if t.IsZero() {
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utc = time.Now().UTC().Unix()
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} else {
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utc = t.UTC().Unix()
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}
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modi := (int64(rr.Inception) - utc) / year68
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mode := (int64(rr.Expiration) - utc) / year68
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ti := int64(rr.Inception) + (modi * year68)
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te := int64(rr.Expiration) + (mode * year68)
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return ti <= utc && utc <= te
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}
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// Return the signatures base64 encodedig sigdata as a byte slice.
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func (rr *RRSIG) sigBuf() []byte {
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sigbuf, err := fromBase64([]byte(rr.Signature))
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if err != nil {
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return nil
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}
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return sigbuf
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}
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// publicKeyRSA returns the RSA public key from a DNSKEY record.
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func (k *DNSKEY) publicKeyRSA() *rsa.PublicKey {
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keybuf, err := fromBase64([]byte(k.PublicKey))
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if err != nil {
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return nil
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}
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// RFC 2537/3110, section 2. RSA Public KEY Resource Records
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// Length is in the 0th byte, unless its zero, then it
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// it in bytes 1 and 2 and its a 16 bit number
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explen := uint16(keybuf[0])
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keyoff := 1
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if explen == 0 {
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explen = uint16(keybuf[1])<<8 | uint16(keybuf[2])
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keyoff = 3
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}
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pubkey := new(rsa.PublicKey)
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pubkey.N = big.NewInt(0)
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shift := uint64((explen - 1) * 8)
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expo := uint64(0)
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for i := int(explen - 1); i > 0; i-- {
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expo += uint64(keybuf[keyoff+i]) << shift
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shift -= 8
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}
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// Remainder
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expo += uint64(keybuf[keyoff])
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if expo > 2<<31 {
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// Larger expo than supported.
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// println("dns: F5 primes (or larger) are not supported")
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return nil
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}
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pubkey.E = int(expo)
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pubkey.N.SetBytes(keybuf[keyoff+int(explen):])
|
|
return pubkey
|
|
}
|
|
|
|
// publicKeyECDSA returns the Curve public key from the DNSKEY record.
|
|
func (k *DNSKEY) publicKeyECDSA() *ecdsa.PublicKey {
|
|
keybuf, err := fromBase64([]byte(k.PublicKey))
|
|
if err != nil {
|
|
return nil
|
|
}
|
|
pubkey := new(ecdsa.PublicKey)
|
|
switch k.Algorithm {
|
|
case ECDSAP256SHA256:
|
|
pubkey.Curve = elliptic.P256()
|
|
if len(keybuf) != 64 {
|
|
// wrongly encoded key
|
|
return nil
|
|
}
|
|
case ECDSAP384SHA384:
|
|
pubkey.Curve = elliptic.P384()
|
|
if len(keybuf) != 96 {
|
|
// Wrongly encoded key
|
|
return nil
|
|
}
|
|
}
|
|
pubkey.X = big.NewInt(0)
|
|
pubkey.X.SetBytes(keybuf[:len(keybuf)/2])
|
|
pubkey.Y = big.NewInt(0)
|
|
pubkey.Y.SetBytes(keybuf[len(keybuf)/2:])
|
|
return pubkey
|
|
}
|
|
|
|
func (k *DNSKEY) publicKeyDSA() *dsa.PublicKey {
|
|
keybuf, err := fromBase64([]byte(k.PublicKey))
|
|
if err != nil {
|
|
return nil
|
|
}
|
|
if len(keybuf) < 22 {
|
|
return nil
|
|
}
|
|
t, keybuf := int(keybuf[0]), keybuf[1:]
|
|
size := 64 + t*8
|
|
q, keybuf := keybuf[:20], keybuf[20:]
|
|
if len(keybuf) != 3*size {
|
|
return nil
|
|
}
|
|
p, keybuf := keybuf[:size], keybuf[size:]
|
|
g, y := keybuf[:size], keybuf[size:]
|
|
pubkey := new(dsa.PublicKey)
|
|
pubkey.Parameters.Q = big.NewInt(0).SetBytes(q)
|
|
pubkey.Parameters.P = big.NewInt(0).SetBytes(p)
|
|
pubkey.Parameters.G = big.NewInt(0).SetBytes(g)
|
|
pubkey.Y = big.NewInt(0).SetBytes(y)
|
|
return pubkey
|
|
}
|
|
|
|
type wireSlice [][]byte
|
|
|
|
func (p wireSlice) Len() int { return len(p) }
|
|
func (p wireSlice) Swap(i, j int) { p[i], p[j] = p[j], p[i] }
|
|
func (p wireSlice) Less(i, j int) bool {
|
|
_, ioff, _ := UnpackDomainName(p[i], 0)
|
|
_, joff, _ := UnpackDomainName(p[j], 0)
|
|
return bytes.Compare(p[i][ioff+10:], p[j][joff+10:]) < 0
|
|
}
|
|
|
|
// Return the raw signature data.
|
|
func rawSignatureData(rrset []RR, s *RRSIG) (buf []byte, err error) {
|
|
wires := make(wireSlice, len(rrset))
|
|
for i, r := range rrset {
|
|
r1 := r.copy()
|
|
r1.Header().Ttl = s.OrigTtl
|
|
labels := SplitDomainName(r1.Header().Name)
|
|
// 6.2. Canonical RR Form. (4) - wildcards
|
|
if len(labels) > int(s.Labels) {
|
|
// Wildcard
|
|
r1.Header().Name = "*." + strings.Join(labels[len(labels)-int(s.Labels):], ".") + "."
|
|
}
|
|
// RFC 4034: 6.2. Canonical RR Form. (2) - domain name to lowercase
|
|
r1.Header().Name = strings.ToLower(r1.Header().Name)
|
|
// 6.2. Canonical RR Form. (3) - domain rdata to lowercase.
|
|
// NS, MD, MF, CNAME, SOA, MB, MG, MR, PTR,
|
|
// HINFO, MINFO, MX, RP, AFSDB, RT, SIG, PX, NXT, NAPTR, KX,
|
|
// SRV, DNAME, A6
|
|
//
|
|
// RFC 6840 - Clarifications and Implementation Notes for DNS Security (DNSSEC):
|
|
// Section 6.2 of [RFC4034] also erroneously lists HINFO as a record
|
|
// that needs conversion to lowercase, and twice at that. Since HINFO
|
|
// records contain no domain names, they are not subject to case
|
|
// conversion.
|
|
switch x := r1.(type) {
|
|
case *NS:
|
|
x.Ns = strings.ToLower(x.Ns)
|
|
case *CNAME:
|
|
x.Target = strings.ToLower(x.Target)
|
|
case *SOA:
|
|
x.Ns = strings.ToLower(x.Ns)
|
|
x.Mbox = strings.ToLower(x.Mbox)
|
|
case *MB:
|
|
x.Mb = strings.ToLower(x.Mb)
|
|
case *MG:
|
|
x.Mg = strings.ToLower(x.Mg)
|
|
case *MR:
|
|
x.Mr = strings.ToLower(x.Mr)
|
|
case *PTR:
|
|
x.Ptr = strings.ToLower(x.Ptr)
|
|
case *MINFO:
|
|
x.Rmail = strings.ToLower(x.Rmail)
|
|
x.Email = strings.ToLower(x.Email)
|
|
case *MX:
|
|
x.Mx = strings.ToLower(x.Mx)
|
|
case *NAPTR:
|
|
x.Replacement = strings.ToLower(x.Replacement)
|
|
case *KX:
|
|
x.Exchanger = strings.ToLower(x.Exchanger)
|
|
case *SRV:
|
|
x.Target = strings.ToLower(x.Target)
|
|
case *DNAME:
|
|
x.Target = strings.ToLower(x.Target)
|
|
}
|
|
// 6.2. Canonical RR Form. (5) - origTTL
|
|
wire := make([]byte, r1.len()+1) // +1 to be safe(r)
|
|
off, err1 := PackRR(r1, wire, 0, nil, false)
|
|
if err1 != nil {
|
|
return nil, err1
|
|
}
|
|
wire = wire[:off]
|
|
wires[i] = wire
|
|
}
|
|
sort.Sort(wires)
|
|
for i, wire := range wires {
|
|
if i > 0 && bytes.Equal(wire, wires[i-1]) {
|
|
continue
|
|
}
|
|
buf = append(buf, wire...)
|
|
}
|
|
return buf, nil
|
|
}
|