3 files changed, 163 insertions, 0 deletions
diff --git a/internal/api/model/webfinger.go b/internal/api/model/webfinger.go
new file mode 100644
index 000000000..bb5008949
--- /dev/null
+++ b/internal/api/model/webfinger.go
@@ -0,0 +1,39 @@
+package model
+
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+// WebfingerAccountResponse represents the response to a webfinger request for an 'acct' resource.
+// For example, it would be returned from https://example.org/.well-known/webfinger?resource=acct:some_username@example.org
+//
+// See https://webfinger.net/
+type WebfingerAccountResponse struct {
+	Subject string          `json:"subject"`
+	Aliases []string        `json:"aliases"`
+	Links   []WebfingerLink `json:"links"`
+}
+
+// WebfingerLink represents one 'link' in a slice of webfinger links returned from a lookup request.
+//
+// See https://webfinger.net/
+type WebfingerLink struct {
+	Rel      string `json:"rel"`
+	Type     string `json:"type,omitempty"`
+	Href     string `json:"href,omitempty"`
+	Template string `json:"template,omitempty"`
+}
diff --git a/internal/api/s2s/webfinger/webfinger.go b/internal/api/s2s/webfinger/webfinger.go
new file mode 100644
index 000000000..c11d3fb61
--- /dev/null
+++ b/internal/api/s2s/webfinger/webfinger.go
@@ -0,0 +1,56 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package webfinger
+
+import (
+	"net/http"
+
+	"github.com/sirupsen/logrus"
+	"github.com/superseriousbusiness/gotosocial/internal/api"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/message"
+	"github.com/superseriousbusiness/gotosocial/internal/router"
+)
+
+const (
+	// The base path for serving webfinger lookup requests
+	WebfingerBasePath = ".well-known/webfinger"
+)
+
+// Module implements the FederationModule interface
+type Module struct {
+	config    *config.Config
+	processor message.Processor
+	log       *logrus.Logger
+}
+
+// New returns a new webfinger module
+func New(config *config.Config, processor message.Processor, log *logrus.Logger) api.FederationModule {
+	return &Module{
+		config:    config,
+		processor: processor,
+		log:       log,
+	}
+}
+
+// Route satisfies the FederationModule interface
+func (m *Module) Route(s router.Router) error {
+	s.AttachHandler(http.MethodGet, WebfingerBasePath, m.WebfingerGETRequest)
+	return nil
+}
diff --git a/internal/api/s2s/webfinger/webfingerget.go b/internal/api/s2s/webfinger/webfingerget.go
new file mode 100644
index 000000000..44d60670d
--- /dev/null
+++ b/internal/api/s2s/webfinger/webfingerget.go
@@ -0,0 +1,68 @@
+/*
+   GoToSocial
+   Copyright (C) 2021 GoToSocial Authors admin@gotosocial.org
+
+   This program is free software: you can redistribute it and/or modify
+   it under the terms of the GNU Affero General Public License as published by
+   the Free Software Foundation, either version 3 of the License, or
+   (at your option) any later version.
+
+   This program is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+   GNU Affero General Public License for more details.
+
+   You should have received a copy of the GNU Affero General Public License
+   along with this program.  If not, see <http://www.gnu.org/licenses/>.
+*/
+
+package webfinger
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/gin-gonic/gin"
+)
+
+// WebfingerGETRequest handles requests to, for example, https://example.org/.well-known/webfinger?resource=acct:some_user@example.org
+func (m *Module) WebfingerGETRequest(c *gin.Context) {
+
+	q, set := c.GetQuery("resource")
+	if !set || q == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "no 'resource' in request query"})
+		return
+	}
+
+	withAcct := strings.Split(q, "acct:")
+	if len(withAcct) != 2 {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "bad request"})
+		return
+	}
+
+	usernameDomain := strings.Split(withAcct[1], "@")
+	if len(usernameDomain) != 2 {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "bad request"})
+		return
+	}
+	username := strings.ToLower(usernameDomain[0])
+	domain := strings.ToLower(usernameDomain[1])
+	if username == "" || domain == "" {
+		c.JSON(http.StatusBadRequest, gin.H{"error": "bad request"})
+		return
+	}
+
+	if domain != m.config.Host {
+		c.JSON(http.StatusBadRequest, gin.H{"error": fmt.Sprintf("domain %s does not belong to this instance", domain)})
+		return
+	}
+
+	resp, err := m.processor.GetWebfingerAccount(username, c.Request)
+	if err != nil {
+		c.JSON(err.Code(), gin.H{"error": err.Safe()})
+		return
+	}
+
+	c.JSON(http.StatusOK, resp)
+}