acme: Support DNS mode

Tested with dynu.com ddns.

Install acme-dnsapi:

    # opkg install acme-dnsapi

Example `/etc/config/acme`:

    config acme
        option state_dir '/etc/acme'
        option account_email email@example.org'
        option debug '0'

    config cert 'foo'
        option enabled '1'
        option use_staging '1'
        option keylength '2048'
        option update_uhttpd '0'
        option dns 'dns_dynu'
        list domains 'foo.dynu.com'
        list domains '*.foo.dynu.com'
        list credentials 'Dynu_ClientId="xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx"'
        list credentials 'Dynu_Secret="yyyyyyyyyyyyyyyyyyyyyyyyy"'

Run:

    # /etc/init.d/acme start

Signed-off-by: Zhong Jianxin <azuwis@gmail.com>

net/acme/files/acme-cbi.lua

@@ -69,4 +69,18 @@ dom = cs:option(DynamicList, "domains", translate("Domain names"),
                           "Note that all domain names must point at the router in the global DNS."))
 dom.datatype = "list(string)"
 
+dns = cs:option(Value, "dns", translate("DNS API"),
+                translate("To use DNS mode to issue certificates, set this to the name of a DNS API supported by acme.sh. " ..
+                          "See https://github.com/Neilpang/acme.sh/tree/master/dnsapi for the list of available APIs. " ..
+                          "In DNS mode, the domain name does not have to resolve to the router IP. " ..
+                          "DNS mode is also the only mode that supports wildcard certificates. " ..
+                          "Using this mode requires the acme-dnsapi package to be installed."))
+dns.rmempty = false
+
+cred = cs:option(DynamicList, "credentials", translate("DNS API credentials"),
+                 translate("The credentials for the DNS API mode selected above. " ..
+                           "See https://github.com/Neilpang/acme.sh/tree/master/dnsapi#how-to-use-dns-api for the format of credentials required by each API. " ..
+                           "Add multiple entries here in KEY=VAL shell variable format to supply multiple credential variables."))
+cred.datatype = "list(string)"
+
 return m

net/acme/files/run.sh

@@ -143,6 +143,7 @@ issue_cert()
     local moved_staging=0
     local failed_dir
     local webroot
+    local dns
 
     config_get_bool enabled "$section" enabled 0
     config_get_bool use_staging "$section" use_staging
@@ -150,6 +151,7 @@ issue_cert()
     config_get domains "$section" domains
     config_get keylength "$section" keylength
     config_get webroot "$section" webroot
+    config_get dns "$section" dns
 
     [ "$enabled" -eq "1" ] || return
 
@@ -158,7 +160,7 @@ issue_cert()
     set -- $domains
     main_domain=$1
 
-    [ -n "$webroot" ] || pre_checks "$main_domain" || return 1
+    [ -n "$webroot" ] || [ -n "$dns" ] || pre_checks "$main_domain" || return 1
 
     log "Running ACME for $main_domain"
 
@@ -180,7 +182,10 @@ issue_cert()
     [ -n "$ACCOUNT_EMAIL" ] && acme_args="$acme_args --accountemail $ACCOUNT_EMAIL"
     [ "$use_staging" -eq "1" ] && acme_args="$acme_args --staging"
 
-    if [ -z "$webroot" ]; then
+    if [ -n "$dns" ]; then
+        log "Using dns mode"
+        acme_args="$acme_args --dns $dns"
+    elif [ -z "$webroot" ]; then
         log "Using standalone mode"
         acme_args="$acme_args --standalone"
     else
@@ -192,6 +197,12 @@ issue_cert()
         acme_args="$acme_args --webroot $webroot"
     fi
 
+    handle_credentials() {
+        local credential="$1"
+        eval export $credential
+    }
+    config_list_foreach "$section" credentials handle_credentials
+
     if ! $ACME --home "$STATE_DIR" --issue $acme_args; then
         failed_dir="$STATE_DIR/${main_domain}.failed-$(date +%s)"
         err "Issuing cert for $main_domain failed. Moving state to $failed_dir"