diff --git a/ui/build/environment.go b/ui/build/environment.go
new file mode 100644
index 0000000..baab101
--- /dev/null
+++ b/ui/build/environment.go
@@ -0,0 +1,152 @@
+// Copyright 2017 Google Inc. All rights reserved.
+//
+// Licensed under the Apache License, Version 2.0 (the "License");
+// you may not use this file except in compliance with the License.
+// You may obtain a copy of the License at
+//
+//     http://www.apache.org/licenses/LICENSE-2.0
+//
+// Unless required by applicable law or agreed to in writing, software
+// distributed under the License is distributed on an "AS IS" BASIS,
+// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+// See the License for the specific language governing permissions and
+// limitations under the License.
+
+package build
+
+import (
+	"bufio"
+	"fmt"
+	"io"
+	"os"
+	"strings"
+)
+
+// Environment adds a number of useful manipulation functions to the list of
+// strings returned by os.Environ() and used in exec.Cmd.Env.
+type Environment []string
+
+// OsEnvironment wraps the current environment returned by os.Environ()
+func OsEnvironment() *Environment {
+	env := Environment(os.Environ())
+	return &env
+}
+
+// Get returns the value associated with the key, and whether it exists.
+// It's equivalent to the os.LookupEnv function, but with this copy of the
+// Environment.
+func (e *Environment) Get(key string) (string, bool) {
+	for _, env := range *e {
+		if k, v, ok := decodeKeyValue(env); ok && k == key {
+			return v, true
+		}
+	}
+	return "", false
+}
+
+// Set sets the value associated with the key, overwriting the current value
+// if it exists.
+func (e *Environment) Set(key, value string) {
+	e.Unset(key)
+	*e = append(*e, key+"="+value)
+}
+
+// Unset removes the specified keys from the Environment.
+func (e *Environment) Unset(keys ...string) {
+	out := (*e)[:0]
+	for _, env := range *e {
+		if key, _, ok := decodeKeyValue(env); ok && inList(key, keys) {
+			continue
+		}
+		out = append(out, env)
+	}
+	*e = out
+}
+
+// Environ returns the []string required for exec.Cmd.Env
+func (e *Environment) Environ() []string {
+	return []string(*e)
+}
+
+// Copy returns a copy of the Environment so that independent changes may be made.
+func (e *Environment) Copy() *Environment {
+	ret := Environment(make([]string, len(*e)))
+	for i, v := range *e {
+		ret[i] = v
+	}
+	return &ret
+}
+
+// IsTrue returns whether an environment variable is set to a positive value (1,y,yes,on,true)
+func (e *Environment) IsEnvTrue(key string) bool {
+	if value, ok := e.Get(key); ok {
+		return value == "1" || value == "y" || value == "yes" || value == "on" || value == "true"
+	}
+	return false
+}
+
+// IsFalse returns whether an environment variable is set to a negative value (0,n,no,off,false)
+func (e *Environment) IsFalse(key string) bool {
+	if value, ok := e.Get(key); ok {
+		return value == "0" || value == "n" || value == "no" || value == "off" || value == "false"
+	}
+	return false
+}
+
+// AppendFromKati reads a shell script written by Kati that exports or unsets
+// environment variables, and applies those to the local Environment.
+func (e *Environment) AppendFromKati(filename string) error {
+	file, err := os.Open(filename)
+	if err != nil {
+		return err
+	}
+	defer file.Close()
+
+	return e.appendFromKati(file)
+}
+
+func (e *Environment) appendFromKati(reader io.Reader) error {
+	scanner := bufio.NewScanner(reader)
+	for scanner.Scan() {
+		text := strings.TrimSpace(scanner.Text())
+
+		if len(text) == 0 || text[0] == '#' {
+			continue
+		}
+
+		cmd := strings.SplitN(text, " ", 2)
+		if len(cmd) != 2 {
+			return fmt.Errorf("Unknown kati environment line: %q", text)
+		}
+
+		if cmd[0] == "unset" {
+			str, ok := singleUnquote(cmd[1])
+			if !ok {
+				fmt.Errorf("Failed to unquote kati line: %q", text)
+			}
+			e.Unset(str)
+		} else if cmd[0] == "export" {
+			key, value, ok := decodeKeyValue(cmd[1])
+			if !ok {
+				return fmt.Errorf("Failed to parse export: %v", cmd)
+			}
+
+			key, ok = singleUnquote(key)
+			if !ok {
+				return fmt.Errorf("Failed to unquote kati line: %q", text)
+			}
+			value, ok = singleUnquote(value)
+			if !ok {
+				return fmt.Errorf("Failed to unquote kati line: %q", text)
+			}
+
+			e.Set(key, value)
+		} else {
+			return fmt.Errorf("Unknown kati environment command: %q", text)
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return err
+	}
+	return nil
+}