Add user configurable password policies available to secret engines (#8637)

* Add random string generator with rules engine

This adds a random string generation library that validates random
strings against a set of rules. The library is designed for use as generating
passwords, but can be used to generate any random strings.

sdk/plugin/grpc_system_test.go

@@ -2,17 +2,17 @@ package plugin
 
 import (
 	"context"
-	"testing"
-
-	"google.golang.org/grpc"
-
 	"reflect"
+	"testing"
+	"time"
 
 	"github.com/golang/protobuf/proto"
 	plugin "github.com/hashicorp/go-plugin"
 	"github.com/hashicorp/vault/sdk/helper/consts"
+	"github.com/hashicorp/vault/sdk/helper/random"
 	"github.com/hashicorp/vault/sdk/logical"
 	"github.com/hashicorp/vault/sdk/plugin/pb"
+	"google.golang.org/grpc"
 )
 
 func TestSystem_GRPC_GRPC_impl(t *testing.T) {
@@ -239,3 +239,63 @@ func TestSystem_GRPC_pluginEnv(t *testing.T) {
 		t.Fatalf("expected: %v, got: %v", expected, actual)
 	}
 }
+
+func TestSystem_GRPC_GeneratePasswordFromPolicy(t *testing.T) {
+	policyName := "testpolicy"
+	expectedPolicy := &random.StringGenerator{
+		Length: 8,
+		Rules: []random.Rule{
+			&random.CharsetRule{
+				Charset:  random.LowercaseRuneset,
+				MinChars: 1,
+			},
+			&random.CharsetRule{
+				Charset:  random.UppercaseRuneset,
+				MinChars: 1,
+			},
+			&random.CharsetRule{
+				Charset:  random.NumericRuneset,
+				MinChars: 1,
+			},
+			&random.CharsetRule{
+				Charset:  random.ShortSymbolRuneset,
+				MinChars: 1,
+			},
+		},
+	}
+	sys := &logical.StaticSystemView{
+		PasswordPolicies: map[string]logical.PasswordPolicy{
+			policyName: logical.PasswordPolicy(expectedPolicy),
+		},
+	}
+
+	client, server := plugin.TestGRPCConn(t, func(s *grpc.Server) {
+		pb.RegisterSystemViewServer(s, &gRPCSystemViewServer{
+			impl: sys,
+		})
+	})
+	defer server.Stop()
+	defer client.Close()
+
+	testSystemView := newGRPCSystemView(client)
+
+	ctx, cancel := context.WithTimeout(context.Background(), 100*time.Millisecond)
+	defer cancel()
+
+	password, err := testSystemView.GeneratePasswordFromPolicy(ctx, policyName)
+	if err != nil {
+		t.Fatalf("no error expected, got: %s", err)
+	}
+
+	passRunes := []rune(password)
+
+	if len(passRunes) != expectedPolicy.Length {
+		t.Fatalf("Generated password should have length %d but was %d", expectedPolicy.Length, len(passRunes))
+	}
+
+	for _, rule := range expectedPolicy.Rules {
+		if !rule.Pass(passRunes) {
+			t.Fatalf("Password [%s] did not pass rule: %#v", password, rule)
+		}
+	}
+}