fix: smarter secret masking based on secret length (#8629)

Co-authored-by: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

backend/windmill-api-integration-tests/tests/sensitive_log_masking.rs

@@ -215,8 +215,8 @@ export async function main() {
                 "scenario 1: secret value leaked in logs\nLogs:\n{logs1}"
             );
             assert!(
-                logs1.contains("The secret value is: alp*****"),
-                "scenario 1: expected masked output with first 3 chars\nLogs:\n{logs1}"
+                logs1.contains("The secret value is: alp*****k2m"),
+                "scenario 1: expected masked output with first 3 + last 3 chars\nLogs:\n{logs1}"
             );
             assert!(
                 logs1.contains("[windmill] secret value was masked for security reasons, use string transformations to display full value"),
@@ -277,11 +277,11 @@ export async function main() {
                 "scenario 3: secret2 leaked\nLogs:\n{logs3}"
             );
             assert!(
-                logs3.contains("secret1=alp*****"),
+                logs3.contains("secret1=alp*****k2m"),
                 "scenario 3: secret1 not masked\nLogs:\n{logs3}"
             );
             assert!(
-                logs3.contains("secret2=bet*****"),
+                logs3.contains("secret2=bet*****n3p"),
                 "scenario 3: secret2 not masked\nLogs:\n{logs3}"
             );
 
@@ -309,7 +309,7 @@ export async function main() {
                 "scenario 4: secret leaked mid-string\nLogs:\n{logs4}"
             );
             assert!(
-                logs4.contains("token=alp*****&user=bob&format=json"),
+                logs4.contains("token=alp*****k2m&user=bob&format=json"),
                 "scenario 4: mid-string masking failed\nLogs:\n{logs4}"
             );
 
@@ -338,7 +338,7 @@ export async function main() {
                 !logs5.contains(secret2),
                 "scenario 5: secret leaked\nLogs:\n{logs5}"
             );
-            let mask_count = logs5.matches("bet*****").count();
+            let mask_count = logs5.matches("bet*****n3p").count();
             assert!(
                 mask_count >= 3,
                 "scenario 5: expected >= 3 masked occurrences, found {mask_count}\nLogs:\n{logs5}"
@@ -374,7 +374,7 @@ export async function main() {
                 "scenario 6: encrypted password leaked\nLogs:\n{logs6}"
             );
             assert!(
-                logs6.contains("password is: enc*****"),
+                logs6.contains("password is: enc*****q5r"),
                 "scenario 6: encrypted password not masked\nLogs:\n{logs6}"
             );
 
@@ -403,7 +403,7 @@ export async function main() {
                 "scenario 7: resource secret leaked\nLogs:\n{logs7}"
             );
             assert!(
-                logs7.contains("db password: res*****"),
+                logs7.contains("db password: res*****7t2"),
                 "scenario 7: resource secret not masked\nLogs:\n{logs7}"
             );
             // Non-secret field should remain visible

backend/windmill-common/src/sensitive_log_masks.rs

@@ -88,8 +88,16 @@ pub fn snapshot(job_id: &Uuid) -> Option<MaskSnapshot> {
     let replacements: Vec<String> = sorted
         .iter()
         .map(|s| {
-            let prefix: String = s.chars().take(3).collect();
-            format!("{}*****", prefix)
+            let char_count = s.chars().count();
+            if char_count > 20 {
+                let prefix: String = s.chars().take(3).collect();
+                let suffix: String = s.chars().skip(char_count - 3).collect();
+                format!("{}*****{}", prefix, suffix)
+            } else {
+                let first: String = s.chars().take(1).collect();
+                let last: String = s.chars().skip(char_count - 1).collect();
+                format!("{}*****{}", first, last)
+            }
         })
         .collect();