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classify.go
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classify.go
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package main
import (
"bytes"
"encoding/json"
"image"
"io"
"io/ioutil"
"log"
"net/http"
"strconv"
"strings"
"github.com/andybalholm/dhash"
"github.com/klauspost/compress/gzip"
"golang.org/x/net/html"
"golang.org/x/net/html/charset"
)
type classificationResponse struct {
URL string `json:"url,omitempty"`
Text string `json:"text,omitempty"`
Categories map[string]int `json:"categories,omitempty"`
Rules map[string]int `json:"rules,omitempty"`
Error string `json:"error,omitempty"`
LogLine []string `json:"logLine,omitempty"`
}
// handleClassification responds to an HTTP request with a url parameter, and
// responds with a JSON object describing how the page would be classified.
func handleClassification(w http.ResponseWriter, r *http.Request) {
conf := getConfig()
var result classificationResponse
url := r.FormValue("url")
result.URL = url
if url == "" {
http.Error(w, "The URL to classify must be supplied as an HTTP form parameter named 'url'.", 400)
return
}
req, err := http.NewRequest("GET", url, nil)
if err != nil {
result.Error = err.Error()
ServeJSON(w, r, result)
log.Printf("Classifier: error creating request for %s: %v", url, err)
return
}
req.Header.Set("User-Agent", "Mozilla/5.0 (Macintosh; Intel Mac OS X 10_11_5) AppleWebKit/537.36 (KHTML, like Gecko) Chrome/51.0.2704.103 Safari/537.36")
resp, err := http.DefaultClient.Do(req)
if err != nil {
result.Error = err.Error()
ServeJSON(w, r, result)
log.Printf("Classifier: error fetching %s: %v", url, err)
return
}
defer resp.Body.Close()
// If the http Client followed redirects, use the final URL, not the one initially specified.
req = resp.Request
result.URL = req.URL.String()
if resp.StatusCode != 200 {
result.Error = resp.Status
ServeJSON(w, r, result)
log.Printf("Classifier: bad HTTP status fetching %s: %s", result.URL, resp.Status)
return
}
reqACLs := conf.ACLs.requestACLs(req, "")
respACLs := conf.ACLs.responseACLs(resp)
acls := unionACLSets(reqACLs, respACLs)
tally := conf.URLRules.MatchingRules(req.URL)
scores := conf.categoryScores(tally)
content, err := ioutil.ReadAll(&io.LimitedReader{
R: resp.Body,
N: int64(conf.MaxContentScanSize),
})
if err != nil {
result.Error = err.Error()
ServeJSON(w, r, result)
log.Printf("Classifier: error reading response body from %s: %v", result.URL, err)
return
}
thisRule, _ := conf.ChooseACLCategoryAction(acls, scores, conf.Threshold, "allow", "block", "block-invisible", "hash-image", "phrase-scan")
modified := false
scoresNeedUpdate := false
switch thisRule.Action {
case "phrase-scan":
contentType := resp.Header.Get("Content-Type")
_, cs, _ := charset.DetermineEncoding(content, contentType)
var doc *html.Node
if strings.Contains(contentType, "html") {
modified = conf.pruneContent(req.URL, &content, cs, &doc)
}
conf.scanContent(content, contentType, cs, tally)
scoresNeedUpdate = true
case "hash-image":
img, _, err := image.Decode(bytes.NewReader(content))
if err != nil {
result.Error = resp.Status
ServeJSON(w, r, result)
log.Printf("Classifier: error decoding image from %v: %v", req.URL, err)
return
}
hash := dhash.New(img)
for _, h := range conf.ImageHashes {
distance := dhash.Distance(hash, h.Hash)
if distance <= h.Threshold || h.Threshold == -1 && distance <= conf.DhashThreshold {
tally[rule{imageHash, h.String()}]++
scoresNeedUpdate = true
}
}
}
if scoresNeedUpdate {
scores = conf.categoryScores(tally)
}
for _, c := range conf.ClassifierIgnoredCategories {
delete(scores, c)
}
for k, v := range scores {
if v < conf.Threshold || conf.Categories[k].action == ACL {
delete(scores, k)
}
}
result.Categories = scores
logLine := logAccess(req, resp, len(content), modified, "", tally, scores, ACLActionRule{Action: "classify"}, "", nil)
if r.URL.Path == "/classify/verbose" {
result.LogLine = logLine
}
ServeJSON(w, r, result)
}
// handleClassifyText is like handleClassify, but it takes the text to be
// classified from the "text" parameter instead of fetching a URL.
func handleClassifyText(w http.ResponseWriter, r *http.Request) {
conf := getConfig()
var result classificationResponse
text := r.FormValue("text")
result.Text = text
if text == "" {
http.Error(w, "The text to classify must be supplied as an HTTP form parameter named 'text'.", 400)
return
}
tally := make(map[rule]int)
conf.scanContent([]byte(text), "text/plain", "utf-8", tally)
scores := conf.categoryScores(tally)
for _, c := range conf.ClassifierIgnoredCategories {
delete(scores, c)
}
result.Categories = scores
if r.URL.Path == "/classify-text/verbose" {
result.Rules = make(map[string]int)
for r, n := range tally {
result.Rules[r.String()] = n
}
}
ServeJSON(w, r, result)
}
// ServeJSON converts v to JSON and sends it on w.
func ServeJSON(w http.ResponseWriter, r *http.Request, v interface{}) {
data, err := json.Marshal(v)
if err != nil {
http.Error(w, err.Error(), 500)
return
}
w.Header().Set("Content-Type", "application/json")
if len(data) > 1000 && strings.Contains(r.Header.Get("Accept-Encoding"), "gzip") {
w.Header().Set("Content-Encoding", "gzip")
gzw := gzip.NewWriter(w)
defer gzw.Close()
gzw.Write(data)
} else {
w.Header().Set("Content-Length", strconv.Itoa(len(data)))
w.Write(data)
}
}