[#142] Fix payroll email: SES domain identity + send-as pin + failure alarm

The weekly-post pay-summary email to payroll failed with SES AccessDenied
every Monday since v1.10.1: the role granted ses:SendEmail on
identity/noreply@seahaven.com, but that address is not a verified SES
identity — it is covered by the verified domain identity seahaven.com,
which is what SES authorizes against. Grant the domain ARN instead.

Pin the grant with a ses:FromAddress condition (= noreply@seahaven.com,
the existing SES_SENDER) so the domain-wide identity can't be used to
send-as any other @seahaven.com mailbox (BEC blast radius). Surfaced by
/sh-security-review; matches the existing single-sender intent.

Add a CloudWatch metric-filter alarm on the swallowed "Failed to send
pay summary" log line -> site-alerts. The email send is wrapped in
try/except so a delivery failure never increments the Lambda Errors
metric; this is the only signal that surfaces a silent payroll failure.

Closes #142

CHANGELOG.md

@@ -10,6 +10,15 @@ fine and still supported.
 
 ---
 
+## v1.13.1 — June 29, 2026
+
+**Fixed: the weekly pay summary email to payroll is sending again.** A
+permissions change had quietly been blocking the Monday pay-summary email to
+payroll since mid-June. The Slack pay report and the schedule post were never
+affected — only the email to payroll. That's now fixed, the two missed weeks
+were re-sent to payroll, and we've added an alert so a future email failure
+can't slip by unnoticed.
+
 ## v1.13.0 — June 27, 2026
 
 **The two-week schedule post now sticks to the bottom of the channel.** It used

src/slack-bot/CHANGELOG.md

@@ -10,6 +10,15 @@ fine and still supported.
 
 ---
 
+## v1.13.1 — June 29, 2026
+
+**Fixed: the weekly pay summary email to payroll is sending again.** A
+permissions change had quietly been blocking the Monday pay-summary email to
+payroll since mid-June. The Slack pay report and the schedule post were never
+affected — only the email to payroll. That's now fixed, the two missed weeks
+were re-sent to payroll, and we've added an alert so a future email failure
+can't slip by unnoticed.
+
 ## v1.13.0 — June 27, 2026
 
 **The two-week schedule post now sticks to the bottom of the channel.** It used

template.yaml

@@ -166,14 +166,26 @@ Resources:
               Action:
                 - ses:SendEmail
               Resource:
-                # Only the single sending identity (noreply@seahaven.com), not
+                # The From address (noreply@seahaven.com) is NOT a standalone
-                # every identity in the account.
+                # verified SES identity — it is covered by the verified DOMAIN
-                - !Sub "arn:aws:ses:${AWS::Region}:${AWS::AccountId}:identity/noreply@seahaven.com"
+                # identity seahaven.com, which is the identity SES authorizes
+                # SendEmail against. Granting identity/noreply@seahaven.com (a
+                # non-existent identity) caused AccessDenied; the domain ARN is
+                # the correct least-privilege resource. Scoped to this one domain,
+                # not identity/* (every identity in the account).
+                - !Sub "arn:aws:ses:${AWS::Region}:${AWS::AccountId}:identity/seahaven.com"
                 # The sending identity has a default configuration set
                 # (seahaven-email-events); SES authorizes SendEmail against the
                 # config-set resource too, so it must be granted alongside the
                 # identity or the send is denied. Scoped to the known set name.
                 - !Sub "arn:aws:ses:${AWS::Region}:${AWS::AccountId}:configuration-set/seahaven-email-events"
+              # The domain identity covers every address under seahaven.com, so
+              # without this the role could send-as any @seahaven.com mailbox.
+              # Pin the From to the one legitimate sender (matches SES_SENDER) so
+              # a compromised function can't spoof internal senders (BEC).
+              Condition:
+                StringEquals:
+                  ses:FromAddress: noreply@seahaven.com
       Events:
         # EST: 7am ET = 12:00 UTC (Nov-Mar)
         WeeklyPostEST:
@@ -551,6 +563,44 @@ Resources:
       AlarmActions:
         - !Sub "arn:aws:sns:${AWS::Region}:${AWS::AccountId}:site-alerts"
 
+  # --- Payroll email delivery failure (log-metric alarm) ---
+  # The pay-summary email send is wrapped in try/except so a delivery failure
+  # never aborts the schedule post — which means it does NOT surface on the
+  # Lambda Errors metric above (the handler exits "success"). This filter turns
+  # the "Failed to send pay summary" log line into a metric so a silent payroll
+  # delivery failure still pages site-alerts. DefaultValue 0 keeps the metric
+  # reporting on every run so the alarm sits in OK, not INSUFFICIENT_DATA.
+  PayrollEmailFailureMetricFilter:
+    Type: AWS::Logs::MetricFilter
+    Properties:
+      # !Ref the stack-managed log group (not a literal name) so CloudFormation
+      # orders this filter after the group exists.
+      LogGroupName: !Ref WeeklyPostLogGroup
+      FilterPattern: '"Failed to send pay summary"'
+      MetricTransformations:
+        - MetricName: PayrollEmailFailures
+          MetricNamespace: AfterHours/WeeklyPost
+          MetricValue: "1"
+          # DefaultValue 0 means non-matching runs emit 0, so the metric stays
+          # populated and the alarm rests in OK rather than INSUFFICIENT_DATA.
+          DefaultValue: 0
+
+  PayrollEmailFailureAlarm:
+    Type: AWS::CloudWatch::Alarm
+    Properties:
+      AlarmName: PayrollEmailFailure-afterhours-weekly-post
+      AlarmDescription: "Weekly-post failed to email the pay summary to payroll (SES send error)"
+      Namespace: AfterHours/WeeklyPost
+      MetricName: PayrollEmailFailures
+      Statistic: Sum
+      Period: 300
+      EvaluationPeriods: 1
+      Threshold: 1
+      ComparisonOperator: GreaterThanOrEqualToThreshold
+      TreatMissingData: notBreaching
+      AlarmActions:
+        - !Sub "arn:aws:sns:${AWS::Region}:${AWS::AccountId}:site-alerts"
+
   # --- Lambda Duration alarms (Maximum, ms; 2-of-3 evaluation) ---
   # Thresholds set to ~80% of each function's timeout, with 2-of-3 evaluation.
   # Timeouts: slack-bot/weekly-post/release-notifier = 30s (global default);