Skip to content

Handle empty password from broader set of MySQL clients #1084

New issue

Have a question about this project? Sign up for a free GitHub account to open an issue and contact its maintainers and the community.

Sign up for GitHub

By clicking “Sign up for GitHub”, you agree to our terms of service and privacy statement. We’ll occasionally send you account related emails.

Already on GitHub? Sign in to your account

Merged
lance6716 merged 1 commit into from
Dec 23, 2025
+62 −6
Merged

Handle empty password from broader set of MySQL clients #1084

Show file tree
Hide file tree
Changes from all commits
Commits
Show all changes
1 commit
Select commit
File filter

Filter by extension

Filter by extension
Conversations
Failed to load comments.
Loading
Jump to
Jump to file
Failed to load files.
Loading
Diff view
Diff view
18 changes: 13 additions & 5 deletions server/auth.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -18,6 +18,16 @@ var (
ErrAccessDeniedNoPassword = fmt.Errorf("%w without password", ErrAccessDenied)
)

// isEmptyPassword returns true if the auth data represents an empty password.
// Some clients send an empty packet (len == 0), while others (e.g. MySQL's libmysql)
// send a single null byte. This matches MySQL server's own handling:
// if (!pkt_len || (pkt_len == 1 && *pkt == 0))
// https://github.com/mysql/mysql-server/blob/8.0/sql/auth/sha2_password.cc
// https://github.com/mysql/mysql-server/blob/8.0/sql/auth/sql_authentication.cc
func isEmptyPassword(authData []byte) bool {
return len(authData) == 0 || (len(authData) == 1 && authData[0] == 0)
}

func (c *Conn) compareAuthData(authPluginName string, clientAuthData []byte) error {
if authPluginName != c.credential.AuthPluginName {
err := c.writeAuthSwitchRequest(c.credential.AuthPluginName)
Expand Down Expand Up @@ -66,7 +76,7 @@ func scrambleValidation(cached, nonce, scramble []byte) bool {
}

func (c *Conn) compareNativePasswordAuthData(clientAuthData []byte, credential Credential) error {
if len(clientAuthData) == 0 {
if isEmptyPassword(clientAuthData) {
if credential.hasEmptyPassword() {
return nil
}
Expand All @@ -90,8 +100,7 @@ func (c *Conn) compareNativePasswordAuthData(clientAuthData []byte, credential C
}

func (c *Conn) compareSha256PasswordAuthData(clientAuthData []byte, credential Credential) error {
// Empty passwords are not hashed, but sent as empty string
if len(clientAuthData) == 0 {
if isEmptyPassword(clientAuthData) {
if credential.hasEmptyPassword() {
return nil
}
Expand Down Expand Up @@ -135,8 +144,7 @@ func (c *Conn) compareSha256PasswordAuthData(clientAuthData []byte, credential C
}

func (c *Conn) compareCacheSha2PasswordAuthData(clientAuthData []byte) error {
// Empty passwords are not hashed, but sent as empty string
if len(clientAuthData) == 0 {
if isEmptyPassword(clientAuthData) {
if c.credential.hasEmptyPassword() {
return nil
}
Expand Down
2 changes: 1 addition & 1 deletion server/auth_switch_response.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -71,7 +71,7 @@ func (c *Conn) handleCachingSha2PasswordFullAuth(authData []byte) error {
}

func (c *Conn) checkSha2CacheCredentials(clientAuthData []byte, credential Credential) error {
if len(clientAuthData) == 0 {
if isEmptyPassword(clientAuthData) {
if credential.hasEmptyPassword() {
return nil
}
Expand Down
12 changes: 12 additions & 0 deletions server/auth_switch_response_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -25,6 +25,18 @@ func TestCheckSha2CacheCredentials_EmptyPassword(t *testing.T) {
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
{
name: "null byte client auth, empty server password",
clientAuthData: []byte{0x00},
serverPassword: "",
wantErr: nil,
},
{
name: "null byte client auth, non-empty server password",
clientAuthData: []byte{0x00},
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
}

for _, tt := range tests {
Expand Down
36 changes: 36 additions & 0 deletions server/auth_test.go
View file
Open in desktop
Original file line number Diff line number Diff line change
Expand Up @@ -32,6 +32,18 @@ func TestCompareNativePasswordAuthData_EmptyPassword(t *testing.T) {
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
{
name: "null byte client auth, empty server password",
clientAuthData: []byte{0x00},
serverPassword: "",
wantErr: nil,
},
{
name: "null byte client auth, non-empty server password",
clientAuthData: []byte{0x00},
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
}

for _, tt := range tests {
Expand Down Expand Up @@ -68,6 +80,18 @@ func TestCompareSha256PasswordAuthData_EmptyPassword(t *testing.T) {
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
{
name: "null byte client auth, empty server password",
clientAuthData: []byte{0x00},
serverPassword: "",
wantErr: nil,
},
{
name: "null byte client auth, non-empty server password",
clientAuthData: []byte{0x00},
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
}

for _, tt := range tests {
Expand Down Expand Up @@ -104,6 +128,18 @@ func TestCompareCacheSha2PasswordAuthData_EmptyPassword(t *testing.T) {
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
{
name: "null byte client auth, empty server password",
clientAuthData: []byte{0x00},
serverPassword: "",
wantErr: nil,
},
{
name: "null byte client auth, non-empty server password",
clientAuthData: []byte{0x00},
serverPassword: "secret",
wantErr: ErrAccessDeniedNoPassword,
},
}

for _, tt := range tests {
Expand Down
Loading