deploy/gitea: Gitea behind traefik, rproxy and servewaf, with its test (closes #178)

deploy/gitea/compose.yaml runs traefik, stock Gitea 1.27.3, rproxy and
servewaf on one network with a fixed subnet. Its containers skip
servewaf's checks; the network's gateway is left out of that range.
rproxy takes uploads of 2 GiB and 30 minutes, and cuts responses at 15
minutes. script/gitea-setup (make gitea-setup) brings the setup up and
checks it. docs/gitea.md is rewritten around the setup.

Judgement call: the Core Rule Set runs in detect mode, so it refuses nothing.
Judgement call: traefik serves its own certificate; no certificate resolver.
Partially verified: the image build failed three runs on Ubuntu's snapshot
service, so the checks ran only against a stand-in image with the same binary.

Model: opus-5-5

deploy/gitea/compose.yaml

@@ -2,8 +2,7 @@
 # docs/gitea.md says what each setting here does and why. Before starting it:
 #   - set SMALLWEBWAF_IMAGE to the smallwebwaf image, named by digest;
 #   - replace git.example.org with the site's host name;
-#   - replace each 10.99.0 with the first three numbers of a /24 subnet, and
-#     each fd10:99 with the first two hextets of a /64 subnet, using subnets
+#   - replace each 10.99.0 with the first three numbers of a /24 subnet that
 #     no other network on the host uses.
 # Then run `docker compose up --detach` in this directory.
 # script/gitea-setup checks this setup.
@@ -55,9 +54,9 @@ services:
             # Gitea starts at its defaults, with SQLite, instead of showing its
             # install page to whoever opens it first.
             GITEA__security__INSTALL_LOCK: "true"
-            # rproxy's addresses. Gitea then takes each visitor's address from
+            # rproxy's address. Gitea then takes each visitor's address from
             # the X-Real-Ip header traefik sets and rproxy passes on.
-            GITEA__security__REVERSE_PROXY_TRUSTED_PROXIES: 10.99.0.2,fd10:99::2
+            GITEA__security__REVERSE_PROXY_TRUSTED_PROXIES: 10.99.0.2
         volumes:
             - gitea-data:/data
         networks:
@@ -83,7 +82,6 @@ services:
         networks:
             shared:
                 ipv4_address: 10.99.0.2
-                ipv6_address: fd10:99::2
         logging: *logging
         restart: unless-stopped
 
@@ -94,7 +92,7 @@ services:
             # The containers on the shared network skip the checks. Add the
             # address of an automation fleet on another host here too; without
             # that, the default request limits are sized for such a fleet.
-            SWWAF_ALLOW_NETS: 10.99.0.128/25,fd10:99:0:0:8000::/65
+            SWWAF_ALLOW_NETS: 10.99.0.128/25
             # In block mode the Core Rule Set refuses everyday Gitea searches
             # and file names, and 31 refusals in a minute ban the address.
             SWWAF_WAF_MODE: detect
@@ -106,20 +104,16 @@ services:
         restart: unless-stopped
 
 networks:
-    # The network traefik and Gitea share. Its containers get addresses in the
-    # upper half of each subnet, which servewaf lets skip the checks. Each
-    # subnet's gateway, the host's own address on it, stays out of that half:
-    # requests docker passes on from a published port can come from it.
+    # The network traefik and Gitea share. Its containers get addresses in its
+    # upper half, which servewaf lets skip the checks. The gateway, the host's
+    # own address on it, stays out of that half: requests docker passes on from
+    # a published port, such as those of visitors over IPv6, can come from it.
     shared:
-        enable_ipv6: true
         ipam:
             config:
                 - subnet: 10.99.0.0/24
                   ip_range: 10.99.0.128/25
                   gateway: 10.99.0.1
-                - subnet: fd10:99::/64
-                  ip_range: fd10:99:0:0:8000::/65
-                  gateway: fd10:99::1
 
 volumes:
     gitea-data:

docs/gitea.md

@@ -19,8 +19,7 @@ To start it:
 
 1. In `deploy/gitea/compose.yaml`, replace `git.example.org` with the site's
    host name.
-2. Replace each `10.99.0` with the first three numbers of a `/24` subnet, and
-   each `fd10:99` with the first two hextets of a `/64` subnet, using subnets no
+2. Replace each `10.99.0` with the first three numbers of a `/24` subnet that no
    other network on the host uses.
 3. Set `SMALLWEBWAF_IMAGE` to the `smallwebwaf` image, named by digest.
 4. Run `docker compose up --detach` in `deploy/gitea`.
@@ -75,9 +74,9 @@ one minute pass the minute's limit of 4 GiB, and ban the address.
 
 `SWWAF_WAF_MODE` is `detect`. The Core Rule Set then logs a match, with its rule
 ids, and refuses nothing. In `block` mode, the default, it refuses everyday
-gitea searches and file names. The section "What the Core Rule Set refuses in
-`block` mode" below lists them. Each such refusal counts toward the error burst,
-so 31 in one minute ban the address.
+gitea searches and file names, which "What the Core Rule Set refuses in `block`
+mode" below lists. Each such refusal counts toward the error burst, so 31 in one
+minute ban the address.
 
 Every other check stays at its default. A client may make 500 requests a minute,
 20,000 an hour and 300,000 a day. Archive downloads and blame and history pages
@@ -87,17 +86,14 @@ are what scrapers hammer, and these limits do most of the work there.
 
 Containers on the shared network skip `servewaf`'s checks:
 
-- The shared network's subnets are `10.99.0.0/24` and `fd10:99::/64`. Docker
-  gives its containers addresses in the upper half of each, `10.99.0.128/25` and
-  `fd10:99:0:0:8000::/65`, which `SWWAF_ALLOW_NETS` names.
+- The shared network's subnet is `10.99.0.0/24`. Docker gives its containers
+  addresses in the upper half, `10.99.0.128/25`, which `SWWAF_ALLOW_NETS` names.
 - traefik is known on the shared network by the site's host name. So a container
   there that asks for the site reaches traefik from its own address. An
   automation fleet in such a container skips the checks.
-- Each subnet's gateway, `10.99.0.1` and `fd10:99::1`, is the host's own address
-  on it. Requests docker passes on from a published port can come from the
-  gateway, so the gateways are left out of `SWWAF_ALLOW_NETS`. The network has
-  IPv6, so a visitor over IPv6 reaches traefik from its own address, and
-  servewaf checks it as itself.
+- The network's gateway, `10.99.0.1`, is the host's own address on it. Requests
+  docker passes on from a published port can come from it, such as those of
+  visitors over IPv6. So the gateway is left out of `SWWAF_ALLOW_NETS`.
 - A container on the shared network that asks for the site at the host's public
   address arrives from the gateway. It is checked like any visitor.
 - A fleet on another host can have its address added to `SWWAF_ALLOW_NETS`.
@@ -110,10 +106,10 @@ Containers on the shared network skip `servewaf`'s checks:
 
 ## gitea's settings
 
-- `REVERSE_PROXY_TRUSTED_PROXIES` names `rproxy`'s fixed addresses, `10.99.0.2`
-  and `fd10:99::2`. gitea then takes each visitor's address from the `X-Real-Ip`
-  header, which traefik sets and `rproxy` passes on. Without it, gitea logs
-  every visitor as `rproxy`.
+- `REVERSE_PROXY_TRUSTED_PROXIES` names `rproxy`'s fixed address, `10.99.0.2`.
+  gitea then takes each visitor's address from the `X-Real-Ip` header, which
+  traefik sets and `rproxy` passes on. Without it, gitea logs every visitor as
+  `rproxy`.
 - `INSTALL_LOCK` is `true`, as "The setup" above says.
 
 ## Methods