mirror of
https://gitlab.torproject.org/tpo/anti-censorship/pluggable-transports/snowflake.git
synced 2025-10-14 14:11:23 -04:00
c9e0dd287f
This package contains a CacheURL function that modifies a URL to be accessed through an AMP cache, and the "AMP armor" data encoding scheme for encoding data into the AMP subset of HTML.
44 lines
1.2 KiB
Go
44 lines
1.2 KiB
Go
package amp
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import (
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"crypto/rand"
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"encoding/base64"
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"fmt"
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"strings"
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)
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// EncodePath encodes data in a way that is suitable for the suffix of an AMP
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// cache URL.
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func EncodePath(data []byte) string {
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var cacheBreaker [9]byte
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_, err := rand.Read(cacheBreaker[:])
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if err != nil {
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panic(err)
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}
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b64 := base64.RawURLEncoding.EncodeToString
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return "0" + b64(cacheBreaker[:]) + "/" + b64(data)
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}
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// DecodePath decodes data from a path suffix as encoded by EncodePath. The path
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// must have already been trimmed of any directory prefix (as might be present
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// in, e.g., an HTTP request). That is, the first character of path should be
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// the "0" message format indicator.
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func DecodePath(path string) ([]byte, error) {
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if len(path) < 1 {
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return nil, fmt.Errorf("missing format indicator")
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}
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version := path[0]
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rest := path[1:]
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switch version {
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case '0':
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// Ignore everything else up to and including the final slash
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// (there must be at least one slash).
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i := strings.LastIndexByte(rest, '/')
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if i == -1 {
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return nil, fmt.Errorf("missing data")
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}
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return base64.RawURLEncoding.DecodeString(rest[i+1:])
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default:
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return nil, fmt.Errorf("unknown format indicator %q", version)
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}
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}
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