caidooss/grafana-auth-proxy

package extraction

import (
    "errors"
    "fmt"
    "net/http"
    "strings"
)

type headerExtractor struct {
    headerName   string
    headerPrefix string
}

func NewHeaderExtractor(headerName string, headerPrefix string) *headerExtractor {
    return &headerExtractor{
        headerName:   headerName,
        headerPrefix: strings.ToLower(headerPrefix),
    }
}

func (he *headerExtractor) Extract(r *http.Request) (string, error) {
    // Extract header
    header := r.Header.Get(he.headerName)
    if header == "" {
        return "", errors.New(fmt.Sprintf("no header %s", he.headerName))
    }

    // Extract token
    values := strings.Split(header, " ")
    if strings.ToLower(values[0]) != he.headerPrefix {
        return "", errors.New(fmt.Sprintf("header must start with %s", he.headerPrefix))
    } else if len(values) == 1 {
        return "", errors.New("token not found in header")
    } else if len(values) > 2 {
        return "", errors.New("too many parts found in header")
    }

    return values[1], nil
}