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