[feature] Fetch + display custom emoji in statuses from remote instances (#807)

* start implementing remote emoji fetcher

* update status where pk

* aaa

* tidy up a little

* check size limits for emojis

* thank you linter, i love you <3

* update swagger docs

* add emoji dereference test

* make emoji max sizes configurable

* normalize db.ErrAlreadyExists

20 files changed, 363 insertions, 34 deletions

diff --git a/internal/api/client/admin/emojicreate.go b/internal/api/client/admin/emojicreate.go
index 39ebd5adf..eef49b2c7 100644
--- a/internal/api/client/admin/emojicreate.go
+++ b/internal/api/client/admin/emojicreate.go
@@ -26,6 +26,7 @@ import (
 	"github.com/gin-gonic/gin"
 	"github.com/superseriousbusiness/gotosocial/internal/api"
 	"github.com/superseriousbusiness/gotosocial/internal/api/model"
+	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/gtserror"
 	"github.com/superseriousbusiness/gotosocial/internal/oauth"
 	"github.com/superseriousbusiness/gotosocial/internal/validate"
@@ -56,7 +57,9 @@ import (
 //   required: true
 // - name: image
 //   in: formData
-//   description: A png or gif image of the emoji. Animated pngs work too!
+//   description: |-
+//     A png or gif image of the emoji. Animated pngs work too!
+//     To ensure compatibility with other fedi implementations, emoji size limit is 50kb by default.
 //   type: file
 //   required: true
 //
@@ -126,5 +129,10 @@ func validateCreateEmoji(form *model.EmojiCreateRequest) error {
 		return errors.New("no emoji given")
 	}
 
+	maxSize := config.GetMediaEmojiLocalMaxSize()
+	if form.Image.Size > int64(maxSize) {
+		return fmt.Errorf("emoji image too large: image is %dKB but size limit for custom emojis is %dKB", form.Image.Size/1024, maxSize/1024)
+	}
+
 	return validate.EmojiShortcode(form.Shortcode)
 }
diff --git a/internal/config/config.go b/internal/config/config.go
index d746bd12a..7efed1815 100644
--- a/internal/config/config.go
+++ b/internal/config/config.go
@@ -79,6 +79,8 @@ type Configuration struct {
 	MediaDescriptionMinChars int `name:"media-description-min-chars" usage:"Min required chars for an image description"`
 	MediaDescriptionMaxChars int `name:"media-description-max-chars" usage:"Max permitted chars for an image description"`
 	MediaRemoteCacheDays     int `name:"media-remote-cache-days" usage:"Number of days to locally cache media from remote instances. If set to 0, remote media will be kept indefinitely."`
+	MediaEmojiLocalMaxSize   int `name:"media-emoji-local-max-size" usage:"Max size in bytes of emojis uploaded to this instance via the admin API."`
+	MediaEmojiRemoteMaxSize  int `name:"media-emoji-remote-max-size" usage:"Max size in bytes of emojis to download from other instances."`
 
 	StorageBackend       string `name:"storage-backend" usage:"Storage backend to use for media attachments"`
 	StorageLocalBasePath string `name:"storage-local-base-path" usage:"Full path to an already-created directory where gts should store/retrieve media files. Subfolders will be created within this dir."`
diff --git a/internal/config/defaults.go b/internal/config/defaults.go
index 48fd8f214..8a4a3129e 100644
--- a/internal/config/defaults.go
+++ b/internal/config/defaults.go
@@ -58,6 +58,8 @@ var Defaults = Configuration{
 	MediaDescriptionMinChars: 0,
 	MediaDescriptionMaxChars: 500,
 	MediaRemoteCacheDays:     30,
+	MediaEmojiLocalMaxSize:   51200,  // 50kb
+	MediaEmojiRemoteMaxSize:  102400, // 100kb
 
 	StorageBackend:       "local",
 	StorageLocalBasePath: "/gotosocial/storage",
diff --git a/internal/config/flags.go b/internal/config/flags.go
index 891449934..9b4c40428 100644
--- a/internal/config/flags.go
+++ b/internal/config/flags.go
@@ -75,6 +75,8 @@ func AddServerFlags(cmd *cobra.Command) {
 		cmd.Flags().Int(MediaDescriptionMinCharsFlag(), cfg.MediaDescriptionMinChars, fieldtag("MediaDescriptionMinChars", "usage"))
 		cmd.Flags().Int(MediaDescriptionMaxCharsFlag(), cfg.MediaDescriptionMaxChars, fieldtag("MediaDescriptionMaxChars", "usage"))
 		cmd.Flags().Int(MediaRemoteCacheDaysFlag(), cfg.MediaRemoteCacheDays, fieldtag("MediaRemoteCacheDays", "usage"))
+		cmd.Flags().Int(MediaEmojiLocalMaxSizeFlag(), cfg.MediaEmojiLocalMaxSize, fieldtag("MediaEmojiLocalMaxSize", "usage"))
+		cmd.Flags().Int(MediaEmojiRemoteMaxSizeFlag(), cfg.MediaEmojiRemoteMaxSize, fieldtag("MediaEmojiRemoteMaxSize", "usage"))
 
 		// Storage
 		cmd.Flags().String(StorageBackendFlag(), cfg.StorageBackend, fieldtag("StorageBackend", "usage"))
diff --git a/internal/config/helpers.gen.go b/internal/config/helpers.gen.go
index a5dcc4c1c..51891a537 100644
--- a/internal/config/helpers.gen.go
+++ b/internal/config/helpers.gen.go
@@ -793,6 +793,56 @@ func GetMediaRemoteCacheDays() int { return global.GetMediaRemoteCacheDays() }
 // SetMediaRemoteCacheDays safely sets the value for global configuration 'MediaRemoteCacheDays' field
 func SetMediaRemoteCacheDays(v int) { global.SetMediaRemoteCacheDays(v) }
 
+// GetMediaEmojiLocalMaxSize safely fetches the Configuration value for state's 'MediaEmojiLocalMaxSize' field
+func (st *ConfigState) GetMediaEmojiLocalMaxSize() (v int) {
+	st.mutex.Lock()
+	v = st.config.MediaEmojiLocalMaxSize
+	st.mutex.Unlock()
+	return
+}
+
+// SetMediaEmojiLocalMaxSize safely sets the Configuration value for state's 'MediaEmojiLocalMaxSize' field
+func (st *ConfigState) SetMediaEmojiLocalMaxSize(v int) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.MediaEmojiLocalMaxSize = v
+	st.reloadToViper()
+}
+
+// MediaEmojiLocalMaxSizeFlag returns the flag name for the 'MediaEmojiLocalMaxSize' field
+func MediaEmojiLocalMaxSizeFlag() string { return "media-emoji-local-max-size" }
+
+// GetMediaEmojiLocalMaxSize safely fetches the value for global configuration 'MediaEmojiLocalMaxSize' field
+func GetMediaEmojiLocalMaxSize() int { return global.GetMediaEmojiLocalMaxSize() }
+
+// SetMediaEmojiLocalMaxSize safely sets the value for global configuration 'MediaEmojiLocalMaxSize' field
+func SetMediaEmojiLocalMaxSize(v int) { global.SetMediaEmojiLocalMaxSize(v) }
+
+// GetMediaEmojiRemoteMaxSize safely fetches the Configuration value for state's 'MediaEmojiRemoteMaxSize' field
+func (st *ConfigState) GetMediaEmojiRemoteMaxSize() (v int) {
+	st.mutex.Lock()
+	v = st.config.MediaEmojiRemoteMaxSize
+	st.mutex.Unlock()
+	return
+}
+
+// SetMediaEmojiRemoteMaxSize safely sets the Configuration value for state's 'MediaEmojiRemoteMaxSize' field
+func (st *ConfigState) SetMediaEmojiRemoteMaxSize(v int) {
+	st.mutex.Lock()
+	defer st.mutex.Unlock()
+	st.config.MediaEmojiRemoteMaxSize = v
+	st.reloadToViper()
+}
+
+// MediaEmojiRemoteMaxSizeFlag returns the flag name for the 'MediaEmojiRemoteMaxSize' field
+func MediaEmojiRemoteMaxSizeFlag() string { return "media-emoji-remote-max-size" }
+
+// GetMediaEmojiRemoteMaxSize safely fetches the value for global configuration 'MediaEmojiRemoteMaxSize' field
+func GetMediaEmojiRemoteMaxSize() int { return global.GetMediaEmojiRemoteMaxSize() }
+
+// SetMediaEmojiRemoteMaxSize safely sets the value for global configuration 'MediaEmojiRemoteMaxSize' field
+func SetMediaEmojiRemoteMaxSize(v int) { global.SetMediaEmojiRemoteMaxSize(v) }
+
 // GetStorageBackend safely fetches the Configuration value for state's 'StorageBackend' field
 func (st *ConfigState) GetStorageBackend() (v string) {
 	st.mutex.Lock()
diff --git a/internal/config/validate.go b/internal/config/validate.go
index 064eae07a..b9fdb013b 100644
--- a/internal/config/validate.go
+++ b/internal/config/validate.go
@@ -67,6 +67,14 @@ func Validate() error {
 		errs = append(errs, fmt.Errorf("%s must be set", WebAssetBaseDirFlag()))
 	}
 
+	if m := GetMediaEmojiLocalMaxSize(); m < 0 {
+		errs = append(errs, fmt.Errorf("%s must not be less than 0", MediaEmojiLocalMaxSizeFlag()))
+	}
+
+	if m := GetMediaEmojiRemoteMaxSize(); m < 0 {
+		errs = append(errs, fmt.Errorf("%s must not be less than 0", MediaEmojiRemoteMaxSizeFlag()))
+	}
+
 	if len(errs) > 0 {
 		errStrings := []string{}
 		for _, err := range errs {
diff --git a/internal/config/validate_test.go b/internal/config/validate_test.go
index c3a998a4a..f7450cdaa 100644
--- a/internal/config/validate_test.go
+++ b/internal/config/validate_test.go
@@ -141,6 +141,16 @@ func (suite *ConfigValidateTestSuite) TestValidateConfigBadProtocolNoHost() {
 	suite.EqualError(err, "host must be set; protocol must be set to either http or https, provided value was foo")
 }
 
+func (suite *ConfigValidateTestSuite) TestValidateConfigBadEmojiSizes() {
+	testrig.InitTestConfig()
+
+	config.SetMediaEmojiLocalMaxSize(-10)
+	config.SetMediaEmojiRemoteMaxSize(-50)
+
+	err := config.Validate()
+	suite.EqualError(err, "media-emoji-local-max-size must not be less than 0; media-emoji-remote-max-size must not be less than 0")
+}
+
 func TestConfigValidateTestSuite(t *testing.T) {
 	suite.Run(t, &ConfigValidateTestSuite{})
 }
diff --git a/internal/db/bundb/errors.go b/internal/db/bundb/errors.go
index 67a673e15..7d0157373 100644
--- a/internal/db/bundb/errors.go
+++ b/internal/db/bundb/errors.go
@@ -19,7 +19,7 @@ func processPostgresError(err error) db.Error {
 	// (https://www.postgresql.org/docs/10/errcodes-appendix.html)
 	switch pgErr.Code {
 	case "23505" /* unique_violation */ :
-		return db.NewErrAlreadyExists(pgErr.Message)
+		return db.ErrAlreadyExists
 	default:
 		return err
 	}
@@ -36,7 +36,7 @@ func processSQLiteError(err error) db.Error {
 	// Handle supplied error code:
 	switch sqliteErr.Code() {
 	case sqlite3.SQLITE_CONSTRAINT_UNIQUE, sqlite3.SQLITE_CONSTRAINT_PRIMARYKEY:
-		return db.NewErrAlreadyExists(err.Error())
+		return db.ErrAlreadyExists
 	default:
 		return err
 	}
diff --git a/internal/db/bundb/status.go b/internal/db/bundb/status.go
index 378ee1a7a..e247e8940 100644
--- a/internal/db/bundb/status.go
+++ b/internal/db/bundb/status.go
@@ -22,6 +22,7 @@ import (
 	"container/list"
 	"context"
 	"database/sql"
+	"errors"
 	"time"
 
 	"github.com/superseriousbusiness/gotosocial/internal/cache"
@@ -175,6 +176,57 @@ func (s *statusDB) PutStatus(ctx context.Context, status *gtsmodel.Status) db.Er
 	})
 }
 
+func (s *statusDB) UpdateStatus(ctx context.Context, status *gtsmodel.Status) (*gtsmodel.Status, db.Error) {
+	err := s.conn.RunInTx(ctx, func(tx bun.Tx) error {
+		// create links between this status and any emojis it uses
+		for _, i := range status.EmojiIDs {
+			if _, err := tx.NewInsert().Model(&gtsmodel.StatusToEmoji{
+				StatusID: status.ID,
+				EmojiID:  i,
+			}).Exec(ctx); err != nil {
+				err = s.conn.errProc(err)
+				if !errors.Is(err, db.ErrAlreadyExists) {
+					return err
+				}
+			}
+		}
+
+		// create links between this status and any tags it uses
+		for _, i := range status.TagIDs {
+			if _, err := tx.NewInsert().Model(&gtsmodel.StatusToTag{
+				StatusID: status.ID,
+				TagID:    i,
+			}).Exec(ctx); err != nil {
+				err = s.conn.errProc(err)
+				if !errors.Is(err, db.ErrAlreadyExists) {
+					return err
+				}
+			}
+		}
+
+		// change the status ID of the media attachments to this status
+		for _, a := range status.Attachments {
+			a.StatusID = status.ID
+			a.UpdatedAt = time.Now()
+			if _, err := tx.NewUpdate().Model(a).
+				Where("id = ?", a.ID).
+				Exec(ctx); err != nil {
+				return err
+			}
+		}
+
+		// Finally, update the status itself
+		if _, err := tx.NewUpdate().Model(status).WherePK().Exec(ctx); err != nil {
+			return err
+		}
+
+		s.cache.Put(status)
+		return nil
+	})
+
+	return status, err
+}
+
 func (s *statusDB) GetStatusParents(ctx context.Context, status *gtsmodel.Status, onlyDirect bool) ([]*gtsmodel.Status, db.Error) {
 	parents := []*gtsmodel.Status{}
 	s.statusParent(ctx, status, &parents, onlyDirect)
diff --git a/internal/db/emoji.go b/internal/db/emoji.go
index 0038e10e4..374fd7b12 100644
--- a/internal/db/emoji.go
+++ b/internal/db/emoji.go
@@ -35,4 +35,6 @@ type Emoji interface {
 	// GetEmojiByShortcodeDomain gets an emoji based on its shortcode and domain.
 	// For local emoji, domain should be an empty string.
 	GetEmojiByShortcodeDomain(ctx context.Context, shortcode string, domain string) (*gtsmodel.Emoji, Error)
+	// GetEmojiByURI returns one emoji based on its ActivityPub URI.
+	GetEmojiByURI(ctx context.Context, uri string) (*gtsmodel.Emoji, Error)
 }
diff --git a/internal/db/error.go b/internal/db/error.go
index 9ac0b6aa0..8dc344360 100644
--- a/internal/db/error.go
+++ b/internal/db/error.go
@@ -28,19 +28,8 @@ var (
 	ErrNoEntries Error = fmt.Errorf("no entries")
 	// ErrMultipleEntries is returned when a caller expected ONE entry for a query, but multiples were found.
 	ErrMultipleEntries Error = fmt.Errorf("multiple entries")
+	// ErrAlreadyExists is returned when a conflict was encountered in the db when doing an insert.
+	ErrAlreadyExists Error = fmt.Errorf("already exists")
 	// ErrUnknown denotes an unknown database error.
 	ErrUnknown Error = fmt.Errorf("unknown error")
 )
-
-// ErrAlreadyExists is returned when a caller tries to insert a database entry that already exists in the db.
-type ErrAlreadyExists struct {
-	message string
-}
-
-func (e *ErrAlreadyExists) Error() string {
-	return e.message
-}
-
-func NewErrAlreadyExists(msg string) error {
-	return &ErrAlreadyExists{message: msg}
-}
diff --git a/internal/db/status.go b/internal/db/status.go
index 74eb0d4ff..307d9ea74 100644
--- a/internal/db/status.go
+++ b/internal/db/status.go
@@ -38,6 +38,9 @@ type Status interface {
 	// PutStatus stores one status in the database.
 	PutStatus(ctx context.Context, status *gtsmodel.Status) Error
 
+	// UpdateStatus updates one status in the database and returns it to the caller.
+	UpdateStatus(ctx context.Context, status *gtsmodel.Status) (*gtsmodel.Status, Error)
+
 	// CountStatusReplies returns the amount of replies recorded for a status, or an error if something goes wrong
 	CountStatusReplies(ctx context.Context, status *gtsmodel.Status) (int, Error)
 
diff --git a/internal/federation/dereferencing/dereferencer.go b/internal/federation/dereferencing/dereferencer.go
index 4f7559be3..0fad2405e 100644
--- a/internal/federation/dereferencing/dereferencer.go
+++ b/internal/federation/dereferencing/dereferencer.go
@@ -41,6 +41,7 @@ type Dereferencer interface {
 	GetRemoteInstance(ctx context.Context, username string, remoteInstanceURI *url.URL) (*gtsmodel.Instance, error)
 
 	GetRemoteMedia(ctx context.Context, requestingUsername string, accountID string, remoteURL string, ai *media.AdditionalMediaInfo) (*media.ProcessingMedia, error)
+	GetRemoteEmoji(ctx context.Context, requestingUsername string, remoteURL string, shortcode string, id string, emojiURI string, ai *media.AdditionalEmojiInfo) (*media.ProcessingEmoji, error)
 
 	DereferenceAnnounce(ctx context.Context, announce *gtsmodel.Status, requestingUsername string) error
 	DereferenceThread(ctx context.Context, username string, statusIRI *url.URL) error
diff --git a/internal/federation/dereferencing/emoji.go b/internal/federation/dereferencing/emoji.go
new file mode 100644
index 000000000..49811b131
--- /dev/null
+++ b/internal/federation/dereferencing/emoji.go
@@ -0,0 +1,51 @@
+/*
+   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 dereferencing
+
+import (
+	"context"
+	"fmt"
+	"io"
+	"net/url"
+
+	"github.com/superseriousbusiness/gotosocial/internal/media"
+)
+
+func (d *deref) GetRemoteEmoji(ctx context.Context, requestingUsername string, remoteURL string, shortcode string, id string, emojiURI string, ai *media.AdditionalEmojiInfo) (*media.ProcessingEmoji, error) {
+	t, err := d.transportController.NewTransportForUsername(ctx, requestingUsername)
+	if err != nil {
+		return nil, fmt.Errorf("GetRemoteEmoji: error creating transport: %s", err)
+	}
+
+	derefURI, err := url.Parse(remoteURL)
+	if err != nil {
+		return nil, fmt.Errorf("GetRemoteEmoji: error parsing url: %s", err)
+	}
+
+	dataFunc := func(innerCtx context.Context) (io.Reader, int, error) {
+		return t.DereferenceMedia(innerCtx, derefURI)
+	}
+
+	processingMedia, err := d.mediaManager.ProcessEmoji(ctx, dataFunc, nil, shortcode, id, emojiURI, ai)
+	if err != nil {
+		return nil, fmt.Errorf("GetRemoteEmoji: error processing emoji: %s", err)
+	}
+
+	return processingMedia, nil
+}
diff --git a/internal/federation/dereferencing/emoji_test.go b/internal/federation/dereferencing/emoji_test.go
new file mode 100644
index 000000000..b03d839ce
--- /dev/null
+++ b/internal/federation/dereferencing/emoji_test.go
@@ -0,0 +1,95 @@
+/*
+   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 dereferencing_test
+
+import (
+	"context"
+	"testing"
+	"time"
+
+	"github.com/stretchr/testify/suite"
+	"github.com/superseriousbusiness/gotosocial/internal/media"
+)
+
+type EmojiTestSuite struct {
+	DereferencerStandardTestSuite
+}
+
+func (suite *EmojiTestSuite) TestDereferenceEmojiBlocking() {
+	ctx := context.Background()
+	fetchingAccount := suite.testAccounts["local_account_1"]
+	emojiImageRemoteURL := "http://example.org/media/emojis/1781772.gif"
+	emojiImageStaticRemoteURL := "http://example.org/media/emojis/1781772.gif"
+	emojiURI := "http://example.org/emojis/1781772"
+	emojiShortcode := "peglin"
+	emojiID := "01GCBMGNZBKMEE1KTZ6PMJEW5D"
+	emojiDomain := "example.org"
+	emojiDisabled := false
+	emojiVisibleInPicker := false
+
+	ai := &media.AdditionalEmojiInfo{
+		Domain:               &emojiDomain,
+		ImageRemoteURL:       &emojiImageRemoteURL,
+		ImageStaticRemoteURL: &emojiImageStaticRemoteURL,
+		Disabled:             &emojiDisabled,
+		VisibleInPicker:      &emojiVisibleInPicker,
+	}
+
+	processingEmoji, err := suite.dereferencer.GetRemoteEmoji(ctx, fetchingAccount.Username, emojiImageRemoteURL, emojiShortcode, emojiID, emojiURI, ai)
+	suite.NoError(err)
+
+	// make a blocking call to load the emoji from the in-process media
+	emoji, err := processingEmoji.LoadEmoji(ctx)
+	suite.NoError(err)
+	suite.NotNil(emoji)
+
+	suite.Equal(emojiID, emoji.ID)
+	suite.WithinDuration(time.Now(), emoji.CreatedAt, 10*time.Second)
+	suite.WithinDuration(time.Now(), emoji.UpdatedAt, 10*time.Second)
+	suite.Equal(emojiShortcode, emoji.Shortcode)
+	suite.Equal(emojiDomain, emoji.Domain)
+	suite.Equal(emojiImageRemoteURL, emoji.ImageRemoteURL)
+	suite.Equal(emojiImageStaticRemoteURL, emoji.ImageStaticRemoteURL)
+	suite.Contains(emoji.ImageURL, "/emoji/original/01GCBMGNZBKMEE1KTZ6PMJEW5D.gif")
+	suite.Contains(emoji.ImageStaticURL, "emoji/static/01GCBMGNZBKMEE1KTZ6PMJEW5D.png")
+	suite.Contains(emoji.ImagePath, "/emoji/original/01GCBMGNZBKMEE1KTZ6PMJEW5D.gif")
+	suite.Contains(emoji.ImageStaticPath, "/emoji/static/01GCBMGNZBKMEE1KTZ6PMJEW5D.png")
+	suite.Equal("image/gif", emoji.ImageContentType)
+	suite.Equal("image/png", emoji.ImageStaticContentType)
+	suite.Equal(37796, emoji.ImageFileSize)
+	suite.Equal(7951, emoji.ImageStaticFileSize)
+	suite.WithinDuration(time.Now(), emoji.ImageUpdatedAt, 10*time.Second)
+	suite.False(*emoji.Disabled)
+	suite.Equal(emojiURI, emoji.URI)
+	suite.False(*emoji.VisibleInPicker)
+	suite.Empty(emoji.CategoryID)
+
+	// ensure that emoji is now in storage
+	stored, err := suite.storage.Get(ctx, emoji.ImagePath)
+	suite.NoError(err)
+	suite.Len(stored, emoji.ImageFileSize)
+
+	storedStatic, err := suite.storage.Get(ctx, emoji.ImageStaticPath)
+	suite.NoError(err)
+	suite.Len(storedStatic, emoji.ImageStaticFileSize)
+}
+
+func TestEmojiTestSuite(t *testing.T) {
+	suite.Run(t, new(EmojiTestSuite))
+}
diff --git a/internal/federation/dereferencing/status.go b/internal/federation/dereferencing/status.go
index e6e03646c..f3b7ee96e 100644
--- a/internal/federation/dereferencing/status.go
+++ b/internal/federation/dereferencing/status.go
@@ -26,10 +26,10 @@ import (
 	"net/url"
 	"strings"
 
-	"codeberg.org/gruf/go-kv"
 	"github.com/superseriousbusiness/activity/streams"
 	"github.com/superseriousbusiness/activity/streams/vocab"
 	"github.com/superseriousbusiness/gotosocial/internal/ap"
+	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/id"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
@@ -46,11 +46,7 @@ func (d *deref) EnrichRemoteStatus(ctx context.Context, username string, status
 		return nil, err
 	}
 
-	if err := d.db.UpdateByPrimaryKey(ctx, status); err != nil {
-		return nil, fmt.Errorf("EnrichRemoteStatus: error updating status: %s", err)
-	}
-
-	return status, nil
+	return d.db.UpdateStatus(ctx, status)
 }
 
 // GetRemoteStatus completely dereferences a remote status, converts it to a GtS model status,
@@ -225,12 +221,6 @@ func (d *deref) dereferenceStatusable(ctx context.Context, username string, remo
 // and attach them to the status. The status itself will not be added to the database yet,
 // that's up the caller to do.
 func (d *deref) populateStatusFields(ctx context.Context, status *gtsmodel.Status, requestingUsername string, includeParent bool) error {
-	l := log.WithFields(kv.Fields{
-
-		{"status", status},
-	}...)
-	l.Debug("entering function")
-
 	statusIRI, err := url.Parse(status.URI)
 	if err != nil {
 		return fmt.Errorf("populateStatusFields: couldn't parse status URI %s: %s", status.URI, err)
@@ -262,7 +252,9 @@ func (d *deref) populateStatusFields(ctx context.Context, status *gtsmodel.Statu
 	// TODO
 
 	// 3. Emojis
-	// TODO
+	if err := d.populateStatusEmojis(ctx, status, requestingUsername); err != nil {
+		return fmt.Errorf("populateStatusFields: error populating status emojis: %s", err)
+	}
 
 	// 4. Mentions
 	// TODO: do we need to handle removing empty mention objects and just using mention IDs slice?
@@ -413,6 +405,64 @@ func (d *deref) populateStatusAttachments(ctx context.Context, status *gtsmodel.
 	return nil
 }
 
+func (d *deref) populateStatusEmojis(ctx context.Context, status *gtsmodel.Status, requestingUsername string) error {
+	// At this point we should know:
+	// * the AP uri of the emoji
+	// * the domain of the emoji
+	// * the shortcode of the emoji
+	// * the remote URL of the image
+	// This should be enough to dereference the emoji
+
+	gotEmojis := make([]*gtsmodel.Emoji, 0, len(status.Emojis))
+	emojiIDs := make([]string, 0, len(status.Emojis))
+
+	for _, e := range status.Emojis {
+		var gotEmoji *gtsmodel.Emoji
+		var err error
+
+		// check if we've already got this emoji in the db
+		if gotEmoji, err = d.db.GetEmojiByURI(ctx, e.URI); err != nil && err != db.ErrNoEntries {
+			log.Errorf("populateStatusEmojis: error checking database for emoji %s: %s", e.URI, err)
+			continue
+		}
+
+		if gotEmoji == nil {
+			// it's new! go get it!
+			newEmojiID, err := id.NewRandomULID()
+			if err != nil {
+				log.Errorf("populateStatusEmojis: error generating id for remote emoji %s: %s", e.URI, err)
+				continue
+			}
+
+			processingEmoji, err := d.GetRemoteEmoji(ctx, requestingUsername, e.ImageRemoteURL, e.Shortcode, newEmojiID, e.URI, &media.AdditionalEmojiInfo{
+				Domain:               &e.Domain,
+				ImageRemoteURL:       &e.ImageRemoteURL,
+				ImageStaticRemoteURL: &e.ImageRemoteURL,
+				Disabled:             e.Disabled,
+				VisibleInPicker:      e.VisibleInPicker,
+			})
+
+			if err != nil {
+				log.Errorf("populateStatusEmojis: couldn't get remote emoji %s: %s", e.URI, err)
+				continue
+			}
+
+			if gotEmoji, err = processingEmoji.LoadEmoji(ctx); err != nil {
+				log.Errorf("populateStatusEmojis: couldn't load remote emoji %s: %s", e.URI, err)
+				continue
+			}
+		}
+
+		// if we get here, we either had the emoji already or we successfully fetched it
+		gotEmojis = append(gotEmojis, gotEmoji)
+		emojiIDs = append(emojiIDs, gotEmoji.ID)
+	}
+
+	status.Emojis = gotEmojis
+	status.EmojiIDs = emojiIDs
+	return nil
+}
+
 func (d *deref) populateStatusRepliedTo(ctx context.Context, status *gtsmodel.Status, requestingUsername string) error {
 	if status.InReplyToURI != "" && status.InReplyToID == "" {
 		statusURI, err := url.Parse(status.InReplyToURI)
diff --git a/internal/federation/federatingdb/create.go b/internal/federation/federatingdb/create.go
index a6e55f2ad..25e961bc3 100644
--- a/internal/federation/federatingdb/create.go
+++ b/internal/federation/federatingdb/create.go
@@ -226,8 +226,7 @@ func (f *federatingDB) createNote(ctx context.Context, note vocab.ActivityStream
 	status.ID = statusID
 
 	if err := f.db.PutStatus(ctx, status); err != nil {
-		var alreadyExistsError *db.ErrAlreadyExists
-		if errors.As(err, &alreadyExistsError) {
+		if errors.Is(err, db.ErrAlreadyExists) {
 			// the status already exists in the database, which means we've already handled everything else,
 			// so we can just return nil here and be done with it.
 			return nil
diff --git a/internal/gtsmodel/emoji.go b/internal/gtsmodel/emoji.go
index 106301041..2cc72a762 100644
--- a/internal/gtsmodel/emoji.go
+++ b/internal/gtsmodel/emoji.go
@@ -20,7 +20,7 @@ package gtsmodel
 
 import "time"
 
-// Emoji represents a custom emoji that's been uploaded through the admin UI, and is useable by instance denizens.
+// Emoji represents a custom emoji that's been uploaded through the admin UI or downloaded from a remote instance.
 type Emoji struct {
 	ID                     string    `validate:"required,ulid" bun:"type:CHAR(26),pk,nullzero,notnull,unique"`                                // id of this item in the database
 	CreatedAt              time.Time `validate:"-" bun:"type:timestamptz,nullzero,notnull,default:current_timestamp"`                         // when was item created
diff --git a/internal/media/processingemoji.go b/internal/media/processingemoji.go
index 3b3023f2a..121f54ddc 100644
--- a/internal/media/processingemoji.go
+++ b/internal/media/processingemoji.go
@@ -28,6 +28,7 @@ import (
 	"sync/atomic"
 	"time"
 
+	"github.com/superseriousbusiness/gotosocial/internal/config"
 	"github.com/superseriousbusiness/gotosocial/internal/db"
 	"github.com/superseriousbusiness/gotosocial/internal/gtsmodel"
 	"github.com/superseriousbusiness/gotosocial/internal/log"
@@ -170,6 +171,11 @@ func (p *ProcessingEmoji) store(ctx context.Context) error {
 		return fmt.Errorf("store: error executing data function: %s", err)
 	}
 
+	maxSize := config.GetMediaEmojiRemoteMaxSize()
+	if fileSize > maxSize {
+		return fmt.Errorf("store: emoji size (%db) is larger than allowed emojiRemoteMaxSize (%db)", fileSize, maxSize)
+	}
+
 	// defer closing the reader when we're done with it
 	defer func() {
 		if rc, ok := reader.(io.ReadCloser); ok {
diff --git a/internal/processing/status/util.go b/internal/processing/status/util.go
index 880de1db3..298d4fbd0 100644
--- a/internal/processing/status/util.go
+++ b/internal/processing/status/util.go
@@ -234,8 +234,7 @@ func (p *processor) ProcessTags(ctx context.Context, form *apimodel.AdvancedStat
 	}
 	for _, tag := range gtsTags {
 		if err := p.db.Put(ctx, tag); err != nil {
-			var alreadyExistsError *db.ErrAlreadyExists
-			if !errors.As(err, &alreadyExistsError) {
+			if !errors.Is(err, db.ErrAlreadyExists) {
 				return fmt.Errorf("error putting tags in db: %s", err)
 			}
 		}