cookie.go

Documentation: net/http

     1  // Copyright 2009 The Go Authors. All rights reserved.
     2  // Use of this source code is governed by a BSD-style
     3  // license that can be found in the LICENSE file.
     4  
     5  package http
     6  
     7  import (
     8  	"errors"
     9  	"fmt"
    10  	"log"
    11  	"net"
    12  	"net/http/internal/ascii"
    13  	"net/textproto"
    14  	"strconv"
    15  	"strings"
    16  	"time"
    17  )
    18  
    19  // A Cookie represents an HTTP cookie as sent in the Set-Cookie header of an
    20  // HTTP response or the Cookie header of an HTTP request.
    21  //
    22  // See https://tools.ietf.org/html/rfc6265 for details.
    23  type Cookie struct {
    24  	Name  string
    25  	Value string
    26  
    27  	Path       string    // optional
    28  	Domain     string    // optional
    29  	Expires    time.Time // optional
    30  	RawExpires string    // for reading cookies only
    31  
    32  	// MaxAge=0 means no 'Max-Age' attribute specified.
    33  	// MaxAge<0 means delete cookie now, equivalently 'Max-Age: 0'
    34  	// MaxAge>0 means Max-Age attribute present and given in seconds
    35  	MaxAge   int
    36  	Secure   bool
    37  	HttpOnly bool
    38  	SameSite SameSite
    39  	Raw      string
    40  	Unparsed []string // Raw text of unparsed attribute-value pairs
    41  }
    42  
    43  // SameSite allows a server to define a cookie attribute making it impossible for
    44  // the browser to send this cookie along with cross-site requests. The main
    45  // goal is to mitigate the risk of cross-origin information leakage, and provide
    46  // some protection against cross-site request forgery attacks.
    47  //
    48  // See https://tools.ietf.org/html/draft-ietf-httpbis-cookie-same-site-00 for details.
    49  type SameSite int
    50  
    51  const (
    52  	SameSiteDefaultMode SameSite = iota + 1
    53  	SameSiteLaxMode
    54  	SameSiteStrictMode
    55  	SameSiteNoneMode
    56  )
    57  
    58  // readSetCookies parses all "Set-Cookie" values from
    59  // the header h and returns the successfully parsed Cookies.
    60  func readSetCookies(h Header) []*Cookie {
    61  	cookieCount := len(h["Set-Cookie"])
    62  	if cookieCount == 0 {
    63  		return []*Cookie{}
    64  	}
    65  	cookies := make([]*Cookie, 0, cookieCount)
    66  	for _, line := range h["Set-Cookie"] {
    67  		parts := strings.Split(textproto.TrimString(line), ";")
    68  		if len(parts) == 1 && parts[0] == "" {
    69  			continue
    70  		}
    71  		parts[0] = textproto.TrimString(parts[0])
    72  		name, value, ok := strings.Cut(parts[0], "=")
    73  		if !ok {
    74  			continue
    75  		}
    76  		if !isCookieNameValid(name) {
    77  			continue
    78  		}
    79  		value, ok = parseCookieValue(value, true)
    80  		if !ok {
    81  			continue
    82  		}
    83  		c := &Cookie{
    84  			Name:  name,
    85  			Value: value,
    86  			Raw:   line,
    87  		}
    88  		for i := 1; i < len(parts); i++ {
    89  			parts[i] = textproto.TrimString(parts[i])
    90  			if len(parts[i]) == 0 {
    91  				continue
    92  			}
    93  
    94  			attr, val, _ := strings.Cut(parts[i], "=")
    95  			lowerAttr, isASCII := ascii.ToLower(attr)
    96  			if !isASCII {
    97  				continue
    98  			}
    99  			val, ok = parseCookieValue(val, false)
   100  			if !ok {
   101  				c.Unparsed = append(c.Unparsed, parts[i])
   102  				continue
   103  			}
   104  
   105  			switch lowerAttr {
   106  			case "samesite":
   107  				lowerVal, ascii := ascii.ToLower(val)
   108  				if !ascii {
   109  					c.SameSite = SameSiteDefaultMode
   110  					continue
   111  				}
   112  				switch lowerVal {
   113  				case "lax":
   114  					c.SameSite = SameSiteLaxMode
   115  				case "strict":
   116  					c.SameSite = SameSiteStrictMode
   117  				case "none":
   118  					c.SameSite = SameSiteNoneMode
   119  				default:
   120  					c.SameSite = SameSiteDefaultMode
   121  				}
   122  				continue
   123  			case "secure":
   124  				c.Secure = true
   125  				continue
   126  			case "httponly":
   127  				c.HttpOnly = true
   128  				continue
   129  			case "domain":
   130  				c.Domain = val
   131  				continue
   132  			case "max-age":
   133  				secs, err := strconv.Atoi(val)
   134  				if err != nil || secs != 0 && val[0] == '0' {
   135  					break
   136  				}
   137  				if secs <= 0 {
   138  					secs = -1
   139  				}
   140  				c.MaxAge = secs
   141  				continue
   142  			case "expires":
   143  				c.RawExpires = val
   144  				exptime, err := time.Parse(time.RFC1123, val)
   145  				if err != nil {
   146  					exptime, err = time.Parse("Mon, 02-Jan-2006 15:04:05 MST", val)
   147  					if err != nil {
   148  						c.Expires = time.Time{}
   149  						break
   150  					}
   151  				}
   152  				c.Expires = exptime.UTC()
   153  				continue
   154  			case "path":
   155  				c.Path = val
   156  				continue
   157  			}
   158  			c.Unparsed = append(c.Unparsed, parts[i])
   159  		}
   160  		cookies = append(cookies, c)
   161  	}
   162  	return cookies
   163  }
   164  
   165  // SetCookie adds a Set-Cookie header to the provided ResponseWriter's headers.
   166  // The provided cookie must have a valid Name. Invalid cookies may be
   167  // silently dropped.
   168  func SetCookie(w ResponseWriter, cookie *Cookie) {
   169  	if v := cookie.String(); v != "" {
   170  		w.Header().Add("Set-Cookie", v)
   171  	}
   172  }
   173  
   174  // String returns the serialization of the cookie for use in a Cookie
   175  // header (if only Name and Value are set) or a Set-Cookie response
   176  // header (if other fields are set).
   177  // If c is nil or c.Name is invalid, the empty string is returned.
   178  func (c *Cookie) String() string {
   179  	if c == nil || !isCookieNameValid(c.Name) {
   180  		return ""
   181  	}
   182  	// extraCookieLength derived from typical length of cookie attributes
   183  	// see RFC 6265 Sec 4.1.
   184  	const extraCookieLength = 110
   185  	var b strings.Builder
   186  	b.Grow(len(c.Name) + len(c.Value) + len(c.Domain) + len(c.Path) + extraCookieLength)
   187  	b.WriteString(c.Name)
   188  	b.WriteRune('=')
   189  	b.WriteString(sanitizeCookieValue(c.Value))
   190  
   191  	if len(c.Path) > 0 {
   192  		b.WriteString("; Path=")
   193  		b.WriteString(sanitizeCookiePath(c.Path))
   194  	}
   195  	if len(c.Domain) > 0 {
   196  		if validCookieDomain(c.Domain) {
   197  			// A c.Domain containing illegal characters is not
   198  			// sanitized but simply dropped which turns the cookie
   199  			// into a host-only cookie. A leading dot is okay
   200  			// but won't be sent.
   201  			d := c.Domain
   202  			if d[0] == '.' {
   203  				d = d[1:]
   204  			}
   205  			b.WriteString("; Domain=")
   206  			b.WriteString(d)
   207  		} else {
   208  			log.Printf("net/http: invalid Cookie.Domain %q; dropping domain attribute", c.Domain)
   209  		}
   210  	}
   211  	var buf [len(TimeFormat)]byte
   212  	if validCookieExpires(c.Expires) {
   213  		b.WriteString("; Expires=")
   214  		b.Write(c.Expires.UTC().AppendFormat(buf[:0], TimeFormat))
   215  	}
   216  	if c.MaxAge > 0 {
   217  		b.WriteString("; Max-Age=")
   218  		b.Write(strconv.AppendInt(buf[:0], int64(c.MaxAge), 10))
   219  	} else if c.MaxAge < 0 {
   220  		b.WriteString("; Max-Age=0")
   221  	}
   222  	if c.HttpOnly {
   223  		b.WriteString("; HttpOnly")
   224  	}
   225  	if c.Secure {
   226  		b.WriteString("; Secure")
   227  	}
   228  	switch c.SameSite {
   229  	case SameSiteDefaultMode:
   230  		// Skip, default mode is obtained by not emitting the attribute.
   231  	case SameSiteNoneMode:
   232  		b.WriteString("; SameSite=None")
   233  	case SameSiteLaxMode:
   234  		b.WriteString("; SameSite=Lax")
   235  	case SameSiteStrictMode:
   236  		b.WriteString("; SameSite=Strict")
   237  	}
   238  	return b.String()
   239  }
   240  
   241  // Valid reports whether the cookie is valid.
   242  func (c *Cookie) Valid() error {
   243  	if c == nil {
   244  		return errors.New("http: nil Cookie")
   245  	}
   246  	if !isCookieNameValid(c.Name) {
   247  		return errors.New("http: invalid Cookie.Name")
   248  	}
   249  	if !validCookieExpires(c.Expires) {
   250  		return errors.New("http: invalid Cookie.Expires")
   251  	}
   252  	for i := 0; i < len(c.Value); i++ {
   253  		if !validCookieValueByte(c.Value[i]) {
   254  			return fmt.Errorf("http: invalid byte %q in Cookie.Value", c.Value[i])
   255  		}
   256  	}
   257  	if len(c.Path) > 0 {
   258  		for i := 0; i < len(c.Path); i++ {
   259  			if !validCookiePathByte(c.Path[i]) {
   260  				return fmt.Errorf("http: invalid byte %q in Cookie.Path", c.Path[i])
   261  			}
   262  		}
   263  	}
   264  	if len(c.Domain) > 0 {
   265  		if !validCookieDomain(c.Domain) {
   266  			return errors.New("http: invalid Cookie.Domain")
   267  		}
   268  	}
   269  	return nil
   270  }
   271  
   272  // readCookies parses all "Cookie" values from the header h and
   273  // returns the successfully parsed Cookies.
   274  //
   275  // if filter isn't empty, only cookies of that name are returned
   276  func readCookies(h Header, filter string) []*Cookie {
   277  	lines := h["Cookie"]
   278  	if len(lines) == 0 {
   279  		return []*Cookie{}
   280  	}
   281  
   282  	cookies := make([]*Cookie, 0, len(lines)+strings.Count(lines[0], ";"))
   283  	for _, line := range lines {
   284  		line = textproto.TrimString(line)
   285  
   286  		var part string
   287  		for len(line) > 0 { // continue since we have rest
   288  			part, line, _ = strings.Cut(line, ";")
   289  			part = textproto.TrimString(part)
   290  			if part == "" {
   291  				continue
   292  			}
   293  			name, val, _ := strings.Cut(part, "=")
   294  			if !isCookieNameValid(name) {
   295  				continue
   296  			}
   297  			if filter != "" && filter != name {
   298  				continue
   299  			}
   300  			val, ok := parseCookieValue(val, true)
   301  			if !ok {
   302  				continue
   303  			}
   304  			cookies = append(cookies, &Cookie{Name: name, Value: val})
   305  		}
   306  	}
   307  	return cookies
   308  }
   309  
   310  // validCookieDomain reports whether v is a valid cookie domain-value.
   311  func validCookieDomain(v string) bool {
   312  	if isCookieDomainName(v) {
   313  		return true
   314  	}
   315  	if net.ParseIP(v) != nil && !strings.Contains(v, ":") {
   316  		return true
   317  	}
   318  	return false
   319  }
   320  
   321  // validCookieExpires reports whether v is a valid cookie expires-value.
   322  func validCookieExpires(t time.Time) bool {
   323  	// IETF RFC 6265 Section 5.1.1.5, the year must not be less than 1601
   324  	return t.Year() >= 1601
   325  }
   326  
   327  // isCookieDomainName reports whether s is a valid domain name or a valid
   328  // domain name with a leading dot '.'.  It is almost a direct copy of
   329  // package net's isDomainName.
   330  func isCookieDomainName(s string) bool {
   331  	if len(s) == 0 {
   332  		return false
   333  	}
   334  	if len(s) > 255 {
   335  		return false
   336  	}
   337  
   338  	if s[0] == '.' {
   339  		// A cookie a domain attribute may start with a leading dot.
   340  		s = s[1:]
   341  	}
   342  	last := byte('.')
   343  	ok := false // Ok once we've seen a letter.
   344  	partlen := 0
   345  	for i := 0; i < len(s); i++ {
   346  		c := s[i]
   347  		switch {
   348  		default:
   349  			return false
   350  		case 'a' <= c && c <= 'z' || 'A' <= c && c <= 'Z':
   351  			// No '_' allowed here (in contrast to package net).
   352  			ok = true
   353  			partlen++
   354  		case '0' <= c && c <= '9':
   355  			// fine
   356  			partlen++
   357  		case c == '-':
   358  			// Byte before dash cannot be dot.
   359  			if last == '.' {
   360  				return false
   361  			}
   362  			partlen++
   363  		case c == '.':
   364  			// Byte before dot cannot be dot, dash.
   365  			if last == '.' || last == '-' {
   366  				return false
   367  			}
   368  			if partlen > 63 || partlen == 0 {
   369  				return false
   370  			}
   371  			partlen = 0
   372  		}
   373  		last = c
   374  	}
   375  	if last == '-' || partlen > 63 {
   376  		return false
   377  	}
   378  
   379  	return ok
   380  }
   381  
   382  var cookieNameSanitizer = strings.NewReplacer("\n", "-", "\r", "-")
   383  
   384  func sanitizeCookieName(n string) string {
   385  	return cookieNameSanitizer.Replace(n)
   386  }
   387  
   388  // sanitizeCookieValue produces a suitable cookie-value from v.
   389  // https://tools.ietf.org/html/rfc6265#section-4.1.1
   390  //
   391  //	cookie-value      = *cookie-octet / ( DQUOTE *cookie-octet DQUOTE )
   392  //	cookie-octet      = %x21 / %x23-2B / %x2D-3A / %x3C-5B / %x5D-7E
   393  //	          ; US-ASCII characters excluding CTLs,
   394  //	          ; whitespace DQUOTE, comma, semicolon,
   395  //	          ; and backslash
   396  //
   397  // We loosen this as spaces and commas are common in cookie values
   398  // but we produce a quoted cookie-value if and only if v contains
   399  // commas or spaces.
   400  // See https://golang.org/issue/7243 for the discussion.
   401  func sanitizeCookieValue(v string) string {
   402  	v = sanitizeOrWarn("Cookie.Value", validCookieValueByte, v)
   403  	if len(v) == 0 {
   404  		return v
   405  	}
   406  	if strings.ContainsAny(v, " ,") {
   407  		return `"` + v + `"`
   408  	}
   409  	return v
   410  }
   411  
   412  func validCookieValueByte(b byte) bool {
   413  	return 0x20 <= b && b < 0x7f && b != '"' && b != ';' && b != '\\'
   414  }
   415  
   416  // path-av           = "Path=" path-value
   417  // path-value        = <any CHAR except CTLs or ";">
   418  func sanitizeCookiePath(v string) string {
   419  	return sanitizeOrWarn("Cookie.Path", validCookiePathByte, v)
   420  }
   421  
   422  func validCookiePathByte(b byte) bool {
   423  	return 0x20 <= b && b < 0x7f && b != ';'
   424  }
   425  
   426  func sanitizeOrWarn(fieldName string, valid func(byte) bool, v string) string {
   427  	ok := true
   428  	for i := 0; i < len(v); i++ {
   429  		if valid(v[i]) {
   430  			continue
   431  		}
   432  		log.Printf("net/http: invalid byte %q in %s; dropping invalid bytes", v[i], fieldName)
   433  		ok = false
   434  		break
   435  	}
   436  	if ok {
   437  		return v
   438  	}
   439  	buf := make([]byte, 0, len(v))
   440  	for i := 0; i < len(v); i++ {
   441  		if b := v[i]; valid(b) {
   442  			buf = append(buf, b)
   443  		}
   444  	}
   445  	return string(buf)
   446  }
   447  
   448  func parseCookieValue(raw string, allowDoubleQuote bool) (string, bool) {
   449  	// Strip the quotes, if present.
   450  	if allowDoubleQuote && len(raw) > 1 && raw[0] == '"' && raw[len(raw)-1] == '"' {
   451  		raw = raw[1 : len(raw)-1]
   452  	}
   453  	for i := 0; i < len(raw); i++ {
   454  		if !validCookieValueByte(raw[i]) {
   455  			return "", false
   456  		}
   457  	}
   458  	return raw, true
   459  }
   460  
   461  func isCookieNameValid(raw string) bool {
   462  	if raw == "" {
   463  		return false
   464  	}
   465  	return strings.IndexFunc(raw, isNotToken) < 0
   466  }
   467
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