fix: sanitize workspace agent logs before insert (#24028)

Workspace agent logs could still fail after the earlier invalid UTF-8
fix because NUL bytes are valid Go/protobuf strings but are rejected by
Postgres text columns. The legacy HTTP log upload path also bypassed the
old sanitization entirely, and both server insert paths computed
logs_length from the unsanitized input.

Add a shared log-output sanitizer in agentsdk, use it in the protobuf
conversion path and both server-side insert paths, and compute
OutputLength from the sanitized string so overflow accounting matches
what is actually stored. This keeps the old invalid UTF-8 behavior while
also handling embedded NUL bytes consistently across DRPC and HTTP log
ingestion.

Refs [#23292 ](https://github.com/coder/coder/issues/23292)
Refs [#13433 ](https://github.com/coder/coder/issues/13433)

coderd/agentapi/logs.go

@@ -77,8 +77,9 @@ func (a *LogsAPI) BatchCreateLogs(ctx context.Context, req *agentproto.BatchCrea
 	level := make([]database.LogLevel, 0)
 	outputLength := 0
 	for _, logEntry := range req.Logs {
-		output = append(output, logEntry.Output)
-		outputLength += len(logEntry.Output)
+		sanitizedOutput := agentsdk.SanitizeLogOutput(logEntry.Output)
+		output = append(output, sanitizedOutput)
+		outputLength += len(sanitizedOutput)
 
 		var dbLevel database.LogLevel
 		switch logEntry.Level {

coderd/agentapi/logs_test.go

@@ -139,6 +139,59 @@ func TestBatchCreateLogs(t *testing.T) {
 		require.True(t, publishWorkspaceAgentLogsUpdateCalled)
 	})
 
+	t.Run("SanitizesOutput", func(t *testing.T) {
+		t.Parallel()
+
+		dbM := dbmock.NewMockStore(gomock.NewController(t))
+		now := dbtime.Now()
+		api := &agentapi.LogsAPI{
+			AgentFn: func(context.Context) (database.WorkspaceAgent, error) {
+				return agent, nil
+			},
+			Database: dbM,
+			Log:      testutil.Logger(t),
+			TimeNowFn: func() time.Time {
+				return now
+			},
+		}
+
+		rawOutput := "before\x00middle\xc3\x28after"
+		sanitizedOutput := agentsdk.SanitizeLogOutput(rawOutput)
+		expectedOutputLength := int32(len(sanitizedOutput)) //nolint:gosec // Test-controlled string length is small.
+		req := &agentproto.BatchCreateLogsRequest{
+			LogSourceId: logSource.ID[:],
+			Logs: []*agentproto.Log{
+				{
+					CreatedAt: timestamppb.New(now),
+					Level:     agentproto.Log_WARN,
+					Output:    rawOutput,
+				},
+			},
+		}
+
+		dbM.EXPECT().InsertWorkspaceAgentLogs(gomock.Any(), database.InsertWorkspaceAgentLogsParams{
+			AgentID:      agent.ID,
+			LogSourceID:  logSource.ID,
+			CreatedAt:    now,
+			Output:       []string{sanitizedOutput},
+			Level:        []database.LogLevel{database.LogLevelWarn},
+			OutputLength: expectedOutputLength,
+		}).Return([]database.WorkspaceAgentLog{
+			{
+				AgentID:     agent.ID,
+				CreatedAt:   now,
+				ID:          1,
+				Output:      sanitizedOutput,
+				Level:       database.LogLevelWarn,
+				LogSourceID: logSource.ID,
+			},
+		}, nil)
+
+		resp, err := api.BatchCreateLogs(context.Background(), req)
+		require.NoError(t, err)
+		require.Equal(t, &agentproto.BatchCreateLogsResponse{}, resp)
+	})
+
 	t.Run("NoWorkspacePublishIfNotFirstLogs", func(t *testing.T) {
 		t.Parallel()
 

coderd/workspaceagents.go

@@ -181,8 +181,9 @@ func (api *API) patchWorkspaceAgentLogs(rw http.ResponseWriter, r *http.Request)
 	level := make([]database.LogLevel, 0)
 	outputLength := 0
 	for _, logEntry := range req.Logs {
-		output = append(output, logEntry.Output)
-		outputLength += len(logEntry.Output)
+		sanitizedOutput := agentsdk.SanitizeLogOutput(logEntry.Output)
+		output = append(output, sanitizedOutput)
+		outputLength += len(sanitizedOutput)
 		if logEntry.Level == "" {
 			// Default to "info" to support older agents that didn't have the level field.
 			logEntry.Level = codersdk.LogLevelInfo

coderd/workspaceagents_test.go

@@ -260,6 +260,50 @@ func TestWorkspaceAgentLogs(t *testing.T) {
 		require.Equal(t, "testing", logChunk[0].Output)
 		require.Equal(t, "testing2", logChunk[1].Output)
 	})
+	t.Run("SanitizesNulBytesAndTracksSanitizedLength", func(t *testing.T) {
+		t.Parallel()
+		ctx := testutil.Context(t, testutil.WaitMedium)
+		client, db := coderdtest.NewWithDatabase(t, nil)
+		user := coderdtest.CreateFirstUser(t, client)
+		r := dbfake.WorkspaceBuild(t, db, database.WorkspaceTable{
+			OrganizationID: user.OrganizationID,
+			OwnerID:        user.UserID,
+		}).WithAgent().Do()
+
+		rawOutput := "before\x00after"
+		sanitizedOutput := agentsdk.SanitizeLogOutput(rawOutput)
+		agentClient := agentsdk.New(client.URL, agentsdk.WithFixedToken(r.AgentToken))
+		err := agentClient.PatchLogs(ctx, agentsdk.PatchLogs{
+			Logs: []agentsdk.Log{
+				{
+					CreatedAt: dbtime.Now(),
+					Output:    rawOutput,
+				},
+			},
+		})
+		require.NoError(t, err)
+
+		agent, err := db.GetWorkspaceAgentByID(dbauthz.AsSystemRestricted(ctx), r.Agents[0].ID)
+		require.NoError(t, err)
+		require.EqualValues(t, len(sanitizedOutput), agent.LogsLength)
+
+		workspace, err := client.Workspace(ctx, r.Workspace.ID)
+		require.NoError(t, err)
+		logs, closer, err := client.WorkspaceAgentLogsAfter(ctx, workspace.LatestBuild.Resources[0].Agents[0].ID, 0, true)
+		require.NoError(t, err)
+		defer func() {
+			_ = closer.Close()
+		}()
+
+		var logChunk []codersdk.WorkspaceAgentLog
+		select {
+		case <-ctx.Done():
+		case logChunk = <-logs:
+		}
+		require.NoError(t, ctx.Err())
+		require.Len(t, logChunk, 1)
+		require.Equal(t, sanitizedOutput, logChunk[0].Output)
+	})
 	t.Run("Close logs on outdated build", func(t *testing.T) {
 		t.Parallel()
 		ctx := testutil.Context(t, testutil.WaitMedium)

codersdk/agentsdk/convert.go

@@ -376,7 +376,7 @@ func ProtoFromLog(log Log) (*proto.Log, error) {
 	}
 	return &proto.Log{
 		CreatedAt: timestamppb.New(log.CreatedAt),
-		Output:    strings.ToValidUTF8(log.Output, "❌"),
+		Output:    SanitizeLogOutput(log.Output),
 		Level:     proto.Log_Level(lvl),
 	}, nil
 }

codersdk/agentsdk/logs_internal_test.go

@@ -229,7 +229,7 @@ func TestLogSender_SkipHugeLog(t *testing.T) {
 	require.ErrorIs(t, err, context.Canceled)
 }
 
-func TestLogSender_InvalidUTF8(t *testing.T) {
+func TestLogSender_SanitizeOutput(t *testing.T) {
 	t.Parallel()
 	testCtx := testutil.Context(t, testutil.WaitShort)
 	ctx, cancel := context.WithCancel(testCtx)
@@ -243,7 +243,7 @@ func TestLogSender_InvalidUTF8(t *testing.T) {
 	uut.Enqueue(ls1,
 		Log{
 			CreatedAt: t0,
-			Output:    "test log 0, src 1\xc3\x28",
+			Output:    "test log 0, src 1\x00\xc3\x28",
 			Level:     codersdk.LogLevelInfo,
 		},
 		Log{
@@ -260,10 +260,10 @@ func TestLogSender_InvalidUTF8(t *testing.T) {
 
 	req := testutil.TryReceive(ctx, t, fDest.reqs)
 	require.NotNil(t, req)
-	require.Len(t, req.Logs, 2, "it should sanitize invalid UTF-8, but still send")
-	// the 0xc3, 0x28 is an invalid 2-byte sequence in UTF-8.  The sanitizer replaces 0xc3 with ❌, and then
-	// interprets 0x28 as a 1-byte sequence "("
-	require.Equal(t, "test log 0, src 1❌(", req.Logs[0].GetOutput())
+	require.Len(t, req.Logs, 2, "it should sanitize invalid output, but still send")
+	// The sanitizer replaces the NUL byte and invalid UTF-8 with ❌ while
+	// preserving the valid "(" byte that follows 0xc3.
+	require.Equal(t, "test log 0, src 1❌❌(", req.Logs[0].GetOutput())
 	require.Equal(t, proto.Log_INFO, req.Logs[0].GetLevel())
 	require.Equal(t, "test log 1, src 1", req.Logs[1].GetOutput())
 	require.Equal(t, proto.Log_INFO, req.Logs[1].GetLevel())

codersdk/agentsdk/logs_sanitize.go

@@ -0,0 +1,11 @@
+package agentsdk
+
+import "strings"
+
+// SanitizeLogOutput replaces invalid UTF-8 and NUL characters in log output.
+// Invalid UTF-8 cannot be transported in protobuf string fields, and PostgreSQL
+// rejects NUL bytes in text columns.
+func SanitizeLogOutput(s string) string {
+	s = strings.ToValidUTF8(s, "❌")
+	return strings.ReplaceAll(s, "\x00", "❌")
+}

codersdk/agentsdk/logs_test.go

@@ -17,6 +17,54 @@ import (
 	"github.com/coder/coder/v2/testutil"
 )
 
+func TestSanitizeLogOutput(t *testing.T) {
+	t.Parallel()
+
+	tests := []struct {
+		name string
+		in   string
+		want string
+	}{
+		{
+			name: "valid",
+			in:   "hello world",
+			want: "hello world",
+		},
+		{
+			name: "invalid utf8",
+			in:   "test log\xc3\x28",
+			want: "test log❌(",
+		},
+		{
+			name: "nul byte",
+			in:   "before\x00after",
+			want: "before❌after",
+		},
+		{
+			name: "invalid utf8 and nul byte",
+			in:   "before\x00middle\xc3\x28after",
+			want: "before❌middle❌(after",
+		},
+		{
+			name: "nul byte at edges",
+			in:   "\x00middle\x00",
+			want: "❌middle❌",
+		},
+		{
+			name: "invalid utf8 at edges",
+			in:   "\xc3middle\xc3",
+			want: "❌middle❌",
+		},
+	}
+
+	for _, tt := range tests {
+		t.Run(tt.name, func(t *testing.T) {
+			t.Parallel()
+			require.Equal(t, tt.want, agentsdk.SanitizeLogOutput(tt.in))
+		})
+	}
+}
+
 func TestStartupLogsWriter_Write(t *testing.T) {
 	t.Parallel()