mirror of
https://github.com/labstack/echo.git
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185 lines
5.9 KiB
Go
185 lines
5.9 KiB
Go
package middleware
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import (
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"errors"
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"fmt"
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"github.com/labstack/echo/v4"
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"net/textproto"
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"strings"
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)
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const (
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// extractorLimit is arbitrary number to limit values extractor can return. this limits possible resource exhaustion
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// attack vector
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extractorLimit = 20
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)
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var errHeaderExtractorValueMissing = errors.New("missing value in request header")
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var errHeaderExtractorValueInvalid = errors.New("invalid value in request header")
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var errQueryExtractorValueMissing = errors.New("missing value in the query string")
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var errParamExtractorValueMissing = errors.New("missing value in path params")
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var errCookieExtractorValueMissing = errors.New("missing value in cookies")
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var errFormExtractorValueMissing = errors.New("missing value in the form")
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// ValuesExtractor defines a function for extracting values (keys/tokens) from the given context.
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type ValuesExtractor func(c echo.Context) ([]string, error)
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func createExtractors(lookups string, authScheme string) ([]ValuesExtractor, error) {
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if lookups == "" {
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return nil, nil
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}
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sources := strings.Split(lookups, ",")
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var extractors = make([]ValuesExtractor, 0)
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for _, source := range sources {
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parts := strings.Split(source, ":")
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if len(parts) < 2 {
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return nil, fmt.Errorf("extractor source for lookup could not be split into needed parts: %v", source)
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}
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switch parts[0] {
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case "query":
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extractors = append(extractors, valuesFromQuery(parts[1]))
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case "param":
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extractors = append(extractors, valuesFromParam(parts[1]))
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case "cookie":
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extractors = append(extractors, valuesFromCookie(parts[1]))
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case "form":
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extractors = append(extractors, valuesFromForm(parts[1]))
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case "header":
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prefix := ""
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if len(parts) > 2 {
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prefix = parts[2]
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} else if authScheme != "" && parts[1] == echo.HeaderAuthorization {
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// backwards compatibility for JWT and KeyAuth:
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// * we only apply this fix to Authorization as header we use and uses prefixes like "Bearer <token-value>" etc
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// * previously header extractor assumed that auth-scheme/prefix had a space as suffix we need to retain that
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// behaviour for default values and Authorization header.
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prefix = authScheme
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if !strings.HasSuffix(prefix, " ") {
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prefix += " "
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}
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}
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extractors = append(extractors, valuesFromHeader(parts[1], prefix))
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}
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}
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return extractors, nil
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}
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// valuesFromHeader returns a functions that extracts values from the request header.
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// valuePrefix is parameter to remove first part (prefix) of the extracted value. This is useful if header value has static
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// prefix like `Authorization: <auth-scheme> <authorisation-parameters>` where part that we want to remove is `<auth-scheme> `
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// note the space at the end. In case of basic authentication `Authorization: Basic <credentials>` prefix we want to remove
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// is `Basic `. In case of JWT tokens `Authorization: Bearer <token>` prefix is `Bearer `.
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// If prefix is left empty the whole value is returned.
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func valuesFromHeader(header string, valuePrefix string) ValuesExtractor {
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prefixLen := len(valuePrefix)
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// standard library parses http.Request header keys in canonical form but we may provide something else so fix this
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header = textproto.CanonicalMIMEHeaderKey(header)
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return func(c echo.Context) ([]string, error) {
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values := c.Request().Header.Values(header)
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if len(values) == 0 {
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return nil, errHeaderExtractorValueMissing
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}
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result := make([]string, 0)
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for i, value := range values {
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if prefixLen == 0 {
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result = append(result, value)
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if i >= extractorLimit-1 {
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break
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}
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continue
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}
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if len(value) > prefixLen && strings.EqualFold(value[:prefixLen], valuePrefix) {
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result = append(result, value[prefixLen:])
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if i >= extractorLimit-1 {
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break
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}
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}
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}
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if len(result) == 0 {
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if prefixLen > 0 {
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return nil, errHeaderExtractorValueInvalid
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}
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return nil, errHeaderExtractorValueMissing
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}
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return result, nil
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}
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}
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// valuesFromQuery returns a function that extracts values from the query string.
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func valuesFromQuery(param string) ValuesExtractor {
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return func(c echo.Context) ([]string, error) {
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result := c.QueryParams()[param]
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if len(result) == 0 {
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return nil, errQueryExtractorValueMissing
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} else if len(result) > extractorLimit-1 {
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result = result[:extractorLimit]
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}
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return result, nil
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}
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}
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// valuesFromParam returns a function that extracts values from the url param string.
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func valuesFromParam(param string) ValuesExtractor {
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return func(c echo.Context) ([]string, error) {
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result := make([]string, 0)
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paramVales := c.ParamValues()
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for i, p := range c.ParamNames() {
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if param == p {
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result = append(result, paramVales[i])
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if i >= extractorLimit-1 {
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break
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}
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}
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}
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if len(result) == 0 {
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return nil, errParamExtractorValueMissing
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}
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return result, nil
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}
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}
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// valuesFromCookie returns a function that extracts values from the named cookie.
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func valuesFromCookie(name string) ValuesExtractor {
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return func(c echo.Context) ([]string, error) {
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cookies := c.Cookies()
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if len(cookies) == 0 {
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return nil, errCookieExtractorValueMissing
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}
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result := make([]string, 0)
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for i, cookie := range cookies {
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if name == cookie.Name {
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result = append(result, cookie.Value)
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if i >= extractorLimit-1 {
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break
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}
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}
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}
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if len(result) == 0 {
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return nil, errCookieExtractorValueMissing
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}
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return result, nil
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}
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}
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// valuesFromForm returns a function that extracts values from the form field.
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func valuesFromForm(name string) ValuesExtractor {
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return func(c echo.Context) ([]string, error) {
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if c.Request().Form == nil {
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_ = c.Request().ParseMultipartForm(32 << 20) // same what `c.Request().FormValue(name)` does
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}
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values := c.Request().Form[name]
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if len(values) == 0 {
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return nil, errFormExtractorValueMissing
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}
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if len(values) > extractorLimit-1 {
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values = values[:extractorLimit]
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}
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result := append([]string{}, values...)
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return result, nil
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}
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}
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