[feature] Implement `/api/v1/instance/peers` endpoint (#660)

* add missing license headers

* start adding instance peers get

* rename domainblock.go

* embed domain in domainblock so it can be reused

* update swagger docs

* add test instances to db

* update tests

* add/update instancepeersget

* update domain model

* add getinstancepeers to db

* instance-expose-peers, instance-expose-suspended

* add auth checks for both current filters

* attach endpoint to router

* include public comment

* obfuscate domain if required

* go mod tidy

* update swagger docs

* remove unnecessary comment

* return 'flat' peerlist if no query params provided

18 files changed, 629 insertions, 14 deletions

diff --git a/internal/api/client/instance/instance.go b/internal/api/client/instance/instance.go
index 758cce376..16ff7c9f9 100644
--- a/internal/api/client/instance/instance.go
+++ b/internal/api/client/instance/instance.go
@@ -1,3 +1,21 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 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 instance
 
 import (
@@ -11,6 +29,10 @@ import (
 const (
 	// InstanceInformationPath is for serving instance info requests
 	InstanceInformationPath = "api/v1/instance"
+	// InstancePeersPath is for serving instance peers requests.
+	InstancePeersPath = InstanceInformationPath + "/peers"
+	// PeersFilterKey is used to provide filters to /api/v1/instance/peers
+	PeersFilterKey = "filter"
 )
 
 // Module implements the ClientModule interface
@@ -29,5 +51,6 @@ func New(processor processing.Processor) api.ClientModule {
 func (m *Module) Route(s router.Router) error {
 	s.AttachHandler(http.MethodGet, InstanceInformationPath, m.InstanceInformationGETHandler)
 	s.AttachHandler(http.MethodPatch, InstanceInformationPath, m.InstanceUpdatePATCHHandler)
+	s.AttachHandler(http.MethodGet, InstancePeersPath, m.InstancePeersGETHandler)
 	return nil
 }
diff --git a/internal/api/client/instance/instance_test.go b/internal/api/client/instance/instance_test.go
index 248b87761..1e5c59c97 100644
--- a/internal/api/client/instance/instance_test.go
+++ b/internal/api/client/instance/instance_test.go
@@ -21,7 +21,6 @@ package instance_test
 import (
 	"bytes"
 	"fmt"
-	"net/http"
 	"net/http/httptest"
 
 	"codeberg.org/gruf/go-store/kv"
@@ -113,7 +112,7 @@ func (suite *InstanceStandardTestSuite) newContext(recorder *httptest.ResponseRe
 	baseURI := fmt.Sprintf("%s://%s", protocol, host)
 	requestURI := fmt.Sprintf("%s/%s", baseURI, requestPath)
 
-	ctx.Request = httptest.NewRequest(http.MethodPatch, requestURI, bytes.NewReader(requestBody)) // the endpoint we're hitting
+	ctx.Request = httptest.NewRequest(requestMethod, requestURI, bytes.NewReader(requestBody)) // the endpoint we're hitting
 
 	if bodyContentType != "" {
 		ctx.Request.Header.Set("Content-Type", bodyContentType)
diff --git a/internal/api/client/instance/instanceget.go b/internal/api/client/instance/instanceget.go
index 35e842102..5250b3b46 100644
--- a/internal/api/client/instance/instanceget.go
+++ b/internal/api/client/instance/instanceget.go
@@ -1,3 +1,21 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 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 instance
 
 import (
diff --git a/internal/api/client/instance/instancepatch.go b/internal/api/client/instance/instancepatch.go
index 4e3f1e454..6f1b3586b 100644
--- a/internal/api/client/instance/instancepatch.go
+++ b/internal/api/client/instance/instancepatch.go
@@ -1,3 +1,21 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 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 instance
 
 import (
diff --git a/internal/api/client/instance/instancepatch_test.go b/internal/api/client/instance/instancepatch_test.go
index 5ca4f2b7a..683fec5a6 100644
--- a/internal/api/client/instance/instancepatch_test.go
+++ b/internal/api/client/instance/instancepatch_test.go
@@ -63,7 +63,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch1() {
 	b, err := io.ReadAll(result.Body)
 	suite.NoError(err)
 
-	suite.Equal(`{"uri":"http://localhost:8080","title":"Example Instance","description":"","short_description":"","email":"someone@example.org","version":"","registrations":true,"approval_required":true,"invites_enabled":false,"urls":{"streaming_api":"wss://localhost:8080"},"stats":{"domain_count":0,"status_count":16,"user_count":4},"thumbnail":"","contact_account":{"id":"01F8MH17FWEB39HZJ76B6VXSKF","username":"admin","acct":"admin","display_name":"","locked":false,"bot":false,"created_at":"2022-05-17T13:10:59.000Z","note":"","url":"http://localhost:8080/@admin","avatar":"","avatar_static":"","header":"","header_static":"","followers_count":1,"following_count":1,"statuses_count":4,"last_status_at":"2021-10-20T10:41:37.000Z","emojis":[],"fields":[]},"max_toot_chars":5000}`, string(b))
+	suite.Equal(`{"uri":"http://localhost:8080","title":"Example Instance","description":"","short_description":"","email":"someone@example.org","version":"","registrations":true,"approval_required":true,"invites_enabled":false,"urls":{"streaming_api":"wss://localhost:8080"},"stats":{"domain_count":2,"status_count":16,"user_count":4},"thumbnail":"","contact_account":{"id":"01F8MH17FWEB39HZJ76B6VXSKF","username":"admin","acct":"admin","display_name":"","locked":false,"bot":false,"created_at":"2022-05-17T13:10:59.000Z","note":"","url":"http://localhost:8080/@admin","avatar":"","avatar_static":"","header":"","header_static":"","followers_count":1,"following_count":1,"statuses_count":4,"last_status_at":"2021-10-20T10:41:37.000Z","emojis":[],"fields":[]},"max_toot_chars":5000}`, string(b))
 }
 
 func (suite *InstancePatchTestSuite) TestInstancePatch2() {
@@ -93,7 +93,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch2() {
 	b, err := io.ReadAll(result.Body)
 	suite.NoError(err)
 
-	suite.Equal(`{"uri":"http://localhost:8080","title":"Geoff's Instance","description":"","short_description":"","email":"","version":"","registrations":true,"approval_required":true,"invites_enabled":false,"urls":{"streaming_api":"wss://localhost:8080"},"stats":{"domain_count":0,"status_count":16,"user_count":4},"thumbnail":"","max_toot_chars":5000}`, string(b))
+	suite.Equal(`{"uri":"http://localhost:8080","title":"Geoff's Instance","description":"","short_description":"","email":"","version":"","registrations":true,"approval_required":true,"invites_enabled":false,"urls":{"streaming_api":"wss://localhost:8080"},"stats":{"domain_count":2,"status_count":16,"user_count":4},"thumbnail":"","max_toot_chars":5000}`, string(b))
 }
 
 func (suite *InstancePatchTestSuite) TestInstancePatch3() {
@@ -123,7 +123,7 @@ func (suite *InstancePatchTestSuite) TestInstancePatch3() {
 	b, err := io.ReadAll(result.Body)
 	suite.NoError(err)
 
-	suite.Equal(`{"uri":"http://localhost:8080","title":"localhost:8080","description":"","short_description":"\u003cp\u003eThis is some html, which is \u003cem\u003eallowed\u003c/em\u003e in short descriptions.\u003c/p\u003e","email":"","version":"","registrations":true,"approval_required":true,"invites_enabled":false,"urls":{"streaming_api":"wss://localhost:8080"},"stats":{"domain_count":0,"status_count":16,"user_count":4},"thumbnail":"","max_toot_chars":5000}`, string(b))
+	suite.Equal(`{"uri":"http://localhost:8080","title":"localhost:8080","description":"","short_description":"\u003cp\u003eThis is some html, which is \u003cem\u003eallowed\u003c/em\u003e in short descriptions.\u003c/p\u003e","email":"","version":"","registrations":true,"approval_required":true,"invites_enabled":false,"urls":{"streaming_api":"wss://localhost:8080"},"stats":{"domain_count":2,"status_count":16,"user_count":4},"thumbnail":"","max_toot_chars":5000}`, string(b))
 }
 
 func (suite *InstancePatchTestSuite) TestInstancePatch4() {
diff --git a/internal/api/client/instance/instancepeersget.go b/internal/api/client/instance/instancepeersget.go
new file mode 100644
index 000000000..d4d33d5bf
--- /dev/null
+++ b/internal/api/client/instance/instancepeersget.go
@@ -0,0 +1,136 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 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 instance
+
+import (
+	"fmt"
+	"net/http"
+	"strings"
+
+	"github.com/superseriousbusiness/gotosocial/internal/api"
+	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
+
+	"github.com/gin-gonic/gin"
+)
+
+// InstancePeersGETHandler swagger:operation GET /api/v1/instance/peers instancePeersGet
+//
+// ---
+// tags:
+// - instance
+//
+// produces:
+// - application/json
+//
+// parameters:
+// - name: filter
+//   type: string
+//   description: |-
+//     Comma-separated list of filters to apply to results. Recognized values are:
+//     'open' -- include peers that are not suspended or silenced
+//     'suspended' -- include peers that have been suspended.
+//     If filter is 'open', only instances that haven't been suspended or silenced will be returned.
+//     If filter is 'suspended', only suspended instances will be shown.
+//     If filter is 'open,suspended', then all known instances will be returned.
+//     If filter is an empty string or not set, then 'open' will be assumed as the default.
+//   in: query
+//   required: false
+//
+// responses:
+//   '200':
+//     description: |-
+//       If no filter parameter is provided, or filter is empty, then a legacy,
+//       Mastodon-API compatible response will be returned. This will consist of
+//       just a 'flat' array of strings like `["example.com", "example.org"]`.
+//
+//       If a filter parameter is provided, then an array of objects with at least
+//       a `domain` key set on each object will be returned.
+//
+//       Domains that are silenced or suspended will also have a key
+//       'suspended_at' or 'silenced_at' that contains an iso8601 date string.
+//       If one of these keys is not present on the domain object, it is open.
+//       Suspended instances may in some cases be obfuscated, which means they
+//       will have some letters replaced by '*' to make it more difficult for
+//       bad actors to target instances with harassment.
+//
+//       Whether a flat response or a more detailed response is returned, domains
+//       will be sorted alphabetically by hostname.
+//     schema:
+//       type: array
+//       items:
+//         "$ref": "#/definitions/domain"
+//   '400':
+//      description: bad request
+//   '401':
+//      description: unauthorized
+//   '403':
+//      description: forbidden
+//   '404':
+//      description: not found
+//   '406':
+//      description: not acceptable
+//   '500':
+//      description: internal server error
+func (m *Module) InstancePeersGETHandler(c *gin.Context) {
+	authed, err := oauth.Authed(c, false, false, false, false)
+	if err != nil {
+		api.ErrorHandler(c, gtserror.NewErrorUnauthorized(err, err.Error()), m.processor.InstanceGet)
+		return
+	}
+
+	if _, err := api.NegotiateAccept(c, api.JSONAcceptHeaders...); err != nil {
+		api.ErrorHandler(c, gtserror.NewErrorNotAcceptable(err, err.Error()), m.processor.InstanceGet)
+		return
+	}
+
+	var includeSuspended bool
+	var includeOpen bool
+	var flat bool
+	if filterParam := c.Query(PeersFilterKey); filterParam != "" {
+		filters := strings.Split(filterParam, ",")
+		for _, f := range filters {
+			trimmed := strings.TrimSpace(f)
+			switch {
+			case strings.EqualFold(trimmed, "suspended"):
+				includeSuspended = true
+			case strings.EqualFold(trimmed, "open"):
+				includeOpen = true
+			default:
+				err := fmt.Errorf("filter %s not recognized; accepted values are 'open', 'suspended'", trimmed)
+				api.ErrorHandler(c, gtserror.NewErrorBadRequest(err, err.Error()), m.processor.InstanceGet)
+				return
+			}
+		}
+	} else {
+		// default is to only include open domains, and present
+		// them in a 'flat' manner (just an array of strings),
+		// to maintain compatibility with mastodon API
+		includeOpen = true
+		flat = true
+	}
+
+	data, errWithCode := m.processor.InstancePeersGet(c.Request.Context(), authed, includeSuspended, includeOpen, flat)
+	if errWithCode != nil {
+		api.ErrorHandler(c, errWithCode, m.processor.InstanceGet)
+		return
+	}
+
+	c.JSON(http.StatusOK, data)
+}
diff --git a/internal/api/client/instance/instancepeersget_test.go b/internal/api/client/instance/instancepeersget_test.go
new file mode 100644
index 000000000..cb35a9e50
--- /dev/null
+++ b/internal/api/client/instance/instancepeersget_test.go
@@ -0,0 +1,247 @@
+/*
+   GoToSocial
+   Copyright (C) 2021-2022 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 instance_test
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/http"
+	"net/http/httptest"
+	"testing"
+
+	"github.com/gin-gonic/gin"
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/api/client/instance"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
+	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/testrig"
+)
+
+type InstancePeersGetTestSuite struct {
+	InstanceStandardTestSuite
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetNoParams() {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`["example.org","fossbros-anonymous.io"]`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetNoParamsUnauthorized() {
+	config.SetInstanceExposePeers(false)
+
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusUnauthorized, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`{"error":"Unauthorized: peers open query requires an authenticated account/user"}`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetNoParamsAuthorized() {
+	config.SetInstanceExposePeers(false)
+
+	recorder := httptest.NewRecorder()
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s", baseURI, instance.InstancePeersPath)
+	ctx := suite.newContext(recorder, http.MethodGet, []byte{}, requestURI, "")
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`["example.org","fossbros-anonymous.io"]`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetOnlySuspended() {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s?filter=suspended", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`[{"domain":"replyguys.com","suspended_at":"2020-05-13T13:29:12.000Z","public_comment":"reply-guying to tech posts"}]`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetOnlySuspendedUnauthorized() {
+	config.SetInstanceExposeSuspended(false)
+
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s?filter=suspended", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusUnauthorized, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`{"error":"Unauthorized: peers suspended query requires an authenticated account/user"}`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetOnlySuspendedAuthorized() {
+	config.SetInstanceExposeSuspended(false)
+
+	recorder := httptest.NewRecorder()
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s?filter=suspended", baseURI, instance.InstancePeersPath)
+	ctx := suite.newContext(recorder, http.MethodGet, []byte{}, requestURI, "")
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`[{"domain":"replyguys.com","suspended_at":"2020-05-13T13:29:12.000Z","public_comment":"reply-guying to tech posts"}]`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetAll() {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s?filter=suspended,open", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`[{"domain":"example.org"},{"domain":"fossbros-anonymous.io"},{"domain":"replyguys.com","suspended_at":"2020-05-13T13:29:12.000Z","public_comment":"reply-guying to tech posts"}]`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetAllWithObfuscated() {
+	err := suite.db.Put(context.Background(), &gtsmodel.DomainBlock{
+		ID:                 "01G633XTNK51GBADQZFZQDP6WR",
+		CreatedAt:          testrig.TimeMustParse("2021-06-09T12:34:55+02:00"),
+		UpdatedAt:          testrig.TimeMustParse("2021-06-09T12:34:55+02:00"),
+		Domain:             "omg.just.the.worst.org.ever",
+		CreatedByAccountID: "01F8MH17FWEB39HZJ76B6VXSKF",
+		PublicComment:      "just absolutely the worst, wowza",
+		Obfuscate:          true,
+	})
+	suite.NoError(err)
+
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s?filter=suspended,open", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusOK, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`[{"domain":"example.org"},{"domain":"fossbros-anonymous.io"},{"domain":"o*g.*u**.t**.*or*t.*r**ev**","suspended_at":"2021-06-09T10:34:55.000Z","public_comment":"just absolutely the worst, wowza"},{"domain":"replyguys.com","suspended_at":"2020-05-13T13:29:12.000Z","public_comment":"reply-guying to tech posts"}]`, string(b))
+}
+
+func (suite *InstancePeersGetTestSuite) TestInstancePeersGetFunkyParams() {
+	recorder := httptest.NewRecorder()
+	ctx, _ := gin.CreateTestContext(recorder)
+
+	baseURI := fmt.Sprintf("%s://%s", config.GetProtocol(), config.GetHost())
+	requestURI := fmt.Sprintf("%s/%s?filter=aaaaaaaaaaaaaaaaa,open", baseURI, instance.InstancePeersPath)
+	ctx.Request = httptest.NewRequest(http.MethodGet, requestURI, nil)
+
+	suite.instanceModule.InstancePeersGETHandler(ctx)
+
+	suite.Equal(http.StatusBadRequest, recorder.Code)
+
+	result := recorder.Result()
+	defer result.Body.Close()
+
+	b, err := io.ReadAll(result.Body)
+	suite.NoError(err)
+
+	suite.Equal(`{"error":"Bad Request: filter aaaaaaaaaaaaaaaaa not recognized; accepted values are 'open', 'suspended'"}`, string(b))
+}
+
+func TestInstancePeersGetTestSuite(t *testing.T) {
+	suite.Run(t, &InstancePeersGetTestSuite{})
+}
diff --git a/internal/api/model/domainblock.go b/internal/api/model/domain.go
index 2911dfbaa..90c08fa6f 100644
--- a/internal/api/model/domainblock.go
+++ b/internal/api/model/domain.go
@@ -20,17 +20,33 @@ package model
 
 import "mime/multipart"
 
+// Domain represents a remote domain
+//
+// swagger:model domain
+type Domain struct {
+	// The hostname of the domain.
+	// example: example.org
+	Domain string `form:"domain" json:"domain" validate:"required"`
+	// Time at which this domain was suspended. Key will not be present on open domains.
+	// example: 2021-07-30T09:20:25+00:00
+	SuspendedAt string `json:"suspended_at,omitempty"`
+	// Time at which this domain was silenced. Key will not be present on open domains.
+	// example: 2021-07-30T09:20:25+00:00
+	SilencedAt string `json:"silenced_at,omitempty"`
+	// If the domain is blocked, what's the publicly-stated reason for the block.
+	// example: they smell
+	PublicComment string `form:"public_comment" json:"public_comment,omitempty"`
+}
+
 // DomainBlock represents a block on one domain
 //
 // swagger:model domainBlock
 type DomainBlock struct {
+	Domain
 	// The ID of the domain block.
 	// example: 01FBW21XJA09XYX51KV5JVBW0F
 	// readonly: true
 	ID string `json:"id,omitempty"`
-	// The hostname of the blocked domain.
-	// example: example.org
-	Domain string `form:"domain" json:"domain" validation:"required"`
 	// Obfuscate the domain name when serving this domain block publicly.
 	// A useful anti-harassment tool.
 	// example: false
@@ -38,9 +54,6 @@ type DomainBlock struct {
 	// Private comment for this block, visible to our instance admins only.
 	// example: they are poopoo
 	PrivateComment string `json:"private_comment,omitempty"`
-	// Public comment for this block, visible if domain blocks are served publicly.
-	// example: they smell
-	PublicComment string `form:"public_comment" json:"public_comment,omitempty"`
 	// The ID of the subscription that created/caused this domain block.
 	// example: 01FBW25TF5J67JW3HFHZCSD23K
 	SubscriptionID string `json:"subscription_id,omitempty"`
diff --git a/internal/config/config.go b/internal/config/config.go
index 3a1775778..0b7fc3d31 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -67,6 +67,9 @@ type Configuration struct {
 	WebTemplateBaseDir string `name:"web-template-base-dir" usage:"Basedir for html templating files for rendering pages and composing emails."`
 	WebAssetBaseDir    string `name:"web-asset-base-dir" usage:"Directory to serve static assets from, accessible at example.org/assets/"`
 
+	InstanceExposePeers     bool `name:"instance-expose-peers" usage:"Allow unauthenticated users to query /api/v1/instance/peers?filter=open"`
+	InstanceExposeSuspended bool `name:"instance-expose-suspended" usage:"Expose suspended instances via web UI, and allow unauthenticated users to query /api/v1/instance/peers?filter=suspended"`
+
 	AccountsRegistrationOpen bool `name:"accounts-registration-open" usage:"Allow anyone to submit an account signup request. If false, server will be invite-only."`
 	AccountsApprovalRequired bool `name:"accounts-approval-required" usage:"Do account signups require approval by an admin or moderator before user can log in? If false, new registrations will be automatically approved."`
 	AccountsReasonRequired   bool `name:"accounts-reason-required" usage:"Do new account signups require a reason to be submitted on registration?"`
diff --git a/internal/config/defaults.go b/internal/config/defaults.go
index f9f0bdba9..5bfd7aa53 100644
--- a/internal/config/defaults.go
+++ b/internal/config/defaults.go
@@ -46,6 +46,9 @@ var Defaults = Configuration{
 	WebTemplateBaseDir: "./web/template/",
 	WebAssetBaseDir:    "./web/assets/",
 
+	InstanceExposePeers:     false,
+	InstanceExposeSuspended: false,
+
 	AccountsRegistrationOpen: true,
 	AccountsApprovalRequired: true,
 	AccountsReasonRequired:   true,
diff --git a/internal/config/flags.go b/internal/config/flags.go
index 6f946f1d6..891449934 100644
--- a/internal/config/flags.go
+++ b/internal/config/flags.go
@@ -60,6 +60,10 @@ func AddServerFlags(cmd *cobra.Command) {
 		cmd.Flags().String(WebTemplateBaseDirFlag(), cfg.WebTemplateBaseDir, fieldtag("WebTemplateBaseDir", "usage"))
 		cmd.Flags().String(WebAssetBaseDirFlag(), cfg.WebAssetBaseDir, fieldtag("WebAssetBaseDir", "usage"))
 
+		// Instance
+		cmd.Flags().Bool(InstanceExposePeersFlag(), cfg.InstanceExposePeers, fieldtag("InstanceExposePeers", "usage"))
+		cmd.Flags().Bool(InstanceExposeSuspendedFlag(), cfg.InstanceExposeSuspended, fieldtag("InstanceExposeSuspended", "usage"))
+
 		// Accounts
 		cmd.Flags().Bool(AccountsRegistrationOpenFlag(), cfg.AccountsRegistrationOpen, fieldtag("AccountsRegistrationOpen", "usage"))
 		cmd.Flags().Bool(AccountsApprovalRequiredFlag(), cfg.AccountsApprovalRequired, fieldtag("AccountsApprovalRequired", "usage"))
diff --git a/internal/config/helpers.gen.go b/internal/config/helpers.gen.go
index a48828059..a4c2adebf 100644
--- a/internal/config/helpers.gen.go
+++ b/internal/config/helpers.gen.go
@@ -543,6 +543,56 @@ func GetWebAssetBaseDir() string { return global.GetWebAssetBaseDir() }
 // SetWebAssetBaseDir safely sets the value for global configuration 'WebAssetBaseDir' field
 func SetWebAssetBaseDir(v string) { global.SetWebAssetBaseDir(v) }
 
+// GetInstanceExposePeers safely fetches the Configuration value for state's 'InstanceExposePeers' field
+func (st *ConfigState) GetInstanceExposePeers() (v bool) {
+	st.mutex.Lock()
+	v = st.config.InstanceExposePeers
+	st.mutex.Unlock()
+	return
+}
+
+// SetInstanceExposePeers safely sets the Configuration value for state's 'InstanceExposePeers' field
+func (st *ConfigState) SetInstanceExposePeers(v bool) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.InstanceExposePeers = v
+	st.reloadToViper()
+}
+
+// InstanceExposePeersFlag returns the flag name for the 'InstanceExposePeers' field
+func InstanceExposePeersFlag() string { return "instance-expose-peers" }
+
+// GetInstanceExposePeers safely fetches the value for global configuration 'InstanceExposePeers' field
+func GetInstanceExposePeers() bool { return global.GetInstanceExposePeers() }
+
+// SetInstanceExposePeers safely sets the value for global configuration 'InstanceExposePeers' field
+func SetInstanceExposePeers(v bool) { global.SetInstanceExposePeers(v) }
+
+// GetInstanceExposeSuspended safely fetches the Configuration value for state's 'InstanceExposeSuspended' field
+func (st *ConfigState) GetInstanceExposeSuspended() (v bool) {
+	st.mutex.Lock()
+	v = st.config.InstanceExposeSuspended
+	st.mutex.Unlock()
+	return
+}
+
+// SetInstanceExposeSuspended safely sets the Configuration value for state's 'InstanceExposeSuspended' field
+func (st *ConfigState) SetInstanceExposeSuspended(v bool) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.InstanceExposeSuspended = v
+	st.reloadToViper()
+}
+
+// InstanceExposeSuspendedFlag returns the flag name for the 'InstanceExposeSuspended' field
+func InstanceExposeSuspendedFlag() string { return "instance-expose-suspended" }
+
+// GetInstanceExposeSuspended safely fetches the value for global configuration 'InstanceExposeSuspended' field
+func GetInstanceExposeSuspended() bool { return global.GetInstanceExposeSuspended() }
+
+// SetInstanceExposeSuspended safely sets the value for global configuration 'InstanceExposeSuspended' field
+func SetInstanceExposeSuspended(v bool) { global.SetInstanceExposeSuspended(v) }
+
 // GetAccountsRegistrationOpen safely fetches the Configuration value for state's 'AccountsRegistrationOpen' field
 func (st *ConfigState) GetAccountsRegistrationOpen() (v bool) {
 	st.mutex.Lock()
diff --git a/internal/db/bundb/instance.go b/internal/db/bundb/instance.go
index d16fac90b..c8a9c5776 100644
--- a/internal/db/bundb/instance.go
+++ b/internal/db/bundb/instance.go
@@ -98,6 +98,25 @@ func (i *instanceDB) CountInstanceDomains(ctx context.Context, domain string) (i
 	return count, nil
 }
 
+func (i *instanceDB) GetInstancePeers(ctx context.Context, includeSuspended bool) ([]*gtsmodel.Instance, db.Error) {
+	instances := []*gtsmodel.Instance{}
+
+	q := i.conn.
+		NewSelect().
+		Model(&instances).
+		Where("domain != ?", config.GetHost())
+
+	if !includeSuspended {
+		q = q.Where("? IS NULL", bun.Ident("suspended_at"))
+	}
+
+	if err := q.Scan(ctx); err != nil {
+		return nil, i.conn.ProcessError(err)
+	}
+
+	return instances, nil
+}
+
 func (i *instanceDB) GetInstanceAccounts(ctx context.Context, domain string, maxID string, limit int) ([]*gtsmodel.Account, db.Error) {
 	logrus.Debug("GetAccountsForInstance")
 
diff --git a/internal/db/instance.go b/internal/db/instance.go
index 45ff7d7b4..9e69d1b9b 100644
--- a/internal/db/instance.go
+++ b/internal/db/instance.go
@@ -37,4 +37,7 @@ type Instance interface {
 
 	// GetInstanceAccounts returns a slice of accounts from the given instance, arranged by ID.
 	GetInstanceAccounts(ctx context.Context, domain string, maxID string, limit int) ([]*gtsmodel.Account, Error)
+
+	// GetInstancePeers returns a slice of instances that the host instance knows about.
+	GetInstancePeers(ctx context.Context, includeSuspended bool) ([]*gtsmodel.Instance, Error)
 }
diff --git a/internal/processing/admin/importdomainblocks.go b/internal/processing/admin/importdomainblocks.go
index 64f02128a..b78589b8a 100644
--- a/internal/processing/admin/importdomainblocks.go
+++ b/internal/processing/admin/importdomainblocks.go
@@ -55,7 +55,7 @@ func (p *processor) DomainBlocksImport(ctx context.Context, account *gtsmodel.Ac
 
 	blocks := []*apimodel.DomainBlock{}
 	for _, d := range d {
-		block, err := p.DomainBlockCreate(ctx, account, d.Domain, false, d.PublicComment, "", "")
+		block, err := p.DomainBlockCreate(ctx, account, d.Domain.Domain, false, d.PublicComment, "", "")
 
 		if err != nil {
 			return nil, err
diff --git a/internal/processing/instance.go b/internal/processing/instance.go
index ab601d3b3..a95f87ebd 100644
--- a/internal/processing/instance.go
+++ b/internal/processing/instance.go
@@ -21,13 +21,16 @@ package processing
 import (
 	"context"
 	"fmt"
+	"sort"
 
 	apimodel "github.com/superseriousbusiness/gotosocial/internal/api/model"
 	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
+	"github.com/superseriousbusiness/gotosocial/internal/oauth"
 	"github.com/superseriousbusiness/gotosocial/internal/text"
+	"github.com/superseriousbusiness/gotosocial/internal/util"
 	"github.com/superseriousbusiness/gotosocial/internal/validate"
 )
 
@@ -45,6 +48,67 @@ func (p *processor) InstanceGet(ctx context.Context, domain string) (*apimodel.I
 	return ai, nil
 }
 
+func (p *processor) InstancePeersGet(ctx context.Context, authed *oauth.Auth, includeSuspended bool, includeOpen bool, flat bool) (interface{}, gtserror.WithCode) {
+	domains := []*apimodel.Domain{}
+
+	if includeOpen {
+		if !config.GetInstanceExposePeers() && (authed.Account == nil || authed.User == nil) {
+			err := fmt.Errorf("peers open query requires an authenticated account/user")
+			return nil, gtserror.NewErrorUnauthorized(err, err.Error())
+		}
+
+		instances, err := p.db.GetInstancePeers(ctx, false)
+		if err != nil && err != db.ErrNoEntries {
+			err = fmt.Errorf("error selecting instance peers: %s", err)
+			return nil, gtserror.NewErrorInternalError(err)
+		}
+
+		for _, i := range instances {
+			domain := &apimodel.Domain{Domain: i.Domain}
+			domains = append(domains, domain)
+		}
+	}
+
+	if includeSuspended {
+		if !config.GetInstanceExposeSuspended() && (authed.Account == nil || authed.User == nil) {
+			err := fmt.Errorf("peers suspended query requires an authenticated account/user")
+			return nil, gtserror.NewErrorUnauthorized(err, err.Error())
+		}
+
+		domainBlocks := []*gtsmodel.DomainBlock{}
+		if err := p.db.GetAll(ctx, &domainBlocks); err != nil && err != db.ErrNoEntries {
+			return nil, gtserror.NewErrorInternalError(err)
+		}
+
+		for _, d := range domainBlocks {
+			if d.Obfuscate {
+				d.Domain = obfuscate(d.Domain)
+			}
+
+			domain := &apimodel.Domain{
+				Domain:        d.Domain,
+				SuspendedAt:   util.FormatISO8601(d.CreatedAt),
+				PublicComment: d.PublicComment,
+			}
+			domains = append(domains, domain)
+		}
+	}
+
+	sort.Slice(domains, func(i, j int) bool {
+		return domains[i].Domain < domains[j].Domain
+	})
+
+	if flat {
+		flattened := []string{}
+		for _, d := range domains {
+			flattened = append(flattened, d.Domain)
+		}
+		return flattened, nil
+	}
+
+	return domains, nil
+}
+
 func (p *processor) InstancePatch(ctx context.Context, form *apimodel.InstanceSettingsUpdateRequest) (*apimodel.Instance, gtserror.WithCode) {
 	// fetch the instance entry from the db for processing
 	i := &gtsmodel.Instance{}
@@ -160,3 +224,15 @@ func (p *processor) InstancePatch(ctx context.Context, form *apimodel.InstanceSe
 
 	return ai, nil
 }
+
+func obfuscate(domain string) string {
+	obfuscated := make([]rune, len(domain))
+	for i, r := range domain {
+		if i%3 == 1 || i%5 == 1 {
+			obfuscated[i] = '*'
+		} else {
+			obfuscated[i] = r
+		}
+	}
+	return string(obfuscated)
+}
diff --git a/internal/processing/processor.go b/internal/processing/processor.go
index 3afc25196..8572b583c 100644
--- a/internal/processing/processor.go
+++ b/internal/processing/processor.go
@@ -137,6 +137,7 @@ type Processor interface {
 
 	// InstanceGet retrieves instance information for serving at api/v1/instance
 	InstanceGet(ctx context.Context, domain string) (*apimodel.Instance, gtserror.WithCode)
+	InstancePeersGet(ctx context.Context, authed *oauth.Auth, includeSuspended bool, includeOpen bool, flat bool) (interface{}, gtserror.WithCode)
 	// InstancePatch updates this instance according to the given form.
 	//
 	// It should already be ascertained that the requesting account is authenticated and an admin.
diff --git a/internal/typeutils/internaltofrontend.go b/internal/typeutils/internaltofrontend.go
index 364e7152c..774739d85 100644
--- a/internal/typeutils/internaltofrontend.go
+++ b/internal/typeutils/internaltofrontend.go
@@ -701,8 +701,10 @@ func (c *converter) NotificationToAPINotification(ctx context.Context, n *gtsmod
 
 func (c *converter) DomainBlockToAPIDomainBlock(ctx context.Context, b *gtsmodel.DomainBlock, export bool) (*model.DomainBlock, error) {
 	domainBlock := &model.DomainBlock{
-		Domain:        b.Domain,
-		PublicComment: b.PublicComment,
+		Domain: model.Domain{
+			Domain:        b.Domain,
+			PublicComment: b.PublicComment,
+		},
 	}
 
 	// if we're exporting a domain block, return it with minimal information attached