[Password Manager] HTML parsing based client-side form type classifier

components/autofill/content/renderer/form_classifier.cc

+// Copyright 2016 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+#include "components/autofill/content/renderer/form_classifier.h"
+
+#include <algorithm>
+
+#include "base/macros.h"
+#include "base/strings/string16.h"
+#include "base/strings/string_util.h"
+#include "components/autofill/content/renderer/form_autofill_util.h"
+#include "third_party/WebKit/public/platform/WebString.h"
+#include "third_party/WebKit/public/platform/WebVector.h"
+#include "third_party/WebKit/public/web/WebFormControlElement.h"
+#include "third_party/WebKit/public/web/WebInputElement.h"
+
+using autofill::form_util::WebFormControlElementToFormField;
+using blink::WebFormControlElement;
+using blink::WebInputElement;
+using blink::WebString;
+using blink::WebVector;
+
+namespace autofill {
+
+namespace {
+
+// The words that frequently appear in attribute values of signin forms.
+const char* const kSigninTextFeatures[] = {"signin", "login", "logon", "auth"};
+constexpr size_t kNumberOfSigninFeatures = arraysize(kSigninTextFeatures);
+
+// The words that frequently appear in attribute values of signup forms.
+const char* const kSignupTextFeatures[] = {"signup", "regist", "creat"};
+constexpr size_t kNumberOfSignupFeatures = arraysize(kSignupTextFeatures);
+
+// The words that frequently appear in attribute values of captcha elements.
+const char* const kCaptchaFeatures[] = {"captcha", "security", "code"};
+constexpr size_t kNumberOfCaptchaFeatures = arraysize(kCaptchaFeatures);
+
+// Minimal number of input fields to classify form as signup or change password
+// form. If at least one of the listed thresholds is reached or exceeded, the
+// form is classified as a form where password generation should be available.
+constexpr size_t MINIMAL_NUMBER_OF_TEXT_FIELDS = 2;
+constexpr size_t MINIMAL_NUMBER_OF_PASSWORD_FIELDS = 2;
+constexpr size_t MINIMAL_NUMBER_OF_CHECKBOX_FIELDS = 3;
+constexpr size_t MINIMAL_NUMBER_OF_OTHER_FIELDS = 2;
+
+// Removes some characters from attribute value.
+void ClearAttributeValue(std::string* value) {
+  value->erase(std::remove_if(value->begin(), value->end(),
+                              [](char x) { return x == '-' || x == '_'; }),
+               value->end());
+}
+
+// Find |features| in |element|'s attribute values. Returns true if at least one
+// text feature was found.
+bool FindTextFeaturesForClass(const blink::WebElement& element,
+                              const char* const features[],
+                              size_t number_of_features) {
+  DCHECK(features);
+
+  for (unsigned i = 0; i < element.attributeCount(); ++i) {
+    std::string filtered_value =
+        base::ToLowerASCII(element.attributeValue(i).utf8());
+    ClearAttributeValue(&filtered_value);
+
+    if (filtered_value.empty())
+      continue;
+    for (size_t j = 0; j < number_of_features; ++j) {
+      if (filtered_value.find(features[j]) != std::string::npos)
+        return true;
+    }
+  }
+  return false;
+}
+
+// Returns true if at least one captcha feature was found in |element|'s
+// attribute values.
+bool IsCaptchaInput(const blink::WebInputElement& element) {
+  return FindTextFeaturesForClass(element, kCaptchaFeatures,
+                                  kNumberOfCaptchaFeatures);
+}
+
+// Finds <img>'s inside |form| and checks if <img>'s attributes contains captcha
+// text features. Returns true, if at least one occurrence was found.
+bool FindCaptchaInImgElements(const blink::WebElement& form,
+                              bool ingnore_invisible) {
+  CR_DEFINE_STATIC_LOCAL(WebString, kImageTag, ("img"));
+
+  blink::WebElementCollection img_elements =
+      form.getElementsByHTMLTagName(kImageTag);
+  for (blink::WebElement element = img_elements.firstItem(); !element.isNull();
+       element = img_elements.nextItem()) {
+    if (ingnore_invisible && !form_util::IsWebNodeVisible(element))
+      continue;
+    if (FindTextFeaturesForClass(element, kCaptchaFeatures,
+                                 kNumberOfCaptchaFeatures)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+// Finds signin and signup features in |element|'s attribute values. Sets to
+// true |found_signin_text_features| or |found_signup_text_features| if
+// appropriate features were found.
+void FindTextFeaturesInElement(const blink::WebElement& element,
+                               bool* found_signin_text_features,
+                               bool* found_signup_text_features) {
+  DCHECK(found_signin_text_features);
+  DCHECK(found_signup_text_features);
+
+  if (!*found_signin_text_features) {
+    *found_signin_text_features = FindTextFeaturesForClass(
+        element, kSigninTextFeatures, kNumberOfSigninFeatures);
+  }
+  if (!*found_signup_text_features) {
+    *found_signup_text_features = FindTextFeaturesForClass(
+        element, kSignupTextFeatures, kNumberOfSignupFeatures);
+  }
+}
+
+// Returns true if |element| has type "button" or "image".
+bool IsButtonOrImageElement(const WebFormControlElement& element) {
+  CR_DEFINE_STATIC_LOCAL(WebString, kButton, ("button"));
+  CR_DEFINE_STATIC_LOCAL(WebString, kImage, ("image"));
+
+  return element.formControlType() == kButton ||
+         element.formControlType() == kImage;
+}
+
+// Returns true if |element| has type "submit".
+bool IsSubmitElement(const WebFormControlElement& element) {
+  CR_DEFINE_STATIC_LOCAL(WebString, kSubmit, ("submit"));
+
+  return element.formControlType() == kSubmit;
+}
+
+// Returns true if |element| has type "hidden";
+bool IsHiddenElement(const WebFormControlElement& element) {
+  CR_DEFINE_STATIC_LOCAL(WebString, kHidden, ("hidden"));
+
+  return element.formControlType() == kHidden;
+}
+
+// Returns true if |element| has type "select-multiple" or "select-one".
+bool IsSelectElement(const WebFormControlElement& element) {
+  CR_DEFINE_STATIC_LOCAL(WebString, kSelectOne, ("select-one"));
+  CR_DEFINE_STATIC_LOCAL(WebString, kSelectMultiple, ("select-multiple"));
+
+  return element.formControlType() == kSelectOne ||
+         element.formControlType() == kSelectMultiple;
+}
+
+// Return true if |form| contains at least one visible password element.
+bool FormContainsVisiblePasswordFields(const blink::WebFormElement& form) {
+  WebVector<WebFormControlElement> control_elements;
+  form.getFormControlElements(control_elements);
+  for (auto& control_element : control_elements) {
+    const WebInputElement* input_element = toWebInputElement(&control_element);
+    if (!input_element)
+      continue;
+    if (input_element->isPasswordField() &&
+        form_util::IsWebNodeVisible(*input_element)) {
+      return true;
+    }
+  }
+  return false;
+}
+
+}  // namespace
+
+bool ClassifyFormAndFindGenerationField(const blink::WebFormElement& form,
+                                        base::string16* generation_field) {
+  DCHECK(generation_field);
+
+  if (form.isNull())
+    return false;
+
+  bool ignore_invisible_elements = FormContainsVisiblePasswordFields(form);
+
+  bool found_signin_text_features = false;
+  bool found_signup_text_features = false;
+  size_t number_of_text_input_fields = 0;
+  size_t number_of_password_input_fields = 0;
+  size_t number_of_checkbox_input_fields = 0;
+  size_t number_of_other_input_fields = 0;
+  bool found_captcha =
+      FindCaptchaInImgElements(form, ignore_invisible_elements);
+
+  FindTextFeaturesInElement(form, &found_signin_text_features,
+                            &found_signup_text_features);
+
+  std::vector<WebInputElement> passwords;
+  WebVector<WebFormControlElement> control_elements;
+  form.getFormControlElements(control_elements);
+
+  for (const WebFormControlElement& control_element : control_elements) {
+    if (IsHiddenElement(control_element))
+      continue;
+    if (ignore_invisible_elements) {
+      if (!form_util::IsWebNodeVisible(control_element))
+        continue;
+    }
+
+    // If type="button" or "image", skip them, because it might be a link
+    // to another form.
+    if (IsButtonOrImageElement(control_element))
+      continue;
+
+    FindTextFeaturesInElement(control_element, &found_signin_text_features,
+                              &found_signup_text_features);
+
+    // Since <select> is not WebInputElement, but WebSelectElement, process
+    // them as a special case.
+    if (IsSelectElement(control_element)) {
+      number_of_other_input_fields++;
+    } else {
+      const WebInputElement* input_element =
+          toWebInputElement(&control_element);
+      if (!input_element)
+        continue;
+
+      if (input_element->isTextField()) {
+        if (input_element->isPasswordField()) {
+          ++number_of_password_input_fields;
+          passwords.push_back(*input_element);
+        } else {
+          ++number_of_text_input_fields;
+          found_captcha = found_captcha || IsCaptchaInput(*input_element);
+        }
+      } else {  // Non-text fields.
+        if (input_element->isCheckbox())
+          ++number_of_checkbox_input_fields;
+        else if (!IsSubmitElement(*input_element))
+          ++number_of_other_input_fields;
+      }
+    }
+  }
+
+  if (number_of_password_input_fields == 0 ||
+      number_of_password_input_fields > 3)
+    return false;
+
+  if ((number_of_text_input_fields - found_captcha >=
+           MINIMAL_NUMBER_OF_TEXT_FIELDS ||
+       number_of_password_input_fields >= MINIMAL_NUMBER_OF_PASSWORD_FIELDS ||
+       number_of_checkbox_input_fields >= MINIMAL_NUMBER_OF_CHECKBOX_FIELDS ||
+       number_of_other_input_fields >= MINIMAL_NUMBER_OF_OTHER_FIELDS) ||
+      (found_signup_text_features && !found_signin_text_features)) {
+    WebInputElement password_creation_field;
+
+    // TODO(crbug.com/618309): Improve local classifier to distinguish password
+    // creation and password usage fields on the change password forms.
+    if (passwords.size() == 3)
+      password_creation_field = passwords[1];
+    else
+      password_creation_field = passwords[0];
+
+    *generation_field = password_creation_field.nameForAutofill();
+    return true;
+  }
+  return false;
+}
+}