util/httphdr: add new package for parsing HTTP headers (#9797)
This adds support for parsing Range and Content-Range headers according to RFC 7230. The package could be extended in the future to handle other headers. Updates tailscale/corp#14772 Signed-off-by: Joe Tsai <joetsai@digital-static.net>
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Joe Tsai
GitHub
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9cb6c5bb78
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@ -0,0 +1,197 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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// Package httphdr implements functionality for parsing and formatting
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// standard HTTP headers.
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package httphdr
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import (
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"bytes"
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"strconv"
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"strings"
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)
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// Range is a range of bytes within some content.
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type Range struct {
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// Start is the starting offset.
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// It is zero if Length is negative; it must not be negative.
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Start int64
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// Length is the length of the content.
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// It is zero if the length extends to the end of the content.
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// It is negative if the length is relative to the end (e.g., last 5 bytes).
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Length int64
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}
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// ows is optional whitespace.
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const ows = " \t" // per RFC 7230, section 3.2.3
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// ParseRange parses a "Range" header per RFC 7233, section 3.
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// It only handles "Range" headers where the units is "bytes".
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// The "Range" header is usually only specified in GET requests.
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func ParseRange(hdr string) (ranges []Range, ok bool) {
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// Grammar per RFC 7233, appendix D:
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// Range = byte-ranges-specifier | other-ranges-specifier
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// byte-ranges-specifier = bytes-unit "=" byte-range-set
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// bytes-unit = "bytes"
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// byte-range-set =
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// *("," OWS)
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// (byte-range-spec | suffix-byte-range-spec)
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// *(OWS "," [OWS ( byte-range-spec | suffix-byte-range-spec )])
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// byte-range-spec = first-byte-pos "-" [last-byte-pos]
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// suffix-byte-range-spec = "-" suffix-length
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// We do not support other-ranges-specifier.
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// All other identifiers are 1*DIGIT.
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hdr = strings.Trim(hdr, ows) // per RFC 7230, section 3.2
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units, elems, hasUnits := strings.Cut(hdr, "=")
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elems = strings.TrimLeft(elems, ","+ows)
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for _, elem := range strings.Split(elems, ",") {
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elem = strings.Trim(elem, ows) // per RFC 7230, section 7
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switch {
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case strings.HasPrefix(elem, "-"): // i.e., "-" suffix-length
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n, ok := parseNumber(strings.TrimPrefix(elem, "-"))
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if !ok {
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return ranges, false
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}
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ranges = append(ranges, Range{0, -n})
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case strings.HasSuffix(elem, "-"): // i.e., first-byte-pos "-"
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n, ok := parseNumber(strings.TrimSuffix(elem, "-"))
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if !ok {
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return ranges, false
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}
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ranges = append(ranges, Range{n, 0})
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default: // i.e., first-byte-pos "-" last-byte-pos
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prefix, suffix, hasDash := strings.Cut(elem, "-")
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n, ok2 := parseNumber(prefix)
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m, ok3 := parseNumber(suffix)
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if !hasDash || !ok2 || !ok3 || m < n {
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return ranges, false
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}
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ranges = append(ranges, Range{n, m - n + 1})
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}
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}
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return ranges, units == "bytes" && hasUnits && len(ranges) > 0 // must see at least one element per RFC 7233, section 2.1
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}
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// FormatRange formats a "Range" header per RFC 7233, section 3.
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// It only handles "Range" headers where the units is "bytes".
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// The "Range" header is usually only specified in GET requests.
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func FormatRange(ranges []Range) (hdr string, ok bool) {
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b := []byte("bytes=")
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for _, r := range ranges {
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switch {
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case r.Length > 0: // i.e., first-byte-pos "-" last-byte-pos
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if r.Start < 0 {
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return string(b), false
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}
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b = strconv.AppendUint(b, uint64(r.Start), 10)
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b = append(b, '-')
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b = strconv.AppendUint(b, uint64(r.Start+r.Length-1), 10)
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b = append(b, ',')
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case r.Length == 0: // i.e., first-byte-pos "-"
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if r.Start < 0 {
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return string(b), false
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}
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b = strconv.AppendUint(b, uint64(r.Start), 10)
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b = append(b, '-')
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b = append(b, ',')
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case r.Length < 0: // i.e., "-" suffix-length
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if r.Start != 0 {
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return string(b), false
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}
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b = append(b, '-')
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b = strconv.AppendUint(b, uint64(-r.Length), 10)
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b = append(b, ',')
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default:
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return string(b), false
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}
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}
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return string(bytes.TrimRight(b, ",")), len(ranges) > 0
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}
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// ParseContentRange parses a "Content-Range" header per RFC 7233, section 4.2.
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// It only handles "Content-Range" headers where the units is "bytes".
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// The "Content-Range" header is usually only specified in HTTP responses.
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//
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// If only the completeLength is specified, then start and length are both zero.
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//
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// Otherwise, the parses the start and length and the optional completeLength,
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// which is -1 if unspecified. The start is non-negative and the length is positive.
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func ParseContentRange(hdr string) (start, length, completeLength int64, ok bool) {
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// Grammar per RFC 7233, appendix D:
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// Content-Range = byte-content-range | other-content-range
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// byte-content-range = bytes-unit SP (byte-range-resp | unsatisfied-range)
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// bytes-unit = "bytes"
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// byte-range-resp = byte-range "/" (complete-length | "*")
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// unsatisfied-range = "*/" complete-length
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// byte-range = first-byte-pos "-" last-byte-pos
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// We do not support other-content-range.
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// All other identifiers are 1*DIGIT.
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hdr = strings.Trim(hdr, ows) // per RFC 7230, section 3.2
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suffix, hasUnits := strings.CutPrefix(hdr, "bytes ")
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suffix, unsatisfied := strings.CutPrefix(suffix, "*/")
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if unsatisfied { // i.e., unsatisfied-range
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n, ok := parseNumber(suffix)
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if !ok {
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return start, length, completeLength, false
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}
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completeLength = n
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} else { // i.e., byte-range "/" (complete-length | "*")
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prefix, suffix, hasDash := strings.Cut(suffix, "-")
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middle, suffix, hasSlash := strings.Cut(suffix, "/")
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n, ok0 := parseNumber(prefix)
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m, ok1 := parseNumber(middle)
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o, ok2 := parseNumber(suffix)
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if suffix == "*" {
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o, ok2 = -1, true
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}
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if !hasDash || !hasSlash || !ok0 || !ok1 || !ok2 || m < n || (o >= 0 && o <= m) {
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return start, length, completeLength, false
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}
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start = n
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length = m - n + 1
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completeLength = o
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}
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return start, length, completeLength, hasUnits
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}
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// FormatContentRange parses a "Content-Range" header per RFC 7233, section 4.2.
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// It only handles "Content-Range" headers where the units is "bytes".
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// The "Content-Range" header is usually only specified in HTTP responses.
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//
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// If start and length are non-positive, then it encodes just the completeLength,
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// which must be a non-negative value.
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//
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// Otherwise, it encodes the start and length as a byte-range,
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// and optionally emits the complete length if it is non-negative.
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// The length must be positive (as RFC 7233 uses inclusive end offsets).
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func FormatContentRange(start, length, completeLength int64) (hdr string, ok bool) {
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b := []byte("bytes ")
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switch {
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case start <= 0 && length <= 0 && completeLength >= 0: // i.e., unsatisfied-range
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b = append(b, "*/"...)
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b = strconv.AppendUint(b, uint64(completeLength), 10)
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ok = true
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case start >= 0 && length > 0: // i.e., byte-range "/" (complete-length | "*")
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b = strconv.AppendUint(b, uint64(start), 10)
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b = append(b, '-')
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b = strconv.AppendUint(b, uint64(start+length-1), 10)
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b = append(b, '/')
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if completeLength >= 0 {
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b = strconv.AppendUint(b, uint64(completeLength), 10)
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ok = completeLength >= start+length && start+length > 0
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} else {
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b = append(b, '*')
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ok = true
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}
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}
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return string(b), ok
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}
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// parseNumber parses s as an unsigned decimal integer.
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// It parses according to the 1*DIGIT grammar, which allows leading zeros.
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func parseNumber(s string) (int64, bool) {
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suffix := strings.TrimLeft(s, "0123456789")
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prefix := s[:len(s)-len(suffix)]
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n, err := strconv.ParseInt(prefix, 10, 64)
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return n, suffix == "" && err == nil
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}
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@ -0,0 +1,96 @@
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// Copyright (c) Tailscale Inc & AUTHORS
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// SPDX-License-Identifier: BSD-3-Clause
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package httphdr
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import (
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"testing"
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"github.com/google/go-cmp/cmp"
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)
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func valOk[T any](v T, ok bool) (out struct {
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V T
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Ok bool
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}) {
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out.V = v
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out.Ok = ok
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return out
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}
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func TestRange(t *testing.T) {
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tests := []struct {
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in string
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want []Range
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wantOk bool
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roundtrip bool
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}{
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{"", nil, false, false},
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{"1-3", nil, false, false},
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{"units=1-3", []Range{{1, 3}}, false, false},
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{"bytes=1-3", []Range{{1, 3}}, true, true},
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{"bytes=#-3", nil, false, false},
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{"bytes=#-", nil, false, false},
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{"bytes=13", nil, false, false},
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{"bytes=1-#", nil, false, false},
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{"bytes=-#", nil, false, false},
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{"bytes= , , , ,\t , \t 1-3", []Range{{1, 3}}, true, false},
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{"bytes=1-1", []Range{{1, 1}}, true, true},
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{"bytes=01-01", []Range{{1, 1}}, true, false},
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{"bytes=1-0", nil, false, false},
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{"bytes=0-5,2-3", []Range{{0, 6}, {2, 2}}, true, true},
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{"bytes=2-3,0-5", []Range{{2, 2}, {0, 6}}, true, true},
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{"bytes=0-5,2-,-5", []Range{{0, 6}, {2, 0}, {0, -5}}, true, true},
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}
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for _, tt := range tests {
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got, gotOk := ParseRange(tt.in)
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if d := cmp.Diff(valOk(got, gotOk), valOk(tt.want, tt.wantOk)); d != "" {
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t.Errorf("ParseRange(%q) mismatch (-got +want):\n%s", tt.in, d)
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}
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if tt.roundtrip {
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got, gotOk := FormatRange(tt.want)
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if d := cmp.Diff(valOk(got, gotOk), valOk(tt.in, tt.wantOk)); d != "" {
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t.Errorf("FormatRange(%v) mismatch (-got +want):\n%s", tt.want, d)
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}
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}
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}
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}
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type contentRange struct{ Start, Length, CompleteLength int64 }
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func TestContentRange(t *testing.T) {
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tests := []struct {
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in string
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want contentRange
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wantOk bool
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roundtrip bool
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}{
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{"", contentRange{}, false, false},
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{"bytes 5-6/*", contentRange{5, 2, -1}, true, true},
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{"units 5-6/*", contentRange{}, false, false},
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{"bytes 5-6/*", contentRange{}, false, false},
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{"bytes 5-5/*", contentRange{5, 1, -1}, true, true},
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{"bytes 5-4/*", contentRange{}, false, false},
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{"bytes 5-5/6", contentRange{5, 1, 6}, true, true},
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{"bytes 05-005/0006", contentRange{5, 1, 6}, true, false},
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{"bytes 5-5/5", contentRange{}, false, false},
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{"bytes #-5/6", contentRange{}, false, false},
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{"bytes 5-#/6", contentRange{}, false, false},
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{"bytes 5-5/#", contentRange{}, false, false},
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}
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for _, tt := range tests {
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start, length, completeLength, gotOk := ParseContentRange(tt.in)
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got := contentRange{start, length, completeLength}
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if d := cmp.Diff(valOk(got, gotOk), valOk(tt.want, tt.wantOk)); d != "" {
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t.Errorf("ParseContentRange mismatch (-got +want):\n%s", d)
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}
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if tt.roundtrip {
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got, gotOk := FormatContentRange(tt.want.Start, tt.want.Length, tt.want.CompleteLength)
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if d := cmp.Diff(valOk(got, gotOk), valOk(tt.in, tt.wantOk)); d != "" {
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t.Errorf("FormatContentRange mismatch (-got +want):\n%s", d)
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}
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}
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}
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}
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