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Make the audit log one shape that a privileged change cannot skip
b1499c729a026cfda32d8a90374b3b8391ca0090 · Keenan Nemetz · 13d ago · parent d74d4de8
Make the audit log one shape that a privileged change cannot skip
Every writer used to format its own line and open its own file, so
data/audit.log held six different column layouts and a write that failed
changed nothing. A log that can be bypassed by a full disk, or by a key
comment containing a tab, is not the security promise the docs make.
internal/audit is now the only writer: one line per action, always
timestamp, action, actor, subject, detail. Every field is escaped and
capped at 4 KiB, so a key comment, an LFS lock path, a repository name or
an admin argument cannot add a column or a record. One write per line
under O_APPEND keeps the web, the SSH server and each hook process from
interleaving, and secure.OpenAppend keeps the file at 0600 including on an
upgrade from 0644.
Privileged changes now fail closed, and they are recorded before they
happen, so a failed write means the change did not occur:
- roster, key and instance-role changes (inside the transaction)
- access-rule changes, and a repository deletion, which records before
removing content and forgets the rules only afterwards
- session creation and revocation
- a forced LFS unlock
- an admin command over SSH, which reports audit_unavailable
- a push that overrides a lock, an approval, a release or history
Ordinary pushes and web actions are reported instead: their changes are
already durable in git, so a write failure is logged at error level (or on
the pusher's terminal from post-receive) rather than making a working push
look rejected.
Opening an instance now checks the log is a regular file at 0600 owned by
the service account and appendable, and refuses to start otherwise. There
is no setting that disables the log or returns it to best effort.
Regression tests cover field injection through key comments, lock paths,
admin argv and repository names; 0600 on create and on upgrade; an
unwritable sink failing an ACL change, an account change, a session, a
forced unlock, an admin command and a push override while leaving the
underlying state unchanged; concurrent appends keeping whole lines; and
startup refusing a symlinked log.
forge/access/store.go +35−30
| @@ -14,16 +14,18 @@ package access | |||
| 14 | 14 | import ( | |
| 15 | 15 | "database/sql" | |
| 16 | 16 | "fmt" | |
| 17 | "github.com/rodent-software/vole/internal/secure" | ||
| 18 | _ "modernc.org/sqlite" | ||
| 19 | 17 | "time" | |
| 18 | |||
| 19 | _ "modernc.org/sqlite" | ||
| 20 | |||
| 21 | "github.com/rodent-software/vole/internal/audit" | ||
| 20 | 22 | ) | |
| 21 | 23 | ||
| 22 | 24 | type Store struct { | |
| 23 | 25 | db *sql.DB | |
| 24 | // AuditPath receives one line per change. Empty means no audit sink, which is only | ||
| 25 | // acceptable for tests: an access change is the one administrative act that must | ||
| 26 | // leave a trace, since the old copy was a commit message. | ||
| 26 | // AuditPath receives one line per change. It is required in practice: an | ||
| 27 | // access change is the one administrative act that must leave a trace, so a | ||
| 28 | // change that cannot be recorded is refused rather than applied silently. | ||
| 27 | 29 | AuditPath string | |
| 28 | 30 | // InstanceRole, when set, resolves an account's instance-wide role. The | |
| 29 | 31 | // roster owns it; the store attaches it to every ACL it returns so RoleFor | |
| @@ -91,42 +93,45 @@ func (s *Store) Set(repoID string, a *ACL, actor string, now time.Time) error { | |||
| 91 | 93 | if err != nil { | |
| 92 | 94 | return err | |
| 93 | 95 | } | |
| 96 | // Recorded before the write, so a rule set that cannot be audited is not | ||
| 97 | // applied. A failed insert leaves an extra line, which is the safe direction. | ||
| 98 | if err := s.audit(audit.Record{Action: "acl.update", Actor: actor, Subject: repoID}); err != nil { | ||
| 99 | return err | ||
| 100 | } | ||
| 94 | 101 | if _, err := s.db.Exec(`INSERT INTO repo_acl (repo_id, acl, updated, updated_by) VALUES (?,?,?,?) | |
| 95 | 102 | ON CONFLICT(repo_id) DO UPDATE SET acl = excluded.acl, | |
| 96 | 103 | updated = excluded.updated, updated_by = excluded.updated_by`, | |
| 97 | 104 | repoID, string(raw), now.UTC().Unix(), actor); err != nil { | |
| 98 | 105 | return err | |
| 99 | 106 | } | |
| 100 | s.audit(fmt.Sprintf("acl %s updated by %s", repoID, actorOr(actor))) | ||
| 101 | 107 | return nil | |
| 102 | 108 | } | |
| 103 | 109 | ||
| 104 | // Delete forgets a repository's rules, which is what deleting the repository does. | ||
| 105 | func (s *Store) Delete(repoID string) error { | ||
| 106 | var actor string | ||
| 107 | _ = s.db.QueryRow(`SELECT updated_by FROM repo_acl WHERE repo_id = ?`, repoID).Scan(&actor) | ||
| 108 | if _, err := s.db.Exec(`DELETE FROM repo_acl WHERE repo_id = ?`, repoID); err != nil { | ||
| 109 | return err | ||
| 110 | // RecordDelete writes the audit line for a repository deletion and reports | ||
| 111 | // whether it was written. Deleting a repository is a two-step operation on | ||
| 112 | // purpose: the line is recorded, the content is removed, and only then are the | ||
| 113 | // rules forgotten. A deletion that cannot be recorded therefore never starts, | ||
| 114 | // and a removal that fails leaves the rules in place rather than a repository | ||
| 115 | // nobody can administer. | ||
| 116 | func (s *Store) RecordDelete(repoID, actor string) error { | ||
| 117 | var lastChangedBy string | ||
| 118 | _ = s.db.QueryRow(`SELECT updated_by FROM repo_acl WHERE repo_id = ?`, repoID).Scan(&lastChangedBy) | ||
| 119 | detail := "repository deleted" | ||
| 120 | if lastChangedBy != "" { | ||
| 121 | detail += "; last changed by " + lastChangedBy | ||
| 110 | 122 | } | |
| 111 | s.audit(fmt.Sprintf("acl %s deleted with the repository (last changed by %s)", repoID, actorOr(actor))) | ||
| 112 | return nil | ||
| 123 | return s.audit(audit.Record{Action: "acl.delete", Actor: actor, Subject: repoID, Detail: detail}) | ||
| 113 | 124 | } | |
| 114 | 125 | ||
| 115 | // audit is best-effort: failing to write the log must not change policy. | ||
| 116 | func (s *Store) audit(line string) { | ||
| 117 | if s.AuditPath == "" { | ||
| 118 | return | ||
| 119 | } | ||
| 120 | f, err := secure.OpenAppend(s.AuditPath) | ||
| 121 | if err != nil { | ||
| 122 | return | ||
| 123 | } | ||
| 124 | defer f.Close() | ||
| 125 | fmt.Fprintf(f, "%s\t%s\n", time.Now().UTC().Format(time.RFC3339), line) | ||
| 126 | // Delete forgets a repository's rules, which is what deleting the repository | ||
| 127 | // does. RecordDelete has already recorded the change. | ||
| 128 | func (s *Store) Delete(repoID string) error { | ||
| 129 | _, err := s.db.Exec(`DELETE FROM repo_acl WHERE repo_id = ?`, repoID) | ||
| 130 | return err | ||
| 126 | 131 | } | |
| 127 | func actorOr(actor string) string { | ||
| 128 | if actor == "" { | ||
| 129 | return "unknown" | ||
| 130 | } | ||
| 131 | return actor | ||
| 132 | |||
| 133 | // audit appends one access change. The error is returned to the caller: a rule set | ||
| 134 | // that cannot be audited is not changed. | ||
| 135 | func (s *Store) audit(r audit.Record) error { | ||
| 136 | return audit.Append(s.AuditPath, r) | ||
| 132 | 137 | } | |