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@@ -0,0 +1,378 @@
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+package cors
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+
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+import (
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+ "log"
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+ "net/http"
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+ "os"
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+ "strconv"
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+ "strings"
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+
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+ "github.com/kataras/iris/context"
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+)
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+
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+// Options is a configuration container to setup the CORS middleware.
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+type Options struct {
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+ // AllowedOrigins is a list of origins a cross-domain request can be executed from.
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+ // If the special "*" value is present in the list, all origins will be allowed.
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+ // An origin may contain a wildcard (*) to replace 0 or more characters
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+ // (i.e.: http://*.domain.com). Usage of wildcards implies a small performance penalty.
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+ // Only one wildcard can be used per origin.
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+ // Default value is ["*"]
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+ AllowedOrigins []string
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+ // AllowOriginFunc is a custom function to validate the origin. It take the origin
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+ // as argument and returns true if allowed or false otherwise. If this option is
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+ // set, the content of AllowedOrigins is ignored.
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+ AllowOriginFunc func(origin string) bool
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+ // AllowedMethods is a list of methods the client is allowed to use with
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+ // cross-domain requests. Default value is simple methods (HEAD, GET and POST).
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+ AllowedMethods []string
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+ // AllowedHeaders is list of non simple headers the client is allowed to use with
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+ // cross-domain requests.
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+ // If the special "*" value is present in the list, all headers will be allowed.
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+ // Default value is [] but "Origin" is always appended to the list.
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+ AllowedHeaders []string
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+ // ExposedHeaders indicates which headers are safe to expose to the API of a CORS
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+ // API specification
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+ ExposedHeaders []string
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+ // MaxAge indicates how long (in seconds) the results of a preflight request
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+ // can be cached
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+ MaxAge int
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+ // AllowCredentials indicates whether the request can include user credentials like
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+ // cookies, HTTP authentication or client side SSL certificates.
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+ AllowCredentials bool
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+ // OptionsPassthrough instructs preflight to let other potential next handlers to
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+ // process the OPTIONS method. Turn this on if your application handles OPTIONS.
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+ OptionsPassthrough bool
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+ // Debugging flag adds additional output to debug server side CORS issues
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+ Debug bool
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+}
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+
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+// Cors http handler
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+type Cors struct {
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+ // Debug logger
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+ Log *log.Logger
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+ // Normalized list of plain allowed origins
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+ allowedOrigins []string
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+ // List of allowed origins containing wildcards
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+ allowedWOrigins []wildcard
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+ // Optional origin validator function
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+ allowOriginFunc func(origin string) bool
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+ // Normalized list of allowed headers
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+ allowedHeaders []string
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+ // Normalized list of allowed methods
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+ allowedMethods []string
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+ // Normalized list of exposed headers
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+ exposedHeaders []string
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+ maxAge int
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+ // Set to true when allowed origins contains a "*"
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+ allowedOriginsAll bool
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+ // Set to true when allowed headers contains a "*"
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+ allowedHeadersAll bool
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+ allowCredentials bool
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+ optionPassthrough bool
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+}
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+
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+// New creates a new Cors handler with the provided options.
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+func New(options Options) context.Handler {
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+ c := &Cors{
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+ exposedHeaders: convert(options.ExposedHeaders, http.CanonicalHeaderKey),
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+ allowOriginFunc: options.AllowOriginFunc,
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+ allowCredentials: options.AllowCredentials,
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+ maxAge: options.MaxAge,
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+ optionPassthrough: options.OptionsPassthrough,
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+ }
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+ if options.Debug {
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+ c.Log = log.New(os.Stdout, "[cors] ", log.LstdFlags)
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+ }
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+
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+ // Normalize options
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+ // Note: for origins and methods matching, the spec requires a case-sensitive matching.
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+ // As it may error prone, we chose to ignore the spec here.
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+
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+ // Allowed Origins
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+ if len(options.AllowedOrigins) == 0 {
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+ if options.AllowOriginFunc == nil {
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+ // Default is all origins
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+ c.allowedOriginsAll = true
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+ }
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+ } else {
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+ c.allowedOrigins = []string{}
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+ c.allowedWOrigins = []wildcard{}
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+ for _, origin := range options.AllowedOrigins {
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+ // Normalize
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+ origin = strings.ToLower(origin)
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+ if origin == "*" {
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+ // If "*" is present in the list, turn the whole list into a match all
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+ c.allowedOriginsAll = true
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+ c.allowedOrigins = nil
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+ c.allowedWOrigins = nil
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+ break
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+ } else if i := strings.IndexByte(origin, '*'); i >= 0 {
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+ // Split the origin in two: start and end string without the *
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+ w := wildcard{origin[0:i], origin[i+1:]}
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+ c.allowedWOrigins = append(c.allowedWOrigins, w)
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+ } else {
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+ c.allowedOrigins = append(c.allowedOrigins, origin)
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+ }
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+ }
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+ }
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+
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+ // Allowed Headers
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+ if len(options.AllowedHeaders) == 0 {
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+ // Use sensible defaults
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+ c.allowedHeaders = []string{"Origin", "Accept", "Content-Type", "X-Requested-With"}
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+ } else {
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+ // Origin is always appended as some browsers will always request for this header at preflight
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+ c.allowedHeaders = convert(append(options.AllowedHeaders, "Origin"), http.CanonicalHeaderKey)
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+ for _, h := range options.AllowedHeaders {
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+ if h == "*" {
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+ c.allowedHeadersAll = true
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+ c.allowedHeaders = nil
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+ break
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+ }
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+ }
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+ }
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+
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+ // Allowed Methods
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+ if len(options.AllowedMethods) == 0 {
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+ // Default is spec's "simple" methods
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+ c.allowedMethods = []string{"GET", "POST", "HEAD"}
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+ } else {
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+ c.allowedMethods = convert(options.AllowedMethods, strings.ToUpper)
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+ }
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+
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+ return c.Serve
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+}
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+
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+// Default creates a new Cors handler with default options.
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+func Default() context.Handler {
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+ return New(Options{})
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+}
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+
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+// AllowAll create a new Cors handler with permissive configuration allowing all
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+// origins with all standard methods with any header and credentials.
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+func AllowAll() context.Handler {
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+ return New(Options{
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+ AllowedOrigins: []string{"*"},
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+ AllowedMethods: []string{"HEAD", "GET", "POST", "PUT", "PATCH", "DELETE"},
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+ AllowedHeaders: []string{"*"},
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+ AllowCredentials: true,
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+ })
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+}
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+
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+// Serve apply the CORS specification on the request, and add relevant CORS headers
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+// as necessary.
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+func (c *Cors) Serve(ctx context.Context) {
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+ if ctx.Method() == http.MethodOptions && ctx.GetHeader("Access-Control-Request-Method") != "" {
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+ c.logf("Serve: Preflight request")
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+ c.handlePreflight(ctx)
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+ if c.optionPassthrough { // handle the options by routes.
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+ ctx.Next()
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+ return
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+ }
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+
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+ if !ctx.IsStopped() {
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+ // just 200.
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+ ctx.StatusCode(http.StatusOK)
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+ ctx.StopExecution()
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+ }
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+
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+ return
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+ }
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+
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+ c.logf("Serve: Actual request")
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+ c.handleActualRequest(ctx)
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+ ctx.Next()
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+}
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+
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+// handlePreflight handles pre-flight CORS requests
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+func (c *Cors) handlePreflight(ctx context.Context) {
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+ origin := ctx.GetHeader("Origin")
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+
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+ if ctx.Method() != http.MethodOptions {
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+ c.logf(" Preflight aborted: %s!=OPTIONS", ctx.Method())
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+ //
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+ ctx.StatusCode(http.StatusForbidden)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+ // Always set Vary headers.
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+ ctx.Header("Vary", "Origin, Access-Control-Request-Method, Access-Control-Request-Headers")
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+
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+ if origin == "" {
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+ c.logf(" Preflight aborted: empty origin")
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+ return
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+ }
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+ if !c.isOriginAllowed(origin) {
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+ c.logf(" Preflight aborted: origin '%s' not allowed", origin)
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+ //
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+ ctx.StatusCode(http.StatusForbidden)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+
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+ reqMethod := ctx.GetHeader("Access-Control-Request-Method")
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+ if !c.isMethodAllowed(reqMethod) {
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+ c.logf(" Preflight aborted: method '%s' not allowed", reqMethod)
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+ //
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+ ctx.StatusCode(http.StatusForbidden)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+ reqHeaders := parseHeaderList(ctx.GetHeader("Access-Control-Request-Headers"))
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+ if !c.areHeadersAllowed(reqHeaders) {
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+ c.logf(" Preflight aborted: headers '%v' not allowed", reqHeaders)
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+ //
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+ ctx.StatusCode(http.StatusForbidden)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+ if c.allowedOriginsAll && !c.allowCredentials {
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+ ctx.Header("Access-Control-Allow-Origin", "*")
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+ } else {
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+ ctx.Header("Access-Control-Allow-Origin", origin)
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+ }
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+ // Spec says: Since the list of methods can be unbounded, simply returning the method indicated
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+ // by Access-Control-Request-Method (if supported) can be enough
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+ ctx.Header("Access-Control-Allow-Methods", strings.ToUpper(reqMethod))
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+ if len(reqHeaders) > 0 {
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+ // Spec says: Since the list of headers can be unbounded, simply returning supported headers
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+ // from Access-Control-Request-Headers can be enough
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+ ctx.Header("Access-Control-Allow-Headers", strings.Join(reqHeaders, ", "))
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+ }
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+ if c.allowCredentials {
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+ ctx.Header("Access-Control-Allow-Credentials", "true")
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+ }
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+ if c.maxAge > 0 {
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+ ctx.Header("Access-Control-Max-Age", strconv.Itoa(c.maxAge))
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+ }
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+ c.logf(" Preflight response headers: %v", ctx.ResponseWriter().Header())
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+}
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+
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+// handleActualRequest handles simple cross-origin requests, actual request or redirects
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+func (c *Cors) handleActualRequest(ctx context.Context) {
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+ origin := ctx.GetHeader("Origin")
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+
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+ if ctx.Method() == http.MethodOptions {
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+ c.logf(" Actual request no headers added: method == %s", ctx.Method())
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+ //
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+ ctx.StatusCode(http.StatusMethodNotAllowed)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+ // Always set Vary, see https://github.com/rs/cors/issues/10
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+ ctx.ResponseWriter().Header().Add("Vary", "Origin")
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+ if origin == "" {
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+ c.logf(" Actual request no headers added: missing origin")
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+ return
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+ }
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+ if !c.isOriginAllowed(origin) {
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+ c.logf(" Actual request no headers added: origin '%s' not allowed", origin)
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+ //
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+ ctx.StatusCode(http.StatusForbidden)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+
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+ // Note that spec does define a way to specifically disallow a simple method like GET or
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+ // POST. Access-Control-Allow-Methods is only used for pre-flight requests and the
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+ // spec doesn't instruct to check the allowed methods for simple cross-origin requests.
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+ // We think it's a nice feature to be able to have control on those methods though.
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+ if !c.isMethodAllowed(ctx.Method()) {
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+ c.logf(" Actual request no headers added: method '%s' not allowed", ctx.Method())
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+ //
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+ ctx.StatusCode(http.StatusForbidden)
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+ ctx.StopExecution()
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+ //
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+ return
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+ }
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+ if c.allowedOriginsAll && !c.allowCredentials {
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+ ctx.Header("Access-Control-Allow-Origin", "*")
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+ } else {
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+ ctx.Header("Access-Control-Allow-Origin", origin)
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+ }
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+ if len(c.exposedHeaders) > 0 {
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+ ctx.Header("Access-Control-Expose-Headers", strings.Join(c.exposedHeaders, ", "))
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+ }
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+ if c.allowCredentials {
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+ ctx.Header("Access-Control-Allow-Credentials", "true")
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+ }
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+ c.logf(" Actual response added headers: %v", ctx.ResponseWriter().Header())
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+}
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+
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+// convenience method. checks if debugging is turned on before printing
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+func (c *Cors) logf(format string, a ...interface{}) {
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+ if c.Log != nil {
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+ c.Log.Printf(format, a...)
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+ }
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+}
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+
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+// isOriginAllowed checks if a given origin is allowed to perform cross-domain requests
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+// on the endpoint
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+func (c *Cors) isOriginAllowed(origin string) bool {
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+ if c.allowOriginFunc != nil {
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+ return c.allowOriginFunc(origin)
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+ }
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+ if c.allowedOriginsAll {
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+ return true
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+ }
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+ origin = strings.ToLower(origin)
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+ for _, o := range c.allowedOrigins {
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+ if o == origin {
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+ return true
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+ }
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+ }
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+ for _, w := range c.allowedWOrigins {
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+ if w.match(origin) {
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+ return true
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+ }
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+ }
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+ return false
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+}
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+
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+// isMethodAllowed checks if a given method can be used as part of a cross-domain request
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+// on the endpoing
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+func (c *Cors) isMethodAllowed(method string) bool {
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+ if len(c.allowedMethods) == 0 {
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+ // If no method allowed, always return false, even for preflight request
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+ return false
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+ }
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+ method = strings.ToUpper(method)
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+ if method == http.MethodOptions {
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+ // Always allow preflight requests
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+ return true
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+ }
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+ for _, m := range c.allowedMethods {
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+ if m == method {
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+ return true
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+ }
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+ }
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+ return false
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+}
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+
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+// areHeadersAllowed checks if a given list of headers are allowed to used within
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+// a cross-domain request.
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+func (c *Cors) areHeadersAllowed(requestedHeaders []string) bool {
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+ if c.allowedHeadersAll || len(requestedHeaders) == 0 {
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+ return true
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+ }
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+ for _, header := range requestedHeaders {
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+ header = http.CanonicalHeaderKey(header)
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+ found := false
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+ for _, h := range c.allowedHeaders {
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+ if h == header {
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+ found = true
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+ }
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+ }
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+ if !found {
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+ return false
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+ }
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+ }
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+ return true
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+}
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