Modify http cred provider resolving logic

.changelog/0593bfc1f00841febcb73c7957839f01.json

@@ -0,0 +1,10 @@
+{
+    "id": "0593bfc1-f008-41fe-bcb7-3c7957839f01",
+    "type": "feature",
+    "collapse": true,
+    "description": "Add support for dynamic auth token from file and EKS container host in absolute/relative URIs in the HTTP credential provider.",
+    "modules": [
+        "config",
+        "credentials"
+    ]
+}

config/resolve_credentials.go

@@ -3,7 +3,10 @@ package config
 import (
 	"context"
 	"fmt"
+	"io/ioutil"
+	"net"
 	"net/url"
+	"os"
 	"time"
 
 	"github.com/aws/aws-sdk-go-v2/aws"
@@ -21,11 +24,33 @@ import (
 
 const (
 	// valid credential source values
-	credSourceEc2Metadata  = "Ec2InstanceMetadata"
-	credSourceEnvironment  = "Environment"
-	credSourceECSContainer = "EcsContainer"
+	credSourceEc2Metadata      = "Ec2InstanceMetadata"
+	credSourceEnvironment      = "Environment"
+	credSourceECSContainer     = "EcsContainer"
+	httpProviderAuthFileEnvVar = "AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE"
 )
 
+// direct representation of the IPv4 address for the ECS container
+// "169.254.170.2"
+var ecsContainerIPv4 net.IP = []byte{
+	169, 254, 170, 2,
+}
+
+// direct representation of the IPv4 address for the EKS container
+// "169.254.170.23"
+var eksContainerIPv4 net.IP = []byte{
+	169, 254, 170, 23,
+}
+
+// direct representation of the IPv6 address for the EKS container
+// "fd00:ec2::23"
+var eksContainerIPv6 net.IP = []byte{
+	0xFD, 0, 0xE, 0xC2,
+	0, 0, 0, 0,
+	0, 0, 0, 0,
+	0, 0, 0, 0x23,
+}
+
 var (
 	ecsContainerEndpoint = "http://169.254.170.2" // not constant to allow for swapping during unit-testing
 )
@@ -222,6 +247,36 @@ func processCredentials(ctx context.Context, cfg *aws.Config, sharedConfig *Shar
 	return nil
 }
 
+// isAllowedHost allows host to be loopback or known ECS/EKS container IPs
+//
+// host can either be an IP address OR an unresolved hostname - resolution will
+// be automatically performed in the latter case
+func isAllowedHost(host string) (bool, error) {
+	if ip := net.ParseIP(host); ip != nil {
+		return isIPAllowed(ip), nil
+	}
+
+	addrs, err := lookupHostFn(host)
+	if err != nil {
+		return false, err
+	}
+
+	for _, addr := range addrs {
+		if ip := net.ParseIP(addr); ip == nil || !isIPAllowed(ip) {
+			return false, nil
+		}
+	}
+
+	return true, nil
+}
+
+func isIPAllowed(ip net.IP) bool {
+	return ip.IsLoopback() ||
+		ip.Equal(ecsContainerIPv4) ||
+		ip.Equal(eksContainerIPv4) ||
+		ip.Equal(eksContainerIPv6)
+}
+
 func resolveLocalHTTPCredProvider(ctx context.Context, cfg *aws.Config, endpointURL, authToken string, configs configs) error {
 	var resolveErr error
 
@@ -232,10 +287,12 @@ func resolveLocalHTTPCredProvider(ctx context.Context, cfg *aws.Config, endpoint
 		host := parsed.Hostname()
 		if len(host) == 0 {
 			resolveErr = fmt.Errorf("unable to parse host from local HTTP cred provider URL")
-		} else if isLoopback, loopbackErr := isLoopbackHost(host); loopbackErr != nil {
-			resolveErr = fmt.Errorf("failed to resolve host %q, %v", host, loopbackErr)
-		} else if !isLoopback {
-			resolveErr = fmt.Errorf("invalid endpoint host, %q, only loopback hosts are allowed", host)
+		} else if parsed.Scheme == "http" {
+			if isAllowedHost, allowHostErr := isAllowedHost(host); allowHostErr != nil {
+				resolveErr = fmt.Errorf("failed to resolve host %q, %v", host, allowHostErr)
+			} else if !isAllowedHost {
+				resolveErr = fmt.Errorf("invalid endpoint host, %q, only loopback/ecs/eks hosts are allowed", host)
+			}
 		}
 	}
 
@@ -252,6 +309,16 @@ func resolveHTTPCredProvider(ctx context.Context, cfg *aws.Config, url, authToke
 			if len(authToken) != 0 {
 				options.AuthorizationToken = authToken
 			}
+			if authFilePath := os.Getenv(httpProviderAuthFileEnvVar); authFilePath != "" {
+				options.AuthorizationTokenProvider = endpointcreds.TokenProviderFunc(func() (string, error) {
+					var contents []byte
+					var err error
+					if contents, err = ioutil.ReadFile(authFilePath); err != nil {
+						return "", fmt.Errorf("failed to read authorization token from %v: %v", authFilePath, err)
+					}
+					return string(contents), nil
+				})
+			}
 			options.APIOptions = cfg.APIOptions
 			if cfg.Retryer != nil {
 				options.Retryer = cfg.Retryer()

credentials/endpointcreds/provider.go

@@ -36,6 +36,7 @@ import (
 	"context"
 	"fmt"
 	"net/http"
+	"strings"
 
 	"github.com/aws/aws-sdk-go-v2/aws"
 	"github.com/aws/aws-sdk-go-v2/credentials/endpointcreds/internal/client"
@@ -81,7 +82,37 @@ type Options struct {
 
 	// Optional authorization token value if set will be used as the value of
 	// the Authorization header of the endpoint credential request.
+	//
+	// When constructed from environment, the provider will use the value of
+	// AWS_CONTAINER_AUTHORIZATION_TOKEN environment variable as the token
+	//
+	// Will be overridden if AuthorizationTokenProvider is configured
 	AuthorizationToken string
+
+	// Optional auth provider func to dynamically load the auth token from a file
+	// everytime a credential is retrieved
+	//
+	// When constructed from environment, the provider will read and use the content
+	// of the file pointed to by AWS_CONTAINER_AUTHORIZATION_TOKEN_FILE environment variable
+	// as the auth token everytime credentials are retrieved
+	//
+	// Will override AuthorizationToken if configured
+	AuthorizationTokenProvider AuthTokenProvider
+}
+
+// AuthTokenProvider defines an interface to dynamically load a value to be passed
+// for the Authorization header of a credentials request.
+type AuthTokenProvider interface {
+	GetToken() (string, error)
+}
+
+// TokenProviderFunc is a func type implementing AuthTokenProvider interface
+// and enables customizing token provider behavior
+type TokenProviderFunc func() (string, error)
+
+// GetToken func retrieves auth token according to TokenProviderFunc implementation
+func (p TokenProviderFunc) GetToken() (string, error) {
+	return p()
 }
 
 // New returns a credentials Provider for retrieving AWS credentials
@@ -132,5 +163,30 @@ func (p *Provider) Retrieve(ctx context.Context) (aws.Credentials, error) {
 }
 
 func (p *Provider) getCredentials(ctx context.Context) (*client.GetCredentialsOutput, error) {
-	return p.client.GetCredentials(ctx, &client.GetCredentialsInput{AuthorizationToken: p.options.AuthorizationToken})
+	authToken, err := p.resolveAuthToken()
+	if err != nil {
+		return nil, fmt.Errorf("resolve auth token: %v", err)
+	}
+
+	return p.client.GetCredentials(ctx, &client.GetCredentialsInput{
+		AuthorizationToken: authToken,
+	})
+}
+
+func (p *Provider) resolveAuthToken() (string, error) {
+	authToken := p.options.AuthorizationToken
+
+	var err error
+	if p.options.AuthorizationTokenProvider != nil {
+		authToken, err = p.options.AuthorizationTokenProvider.GetToken()
+		if err != nil {
+			return "", err
+		}
+	}
+
+	if strings.ContainsAny(authToken, "\r\n") {
+		return "", fmt.Errorf("authorization token contains invalid newline sequence")
+	}
+
+	return authToken, nil
 }

credentials/endpointcreds/provider_test.go

@@ -108,6 +108,90 @@ func TestRetrieveStaticCredentials(t *testing.T) {
 	}
 }
 
+func TestAuthTokenProvider(t *testing.T) {
+	cases := map[string]struct {
+		AuthToken         string
+		AuthTokenProvider endpointcreds.AuthTokenProvider
+		ExpectAuthToken   string
+		ExpectError       bool
+	}{
+		"AuthToken": {
+			AuthToken:       "Basic abc123",
+			ExpectAuthToken: "Basic abc123",
+		},
+		"AuthFileToken": {
+			AuthToken: "Basic abc123",
+			AuthTokenProvider: endpointcreds.TokenProviderFunc(func() (string, error) {
+				return "Hello %20world", nil
+			}),
+			ExpectAuthToken: "Hello %20world",
+		},
+		"RetrieveFileTokenError": {
+			AuthToken: "Basic abc123",
+			AuthTokenProvider: endpointcreds.TokenProviderFunc(func() (string, error) {
+				return "", fmt.Errorf("test error")
+			}),
+			ExpectAuthToken: "Hello %20world",
+			ExpectError:     true,
+		},
+	}
+
+	for name, c := range cases {
+		t.Run(name, func(t *testing.T) {
+			orig := sdk.NowTime
+			defer func() { sdk.NowTime = orig }()
+
+			var actualToken string
+			p := endpointcreds.New("http://127.0.0.1", func(o *endpointcreds.Options) {
+				o.HTTPClient = mockClient(func(r *http.Request) (*http.Response, error) {
+					actualToken = r.Header["Authorization"][0]
+					return &http.Response{
+						StatusCode: 200,
+						Body: ioutil.NopCloser(bytes.NewReader([]byte(`{
+  "AccessKeyID": "AKID",
+  "SecretAccessKey": "SECRET"
+}`))),
+					}, nil
+				})
+				o.AuthorizationToken = c.AuthToken
+				o.AuthorizationTokenProvider = c.AuthTokenProvider
+			})
+			creds, err := p.Retrieve(context.Background())
+
+			if err != nil && !c.ExpectError {
+				t.Errorf("expect no error, got %v", err)
+			} else if err == nil && c.ExpectError {
+				t.Errorf("expect error, got nil")
+			}
+
+			if c.ExpectError {
+				return
+			}
+
+			if e, a := "AKID", creds.AccessKeyID; e != a {
+				t.Errorf("expect %v, got %v", e, a)
+			}
+			if e, a := "SECRET", creds.SecretAccessKey; e != a {
+				t.Errorf("expect %v, got %v", e, a)
+			}
+			if v := creds.SessionToken; len(v) != 0 {
+				t.Errorf("expect empty, got %v", v)
+			}
+			if e, a := c.ExpectAuthToken, actualToken; e != a {
+				t.Errorf("Expect %v, got %v", e, a)
+			}
+
+			sdk.NowTime = func() time.Time {
+				return time.Date(3000, 12, 16, 1, 30, 37, 0, time.UTC)
+			}
+
+			if creds.Expired() {
+				t.Errorf("expect not to be expired")
+			}
+		})
+	}
+}
+
 func TestFailedRetrieveCredentials(t *testing.T) {
 	p := endpointcreds.New("http://127.0.0.1", func(o *endpointcreds.Options) {
 		o.HTTPClient = mockClient(func(r *http.Request) (*http.Response, error) {