Implement GET channels endpoints for APIv4 (#5363)

* implement get channels endpoints and updated drivers and unittests

* removed channel deletion on tear down, removed manage permission on get channels endpoints, and updated utils to add constant channel length

* added constants for user, team and channel length, updated context to use the model functions

* make sure team name length should be less than the minimum length and revert underscore to team name validity

* changed post test condition from notfound to unauthorized

14 files changed, 293 insertions, 42 deletions

diff --git a/api4/api.go b/api4/api.go
index 6348714b2..b05c1a7db 100644
--- a/api4/api.go
+++ b/api4/api.go
@@ -32,13 +32,14 @@ type Routes struct {
 	TeamMembers  *mux.Router // 'api/v4/teams/{team_id:[A-Za-z0-9_-]+}/members'
 	TeamMember   *mux.Router // 'api/v4/teams/{team_id:[A-Za-z0-9_-]+}/members/{user_id:[A-Za-z0-9_-]+}'
 
-	Channels              *mux.Router // 'api/v4/channels'
-	Channel               *mux.Router // 'api/v4/channels/{channel_id:[A-Za-z0-9]+}'
-	ChannelByName         *mux.Router // 'api/v4/teams/{team_id:[A-Za-z0-9]+}/channels/name/{channel_name:[A-Za-z0-9_-]+}'
-	ChannelsForTeam       *mux.Router // 'api/v4/teams/{team_id:[A-Za-z0-9]+}/channels'
-	ChannelMembers        *mux.Router // 'api/v4/channels/{channel_id:[A-Za-z0-9]+}/members'
-	ChannelMember         *mux.Router // 'api/v4/channels/{channel_id:[A-Za-z0-9]+}/members/{user_id:[A-Za-z0-9]+}'
-	ChannelMembersForUser *mux.Router // 'api/v4/users/{user_id:[A-Za-z0-9]+}/teams/{team_id:[A-Za-z0-9]+}/channels/members'
+	Channels                 *mux.Router // 'api/v4/channels'
+	Channel                  *mux.Router // 'api/v4/channels/{channel_id:[A-Za-z0-9]+}'
+	ChannelByName            *mux.Router // 'api/v4/teams/{team_id:[A-Za-z0-9]+}/channels/name/{channel_name:[A-Za-z0-9_-]+}'
+	ChannelByNameForTeamName *mux.Router // 'api/v4/teams/name/{team_name:[A-Za-z0-9_-]+}/channels/name/{channel_name:[A-Za-z0-9_-]+}'
+	ChannelsForTeam          *mux.Router // 'api/v4/teams/{team_id:[A-Za-z0-9]+}/channels'
+	ChannelMembers           *mux.Router // 'api/v4/channels/{channel_id:[A-Za-z0-9]+}/members'
+	ChannelMember            *mux.Router // 'api/v4/channels/{channel_id:[A-Za-z0-9]+}/members/{user_id:[A-Za-z0-9]+}'
+	ChannelMembersForUser    *mux.Router // 'api/v4/users/{user_id:[A-Za-z0-9]+}/teams/{team_id:[A-Za-z0-9]+}/channels/members'
 
 	Posts           *mux.Router // 'api/v4/posts'
 	Post            *mux.Router // 'api/v4/posts/{post_id:[A-Za-z0-9]+}'
@@ -102,7 +103,8 @@ func InitApi(full bool) {
 
 	BaseRoutes.Channels = BaseRoutes.ApiRoot.PathPrefix("/channels").Subrouter()
 	BaseRoutes.Channel = BaseRoutes.Channels.PathPrefix("/{channel_id:[A-Za-z0-9]+}").Subrouter()
-	BaseRoutes.ChannelByName = BaseRoutes.Team.PathPrefix("/name/{channel_name:[A-Za-z0-9_-]+}").Subrouter()
+	BaseRoutes.ChannelByName = BaseRoutes.Team.PathPrefix("/channels/name/{channel_name:[A-Za-z0-9_-]+}").Subrouter()
+	BaseRoutes.ChannelByNameForTeamName = BaseRoutes.TeamByName.PathPrefix("/channels/name/{channel_name:[A-Za-z0-9_-]+}").Subrouter()
 	BaseRoutes.ChannelsForTeam = BaseRoutes.Team.PathPrefix("/channels").Subrouter()
 	BaseRoutes.ChannelMembers = BaseRoutes.Channel.PathPrefix("/members").Subrouter()
 	BaseRoutes.ChannelMember = BaseRoutes.ChannelMembers.PathPrefix("/{user_id:[A-Za-z0-9]+}").Subrouter()
diff --git a/api4/apitestlib.go b/api4/apitestlib.go
index 0761a8b15..08ca338c5 100644
--- a/api4/apitestlib.go
+++ b/api4/apitestlib.go
@@ -278,11 +278,11 @@ func GenerateTestUsername() string {
 }
 
 func GenerateTestTeamName() string {
-	return "faketeam" + model.NewId()
+	return "faketeam" + model.NewRandomString(6)
 }
 
 func GenerateTestChannelName() string {
-	return "fakechannel" + model.NewId()
+	return "fakechannel" + model.NewRandomString(10)
 }
 
 func VerifyUserEmail(userId string) {
diff --git a/api4/channel.go b/api4/channel.go
index 09ed4b571..938511c14 100644
--- a/api4/channel.go
+++ b/api4/channel.go
@@ -18,6 +18,10 @@ func InitChannel() {
 	BaseRoutes.Channels.Handle("", ApiSessionRequired(createChannel)).Methods("POST")
 	BaseRoutes.Channels.Handle("/direct", ApiSessionRequired(createDirectChannel)).Methods("POST")
 
+	BaseRoutes.Channel.Handle("", ApiSessionRequired(getChannel)).Methods("GET")
+	BaseRoutes.ChannelByName.Handle("", ApiSessionRequired(getChannelByName)).Methods("GET")
+	BaseRoutes.ChannelByNameForTeamName.Handle("", ApiSessionRequired(getChannelByNameForTeamName)).Methods("GET")
+
 	BaseRoutes.ChannelMembers.Handle("", ApiSessionRequired(getChannelMembers)).Methods("GET")
 	BaseRoutes.ChannelMembersForUser.Handle("", ApiSessionRequired(getChannelMembersForUser)).Methods("GET")
 	BaseRoutes.ChannelMember.Handle("", ApiSessionRequired(getChannelMember)).Methods("GET")
@@ -88,6 +92,72 @@ func createDirectChannel(c *Context, w http.ResponseWriter, r *http.Request) {
 	}
 }
 
+func getChannel(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireChannelId()
+	if c.Err != nil {
+		return
+	}
+
+	if !app.SessionHasPermissionToChannel(c.Session, c.Params.ChannelId, model.PERMISSION_READ_CHANNEL) {
+		c.SetPermissionError(model.PERMISSION_READ_CHANNEL)
+		return
+	} 
+
+	if channel, err := app.GetChannel(c.Params.ChannelId); err != nil {
+		c.Err = err
+		return
+	} else {
+		w.Write([]byte(channel.ToJson()))
+		return
+	}
+}
+
+func getChannelByName(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireTeamId().RequireChannelName()
+	if c.Err != nil {
+		return
+	}
+
+	var channel *model.Channel
+	var err *model.AppError
+
+	if channel, err = app.GetChannelByName(c.Params.ChannelName, c.Params.TeamId); err != nil {
+		c.Err = err
+		return
+	} 
+
+	if !app.SessionHasPermissionToChannel(c.Session, channel.Id, model.PERMISSION_READ_CHANNEL) {
+		c.SetPermissionError(model.PERMISSION_READ_CHANNEL)
+		return
+	}
+	
+	w.Write([]byte(channel.ToJson()))
+	return
+}
+
+func getChannelByNameForTeamName(c *Context, w http.ResponseWriter, r *http.Request) {
+	c.RequireTeamName().RequireChannelName()
+	if c.Err != nil {
+		return
+	}
+
+	var channel *model.Channel
+	var err *model.AppError
+
+	if channel, err = app.GetChannelByNameForTeamName(c.Params.ChannelName, c.Params.TeamName); err != nil {
+		c.Err = err
+		return
+	}
+
+	if !app.SessionHasPermissionToChannel(c.Session, channel.Id, model.PERMISSION_READ_CHANNEL) {
+		c.SetPermissionError(model.PERMISSION_READ_CHANNEL)
+		return
+	} 
+
+	w.Write([]byte(channel.ToJson()))
+	return
+}
+
 func getChannelMembers(c *Context, w http.ResponseWriter, r *http.Request) {
 	c.RequireChannelId()
 	if c.Err != nil {
diff --git a/api4/channel_test.go b/api4/channel_test.go
index 91d055bff..7e59f60e8 100644
--- a/api4/channel_test.go
+++ b/api4/channel_test.go
@@ -221,6 +221,84 @@ func TestCreateDirectChannel(t *testing.T) {
 	CheckNoError(t, resp)
 }
 
+func TestGetChannel(t *testing.T) {
+	th := Setup().InitBasic().InitSystemAdmin()
+	defer TearDown()
+	Client := th.Client
+
+	_, resp := Client.GetChannel(th.BasicChannel.Id, "")
+	CheckNoError(t, resp)
+
+	_, resp = Client.GetChannel(model.NewId(), "")
+	CheckForbiddenStatus(t, resp)
+
+	Client.Logout()
+	_, resp = Client.GetChannel(th.BasicChannel.Id, "")
+	CheckUnauthorizedStatus(t, resp)
+
+	user := th.CreateUser()
+	Client.Login(user.Email, user.Password)
+	_, resp = Client.GetChannel(th.BasicChannel.Id, "")
+	CheckForbiddenStatus(t, resp)
+
+	_, resp = th.SystemAdminClient.GetChannel(th.BasicChannel.Id, "")
+	CheckNoError(t, resp)
+
+	_, resp = th.SystemAdminClient.GetChannel(th.BasicUser.Id, "")
+	CheckNotFoundStatus(t, resp)
+}
+
+func TestGetChannelByName(t *testing.T) {
+	th := Setup().InitBasic().InitSystemAdmin()
+	defer TearDown()
+	Client := th.Client
+
+	_, resp := Client.GetChannelByName(th.BasicChannel.Name, th.BasicTeam.Id, "")
+	CheckNoError(t, resp)
+
+	_, resp = Client.GetChannelByName(GenerateTestChannelName(), th.BasicTeam.Id, "")
+	CheckNotFoundStatus(t, resp)
+
+	Client.Logout()
+	_, resp = Client.GetChannelByName(th.BasicChannel.Name, th.BasicTeam.Id, "")
+	CheckUnauthorizedStatus(t, resp)
+
+	user := th.CreateUser()
+	Client.Login(user.Email, user.Password)
+	_, resp = Client.GetChannelByName(th.BasicChannel.Name, th.BasicTeam.Id, "")
+	CheckForbiddenStatus(t, resp)
+
+	_, resp = th.SystemAdminClient.GetChannelByName(th.BasicChannel.Name, th.BasicTeam.Id, "")
+	CheckNoError(t, resp)
+}
+
+func TestGetChannelByNameForTeamName(t *testing.T) {
+	th := Setup().InitBasic().InitSystemAdmin()
+	defer TearDown()
+	Client := th.Client
+
+	_, resp := th.SystemAdminClient.GetChannelByNameForTeamName(th.BasicChannel.Name, th.BasicTeam.Name, "")
+	CheckNoError(t, resp)
+
+	_, resp = Client.GetChannelByNameForTeamName(th.BasicChannel.Name, th.BasicTeam.Name, "")
+	CheckNoError(t, resp)
+
+	_, resp = Client.GetChannelByNameForTeamName(th.BasicChannel.Name, model.NewRandomString(15), "")
+	CheckNotFoundStatus(t, resp)
+
+	_, resp = Client.GetChannelByNameForTeamName(GenerateTestChannelName(), th.BasicTeam.Name, "")
+	CheckNotFoundStatus(t, resp)
+
+	Client.Logout()
+	_, resp = Client.GetChannelByNameForTeamName(th.BasicChannel.Name, th.BasicTeam.Name, "")
+	CheckUnauthorizedStatus(t, resp)
+
+	user := th.CreateUser()
+	Client.Login(user.Email, user.Password)
+	_, resp = Client.GetChannelByNameForTeamName(th.BasicChannel.Name, th.BasicTeam.Name, "")
+	CheckForbiddenStatus(t, resp)
+}
+
 func TestGetChannelMembers(t *testing.T) {
 	th := Setup().InitBasic().InitSystemAdmin()
 	defer TearDown()
@@ -255,7 +333,7 @@ func TestGetChannelMembers(t *testing.T) {
 	}
 
 	_, resp = Client.GetChannelMembers("", 0, 60, "")
-	CheckNotFoundStatus(t, resp)
+	CheckUnauthorizedStatus(t, resp)
 
 	_, resp = Client.GetChannelMembers("junk", 0, 60, "")
 	CheckBadRequestStatus(t, resp)
diff --git a/api4/context.go b/api4/context.go
index 06523152f..6a844795f 100644
--- a/api4/context.go
+++ b/api4/context.go
@@ -364,12 +364,8 @@ func (c *Context) RequireUsername() *Context {
 		return c
 	}
 
-	if len(c.Params.Username) < 3 {
-		c.SetInvalidUrlParam("username")
-	} 
-
-	if len(c.Params.Username) > 22 {
-		c.SetInvalidUrlParam("username")
+	if !model.IsValidUsername(c.Params.Username) {
+		c.SetInvalidParam("username")
 	}
 
 	return c
@@ -386,16 +382,40 @@ func (c *Context) RequirePostId() *Context {
 	return c
 }
 
+func (c *Context) RequireTeamName() *Context {
+	if c.Err != nil {
+		return c
+	}
+
+	if !model.IsValidTeamName(c.Params.TeamName){
+		c.SetInvalidUrlParam("team_name")
+	}
+
+	return c
+}
+
+func (c *Context) RequireChannelName() *Context {
+	if c.Err != nil {
+		return c
+	}
+
+	if !model.IsValidChannelIdentifier(c.Params.ChannelName) {
+		c.SetInvalidUrlParam("channel_name")
+	} 
+
+	return c
+}
+
 func (c *Context) RequireEmail() *Context {
 	if c.Err != nil {
 		return c
 	}
 
-	pos := strings.Index(c.Params.Email, "@")
-	if pos < 0 {
+	if !model.IsValidEmail(c.Params.Email) {
 		c.SetInvalidUrlParam("email")
 	}
 
 	return c
 }
 
+
diff --git a/api4/params.go b/api4/params.go
index 4de1da401..9b371e71a 100644
--- a/api4/params.go
+++ b/api4/params.go
@@ -17,18 +17,20 @@ const (
 )
 
 type ApiParams struct {
-	UserId    string
-	TeamId    string
-	ChannelId string
-	PostId    string
-	FileId    string
-	CommandId string
-	HookId    string
-	EmojiId   string
-	Email     string
-	Username  string
-	Page      int
-	PerPage   int
+	UserId      string
+	TeamId      string
+	ChannelId   string
+	PostId      string
+	FileId      string
+	CommandId   string
+	HookId      string
+	EmojiId     string
+	Email       string
+	Username    string
+	TeamName    string
+	ChannelName string
+	Page        int
+	PerPage     int
 }
 
 func ApiParamsFromRequest(r *http.Request) *ApiParams {
@@ -76,6 +78,14 @@ func ApiParamsFromRequest(r *http.Request) *ApiParams {
 		params.Username = val
 	}
 
+	if val, ok := props["team_name"]; ok {
+		params.TeamName = val
+	}
+
+	if val, ok := props["channel_name"]; ok {
+		params.ChannelName = val
+	}
+
 	if val, err := strconv.Atoi(r.URL.Query().Get("page")); err != nil {
 		params.Page = PAGE_DEFAULT
 	} else {
diff --git a/api4/post_test.go b/api4/post_test.go
index 32f259d3d..604920b96 100644
--- a/api4/post_test.go
+++ b/api4/post_test.go
@@ -159,7 +159,7 @@ func TestGetPostsForChannel(t *testing.T) {
 	}
 
 	_, resp = Client.GetPostsForChannel("", 0, 60, "")
-	CheckNotFoundStatus(t, resp)
+	CheckUnauthorizedStatus(t, resp)
 
 	_, resp = Client.GetPostsForChannel("junk", 0, 60, "")
 	CheckBadRequestStatus(t, resp)
diff --git a/api4/user_test.go b/api4/user_test.go
index 82c7f921d..79589bdad 100644
--- a/api4/user_test.go
+++ b/api4/user_test.go
@@ -154,7 +154,7 @@ func TestGetUserByUsername(t *testing.T) {
 	_, resp = Client.GetUserByUsername(GenerateTestUsername(), "")
 	CheckNotFoundStatus(t, resp)
 
-	_, resp = Client.GetUserByUsername(model.NewRandomString(25), "")
+	_, resp = Client.GetUserByUsername(model.NewRandomString(1), "")
 	CheckBadRequestStatus(t, resp)
 
 	// Check against privacy config settings
diff --git a/app/channel.go b/app/channel.go
index ab832693f..a95a38327 100644
--- a/app/channel.go
+++ b/app/channel.go
@@ -543,7 +543,11 @@ func PostUpdateChannelDisplayNameMessage(userId string, channelId string, teamId
 }
 
 func GetChannel(channelId string) (*model.Channel, *model.AppError) {
-	if result := <-Srv.Store.Channel().Get(channelId, true); result.Err != nil {
+	if result := <-Srv.Store.Channel().Get(channelId, true); result.Err != nil && result.Err.Id == "store.sql_channel.get.existing.app_error" {
+		result.Err.StatusCode = http.StatusNotFound
+		return nil, result.Err
+	} else if result.Err != nil {
+		result.Err.StatusCode = http.StatusBadRequest
 		return nil, result.Err
 	} else {
 		return result.Data.(*model.Channel), nil
@@ -551,7 +555,32 @@ func GetChannel(channelId string) (*model.Channel, *model.AppError) {
 }
 
 func GetChannelByName(channelName, teamId string) (*model.Channel, *model.AppError) {
-	if result := <-Srv.Store.Channel().GetByName(teamId, channelName, true); result.Err != nil {
+	if result := <-Srv.Store.Channel().GetByName(teamId, channelName, true); result.Err != nil && result.Err.Id == "store.sql_channel.get_by_name.missing.app_error" {
+		result.Err.StatusCode = http.StatusNotFound
+		return nil, result.Err
+	} else if result.Err != nil {
+		result.Err.StatusCode = http.StatusBadRequest
+		return nil, result.Err
+	} else {
+		return result.Data.(*model.Channel), nil
+	}
+}
+
+func GetChannelByNameForTeamName(channelName, teamName string) (*model.Channel, *model.AppError) {
+	var team *model.Team
+
+	if result := <-Srv.Store.Team().GetByName(teamName); result.Err != nil {
+		result.Err.StatusCode = http.StatusNotFound
+		return nil, result.Err
+	} else {
+		team = result.Data.(*model.Team)
+	}
+
+	if result := <-Srv.Store.Channel().GetByName(team.Id, channelName, true); result.Err != nil && result.Err.Id == "store.sql_channel.get_by_name.missing.app_error" {
+		result.Err.StatusCode = http.StatusNotFound
+		return nil, result.Err
+	} else if result.Err != nil {
+		result.Err.StatusCode = http.StatusBadRequest
 		return nil, result.Err
 	} else {
 		return result.Data.(*model.Channel), nil
diff --git a/model/channel.go b/model/channel.go
index 2ad257ccc..3ad7da1fa 100644
--- a/model/channel.go
+++ b/model/channel.go
@@ -15,6 +15,7 @@ const (
 	CHANNEL_DIRECT                 = "D"
 	DEFAULT_CHANNEL                = "town-square"
 	CHANNEL_DISPLAY_NAME_MAX_RUNES = 64
+	CHANNEL_NAME_MIN_LENGTH        = 3
 	CHANNEL_NAME_MAX_LENGTH        = 64
 	CHANNEL_HEADER_MAX_RUNES       = 1024
 	CHANNEL_PURPOSE_MAX_RUNES      = 250
@@ -83,10 +84,6 @@ func (o *Channel) IsValid() *AppError {
 		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.display_name.app_error", nil, "id="+o.Id)
 	}
 
-	if len(o.Name) > CHANNEL_NAME_MAX_LENGTH {
-		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.name.app_error", nil, "id="+o.Id)
-	}
-
 	if !IsValidChannelIdentifier(o.Name) {
 		return NewLocAppError("Channel.IsValid", "model.channel.is_valid.2_or_more.app_error", nil, "id="+o.Id)
 	}
diff --git a/model/client4.go b/model/client4.go
index 7afc63359..5c51026a9 100644
--- a/model/client4.go
+++ b/model/client4.go
@@ -72,6 +72,10 @@ func (c *Client4) GetTeamRoute(teamId string) string {
 	return fmt.Sprintf(c.GetTeamsRoute()+"/%v", teamId)
 }
 
+func (c *Client4) GetTeamByNameRoute(teamName string) string {
+	return fmt.Sprintf(c.GetTeamsRoute()+"/name/%v", teamName)
+}
+
 func (c *Client4) GetTeamMemberRoute(teamId, userId string) string {
 	return fmt.Sprintf(c.GetTeamRoute(teamId)+"/members/%v", userId)
 }
@@ -84,6 +88,14 @@ func (c *Client4) GetChannelRoute(channelId string) string {
 	return fmt.Sprintf(c.GetChannelsRoute()+"/%v", channelId)
 }
 
+func (c *Client4) GetChannelByNameRoute(channelName, teamId string) string {
+	return fmt.Sprintf(c.GetTeamRoute(teamId)+"/channels/name/%v", channelName)
+}
+
+func (c *Client4) GetChannelByNameForTeamNameRoute(channelName, teamName string) string {
+	return fmt.Sprintf(c.GetTeamByNameRoute(teamName)+"/channels/name/%v", channelName)
+}
+
 func (c *Client4) GetChannelMembersRoute(channelId string) string {
 	return fmt.Sprintf(c.GetChannelRoute(channelId) + "/members")
 }
@@ -444,6 +456,36 @@ func (c *Client4) CreateDirectChannel(userId1, userId2 string) (*Channel, *Respo
 	}
 }
 
+// GetChannel returns a channel based on the provided channel id string.
+func (c *Client4) GetChannel(channelId, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelRoute(channelId), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetChannelByName returns a channel based on the provided channel name and team id strings.
+func (c *Client4) GetChannelByName(channelName, teamId string, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelByNameRoute(channelName, teamId), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
+// GetChannelByNameForTeamName returns a channel based on the provided channel name and team name strings.
+func (c *Client4) GetChannelByNameForTeamName(channelName, teamName string, etag string) (*User, *Response) {
+	if r, err := c.DoApiGet(c.GetChannelByNameForTeamNameRoute(channelName, teamName), etag); err != nil {
+		return nil, &Response{StatusCode: r.StatusCode, Error: err}
+	} else {
+		defer closeBody(r)
+		return UserFromJson(r.Body), BuildResponse(r)
+	}
+}
+
 // GetChannelMembers gets a page of channel members.
 func (c *Client4) GetChannelMembers(channelId string, page, perPage int, etag string) (*ChannelMembers, *Response) {
 	query := fmt.Sprintf("?page=%v&per_page=%v", page, perPage)
diff --git a/model/team.go b/model/team.go
index 310ad2d91..99444bc5e 100644
--- a/model/team.go
+++ b/model/team.go
@@ -22,6 +22,7 @@ const (
 	TEAM_DISPLAY_NAME_MAX_RUNES     = 64
 	TEAM_EMAIL_MAX_LENGTH           = 128
 	TEAM_NAME_MAX_LENGTH            = 64
+	TEAM_NAME_MIN_LENGTH            = 2
 )
 
 type Team struct {
@@ -228,7 +229,7 @@ func IsValidTeamName(s string) bool {
 		return false
 	}
 
-	if len(s) <= 1 {
+	if len(s) < TEAM_NAME_MIN_LENGTH {
 		return false
 	}
 
diff --git a/model/user.go b/model/user.go
index b2b077e5f..8e02fe1ab 100644
--- a/model/user.go
+++ b/model/user.go
@@ -29,6 +29,8 @@ const (
 	USER_FIRST_NAME_MAX_RUNES = 64
 	USER_LAST_NAME_MAX_RUNES  = 64
 	USER_AUTH_DATA_MAX_LENGTH = 128
+	USER_NAME_MAX_LENGTH      = 64
+	USER_NAME_MIN_LENGTH      = 3
 )
 
 type User struct {
@@ -487,7 +489,7 @@ var restrictedUsernames = []string{
 }
 
 func IsValidUsername(s string) bool {
-	if len(s) == 0 || len(s) > 64 {
+	if len(s) < USER_NAME_MIN_LENGTH || len(s) > USER_NAME_MAX_LENGTH {
 		return false
 	}
 
diff --git a/model/utils.go b/model/utils.go
index 9ecc19595..fcdf5b5cd 100644
--- a/model/utils.go
+++ b/model/utils.go
@@ -280,7 +280,7 @@ func IsValidChannelIdentifier(s string) bool {
 		return false
 	}
 
-	if len(s) < 2 {
+	if len(s) < CHANNEL_NAME_MIN_LENGTH {
 		return false
 	}