auth: support caching of values retrieves from Azure CLI to avoid unnecessary repeated invocations

sdk/auth/azure_cli_authorizer.go

@@ -5,7 +5,6 @@ package auth
 
 import (
 	"context"
-	"errors"
 	"fmt"
 	"net/http"
 	"os"
@@ -60,11 +59,6 @@ func (a *AzureCliAuthorizer) Token(_ context.Context, _ *http.Request) (*oauth2.
 
 	azArgs := []string{"account", "get-access-token"}
 
-	// verify that the Azure CLI supports MSAL - ADAL is no longer supported
-	err := azurecli.CheckAzVersion(azurecli.MsalVersion, nil)
-	if err != nil {
-		return nil, fmt.Errorf("checking the version of the Azure CLI: %+v", err)
-	}
 	scope, err := environments.Scope(a.conf.Api)
 	if err != nil {
 		return nil, fmt.Errorf("determining scope for %q: %+v", a.conf.Api.Name(), err)
@@ -78,7 +72,7 @@ func (a *AzureCliAuthorizer) Token(_ context.Context, _ *http.Request) (*oauth2.
 	}
 
 	var token azureCliToken
-	if err := azurecli.JSONUnmarshalAzCmd(&token, azArgs...); err != nil {
+	if err = azurecli.JSONUnmarshalAzCmd(false, &token, azArgs...); err != nil {
 		return nil, err
 	}
 
@@ -114,11 +108,6 @@ func (a *AzureCliAuthorizer) AuxiliaryTokens(_ context.Context, _ *http.Request)
 
 	azArgs := []string{"account", "get-access-token"}
 
-	// verify that the Azure CLI supports MSAL - ADAL is no longer supported
-	err := azurecli.CheckAzVersion(AzureCliMsalVersion, nil)
-	if err != nil {
-		return nil, fmt.Errorf("checking the version of the Azure CLI: %+v", err)
-	}
 	scope, err := environments.Scope(a.conf.Api)
 	if err != nil {
 		return nil, fmt.Errorf("determining scope for %q: %+v", a.conf.Api.Name(), err)
@@ -130,7 +119,7 @@ func (a *AzureCliAuthorizer) AuxiliaryTokens(_ context.Context, _ *http.Request)
 		argsWithTenant := append(azArgs, "--tenant", tenantId)
 
 		var token azureCliToken
-		if err := azurecli.JSONUnmarshalAzCmd(&token, argsWithTenant...); err != nil {
+		if err = azurecli.JSONUnmarshalAzCmd(false, &token, argsWithTenant...); err != nil {
 			return nil, err
 		}
 
@@ -143,12 +132,6 @@ func (a *AzureCliAuthorizer) AuxiliaryTokens(_ context.Context, _ *http.Request)
 	return tokens, nil
 }
 
-const (
-	AzureCliMinimumVersion   = "2.0.81"
-	AzureCliMsalVersion      = "2.30.0"
-	AzureCliNextMajorVersion = "3.0.0"
-)
-
 // azureCliConfig configures an AzureCliAuthorizer.
 type azureCliConfig struct {
 	Api environments.Api
@@ -165,27 +148,35 @@ type azureCliConfig struct {
 
 // newAzureCliConfig validates the supplied tenant ID and returns a new azureCliConfig.
 func newAzureCliConfig(api environments.Api, tenantId string, auxiliaryTenantIds []string) (*azureCliConfig, error) {
-	var err error
-
-	// check az-cli version
-	nextMajor := azurecli.NextMajorVersion
-	if err = azurecli.CheckAzVersion(azurecli.MinimumVersion, &nextMajor); err != nil {
+	// check az-cli version, ensure that MSAL is supported
+	if err := azurecli.CheckAzVersion(); err != nil {
 		return nil, err
 	}
 
-	// check tenant ID
-	tenantId, err = azurecli.CheckTenantID(tenantId)
-	if err != nil {
-		return nil, err
+	// obtain default tenant ID if no tenant ID was provided
+	if strings.TrimSpace(tenantId) == "" {
+		if defaultTenantId, err := azurecli.GetDefaultTenantID(); err != nil {
+			return nil, fmt.Errorf("tenant ID was not specified and the default tenant ID could not be determined: %v", err)
+		} else if defaultTenantId == nil {
+			return nil, fmt.Errorf("tenant ID was not specified and the default tenant ID could not be determined")
+		} else {
+			tenantId = *defaultTenantId
+		}
 	}
-	if tenantId == "" {
-		return nil, errors.New("invalid tenantId or unable to determine tenantId")
+
+	// validate tenant ID
+	if valid, err := azurecli.ValidateTenantID(tenantId); err != nil {
+		return nil, err
+	} else if !valid {
+		return nil, fmt.Errorf("invalid tenant ID was provided")
 	}
 
 	// get the default subscription ID
-	subscriptionId, err := azurecli.GetDefaultSubscriptionID()
-	if err != nil {
+	var subscriptionId string
+	if defaultSubscriptionId, err := azurecli.GetDefaultSubscriptionID(); err != nil {
 		return nil, err
+	} else if defaultSubscriptionId != nil {
+		subscriptionId = *defaultSubscriptionId
 	}
 
 	return &azureCliConfig{

sdk/internal/azurecli/azcli.go

@@ -7,6 +7,7 @@ import (
 	"bytes"
 	"encoding/json"
 	"fmt"
+	"log"
 	"os/exec"
 	"regexp"
 	"strings"
@@ -15,41 +16,29 @@ import (
 )
 
 // CheckAzVersion tries to determine the version of Azure CLI in the path and checks for a compatible version
-func CheckAzVersion(minVersion string, nextMajorVersion *string) error {
-	var cliVersion *struct {
-		AzureCli          *string      `json:"azure-cli,omitempty"`
-		AzureCliCore      *string      `json:"azure-cli-core,omitempty"`
-		AzureCliTelemetry *string      `json:"azure-cli-telemetry,omitempty"`
-		Extensions        *interface{} `json:"extensions,omitempty"`
-	}
-	err := JSONUnmarshalAzCmd(&cliVersion, "version")
+func CheckAzVersion() error {
+	currentVersion, err := getAzVersion()
 	if err != nil {
-		return fmt.Errorf("could not parse Azure CLI version: %v", err)
-	}
-
-	if cliVersion.AzureCli == nil {
-		return fmt.Errorf("could not detect Azure CLI version. Please ensure you have installed Azure CLI version %s or newer", minVersion)
+		return err
 	}
 
-	actual, err := version.NewVersion(*cliVersion.AzureCli)
+	actual, err := version.NewVersion(*currentVersion)
 	if err != nil {
-		return fmt.Errorf("could not parse detected Azure CLI version %q: %+v", *cliVersion.AzureCli, err)
+		return fmt.Errorf("could not parse detected Azure CLI version %q: %+v", *currentVersion, err)
 	}
 
-	supported, err := version.NewVersion(minVersion)
+	supported, err := version.NewVersion(MinimumVersion)
 	if err != nil {
 		return fmt.Errorf("could not parse supported Azure CLI version: %+v", err)
 	}
 
-	if nextMajorVersion != nil {
-		nextMajor, err := version.NewVersion(*nextMajorVersion)
-		if err != nil {
-			return fmt.Errorf("could not parse next major Azure CLI version: %+v", err)
-		}
+	nextMajor, err := version.NewVersion(NextMajorVersion)
+	if err != nil {
+		return fmt.Errorf("could not parse next major Azure CLI version: %+v", err)
+	}
 
-		if nextMajor.LessThanOrEqual(actual) {
-			return fmt.Errorf("unsupported Azure CLI version %q detected, please install a version newer than %s but older than %s", actual, supported, nextMajor)
-		}
+	if nextMajor.LessThanOrEqual(actual) {
+		return fmt.Errorf("unsupported Azure CLI version %q detected, please install a version newer than %s but older than %s", actual, supported, nextMajor)
 	}
 
 	if actual.LessThan(supported) {
@@ -59,68 +48,108 @@ func CheckAzVersion(minVersion string, nextMajorVersion *string) error {
 	return nil
 }
 
+// ValidateTenantID validates the supplied tenant ID, and tries to determine the default tenant if a valid one is not supplied.
+func ValidateTenantID(tenantId string) (bool, error) {
+	validTenantId, err := regexp.MatchString("^[a-zA-Z0-9._-]+$", tenantId)
+	if err != nil {
+		return false, fmt.Errorf("could not parse tenant ID %q: %s", tenantId, err)
+	}
+
+	return validTenantId, nil
+}
+
+// GetDefaultTenantID tries to determine the default tenant
+func GetDefaultTenantID() (*string, error) {
+	var account struct {
+		TenantID string `json:"tenantId"`
+	}
+	if err := JSONUnmarshalAzCmd(true, &account, "account", "show"); err != nil {
+		return nil, fmt.Errorf("obtaining tenant ID: %s", err)
+	}
+
+	return &account.TenantID, nil
+}
+
 // GetDefaultSubscriptionID tries to determine the default subscription
-func GetDefaultSubscriptionID() (string, error) {
+func GetDefaultSubscriptionID() (*string, error) {
 	var account struct {
 		SubscriptionID string `json:"id"`
 	}
-	err := JSONUnmarshalAzCmd(&account, "account", "show")
+	err := JSONUnmarshalAzCmd(true, &account, "account", "show")
 	if err != nil {
-		return "", fmt.Errorf("obtaining subscription ID: %s", err)
+		return nil, fmt.Errorf("obtaining subscription ID: %s", err)
 	}
 
-	return account.SubscriptionID, nil
+	return &account.SubscriptionID, nil
 }
 
-// CheckTenantID validates the supplied tenant ID, and tries to determine the default tenant if a valid one is not supplied.
-func CheckTenantID(tenantId string) (string, error) {
-	validTenantId, err := regexp.MatchString("^[a-zA-Z0-9._-]+$", tenantId)
+// getAzVersion tries to determine the version of Azure CLI in the path.
+func getAzVersion() (*string, error) {
+	var cliVersion *struct {
+		AzureCli          *string      `json:"azure-cli,omitempty"`
+		AzureCliCore      *string      `json:"azure-cli-core,omitempty"`
+		AzureCliTelemetry *string      `json:"azure-cli-telemetry,omitempty"`
+		Extensions        *interface{} `json:"extensions,omitempty"`
+	}
+	err := JSONUnmarshalAzCmd(true, &cliVersion, "version")
 	if err != nil {
-		return "", fmt.Errorf("could not parse tenant ID %q: %s", tenantId, err)
+		return nil, fmt.Errorf("could not parse Azure CLI version: %v", err)
 	}
 
-	if !validTenantId {
-		var account struct {
-			ID       string `json:"id"`
-			TenantID string `json:"tenantId"`
-		}
-		err := JSONUnmarshalAzCmd(&account, "account", "show")
-		if err != nil {
-			return "", fmt.Errorf("obtaining tenant ID: %s", err)
-		}
-		tenantId = account.TenantID
+	if cliVersion.AzureCli == nil {
+		return nil, fmt.Errorf("could not detect Azure CLI version")
 	}
 
-	return tenantId, nil
+	return cliVersion.AzureCli, nil
 }
 
-// JSONUnmarshalAzCmd executes an Azure CLI command and unmarshalls the JSON output.
-func JSONUnmarshalAzCmd(i interface{}, arg ...string) error {
+// JSONUnmarshalAzCmd executes an Azure CLI command and unmarshalls the JSON output, optionally retrieving from and
+// populating the command result cache, to avoid unnecessary repeated invocations of Azure CLI.
+func JSONUnmarshalAzCmd(cacheable bool, i interface{}, arg ...string) error {
 	var stderr bytes.Buffer
 	var stdout bytes.Buffer
 
 	arg = append(arg, "-o=json")
-	cmd := exec.Command("az", arg...)
-	cmd.Stderr = &stderr
-	cmd.Stdout = &stdout
-
-	if err := cmd.Start(); err != nil {
-		err := fmt.Errorf("launching Azure CLI: %+v", err)
-		if stdErrStr := stderr.String(); stdErrStr != "" {
-			err = fmt.Errorf("%s: %s", err, strings.TrimSpace(stdErrStr))
+	argstring := strings.Join(arg, " ")
+
+	var result []byte
+	if cacheable {
+		if cachedResult, ok := cache.Get(argstring); ok {
+			result = cachedResult
 		}
-		return err
 	}
 
-	if err := cmd.Wait(); err != nil {
-		err := fmt.Errorf("running Azure CLI: %+v", err)
-		if stdErrStr := stderr.String(); stdErrStr != "" {
-			err = fmt.Errorf("%s: %s", err, strings.TrimSpace(stdErrStr))
+	if result == nil {
+		log.Printf("[DEBUG] az-cli invocation: az %s", argstring)
+
+		cmd := exec.Command("az", arg...)
+		cmd.Stderr = &stderr
+		cmd.Stdout = &stdout
+
+		if err := cmd.Start(); err != nil {
+			err := fmt.Errorf("launching Azure CLI: %+v", err)
+			if stdErrStr := stderr.String(); stdErrStr != "" {
+				err = fmt.Errorf("%s: %s", err, strings.TrimSpace(stdErrStr))
+			}
+			return err
+		}
+
+		if err := cmd.Wait(); err != nil {
+			err := fmt.Errorf("running Azure CLI: %+v", err)
+			if stdErrStr := stderr.String(); stdErrStr != "" {
+				err = fmt.Errorf("%s: %s", err, strings.TrimSpace(stdErrStr))
+			}
+			return err
+		}
+
+		result = stdout.Bytes()
+
+		if cacheable {
+			cache.Set(argstring, result)
 		}
-		return err
 	}
 
-	if err := json.Unmarshal(stdout.Bytes(), &i); err != nil {
+	if err := json.Unmarshal(result, &i); err != nil {
 		return fmt.Errorf("unmarshaling the output of Azure CLI: %v", err)
 	}
 

sdk/internal/azurecli/cache.go

@@ -0,0 +1,24 @@
+package azurecli
+
+var cache *cachedCliData
+
+type cachedCliData struct {
+	data map[string][]byte
+}
+
+func (c *cachedCliData) Set(index string, data []byte) {
+	c.data[index] = data
+}
+
+func (c *cachedCliData) Get(index string) ([]byte, bool) {
+	if data, ok := c.data[index]; ok {
+		return data, true
+	}
+	return nil, false
+}
+
+func init() {
+	cache = &cachedCliData{
+		data: make(map[string][]byte),
+	}
+}

sdk/internal/azurecli/versions.go

@@ -4,7 +4,12 @@
 package azurecli
 
 const (
-	MinimumVersion   = "2.0.81"
-	MsalVersion      = "2.30.0"
+	// MsalVersion is the first known version of Azure CLI to support MSAL / v2 tokens
+	MsalVersion = "2.30.0"
+
+	// MinimumVersion is the oldest supported version of Azure CLI by this package
+	MinimumVersion = "2.0.81"
+
+	// NextMajorVersion is the next (possibly upcoming) major version that is not yet supported by this package
 	NextMajorVersion = "3.0.0"
 )