Provide the ability to set password hash algorithm parameters (#22942)

This PR refactors and improves the password hashing code within gitea
and makes it possible for server administrators to set the password
hashing parameters

In addition it takes the opportunity to adjust the settings for `pbkdf2`
in order to make the hashing a little stronger.

The majority of this work was inspired by PR #14751 and I would like to
thank @boppy for their work on this.

Thanks to @gusted for the suggestion to adjust the `pbkdf2` hashing
parameters.

Close #14751

---------

Signed-off-by: Andrew Thornton <art27@cantab.net>
Co-authored-by: delvh <dev.lh@web.de>
Co-authored-by: John Olheiser <john.olheiser@gmail.com>
Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

modules/auth/password/password_test.go

@@ -0,0 +1,76 @@
+// Copyright 2019 The Gitea Authors. All rights reserved.
+// SPDX-License-Identifier: MIT
+
+package password
+
+import (
+	"testing"
+
+	"github.com/stretchr/testify/assert"
+)
+
+func TestComplexity_IsComplexEnough(t *testing.T) {
+	matchComplexityOnce.Do(func() {})
+
+	testlist := []struct {
+		complexity  []string
+		truevalues  []string
+		falsevalues []string
+	}{
+		{[]string{"off"}, []string{"1", "-", "a", "A", "ñ", "日本語"}, []string{}},
+		{[]string{"lower"}, []string{"abc", "abc!"}, []string{"ABC", "123", "=!$", ""}},
+		{[]string{"upper"}, []string{"ABC"}, []string{"abc", "123", "=!$", "abc!", ""}},
+		{[]string{"digit"}, []string{"123"}, []string{"abc", "ABC", "=!$", "abc!", ""}},
+		{[]string{"spec"}, []string{"=!$", "abc!"}, []string{"abc", "ABC", "123", ""}},
+		{[]string{"off"}, []string{"abc", "ABC", "123", "=!$", "abc!", ""}, nil},
+		{[]string{"lower", "spec"}, []string{"abc!"}, []string{"abc", "ABC", "123", "=!$", "abcABC123", ""}},
+		{[]string{"lower", "upper", "digit"}, []string{"abcABC123"}, []string{"abc", "ABC", "123", "=!$", "abc!", ""}},
+		{[]string{""}, []string{"abC=1", "abc!9D"}, []string{"ABC", "123", "=!$", ""}},
+	}
+
+	for _, test := range testlist {
+		testComplextity(test.complexity)
+		for _, val := range test.truevalues {
+			assert.True(t, IsComplexEnough(val))
+		}
+		for _, val := range test.falsevalues {
+			assert.False(t, IsComplexEnough(val))
+		}
+	}
+
+	// Remove settings for other tests
+	testComplextity([]string{"off"})
+}
+
+func TestComplexity_Generate(t *testing.T) {
+	matchComplexityOnce.Do(func() {})
+
+	const maxCount = 50
+	const pwdLen = 50
+
+	test := func(t *testing.T, modes []string) {
+		testComplextity(modes)
+		for i := 0; i < maxCount; i++ {
+			pwd, err := Generate(pwdLen)
+			assert.NoError(t, err)
+			assert.Len(t, pwd, pwdLen)
+			assert.True(t, IsComplexEnough(pwd), "Failed complexities with modes %+v for generated: %s", modes, pwd)
+		}
+	}
+
+	test(t, []string{"lower"})
+	test(t, []string{"upper"})
+	test(t, []string{"lower", "upper", "spec"})
+	test(t, []string{"off"})
+	test(t, []string{""})
+
+	// Remove settings for other tests
+	testComplextity([]string{"off"})
+}
+
+func testComplextity(values []string) {
+	// Cleanup previous values
+	validChars = ""
+	requiredList = make([]complexity, 0, len(values))
+	setupComplexity(values)
+}