GHSA-6mwx-4547-5vc9 OpenBao: LDAPi ldaputil (wrong escape func)
1. DescriptionComponent`sdk/helper/ldaputil/client.go` — the shared LDAP utility library used by both the LDAP authentication backend and OpenLDAP secrets engine to construct LDAP search filters and bind DNs.Root CauseThe LDAP utility contains a **function selection error** that causes incorrect escaping of user-controlled input in LDAP filter construction. Two lines construct the `bindDN` using `EscapeLDAPValue()`:The problem: `EscapeLDAPValue()` implements **RFC 4514** escaping, which is designed for Distinguished Name (DN) components. It only escapes characters meaningful in DNs: `+`, `,`, `;`, `"`, `\`, `<`, `>`, and leading/trailing spaces.LDAP **search filters** (RFC 4515) have a different set of special characters: `*`, `(`, `)`, `\`, and NUL (`\x00`). None of these are escaped by `EscapeLDAPValue()`. The correct function is `ldap.EscapeFilter()` from the `github.com/go-ldap/ldap/v3` package.The irony: the same file uses `ldap.EscapeFilter()` correctly at lines 225-226 in `RenderUserSearchFilter()` for the `UserFilter` template path, but the `GetUserDN()` function at lines 191-193 uses the wrong escape function.Exploitation MechanicsThe filter `(&(objectClass=user)(sAMAccountName=alice)(objectClass=*))` is logically equivalent to:`sAMAccountName=alice` AND `objectClass=user` AND `objectClass=*`Since all entries match `objectClass=*`, the filter matches **any user entry** where `sAMAccountName` is `alice`, effectively ignoring the `objectClass=user` constraint. By crafting more sophisticated injections (e.g., `alice)(|(sAMAccountName=admin`), the attacker can match arbitrary different user entries.PreconditionsLDAP authentication backend must be configuredDirectory must be Active Directory (UPNDomain path) or use UserDN/UserAttr bindingAttacker controls the `username` field at login time2. Proof of ConceptThe LDAP search returns whichever entry the server ranks highest among results. In Active Directory with default sorting, this is often the oldest or alphabetically first user — potentially an administrative account.3. Impact| Impact | Detail |
|--------|--------|
| **Confidentiality** | Token bound to a different LDAP user (e.g., admin) grants access to all secrets and policies belonging to that entity |
| **Integrity** | Ability to modify secrets, write policies, or configure backends as the impersonated user |
| **Availability** | Low direct impact, but administrative access enables disabling or misconfiguring the entire OpenBao instance |**Likelihood: HIGH** — the escape function mismatch is a well-documented antipattern in OWASP LDAP Injection guidance. The attack is trivially exploitable with no special tooling beyond `curl`.Why This Is High SeverityThe LDAP auth backend is frequently used as a **primary authentication method** for enterprise OpenBao deployments. A successful LDAP injection against this backend can bypass the entire authentication chain, granting administrative access to the secrets store without needing to compromise an actual admin account.4. RemediationPrimary Fix: Use ldap.EscapeFilterReplace `EscapeLDAPValue` with `ldap.EscapeFilter` in both filter construction paths:`EscapeLDAPValue` is still the correct choice for actual DN construction (where values are used as RDN components rather than filter values), but any value interpolated into an LDAP filter string must use `ldap.EscapeFilter`.Audit: All Call SitesReview all usages of `EscapeLDAPValue` across the codebase to ensure none are used in filter context:Defense-in-DepthApply the principle of least privilege to LDAP service accounts used by OpenBaoUse `UserFilter` with explicit attribute constraints to limit the search scope
CVSS v3.1 score: 6.8