Use mcdsl/terminal for all password prompts

Replace direct golang.org/x/term calls with mcdsl/terminal.ReadPassword
across mciasctl (6 sites), mciasgrpcctl (1 site), and mciasdb (1 site).
Aligns with the new CLI security standard in engineering-standards.md.

Co-Authored-By: Claude Opus 4.6 (1M context) <noreply@anthropic.com>

vendor/google.golang.org/grpc/mem/buffer_pool.go

@@ -32,12 +32,17 @@ type BufferPool interface {
 	Get(length int) *[]byte
 
 	// Put returns a buffer to the pool.
+	//
+	// The provided pointer must hold a prefix of the buffer obtained via
+	// BufferPool.Get to ensure the buffer's entire capacity can be re-used.
 	Put(*[]byte)
 }
 
+const goPageSize = 4 << 10 // 4KiB. N.B. this must be a power of 2.
+
 var defaultBufferPoolSizes = []int{
 	256,
-	4 << 10,  // 4KB (go page size)
+	goPageSize,
 	16 << 10, // 16KB (max HTTP/2 frame size used by gRPC)
 	32 << 10, // 32KB (default buffer size for io.Copy)
 	1 << 20,  // 1MB
@@ -48,7 +53,7 @@ var defaultBufferPool BufferPool
 func init() {
 	defaultBufferPool = NewTieredBufferPool(defaultBufferPoolSizes...)
 
-	internal.SetDefaultBufferPoolForTesting = func(pool BufferPool) {
+	internal.SetDefaultBufferPool = func(pool BufferPool) {
 		defaultBufferPool = pool
 	}
 
@@ -118,7 +123,11 @@ type sizedBufferPool struct {
 }
 
 func (p *sizedBufferPool) Get(size int) *[]byte {
-	buf := p.pool.Get().(*[]byte)
+	buf, ok := p.pool.Get().(*[]byte)
+	if !ok {
+		buf := make([]byte, size, p.defaultSize)
+		return &buf
+	}
 	b := *buf
 	clear(b[:cap(b)])
 	*buf = b[:size]
@@ -137,12 +146,6 @@ func (p *sizedBufferPool) Put(buf *[]byte) {
 
 func newSizedBufferPool(size int) *sizedBufferPool {
 	return &sizedBufferPool{
-		pool: sync.Pool{
-			New: func() any {
-				buf := make([]byte, size)
-				return &buf
-			},
-		},
 		defaultSize: size,
 	}
 }
@@ -160,6 +163,7 @@ type simpleBufferPool struct {
 func (p *simpleBufferPool) Get(size int) *[]byte {
 	bs, ok := p.pool.Get().(*[]byte)
 	if ok && cap(*bs) >= size {
+		clear((*bs)[:cap(*bs)])
 		*bs = (*bs)[:size]
 		return bs
 	}
@@ -170,7 +174,14 @@ func (p *simpleBufferPool) Get(size int) *[]byte {
 		p.pool.Put(bs)
 	}
 
-	b := make([]byte, size)
+	// If we're going to allocate, round up to the nearest page. This way if
+	// requests frequently arrive with small variation we don't allocate
+	// repeatedly if we get unlucky and they increase over time. By default we
+	// only allocate here if size > 1MiB. Because goPageSize is a power of 2, we
+	// can round up efficiently.
+	allocSize := (size + goPageSize - 1) & ^(goPageSize - 1)
+
+	b := make([]byte, size, allocSize)
 	return &b
 }