Prevent hash error bcrypt.ErrPasswordTooLong for passwords > 72 bytes in length (#397)

* Truncating passwords that are longer than 72 bytes (#396)

* Adding changelog entry (#396)

* Updating changelog entry and docs (#396)

* Updating changelog entry (#396)

* updated comment msg

Author: bendbennett

.changes/unreleased/BUG FIXES-20230412-132501.yaml

@@ -0,0 +1,6 @@
+kind: BUG FIXES
+body: 'resource/random_password: Prevent error with `bcrypt` by truncating the bytes
+  that are hashed to a maximum length of 72'
+time: 2023-04-12T13:25:01.113462+01:00
+custom:
+  Issue: "397"

docs/resources/password.md

@@ -53,7 +53,7 @@ resource "aws_db_instance" "example" {
 
 ### Read-Only
 
-- `bcrypt_hash` (String, Sensitive) A bcrypt hash of the generated random string.
+- `bcrypt_hash` (String, Sensitive) A bcrypt hash of the generated random string. **NOTE**: If the generated random string is greater than 72 bytes in length, `bcrypt_hash` will contain a hash of the first 72 bytes.
 - `id` (String) A static value used internally by Terraform, this should not be referenced in configurations.
 - `result` (String, Sensitive) The generated random string.
 

internal/provider/resource_password.go

@@ -535,8 +535,18 @@ func upgradePasswordStateV2toV3(ctx context.Context, req resource.UpgradeStateRe
 	resp.Diagnostics.Append(resp.State.Set(ctx, passwordDataV3)...)
 }
 
+// generateHash truncates strings that are longer than 72 bytes in
+// order to avoid the error returned from bcrypt.GenerateFromPassword
+// in versions v0.5.0 and above: https://pkg.go.dev/golang.org/x/[email protected]/bcrypt#GenerateFromPassword
 func generateHash(toHash string) (string, error) {
-	hash, err := bcrypt.GenerateFromPassword([]byte(toHash), bcrypt.DefaultCost)
+	bytesHash := []byte(toHash)
+	bytesToHash := bytesHash
+
+	if len(bytesHash) > 72 {
+		bytesToHash = bytesHash[:72]
+	}
+
+	hash, err := bcrypt.GenerateFromPassword(bytesToHash, bcrypt.DefaultCost)
 
 	return string(hash), err
 }
@@ -693,9 +703,11 @@ func passwordSchemaV3() schema.Schema {
 			},
 
 			"bcrypt_hash": schema.StringAttribute{
-				Description: "A bcrypt hash of the generated random string.",
-				Computed:    true,
-				Sensitive:   true,
+				Description: "A bcrypt hash of the generated random string. " +
+					"**NOTE**: If the generated random string is greater than 72 bytes in length, " +
+					"`bcrypt_hash` will contain a hash of the first 72 bytes.",
+				Computed:  true,
+				Sensitive: true,
 				PlanModifiers: []planmodifier.String{
 					stringplanmodifier.UseStateForUnknown(),
 				},
@@ -805,9 +817,11 @@ func passwordSchemaV2() schema.Schema {
 			},
 
 			"bcrypt_hash": schema.StringAttribute{
-				Description: "A bcrypt hash of the generated random string.",
-				Computed:    true,
-				Sensitive:   true,
+				Description: "A bcrypt hash of the generated random string. " +
+					"**NOTE**: If the generated random string is greater than 72 bytes in length, " +
+					"`bcrypt_hash` will contain a hash of the first 72 bytes.",
+				Computed:  true,
+				Sensitive: true,
 			},
 
 			"id": schema.StringAttribute{
@@ -903,9 +917,11 @@ func passwordSchemaV1() schema.Schema {
 			},
 
 			"bcrypt_hash": schema.StringAttribute{
-				Description: "A bcrypt hash of the generated random string.",
-				Computed:    true,
-				Sensitive:   true,
+				Description: "A bcrypt hash of the generated random string. " +
+					"**NOTE**: If the generated random string is greater than 72 bytes in length, " +
+					"`bcrypt_hash` will contain a hash of the first 72 bytes.",
+				Computed:  true,
+				Sensitive: true,
 			},
 
 			"id": schema.StringAttribute{

internal/provider/resource_password_test.go

@@ -28,7 +28,7 @@ func TestGenerateHash(t *testing.T) {
 	}{
 		"defaults": {
 			input: random.StringParams{
-				Length:  32, // Required
+				Length:  73, // Required
 				Lower:   true,
 				Numeric: true,
 				Special: true,
@@ -111,7 +111,7 @@ func TestAccResourcePassword_BcryptHash(t *testing.T) {
 		Steps: []resource.TestStep{
 			{
 				Config: `resource "random_password" "test" {
-							length = 12
+							length = 73
 						}`,
 				Check: resource.ComposeTestCheckFunc(
 					testExtractResourceAttr("random_password.test", "bcrypt_hash", &bcryptHash),