Refactor POC into actual package (#1)

* Add internal envparser

* Update documentation

* Add GCP Secret Manager provider

* Add initial client api

* Add comment token as a const

* Flip if condition to be more readable

* Remove cmd folder

* Update property name

* Move serum.go into its own folder

internal/envparser/envparser.go

@@ -0,0 +1,85 @@
+package envparser
+
+import (
+	"bufio"
+	"fmt"
+	"os"
+	"regexp"
+	"strings"
+)
+
+const (
+	commentToken = "#"
+	kvSeparator  = "="
+	secretRegex  = `^${(?P<secretval>.+)}$`
+)
+
+var secretRe *regexp.Regexp
+
+func init() {
+	secretRe = regexp.MustCompile(secretRegex)
+}
+
+//EnvVars contains the plain text key value mappings as well as the encrypted secret key value mappings
+//parsed from an env file
+type EnvVars struct {
+	Plain   map[string]string
+	Secrets map[string]string
+}
+
+//ParseFile parses a .env file at path and returns the key value
+//mappings for plain text variables and secret variables
+func ParseFile(path string) (*EnvVars, error) {
+	f, err := os.Open(path)
+	if err != nil {
+		return nil, fmt.Errorf("error opening file %s: %s", path, err)
+	}
+	defer f.Close()
+
+	envVars := &EnvVars{
+		Plain:   make(map[string]string),
+		Secrets: make(map[string]string),
+	}
+
+	scanner := bufio.NewScanner(f)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if err := parseLine(envVars, line); err != nil {
+			return nil, fmt.Errorf("error parsing line: %s: %s", line, err)
+		}
+	}
+	if err := scanner.Err(); err != nil {
+		return nil, fmt.Errorf("error parsing file: %s", err)
+	}
+
+	return envVars, nil
+}
+
+func parseLine(envVars *EnvVars, l string) error {
+	//ignore commented line
+	//TODO: remove inline comments
+	if strings.HasPrefix(l, commentToken) {
+		return nil
+	}
+
+	//split line into two pieces (k,v) based on key value seperator
+	splits := strings.SplitN(l, kvSeparator, 2)
+	if len(splits) != 2 {
+		return fmt.Errorf("invalid format %s", l)
+	}
+
+	//key is first index, value is second
+	k := strings.TrimSpace(splits[0])
+	v := strings.TrimSpace(splits[1])
+
+	//check if value is encrypted secret
+	if secretRe.MatchString(v) {
+		//fill in secret value - replace template value with capture group "secretval"
+		envVars.Secrets[k] = secretRe.ReplaceAllString(v, "$secretval")
+		return nil
+	}
+
+	//not a secret, fill in plain text value
+	envVars.Plain[k] = v
+	return nil
+}

secretprovider/gsmanager.go

@@ -0,0 +1,44 @@
+package secretprovider
+
+import (
+	"context"
+	"fmt"
+
+	secretmanager "cloud.google.com/go/secretmanager/apiv1"
+	secretmanagerpb "google.golang.org/genproto/googleapis/cloud/secretmanager/v1"
+)
+
+//GSManager is a secret provider that communicates with Google Cloud Platform's Secret Manager
+//to decrypt secrets. Internally it uses the Google Cloud SDK.
+type GSManager struct {
+	smClient *secretmanager.Client
+}
+
+//NewGSManager return's an initialized GSManager using a new secret manager client.
+func NewGSManager() (*GSManager, error) {
+	c, err := secretmanager.NewClient(context.Background())
+	if err != nil {
+		return nil, fmt.Errorf("gsmanager: failed to initialize client: %w", err)
+	}
+
+	return &GSManager{smClient: c}, nil
+}
+
+//Decrypt will access the secret on GCP Secret Manager and return the plain text string.
+func (g *GSManager) Decrypt(secret string) (string, error) {
+	req := &secretmanagerpb.AccessSecretVersionRequest{
+		Name: secret,
+	}
+
+	result, err := g.smClient.AccessSecretVersion(context.Background(), req)
+	if err != nil {
+		return "", fmt.Errorf("gsmanager: failed to access secret version: %w", err)
+	}
+
+	return result.Payload.String(), nil
+}
+
+//Close closes the connection to the secret manager API.
+func (g *GSManager) Close() error {
+	return g.smClient.Close()
+}

secretprovider/secretprovider.go

@@ -0,0 +1,9 @@
+package secretprovider
+
+//SecretProvider is an interface that wraps the decrypt and close methods.
+//Close should be called when the secret provier is no longer needed.
+//It may be a no-op in cases where there's no underlying connection to be closed.
+type SecretProvider interface {
+	Decrypt(secret string) (string, error)
+	Close() error
+}

serum/serum.go

@@ -0,0 +1,56 @@
+package serum
+
+import (
+	"fmt"
+	"os"
+	"wingocard/serum/internal/envparser"
+	"wingocard/serum/secretprovider"
+)
+
+//Injector injects environment variables into the current running process. Key/value pairs can
+//be read in from a .env file using the load method.
+type Injector struct {
+	SecretProvider secretprovider.SecretProvider
+	envVars        *envparser.EnvVars
+}
+
+//Inject will inject the loaded environment variables into the current running process' environment.
+//Any secret values found will attempt to be decrypted using the provided secret provider.
+//The presence of secrets with a nil SecretProvider will return an error.
+func (in *Injector) Inject() error {
+	if len(in.envVars.Secrets) > 0 && in.SecretProvider == nil {
+		return fmt.Errorf("serum: error injecting env vars: secrets were loaded but the SecretProvider is nil")
+	}
+
+	//inject secrets
+	for k, v := range in.envVars.Secrets {
+		decrypted, err := in.SecretProvider.Decrypt(v)
+		if err != nil {
+			return fmt.Errorf("serum: error decrypting secret %s: %s", v, err)
+		}
+
+		if err := os.Setenv(k, decrypted); err != nil {
+			return fmt.Errorf("serum: error setting env var %s: %s", k, err)
+		}
+	}
+
+	//inject plain text vars
+	for k, v := range in.envVars.Plain {
+		if err := os.Setenv(k, v); err != nil {
+			return fmt.Errorf("serum: error setting env var %s: %s", k, err)
+		}
+	}
+	return nil
+}
+
+//Load will parse a .env file for key/value pairs and prepair them to be injected using the
+//Inject method.
+func (in *Injector) Load(path string) error {
+	envVars, err := envparser.ParseFile(path)
+	if err != nil {
+		return fmt.Errorf("serum: error loading env vars: %s", err)
+	}
+
+	in.envVars = envVars
+	return nil
+}