136 lines
3.7 KiB
Go
136 lines
3.7 KiB
Go
package common
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/*
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I2P Certificate
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https://geti2p.net/spec/common-structures#type-certificate
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Accurate for version 0.9.24
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+----+----+----+----+----+-//
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|type| length | payload
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+----+----+----+----+----+-//
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type :: Integer
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length -> 1 byte
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case 0 -> NULL
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case 1 -> HASHCASH
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case 2 -> HIDDEN
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case 3 -> SIGNED
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case 4 -> MULTIPLE
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case 5 -> KEY
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length :: Integer
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length -> 2 bytes
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payload :: data
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length -> $length bytes
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*/
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import (
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"errors"
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log "github.com/Sirupsen/logrus"
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)
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// Certificate Types
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const (
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CERT_NULL = iota
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CERT_HASHCASH
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CERT_HIDDEN
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CERT_SIGNED
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CERT_MULTIPLE
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CERT_KEY
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)
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const (
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CERT_MIN_SIZE = 3
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)
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type Certificate []byte
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//
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// Return the Certificate Type specified in the first byte of the Certificate,
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// and an error if the certificate is shorter than the minimum certificate size.
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//
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func (certificate Certificate) Type() (cert_type int, err error) {
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cert_len := len(certificate)
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if cert_len < CERT_MIN_SIZE {
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log.WithFields(log.Fields{
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"certificate_bytes_length": cert_len,
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"reason": "too short (len < CERT_MIN_SIZE)",
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}).Error("invalid certificate")
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err = errors.New("error parsing certificate length: certificate is too short")
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return
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}
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cert_type = Integer([]byte{certificate[0]})
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return
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}
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//
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// Look up the length of the Certificate, reporting errors if the certificate is
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// shorter than the minimum certificate size or if the reported length doesn't
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// match the provided data.
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//
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func (certificate Certificate) Length() (length int, err error) {
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cert_len := len(certificate)
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_, err = certificate.Type()
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if err != nil {
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return
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}
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length = Integer(certificate[1:CERT_MIN_SIZE])
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inferred_len := length + CERT_MIN_SIZE
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if inferred_len > cert_len {
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log.WithFields(log.Fields{
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"certificate_bytes_length": cert_len,
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"certificate_length_field": length,
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"expected_bytes_length": inferred_len,
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"reason": "data shorter than specified",
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}).Warn("certificate format warning")
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err = errors.New("certificate parsing warning: certificate data is shorter than specified by length")
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} else if cert_len > inferred_len {
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log.WithFields(log.Fields{
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"certificate_bytes_length": cert_len,
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"certificate_length_field": length,
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"expected_bytes_length": inferred_len,
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"reason": "data longer than expected",
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}).Warn("certificate format warning")
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err = errors.New("certificate parsing warning: certificate contains data beyond length")
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}
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return
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}
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//
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// Return the Certificate data and any errors encountered parsing the Certificate.
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//
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func (certificate Certificate) Data() (data []byte, err error) {
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length, err := certificate.Length()
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if err != nil {
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switch err.Error() {
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case "error parsing certificate length: certificate is too short":
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return
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case "certificate parsing warning: certificate data is shorter than specified by length":
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data = certificate[CERT_MIN_SIZE:]
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return
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case "certificate parsing warning: certificate contains data beyond length":
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data = certificate[CERT_MIN_SIZE : length+CERT_MIN_SIZE]
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return
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}
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}
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data = certificate[CERT_MIN_SIZE:]
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return
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}
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//
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// Read a Certificate from a slice of bytes, returning any extra data on the end of the slice
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// and any errors if a valid Certificate could not be read.
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//
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func ReadCertificate(data []byte) (certificate Certificate, remainder []byte, err error) {
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certificate = Certificate(data)
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length, err := certificate.Length()
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if err != nil && err.Error() == "certificate parsing warning: certificate contains data beyond length" {
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certificate = Certificate(data[:length+CERT_MIN_SIZE])
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remainder = data[length+CERT_MIN_SIZE:]
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err = nil
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}
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return
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}
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