Add changes to ensure session policy is enforced in LDAP STS (#12716)

- Bonus: Fix bug in webidentity sts that doesnt parse session policy correctly.

- update ldap.go to support session policy argument

cmd/iam.go

@@ -2199,6 +2199,11 @@ func (sys *IAMSys) IsAllowedLDAPSTS(args iampolicy.Args, parentUser string) bool
 				availablePolicies[i].Statements...)
 	}
 
+	hasSessionPolicy, isAllowedSP := isAllowedBySessionPolicy(args)
+	if hasSessionPolicy {
+		return isAllowedSP && combinedPolicy.IsAllowed(args)
+	}
+
 	return combinedPolicy.IsAllowed(args)
 }
 
@@ -2263,30 +2268,9 @@ func (sys *IAMSys) IsAllowedSTS(args iampolicy.Args, parentUser string) bool {
 	args.ConditionValues["userid"] = []string{parentUser}
 
 	// Now check if we have a sessionPolicy.
-	spolicy, ok := args.Claims[iampolicy.SessionPolicyName]
+	hasSessionPolicy, isAllowedSP := isAllowedBySessionPolicy(args)
-	if ok {
+	if hasSessionPolicy {
-		spolicyStr, ok := spolicy.(string)
+		return isAllowedSP && combinedPolicy.IsAllowed(args)
-		if !ok {
-			// Sub policy if set, should be a string reject
-			// malformed/malicious requests.
-			return false
-		}
-
-		// Check if policy is parseable.
-		subPolicy, err := iampolicy.ParseConfig(bytes.NewReader([]byte(spolicyStr)))
-		if err != nil {
-			// Log any error in input session policy config.
-			logger.LogIf(GlobalContext, err)
-			return false
-		}
-
-		// Policy without Version string value reject it.
-		if subPolicy.Version == "" {
-			return false
-		}
-
-		// Sub policy is set and valid.
-		return combinedPolicy.IsAllowed(args) && subPolicy.IsAllowed(args)
 	}
 
 	// Sub policy not set, this is most common since subPolicy
@@ -2294,6 +2278,49 @@ func (sys *IAMSys) IsAllowedSTS(args iampolicy.Args, parentUser string) bool {
 	return combinedPolicy.IsAllowed(args)
 }
 
+func isAllowedBySessionPolicy(args iampolicy.Args) (hasSessionPolicy bool, isAllowed bool) {
+	hasSessionPolicy = false
+	isAllowed = false
+
+	// Now check if we have a sessionPolicy.
+	spolicy, ok := args.Claims[iampolicy.SessionPolicyName]
+	if !ok {
+		return
+	}
+
+	hasSessionPolicy = true
+
+	spolicyStr, ok := spolicy.(string)
+	if !ok {
+		// Sub policy if set, should be a string reject
+		// malformed/malicious requests.
+		return
+	}
+
+	policyBytes, err := base64.StdEncoding.DecodeString(spolicyStr)
+	if err != nil {
+		// Got a malformed base64 string
+		return
+	}
+	spolicyStr = string(policyBytes)
+
+	// Check if policy is parseable.
+	subPolicy, err := iampolicy.ParseConfig(bytes.NewReader([]byte(spolicyStr)))
+	if err != nil {
+		// Log any error in input session policy config.
+		logger.LogIf(GlobalContext, err)
+		return
+	}
+
+	// Policy without Version string value reject it.
+	if subPolicy.Version == "" {
+		return
+	}
+
+	// Sub policy is set and valid.
+	return hasSessionPolicy, subPolicy.IsAllowed(args)
+}
+
 // GetCombinedPolicy returns a combined policy combining all policies
 func (sys *IAMSys) GetCombinedPolicy(policies ...string) iampolicy.Policy {
 	// Policies were found, evaluate all of them.

docs/sts/ldap.go

@@ -23,8 +23,10 @@ import (
 	"context"
 	"flag"
 	"fmt"
+	"io/ioutil"
 	"log"
 	"net/url"
+	"os"
 
 	"github.com/minio/minio-go/v7"
 	cr "github.com/minio/minio-go/v7/pkg/credentials"
@@ -37,12 +39,24 @@ var (
 	// LDAP credentials
 	ldapUsername string
 	ldapPassword string
+
+	// Display credentials flag
+	displayCreds bool
+
+	// Bucket to list
+	bucketToList string
+
+	// Session policy file
+	sessionPolicyFile string
 )
 
 func init() {
 	flag.StringVar(&stsEndpoint, "sts-ep", "http://localhost:9000", "STS endpoint")
 	flag.StringVar(&ldapUsername, "u", "", "AD/LDAP Username")
 	flag.StringVar(&ldapPassword, "p", "", "AD/LDAP Password")
+	flag.BoolVar(&displayCreds, "d", false, "Only show generated credentials")
+	flag.StringVar(&bucketToList, "b", "", "Bucket to list (defaults to ldap username)")
+	flag.StringVar(&sessionPolicyFile, "s", "", "File containing session policy to apply to the STS request")
 }
 
 func main() {
@@ -56,11 +70,30 @@ func main() {
 	// LDAP STS API.
 
 	// Initialize LDAP credentials
-	li, _ := cr.NewLDAPIdentity(stsEndpoint, ldapUsername, ldapPassword)
+	var li *cr.Credentials
+	var err error
+	if sessionPolicyFile == "" {
+		li, err = cr.NewLDAPIdentity(stsEndpoint, ldapUsername, ldapPassword)
+	} else {
+		var policy string
+		if f, err := os.Open(sessionPolicyFile); err != nil {
+			log.Fatalf("Unable to open session policy file: %v", sessionPolicyFile, err)
+		} else {
+			bs, err := ioutil.ReadAll(f)
+			if err != nil {
+				log.Fatalf("Error reading session policy file: %v", err)
+			}
+			policy = string(bs)
+		}
+		li, err = cr.NewLDAPIdentityWithSessionPolicy(stsEndpoint, ldapUsername, ldapPassword, policy)
+	}
+	if err != nil {
+		log.Fatalf("Error initializing LDAP Identity: %v", err)
+	}
 
 	stsEndpointURL, err := url.Parse(stsEndpoint)
 	if err != nil {
-		log.Fatalf("Err: %v", err)
+		log.Fatalf("Error parsing sts endpoint: %v", err)
 	}
 
 	opts := &minio.Options{
@@ -68,22 +101,35 @@ func main() {
 		Secure: stsEndpointURL.Scheme == "https",
 	}
 
-	fmt.Println(li.Get())
+	v, err := li.Get()
+	if err != nil {
+		log.Fatalf("Error retrieving STS credentials: %v", err)
+	}
+
+	if displayCreds {
+		fmt.Println("Only displaying credentials:")
+		fmt.Println("AccessKeyID:", v.AccessKeyID)
+		fmt.Println("SecretAccessKey:", v.SecretAccessKey)
+		fmt.Println("SessionToken:", v.SessionToken)
+		return
+	}
+
 	// Use generated credentials to authenticate with MinIO server
 	minioClient, err := minio.New(stsEndpointURL.Host, opts)
 	if err != nil {
-		log.Fatalln(err)
+		log.Fatalf("Error initializing client: ", err)
 	}
 
 	// Use minIO Client object normally like the regular client.
-	fmt.Println("Calling list objects with temp creds: ")
+	if bucketToList == "" {
-	objCh := minioClient.ListObjects(context.Background(), ldapUsername, minio.ListObjectsOptions{})
+		bucketToList = ldapUsername
+	}
+	fmt.Printf("Calling list objects on bucket named `%s` with temp creds:\n===\n", bucketToList)
+	objCh := minioClient.ListObjects(context.Background(), bucketToList, minio.ListObjectsOptions{})
 	for obj := range objCh {
 		if obj.Err != nil {
-			if err != nil {
+			log.Fatalf("Listing error: %v", obj.Err)
-				log.Fatalln(err)
-			}
 		}
-		fmt.Println(obj)
+		fmt.Printf("Key: %s\nSize: %d\nLast Modified: %s\n===\n", obj.Key, obj.Size, obj.LastModified)
 	}
 }