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

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