Support policy variable replacement (#7085)

This PR supports iam and bucket policies to have
policy variable replacements in resource and
condition key values.

For example
- ${aws:username}
- ${aws:userid}

pkg/policy/condition/binaryequalsfunc.go

@@ -51,7 +51,8 @@ func (f binaryEqualsFunc) evaluate(values map[string][]string) bool {
 		requestValue = values[f.k.Name()]
 	}
 
-	return !f.values.Intersection(set.CreateStringSet(requestValue...)).IsEmpty()
+	fvalues := f.values.ApplyFunc(substFuncFromValues(values))
+	return !fvalues.Intersection(set.CreateStringSet(requestValue...)).IsEmpty()
 }
 
 // key() - returns condition key which is used by this condition function.

pkg/policy/condition/key.go

@@ -33,49 +33,58 @@ const (
 
 	// S3XAmzServerSideEncryption - key representing x-amz-server-side-encryption HTTP header applicable
 	// to PutObject API only.
-	S3XAmzServerSideEncryption = "s3:x-amz-server-side-encryption"
+	S3XAmzServerSideEncryption Key = "s3:x-amz-server-side-encryption"
 
 	// S3XAmzServerSideEncryptionCustomerAlgorithm - key representing
 	// x-amz-server-side-encryption-customer-algorithm HTTP header applicable to PutObject API only.
-	S3XAmzServerSideEncryptionCustomerAlgorithm = "s3:x-amz-server-side-encryption-customer-algorithm"
+	S3XAmzServerSideEncryptionCustomerAlgorithm Key = "s3:x-amz-server-side-encryption-customer-algorithm"
 
 	// S3XAmzMetadataDirective - key representing x-amz-metadata-directive HTTP header applicable to
 	// PutObject API only.
-	S3XAmzMetadataDirective = "s3:x-amz-metadata-directive"
+	S3XAmzMetadataDirective Key = "s3:x-amz-metadata-directive"
 
 	// S3XAmzStorageClass - key representing x-amz-storage-class HTTP header applicable to PutObject API
 	// only.
-	S3XAmzStorageClass = "s3:x-amz-storage-class"
+	S3XAmzStorageClass Key = "s3:x-amz-storage-class"
 
 	// S3LocationConstraint - key representing LocationConstraint XML tag of CreateBucket API only.
-	S3LocationConstraint = "s3:LocationConstraint"
+	S3LocationConstraint Key = "s3:LocationConstraint"
 
 	// S3Prefix - key representing prefix query parameter of ListBucket API only.
-	S3Prefix = "s3:prefix"
+	S3Prefix Key = "s3:prefix"
 
 	// S3Delimiter - key representing delimiter query parameter of ListBucket API only.
-	S3Delimiter = "s3:delimiter"
+	S3Delimiter Key = "s3:delimiter"
 
 	// S3MaxKeys - key representing max-keys query parameter of ListBucket API only.
-	S3MaxKeys = "s3:max-keys"
+	S3MaxKeys Key = "s3:max-keys"
 
 	// AWSReferer - key representing Referer header of any API.
-	AWSReferer = "aws:Referer"
+	AWSReferer Key = "aws:Referer"
 
 	// AWSSourceIP - key representing client's IP address (not intermittent proxies) of any API.
-	AWSSourceIP = "aws:SourceIp"
+	AWSSourceIP Key = "aws:SourceIp"
 
 	// AWSUserAgent - key representing UserAgent header for any API.
-	AWSUserAgent = "aws:UserAgent"
+	AWSUserAgent Key = "aws:UserAgent"
 
 	// AWSSecureTransport - key representing if the clients request is authenticated or not.
-	AWSSecureTransport = "aws:SecureTransport"
+	AWSSecureTransport Key = "aws:SecureTransport"
 
 	// AWSCurrentTime - key representing the current time.
-	AWSCurrentTime = "aws:CurrentTime"
+	AWSCurrentTime Key = "aws:CurrentTime"
 
 	// AWSEpochTime - key representing the current epoch time.
-	AWSEpochTime = "aws:EpochTime"
+	AWSEpochTime Key = "aws:EpochTime"
+
+	// AWSPrincipalType - user principal type currently supported values are "User" and "Anonymous".
+	AWSPrincipalType Key = "aws:principaltype"
+
+	// AWSUserID - user unique ID, in Minio this value is same as your user Access Key.
+	AWSUserID Key = "aws:userid"
+
+	// AWSUsername - user friendly name, in Minio this value is same as your user Access Key.
+	AWSUsername Key = "aws:username"
 )
 
 // AllSupportedKeys - is list of all all supported keys.
@@ -95,6 +104,9 @@ var AllSupportedKeys = []Key{
 	AWSSecureTransport,
 	AWSCurrentTime,
 	AWSEpochTime,
+	AWSPrincipalType,
+	AWSUserID,
+	AWSUsername,
 	// Add new supported condition keys.
 }
 
@@ -106,6 +118,21 @@ var CommonKeys = []Key{
 	AWSSecureTransport,
 	AWSCurrentTime,
 	AWSEpochTime,
+	AWSPrincipalType,
+	AWSUserID,
+	AWSUsername,
+}
+
+func substFuncFromValues(values map[string][]string) func(string) string {
+	return func(v string) string {
+		for _, key := range CommonKeys {
+			// Empty values are not supported for policy variables.
+			if rvalues, ok := values[key.Name()]; ok && rvalues[0] != "" {
+				v = strings.Replace(v, key.VarName(), rvalues[0], -1)
+			}
+		}
+		return v
+	}
 }
 
 // IsValid - checks if key is valid or not.
@@ -128,6 +155,11 @@ func (key Key) MarshalJSON() ([]byte, error) {
 	return json.Marshal(string(key))
 }
 
+// VarName - returns variable key name, such as "${aws:username}"
+func (key Key) VarName() string {
+	return fmt.Sprintf("${%s}", key)
+}
+
 // Name - returns key name which is stripped value of prefixes "aws:" and "s3:"
 func (key Key) Name() string {
 	keyString := string(key)

pkg/policy/condition/stringequalsfunc.go

@@ -50,7 +50,8 @@ func (f stringEqualsFunc) evaluate(values map[string][]string) bool {
 		requestValue = values[f.k.Name()]
 	}
 
-	return !f.values.Intersection(set.CreateStringSet(requestValue...)).IsEmpty()
+	fvalues := f.values.ApplyFunc(substFuncFromValues(values))
+	return !fvalues.Intersection(set.CreateStringSet(requestValue...)).IsEmpty()
 }
 
 // key() - returns condition key which is used by this condition function.

pkg/policy/condition/stringequalsignorecasefunc.go

@@ -50,11 +50,14 @@ func (f stringEqualsIgnoreCaseFunc) evaluate(values map[string][]string) bool {
 		requestValue = values[f.k.Name()]
 	}
 
+	fvalues := f.values.ApplyFunc(substFuncFromValues(values))
+
 	for _, v := range requestValue {
-		if !f.values.FuncMatch(strings.EqualFold, v).IsEmpty() {
+		if !fvalues.FuncMatch(strings.EqualFold, v).IsEmpty() {
 			return true
 		}
 	}
+
 	return false
 }
 

pkg/policy/condition/stringlikefunc.go

@@ -51,8 +51,10 @@ func (f stringLikeFunc) evaluate(values map[string][]string) bool {
 		requestValue = values[f.k.Name()]
 	}
 
+	fvalues := f.values.ApplyFunc(substFuncFromValues(values))
+
 	for _, v := range requestValue {
-		if !f.values.FuncMatch(wildcard.Match, v).IsEmpty() {
+		if !fvalues.FuncMatch(wildcard.Match, v).IsEmpty() {
 			return true
 		}
 	}