diff --git a/README.md b/README.md
index 92f73cdfbf..f69c623ff8 100644
--- a/README.md
+++ b/README.md
@@ -2,20 +2,17 @@
 
 [![Go Reference](https://pkg.go.dev/badge/golang.org/x/crypto.svg)](https://pkg.go.dev/golang.org/x/crypto)
 
-This repository holds supplementary Go cryptography libraries.
-
-## Download/Install
-
-The easiest way to install is to run `go get -u golang.org/x/crypto/...`. You
-can also manually git clone the repository to `$GOPATH/src/golang.org/x/crypto`.
+This repository holds supplementary Go cryptography packages.
 
 ## Report Issues / Send Patches
 
 This repository uses Gerrit for code changes. To learn how to submit changes to
-this repository, see https://golang.org/doc/contribute.html.
+this repository, see https://go.dev/doc/contribute.
+
+The git repository is https://go.googlesource.com/crypto.
 
 The main issue tracker for the crypto repository is located at
-https://github.com/golang/go/issues. Prefix your issue with "x/crypto:" in the
+https://go.dev/issues. Prefix your issue with "x/crypto:" in the
 subject line, so it is easy to find.
 
 Note that contributions to the cryptography package receive additional scrutiny
diff --git a/chacha20/chacha_noasm.go b/chacha20/chacha_noasm.go
index db42e6676a..c709b72847 100644
--- a/chacha20/chacha_noasm.go
+++ b/chacha20/chacha_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (!arm64 && !s390x && !ppc64le) || !gc || purego
+//go:build (!arm64 && !s390x && !ppc64 && !ppc64le) || !gc || purego
 
 package chacha20
 
diff --git a/chacha20/chacha_ppc64le.go b/chacha20/chacha_ppc64x.go
similarity index 89%
rename from chacha20/chacha_ppc64le.go
rename to chacha20/chacha_ppc64x.go
index 3a4287f990..bd183d9ba1 100644
--- a/chacha20/chacha_ppc64le.go
+++ b/chacha20/chacha_ppc64x.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build gc && !purego
+//go:build gc && !purego && (ppc64 || ppc64le)
 
 package chacha20
 
diff --git a/chacha20/chacha_ppc64le.s b/chacha20/chacha_ppc64x.s
similarity index 76%
rename from chacha20/chacha_ppc64le.s
rename to chacha20/chacha_ppc64x.s
index c672ccf698..a660b4112f 100644
--- a/chacha20/chacha_ppc64le.s
+++ b/chacha20/chacha_ppc64x.s
@@ -19,7 +19,7 @@
 // The differences in this and the original implementation are
 // due to the calling conventions and initialization of constants.
 
-//go:build gc && !purego
+//go:build gc && !purego && (ppc64 || ppc64le)
 
 #include "textflag.h"
 
@@ -36,32 +36,68 @@
 // for VPERMXOR
 #define MASK  R18
 
-DATA consts<>+0x00(SB)/8, $0x3320646e61707865
-DATA consts<>+0x08(SB)/8, $0x6b20657479622d32
-DATA consts<>+0x10(SB)/8, $0x0000000000000001
-DATA consts<>+0x18(SB)/8, $0x0000000000000000
-DATA consts<>+0x20(SB)/8, $0x0000000000000004
-DATA consts<>+0x28(SB)/8, $0x0000000000000000
-DATA consts<>+0x30(SB)/8, $0x0a0b08090e0f0c0d
-DATA consts<>+0x38(SB)/8, $0x0203000106070405
-DATA consts<>+0x40(SB)/8, $0x090a0b080d0e0f0c
-DATA consts<>+0x48(SB)/8, $0x0102030005060704
-DATA consts<>+0x50(SB)/8, $0x6170786561707865
-DATA consts<>+0x58(SB)/8, $0x6170786561707865
-DATA consts<>+0x60(SB)/8, $0x3320646e3320646e
-DATA consts<>+0x68(SB)/8, $0x3320646e3320646e
-DATA consts<>+0x70(SB)/8, $0x79622d3279622d32
-DATA consts<>+0x78(SB)/8, $0x79622d3279622d32
-DATA consts<>+0x80(SB)/8, $0x6b2065746b206574
-DATA consts<>+0x88(SB)/8, $0x6b2065746b206574
-DATA consts<>+0x90(SB)/8, $0x0000000100000000
-DATA consts<>+0x98(SB)/8, $0x0000000300000002
-DATA consts<>+0xa0(SB)/8, $0x5566774411223300
-DATA consts<>+0xa8(SB)/8, $0xddeeffcc99aabb88
-DATA consts<>+0xb0(SB)/8, $0x6677445522330011
-DATA consts<>+0xb8(SB)/8, $0xeeffccddaabb8899
+DATA consts<>+0x00(SB)/4, $0x61707865
+DATA consts<>+0x04(SB)/4, $0x3320646e
+DATA consts<>+0x08(SB)/4, $0x79622d32
+DATA consts<>+0x0c(SB)/4, $0x6b206574
+DATA consts<>+0x10(SB)/4, $0x00000001
+DATA consts<>+0x14(SB)/4, $0x00000000
+DATA consts<>+0x18(SB)/4, $0x00000000
+DATA consts<>+0x1c(SB)/4, $0x00000000
+DATA consts<>+0x20(SB)/4, $0x00000004
+DATA consts<>+0x24(SB)/4, $0x00000000
+DATA consts<>+0x28(SB)/4, $0x00000000
+DATA consts<>+0x2c(SB)/4, $0x00000000
+DATA consts<>+0x30(SB)/4, $0x0e0f0c0d
+DATA consts<>+0x34(SB)/4, $0x0a0b0809
+DATA consts<>+0x38(SB)/4, $0x06070405
+DATA consts<>+0x3c(SB)/4, $0x02030001
+DATA consts<>+0x40(SB)/4, $0x0d0e0f0c
+DATA consts<>+0x44(SB)/4, $0x090a0b08
+DATA consts<>+0x48(SB)/4, $0x05060704
+DATA consts<>+0x4c(SB)/4, $0x01020300
+DATA consts<>+0x50(SB)/4, $0x61707865
+DATA consts<>+0x54(SB)/4, $0x61707865
+DATA consts<>+0x58(SB)/4, $0x61707865
+DATA consts<>+0x5c(SB)/4, $0x61707865
+DATA consts<>+0x60(SB)/4, $0x3320646e
+DATA consts<>+0x64(SB)/4, $0x3320646e
+DATA consts<>+0x68(SB)/4, $0x3320646e
+DATA consts<>+0x6c(SB)/4, $0x3320646e
+DATA consts<>+0x70(SB)/4, $0x79622d32
+DATA consts<>+0x74(SB)/4, $0x79622d32
+DATA consts<>+0x78(SB)/4, $0x79622d32
+DATA consts<>+0x7c(SB)/4, $0x79622d32
+DATA consts<>+0x80(SB)/4, $0x6b206574
+DATA consts<>+0x84(SB)/4, $0x6b206574
+DATA consts<>+0x88(SB)/4, $0x6b206574
+DATA consts<>+0x8c(SB)/4, $0x6b206574
+DATA consts<>+0x90(SB)/4, $0x00000000
+DATA consts<>+0x94(SB)/4, $0x00000001
+DATA consts<>+0x98(SB)/4, $0x00000002
+DATA consts<>+0x9c(SB)/4, $0x00000003
+DATA consts<>+0xa0(SB)/4, $0x11223300
+DATA consts<>+0xa4(SB)/4, $0x55667744
+DATA consts<>+0xa8(SB)/4, $0x99aabb88
+DATA consts<>+0xac(SB)/4, $0xddeeffcc
+DATA consts<>+0xb0(SB)/4, $0x22330011
+DATA consts<>+0xb4(SB)/4, $0x66774455
+DATA consts<>+0xb8(SB)/4, $0xaabb8899
+DATA consts<>+0xbc(SB)/4, $0xeeffccdd
 GLOBL consts<>(SB), RODATA, $0xc0
 
+#ifdef GOARCH_ppc64
+#define BE_XXBRW_INIT() \
+		LVSL (R0)(R0), V24 \
+		VSPLTISB $3, V25   \
+		VXOR V24, V25, V24 \
+
+#define BE_XXBRW(vr) VPERM vr, vr, V24, vr
+#else
+#define BE_XXBRW_INIT()
+#define BE_XXBRW(vr)
+#endif
+
 //func chaCha20_ctr32_vsx(out, inp *byte, len int, key *[8]uint32, counter *uint32)
 TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 	MOVD out+0(FP), OUT
@@ -94,6 +130,8 @@ TEXT ·chaCha20_ctr32_vsx(SB),NOSPLIT,$64-40
 	// Clear V27
 	VXOR V27, V27, V27
 
+	BE_XXBRW_INIT()
+
 	// V28
 	LXVW4X (CONSTBASE)(R11), VS60
 
@@ -299,6 +337,11 @@ loop_vsx:
 	VADDUWM V8, V18, V8
 	VADDUWM V12, V19, V12
 
+	BE_XXBRW(V0)
+	BE_XXBRW(V4)
+	BE_XXBRW(V8)
+	BE_XXBRW(V12)
+
 	CMPU LEN, $64
 	BLT tail_vsx
 
@@ -327,6 +370,11 @@ loop_vsx:
 	VADDUWM V9, V18, V8
 	VADDUWM V13, V19, V12
 
+	BE_XXBRW(V0)
+	BE_XXBRW(V4)
+	BE_XXBRW(V8)
+	BE_XXBRW(V12)
+
 	CMPU  LEN, $64
 	BLT   tail_vsx
 
@@ -334,8 +382,8 @@ loop_vsx:
 	LXVW4X (INP)(R8), VS60
 	LXVW4X (INP)(R9), VS61
 	LXVW4X (INP)(R10), VS62
-	VXOR   V27, V0, V27
 
+	VXOR V27, V0, V27
 	VXOR V28, V4, V28
 	VXOR V29, V8, V29
 	VXOR V30, V12, V30
@@ -354,6 +402,11 @@ loop_vsx:
 	VADDUWM V10, V18, V8
 	VADDUWM V14, V19, V12
 
+	BE_XXBRW(V0)
+	BE_XXBRW(V4)
+	BE_XXBRW(V8)
+	BE_XXBRW(V12)
+
 	CMPU LEN, $64
 	BLT  tail_vsx
 
@@ -381,6 +434,11 @@ loop_vsx:
 	VADDUWM V11, V18, V8
 	VADDUWM V15, V19, V12
 
+	BE_XXBRW(V0)
+	BE_XXBRW(V4)
+	BE_XXBRW(V8)
+	BE_XXBRW(V12)
+
 	CMPU  LEN, $64
 	BLT   tail_vsx
 
@@ -408,9 +466,9 @@ loop_vsx:
 
 done_vsx:
 	// Increment counter by number of 64 byte blocks
-	MOVD (CNT), R14
+	MOVWZ (CNT), R14
 	ADD  BLOCKS, R14
-	MOVD R14, (CNT)
+	MOVWZ R14, (CNT)
 	RET
 
 tail_vsx:
diff --git a/go.mod b/go.mod
index ecf61b3e18..d4bb2e13f3 100644
--- a/go.mod
+++ b/go.mod
@@ -4,8 +4,8 @@ go 1.20
 
 require (
 	golang.org/x/net v0.21.0 // tagx:ignore
-	golang.org/x/sys v0.26.0
-	golang.org/x/term v0.25.0
+	golang.org/x/sys v0.27.0
+	golang.org/x/term v0.26.0
 )
 
-require golang.org/x/text v0.19.0 // indirect
+require golang.org/x/text v0.20.0 // indirect
diff --git a/go.sum b/go.sum
index 5b12ab8eee..b626a3d76d 100644
--- a/go.sum
+++ b/go.sum
@@ -1,8 +1,8 @@
 golang.org/x/net v0.21.0 h1:AQyQV4dYCvJ7vGmJyKki9+PBdyvhkSd8EIx/qb0AYv4=
 golang.org/x/net v0.21.0/go.mod h1:bIjVDfnllIU7BJ2DNgfnXvpSvtn8VRwhlsaeUTyUS44=
-golang.org/x/sys v0.26.0 h1:KHjCJyddX0LoSTb3J+vWpupP9p0oznkqVk/IfjymZbo=
-golang.org/x/sys v0.26.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
-golang.org/x/term v0.25.0 h1:WtHI/ltw4NvSUig5KARz9h521QvRC8RmF/cuYqifU24=
-golang.org/x/term v0.25.0/go.mod h1:RPyXicDX+6vLxogjjRxjgD2TKtmAO6NZBsBRfrOLu7M=
-golang.org/x/text v0.19.0 h1:kTxAhCbGbxhK0IwgSKiMO5awPoDQ0RpfiVYBfK860YM=
-golang.org/x/text v0.19.0/go.mod h1:BuEKDfySbSR4drPmRPG/7iBdf8hvFMuRexcpahXilzY=
+golang.org/x/sys v0.27.0 h1:wBqf8DvsY9Y/2P8gAfPDEYNuS30J4lPHJxXSb/nJZ+s=
+golang.org/x/sys v0.27.0/go.mod h1:/VUhepiaJMQUp4+oa/7Zr1D23ma6VTLIYjOOTFZPUcA=
+golang.org/x/term v0.26.0 h1:WEQa6V3Gja/BhNxg540hBip/kkaYtRg3cxg4oXSw4AU=
+golang.org/x/term v0.26.0/go.mod h1:Si5m1o57C5nBNQo5z1iq+XDijt21BDBDp2bK0QI8e3E=
+golang.org/x/text v0.20.0 h1:gK/Kv2otX8gz+wn7Rmb3vT96ZwuoxnQlY+HlJVj7Qug=
+golang.org/x/text v0.20.0/go.mod h1:D4IsuqiFMhST5bX19pQ9ikHC2GsaKyk/oF+pn3ducp4=
diff --git a/internal/poly1305/mac_noasm.go b/internal/poly1305/mac_noasm.go
index 333da285b3..bd896bdc76 100644
--- a/internal/poly1305/mac_noasm.go
+++ b/internal/poly1305/mac_noasm.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build (!amd64 && !ppc64le && !s390x) || !gc || purego
+//go:build (!amd64 && !ppc64le && !ppc64 && !s390x) || !gc || purego
 
 package poly1305
 
diff --git a/internal/poly1305/sum_ppc64le.go b/internal/poly1305/sum_ppc64x.go
similarity index 95%
rename from internal/poly1305/sum_ppc64le.go
rename to internal/poly1305/sum_ppc64x.go
index 4aec4874b5..1a1679aaad 100644
--- a/internal/poly1305/sum_ppc64le.go
+++ b/internal/poly1305/sum_ppc64x.go
@@ -2,7 +2,7 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build gc && !purego
+//go:build gc && !purego && (ppc64 || ppc64le)
 
 package poly1305
 
diff --git a/internal/poly1305/sum_ppc64le.s b/internal/poly1305/sum_ppc64x.s
similarity index 89%
rename from internal/poly1305/sum_ppc64le.s
rename to internal/poly1305/sum_ppc64x.s
index b3c1699bff..6899a1dabc 100644
--- a/internal/poly1305/sum_ppc64le.s
+++ b/internal/poly1305/sum_ppc64x.s
@@ -2,15 +2,25 @@
 // Use of this source code is governed by a BSD-style
 // license that can be found in the LICENSE file.
 
-//go:build gc && !purego
+//go:build gc && !purego && (ppc64 || ppc64le)
 
 #include "textflag.h"
 
 // This was ported from the amd64 implementation.
 
+#ifdef GOARCH_ppc64le
+#define LE_MOVD MOVD
+#define LE_MOVWZ MOVWZ
+#define LE_MOVHZ MOVHZ
+#else
+#define LE_MOVD MOVDBR
+#define LE_MOVWZ MOVWBR
+#define LE_MOVHZ MOVHBR
+#endif
+
 #define POLY1305_ADD(msg, h0, h1, h2, t0, t1, t2) \
-	MOVD (msg), t0;  \
-	MOVD 8(msg), t1; \
+	LE_MOVD (msg)( R0), t0; \
+	LE_MOVD (msg)(R24), t1; \
 	MOVD $1, t2;     \
 	ADDC t0, h0, h0; \
 	ADDE t1, h1, h1; \
@@ -50,10 +60,6 @@
 	ADDE   t3, h1, h1;  \
 	ADDZE  h2
 
-DATA ·poly1305Mask<>+0x00(SB)/8, $0x0FFFFFFC0FFFFFFF
-DATA ·poly1305Mask<>+0x08(SB)/8, $0x0FFFFFFC0FFFFFFC
-GLOBL ·poly1305Mask<>(SB), RODATA, $16
-
 // func update(state *[7]uint64, msg []byte)
 TEXT ·update(SB), $0-32
 	MOVD state+0(FP), R3
@@ -66,6 +72,8 @@ TEXT ·update(SB), $0-32
 	MOVD 24(R3), R11 // r0
 	MOVD 32(R3), R12 // r1
 
+	MOVD $8, R24
+
 	CMP R5, $16
 	BLT bytes_between_0_and_15
 
@@ -94,7 +102,7 @@ flush_buffer:
 
 	// Greater than 8 -- load the rightmost remaining bytes in msg
 	// and put into R17 (h1)
-	MOVD (R4)(R21), R17
+	LE_MOVD (R4)(R21), R17
 	MOVD $16, R22
 
 	// Find the offset to those bytes
@@ -118,7 +126,7 @@ just1:
 	BLT less8
 
 	// Exactly 8
-	MOVD (R4), R16
+	LE_MOVD (R4), R16
 
 	CMP R17, $0
 
@@ -133,7 +141,7 @@ less8:
 	MOVD  $0, R22   // shift count
 	CMP   R5, $4
 	BLT   less4
-	MOVWZ (R4), R16
+	LE_MOVWZ (R4), R16
 	ADD   $4, R4
 	ADD   $-4, R5
 	MOVD  $32, R22
@@ -141,7 +149,7 @@ less8:
 less4:
 	CMP   R5, $2
 	BLT   less2
-	MOVHZ (R4), R21
+	LE_MOVHZ (R4), R21
 	SLD   R22, R21, R21
 	OR    R16, R21, R16
 	ADD   $16, R22
diff --git a/sha3/doc.go b/sha3/doc.go
index 7e02309070..bbf391fe6e 100644
--- a/sha3/doc.go
+++ b/sha3/doc.go
@@ -5,6 +5,10 @@
 // Package sha3 implements the SHA-3 fixed-output-length hash functions and
 // the SHAKE variable-output-length hash functions defined by FIPS-202.
 //
+// All types in this package also implement [encoding.BinaryMarshaler],
+// [encoding.BinaryAppender] and [encoding.BinaryUnmarshaler] to marshal and
+// unmarshal the internal state of the hash.
+//
 // Both types of hash function use the "sponge" construction and the Keccak
 // permutation. For a detailed specification see http://keccak.noekeon.org/
 //
diff --git a/sha3/hashes.go b/sha3/hashes.go
index c544b29e5f..31fffbe044 100644
--- a/sha3/hashes.go
+++ b/sha3/hashes.go
@@ -48,33 +48,52 @@ func init() {
 	crypto.RegisterHash(crypto.SHA3_512, New512)
 }
 
+const (
+	dsbyteSHA3   = 0b00000110
+	dsbyteKeccak = 0b00000001
+	dsbyteShake  = 0b00011111
+	dsbyteCShake = 0b00000100
+
+	// rateK[c] is the rate in bytes for Keccak[c] where c is the capacity in
+	// bits. Given the sponge size is 1600 bits, the rate is 1600 - c bits.
+	rateK256  = (1600 - 256) / 8
+	rateK448  = (1600 - 448) / 8
+	rateK512  = (1600 - 512) / 8
+	rateK768  = (1600 - 768) / 8
+	rateK1024 = (1600 - 1024) / 8
+)
+
 func new224Generic() *state {
-	return &state{rate: 144, outputLen: 28, dsbyte: 0x06}
+	return &state{rate: rateK448, outputLen: 28, dsbyte: dsbyteSHA3}
 }
 
 func new256Generic() *state {
-	return &state{rate: 136, outputLen: 32, dsbyte: 0x06}
+	return &state{rate: rateK512, outputLen: 32, dsbyte: dsbyteSHA3}
 }
 
 func new384Generic() *state {
-	return &state{rate: 104, outputLen: 48, dsbyte: 0x06}
+	return &state{rate: rateK768, outputLen: 48, dsbyte: dsbyteSHA3}
 }
 
 func new512Generic() *state {
-	return &state{rate: 72, outputLen: 64, dsbyte: 0x06}
+	return &state{rate: rateK1024, outputLen: 64, dsbyte: dsbyteSHA3}
 }
 
 // NewLegacyKeccak256 creates a new Keccak-256 hash.
 //
 // Only use this function if you require compatibility with an existing cryptosystem
 // that uses non-standard padding. All other users should use New256 instead.
-func NewLegacyKeccak256() hash.Hash { return &state{rate: 136, outputLen: 32, dsbyte: 0x01} }
+func NewLegacyKeccak256() hash.Hash {
+	return &state{rate: rateK512, outputLen: 32, dsbyte: dsbyteKeccak}
+}
 
 // NewLegacyKeccak512 creates a new Keccak-512 hash.
 //
 // Only use this function if you require compatibility with an existing cryptosystem
 // that uses non-standard padding. All other users should use New512 instead.
-func NewLegacyKeccak512() hash.Hash { return &state{rate: 72, outputLen: 64, dsbyte: 0x01} }
+func NewLegacyKeccak512() hash.Hash {
+	return &state{rate: rateK1024, outputLen: 64, dsbyte: dsbyteKeccak}
+}
 
 // Sum224 returns the SHA3-224 digest of the data.
 func Sum224(data []byte) (digest [28]byte) {
diff --git a/sha3/sha3.go b/sha3/sha3.go
index afedde5abf..6658c44479 100644
--- a/sha3/sha3.go
+++ b/sha3/sha3.go
@@ -4,6 +4,15 @@
 
 package sha3
 
+import (
+	"crypto/subtle"
+	"encoding/binary"
+	"errors"
+	"unsafe"
+
+	"golang.org/x/sys/cpu"
+)
+
 // spongeDirection indicates the direction bytes are flowing through the sponge.
 type spongeDirection int
 
@@ -14,16 +23,13 @@ const (
 	spongeSqueezing
 )
 
-const (
-	// maxRate is the maximum size of the internal buffer. SHAKE-256
-	// currently needs the largest buffer.
-	maxRate = 168
-)
-
 type state struct {
-	// Generic sponge components.
-	a    [25]uint64 // main state of the hash
-	rate int        // the number of bytes of state to use
+	a [1600 / 8]byte // main state of the hash
+
+	// a[n:rate] is the buffer. If absorbing, it's the remaining space to XOR
+	// into before running the permutation. If squeezing, it's the remaining
+	// output to produce before running the permutation.
+	n, rate int
 
 	// dsbyte contains the "domain separation" bits and the first bit of
 	// the padding. Sections 6.1 and 6.2 of [1] separate the outputs of the
@@ -39,10 +45,6 @@ type state struct {
 	//      Extendable-Output Functions (May 2014)"
 	dsbyte byte
 
-	i, n    int // storage[i:n] is the buffer, i is only used while squeezing
-	storage [maxRate]byte
-
-	// Specific to SHA-3 and SHAKE.
 	outputLen int             // the default output size in bytes
 	state     spongeDirection // whether the sponge is absorbing or squeezing
 }
@@ -61,7 +63,7 @@ func (d *state) Reset() {
 		d.a[i] = 0
 	}
 	d.state = spongeAbsorbing
-	d.i, d.n = 0, 0
+	d.n = 0
 }
 
 func (d *state) clone() *state {
@@ -69,22 +71,25 @@ func (d *state) clone() *state {
 	return &ret
 }
 
-// permute applies the KeccakF-1600 permutation. It handles
-// any input-output buffering.
+// permute applies the KeccakF-1600 permutation.
 func (d *state) permute() {
-	switch d.state {
-	case spongeAbsorbing:
-		// If we're absorbing, we need to xor the input into the state
-		// before applying the permutation.
-		xorIn(d, d.storage[:d.rate])
-		d.n = 0
-		keccakF1600(&d.a)
-	case spongeSqueezing:
-		// If we're squeezing, we need to apply the permutation before
-		// copying more output.
-		keccakF1600(&d.a)
-		d.i = 0
-		copyOut(d, d.storage[:d.rate])
+	var a *[25]uint64
+	if cpu.IsBigEndian {
+		a = new([25]uint64)
+		for i := range a {
+			a[i] = binary.LittleEndian.Uint64(d.a[i*8:])
+		}
+	} else {
+		a = (*[25]uint64)(unsafe.Pointer(&d.a))
+	}
+
+	keccakF1600(a)
+	d.n = 0
+
+	if cpu.IsBigEndian {
+		for i := range a {
+			binary.LittleEndian.PutUint64(d.a[i*8:], a[i])
+		}
 	}
 }
 
@@ -92,53 +97,36 @@ func (d *state) permute() {
 // the multi-bitrate 10..1 padding rule, and permutes the state.
 func (d *state) padAndPermute() {
 	// Pad with this instance's domain-separator bits. We know that there's
-	// at least one byte of space in d.buf because, if it were full,
+	// at least one byte of space in the sponge because, if it were full,
 	// permute would have been called to empty it. dsbyte also contains the
 	// first one bit for the padding. See the comment in the state struct.
-	d.storage[d.n] = d.dsbyte
-	d.n++
-	for d.n < d.rate {
-		d.storage[d.n] = 0
-		d.n++
-	}
+	d.a[d.n] ^= d.dsbyte
 	// This adds the final one bit for the padding. Because of the way that
 	// bits are numbered from the LSB upwards, the final bit is the MSB of
 	// the last byte.
-	d.storage[d.rate-1] ^= 0x80
+	d.a[d.rate-1] ^= 0x80
 	// Apply the permutation
 	d.permute()
 	d.state = spongeSqueezing
-	d.n = d.rate
-	copyOut(d, d.storage[:d.rate])
 }
 
 // Write absorbs more data into the hash's state. It panics if any
 // output has already been read.
-func (d *state) Write(p []byte) (written int, err error) {
+func (d *state) Write(p []byte) (n int, err error) {
 	if d.state != spongeAbsorbing {
 		panic("sha3: Write after Read")
 	}
-	written = len(p)
+
+	n = len(p)
 
 	for len(p) > 0 {
-		if d.n == 0 && len(p) >= d.rate {
-			// The fast path; absorb a full "rate" bytes of input and apply the permutation.
-			xorIn(d, p[:d.rate])
-			p = p[d.rate:]
-			keccakF1600(&d.a)
-		} else {
-			// The slow path; buffer the input until we can fill the sponge, and then xor it in.
-			todo := d.rate - d.n
-			if todo > len(p) {
-				todo = len(p)
-			}
-			d.n += copy(d.storage[d.n:], p[:todo])
-			p = p[todo:]
-
-			// If the sponge is full, apply the permutation.
-			if d.n == d.rate {
-				d.permute()
-			}
+		x := subtle.XORBytes(d.a[d.n:d.rate], d.a[d.n:d.rate], p)
+		d.n += x
+		p = p[x:]
+
+		// If the sponge is full, apply the permutation.
+		if d.n == d.rate {
+			d.permute()
 		}
 	}
 
@@ -156,14 +144,14 @@ func (d *state) Read(out []byte) (n int, err error) {
 
 	// Now, do the squeezing.
 	for len(out) > 0 {
-		n := copy(out, d.storage[d.i:d.n])
-		d.i += n
-		out = out[n:]
-
 		// Apply the permutation if we've squeezed the sponge dry.
-		if d.i == d.rate {
+		if d.n == d.rate {
 			d.permute()
 		}
+
+		x := copy(out, d.a[d.n:d.rate])
+		d.n += x
+		out = out[x:]
 	}
 
 	return
@@ -183,3 +171,74 @@ func (d *state) Sum(in []byte) []byte {
 	dup.Read(hash)
 	return append(in, hash...)
 }
+
+const (
+	magicSHA3   = "sha\x08"
+	magicShake  = "sha\x09"
+	magicCShake = "sha\x0a"
+	magicKeccak = "sha\x0b"
+	// magic || rate || main state || n || sponge direction
+	marshaledSize = len(magicSHA3) + 1 + 200 + 1 + 1
+)
+
+func (d *state) MarshalBinary() ([]byte, error) {
+	return d.AppendBinary(make([]byte, 0, marshaledSize))
+}
+
+func (d *state) AppendBinary(b []byte) ([]byte, error) {
+	switch d.dsbyte {
+	case dsbyteSHA3:
+		b = append(b, magicSHA3...)
+	case dsbyteShake:
+		b = append(b, magicShake...)
+	case dsbyteCShake:
+		b = append(b, magicCShake...)
+	case dsbyteKeccak:
+		b = append(b, magicKeccak...)
+	default:
+		panic("unknown dsbyte")
+	}
+	// rate is at most 168, and n is at most rate.
+	b = append(b, byte(d.rate))
+	b = append(b, d.a[:]...)
+	b = append(b, byte(d.n), byte(d.state))
+	return b, nil
+}
+
+func (d *state) UnmarshalBinary(b []byte) error {
+	if len(b) != marshaledSize {
+		return errors.New("sha3: invalid hash state")
+	}
+
+	magic := string(b[:len(magicSHA3)])
+	b = b[len(magicSHA3):]
+	switch {
+	case magic == magicSHA3 && d.dsbyte == dsbyteSHA3:
+	case magic == magicShake && d.dsbyte == dsbyteShake:
+	case magic == magicCShake && d.dsbyte == dsbyteCShake:
+	case magic == magicKeccak && d.dsbyte == dsbyteKeccak:
+	default:
+		return errors.New("sha3: invalid hash state identifier")
+	}
+
+	rate := int(b[0])
+	b = b[1:]
+	if rate != d.rate {
+		return errors.New("sha3: invalid hash state function")
+	}
+
+	copy(d.a[:], b)
+	b = b[len(d.a):]
+
+	n, state := int(b[0]), spongeDirection(b[1])
+	if n > d.rate {
+		return errors.New("sha3: invalid hash state")
+	}
+	d.n = n
+	if state != spongeAbsorbing && state != spongeSqueezing {
+		return errors.New("sha3: invalid hash state")
+	}
+	d.state = state
+
+	return nil
+}
diff --git a/sha3/sha3_test.go b/sha3/sha3_test.go
index 21e8cbad7b..d97a970b1a 100644
--- a/sha3/sha3_test.go
+++ b/sha3/sha3_test.go
@@ -13,10 +13,12 @@ package sha3
 import (
 	"bytes"
 	"compress/flate"
+	"encoding"
 	"encoding/hex"
 	"encoding/json"
 	"fmt"
 	"hash"
+	"io"
 	"math/rand"
 	"os"
 	"strings"
@@ -375,6 +377,153 @@ func TestClone(t *testing.T) {
 	}
 }
 
+func TestCSHAKEAccumulated(t *testing.T) {
+	// Generated with pycryptodome@3.20.0
+	//
+	//    from Crypto.Hash import cSHAKE128
+	//    rng = cSHAKE128.new()
+	//    acc = cSHAKE128.new()
+	//    for n in range(200):
+	//        N = rng.read(n)
+	//        for s in range(200):
+	//            S = rng.read(s)
+	//            c = cSHAKE128.cSHAKE_XOF(data=None, custom=S, capacity=256, function=N)
+	//            c.update(rng.read(100))
+	//            acc.update(c.read(200))
+	//            c = cSHAKE128.cSHAKE_XOF(data=None, custom=S, capacity=256, function=N)
+	//            c.update(rng.read(168))
+	//            acc.update(c.read(200))
+	//            c = cSHAKE128.cSHAKE_XOF(data=None, custom=S, capacity=256, function=N)
+	//            c.update(rng.read(200))
+	//            acc.update(c.read(200))
+	//    print(acc.read(32).hex())
+	//
+	// and with @noble/hashes@v1.5.0
+	//
+	//    import { bytesToHex } from "@noble/hashes/utils";
+	//    import { cshake128 } from "@noble/hashes/sha3-addons";
+	//    const rng = cshake128.create();
+	//    const acc = cshake128.create();
+	//    for (let n = 0; n < 200; n++) {
+	//        const N = rng.xof(n);
+	//        for (let s = 0; s < 200; s++) {
+	//            const S = rng.xof(s);
+	//            let c = cshake128.create({ NISTfn: N, personalization: S });
+	//            c.update(rng.xof(100));
+	//            acc.update(c.xof(200));
+	//            c = cshake128.create({ NISTfn: N, personalization: S });
+	//            c.update(rng.xof(168));
+	//            acc.update(c.xof(200));
+	//            c = cshake128.create({ NISTfn: N, personalization: S });
+	//            c.update(rng.xof(200));
+	//            acc.update(c.xof(200));
+	//        }
+	//    }
+	//    console.log(bytesToHex(acc.xof(32)));
+	//
+	t.Run("cSHAKE128", func(t *testing.T) {
+		testCSHAKEAccumulated(t, NewCShake128, rateK256,
+			"bb14f8657c6ec5403d0b0e2ef3d3393497e9d3b1a9a9e8e6c81dbaa5fd809252")
+	})
+	t.Run("cSHAKE256", func(t *testing.T) {
+		testCSHAKEAccumulated(t, NewCShake256, rateK512,
+			"0baaf9250c6e25f0c14ea5c7f9bfde54c8a922c8276437db28f3895bdf6eeeef")
+	})
+}
+
+func testCSHAKEAccumulated(t *testing.T, newCShake func(N, S []byte) ShakeHash, rate int64, exp string) {
+	rnd := newCShake(nil, nil)
+	acc := newCShake(nil, nil)
+	for n := 0; n < 200; n++ {
+		N := make([]byte, n)
+		rnd.Read(N)
+		for s := 0; s < 200; s++ {
+			S := make([]byte, s)
+			rnd.Read(S)
+
+			c := newCShake(N, S)
+			io.CopyN(c, rnd, 100 /* < rate */)
+			io.CopyN(acc, c, 200)
+
+			c.Reset()
+			io.CopyN(c, rnd, rate)
+			io.CopyN(acc, c, 200)
+
+			c.Reset()
+			io.CopyN(c, rnd, 200 /* > rate */)
+			io.CopyN(acc, c, 200)
+		}
+	}
+	if got := hex.EncodeToString(acc.Sum(nil)[:32]); got != exp {
+		t.Errorf("got %s, want %s", got, exp)
+	}
+}
+
+func TestCSHAKELargeS(t *testing.T) {
+	if testing.Short() {
+		t.Skip("skipping test in short mode.")
+	}
+
+	// See https://go.dev/issue/66232.
+	const s = (1<<32)/8 + 1000 // s * 8 > 2^32
+	S := make([]byte, s)
+	rnd := NewShake128()
+	rnd.Read(S)
+	c := NewCShake128(nil, S)
+	io.CopyN(c, rnd, 1000)
+
+	// Generated with pycryptodome@3.20.0
+	//
+	//    from Crypto.Hash import cSHAKE128
+	//    rng = cSHAKE128.new()
+	//    S = rng.read(536871912)
+	//    c = cSHAKE128.new(custom=S)
+	//    c.update(rng.read(1000))
+	//    print(c.read(32).hex())
+	//
+	exp := "2cb9f237767e98f2614b8779cf096a52da9b3a849280bbddec820771ae529cf0"
+	if got := hex.EncodeToString(c.Sum(nil)); got != exp {
+		t.Errorf("got %s, want %s", got, exp)
+	}
+}
+
+func TestMarshalUnmarshal(t *testing.T) {
+	t.Run("SHA3-224", func(t *testing.T) { testMarshalUnmarshal(t, New224()) })
+	t.Run("SHA3-256", func(t *testing.T) { testMarshalUnmarshal(t, New256()) })
+	t.Run("SHA3-384", func(t *testing.T) { testMarshalUnmarshal(t, New384()) })
+	t.Run("SHA3-512", func(t *testing.T) { testMarshalUnmarshal(t, New512()) })
+	t.Run("SHAKE128", func(t *testing.T) { testMarshalUnmarshal(t, NewShake128()) })
+	t.Run("SHAKE256", func(t *testing.T) { testMarshalUnmarshal(t, NewShake256()) })
+	t.Run("cSHAKE128", func(t *testing.T) { testMarshalUnmarshal(t, NewCShake128([]byte("N"), []byte("S"))) })
+	t.Run("cSHAKE256", func(t *testing.T) { testMarshalUnmarshal(t, NewCShake256([]byte("N"), []byte("S"))) })
+	t.Run("Keccak-256", func(t *testing.T) { testMarshalUnmarshal(t, NewLegacyKeccak256()) })
+	t.Run("Keccak-512", func(t *testing.T) { testMarshalUnmarshal(t, NewLegacyKeccak512()) })
+}
+
+// TODO(filippo): move this to crypto/internal/cryptotest.
+func testMarshalUnmarshal(t *testing.T, h hash.Hash) {
+	buf := make([]byte, 200)
+	rand.Read(buf)
+	n := rand.Intn(200)
+	h.Write(buf)
+	want := h.Sum(nil)
+	h.Reset()
+	h.Write(buf[:n])
+	b, err := h.(encoding.BinaryMarshaler).MarshalBinary()
+	if err != nil {
+		t.Errorf("MarshalBinary: %v", err)
+	}
+	h.Write(bytes.Repeat([]byte{0}, 200))
+	if err := h.(encoding.BinaryUnmarshaler).UnmarshalBinary(b); err != nil {
+		t.Errorf("UnmarshalBinary: %v", err)
+	}
+	h.Write(buf[n:])
+	got := h.Sum(nil)
+	if !bytes.Equal(got, want) {
+		t.Errorf("got %x, want %x", got, want)
+	}
+}
+
 // BenchmarkPermutationFunction measures the speed of the permutation function
 // with no input data.
 func BenchmarkPermutationFunction(b *testing.B) {
diff --git a/sha3/shake.go b/sha3/shake.go
index a01ef43577..a6b3a4281f 100644
--- a/sha3/shake.go
+++ b/sha3/shake.go
@@ -16,9 +16,12 @@ package sha3
 // [2] https://doi.org/10.6028/NIST.SP.800-185
 
 import (
+	"bytes"
 	"encoding/binary"
+	"errors"
 	"hash"
 	"io"
+	"math/bits"
 )
 
 // ShakeHash defines the interface to hash functions that support
@@ -50,41 +53,33 @@ type cshakeState struct {
 	initBlock []byte
 }
 
-// Consts for configuring initial SHA-3 state
-const (
-	dsbyteShake  = 0x1f
-	dsbyteCShake = 0x04
-	rate128      = 168
-	rate256      = 136
-)
+func bytepad(data []byte, rate int) []byte {
+	out := make([]byte, 0, 9+len(data)+rate-1)
+	out = append(out, leftEncode(uint64(rate))...)
+	out = append(out, data...)
+	if padlen := rate - len(out)%rate; padlen < rate {
+		out = append(out, make([]byte, padlen)...)
+	}
+	return out
+}
 
-func bytepad(input []byte, w int) []byte {
-	// leftEncode always returns max 9 bytes
-	buf := make([]byte, 0, 9+len(input)+w)
-	buf = append(buf, leftEncode(uint64(w))...)
-	buf = append(buf, input...)
-	padlen := w - (len(buf) % w)
-	return append(buf, make([]byte, padlen)...)
-}
-
-func leftEncode(value uint64) []byte {
-	var b [9]byte
-	binary.BigEndian.PutUint64(b[1:], value)
-	// Trim all but last leading zero bytes
-	i := byte(1)
-	for i < 8 && b[i] == 0 {
-		i++
+func leftEncode(x uint64) []byte {
+	// Let n be the smallest positive integer for which 2^(8n) > x.
+	n := (bits.Len64(x) + 7) / 8
+	if n == 0 {
+		n = 1
 	}
-	// Prepend number of encoded bytes
-	b[i-1] = 9 - i
-	return b[i-1:]
+	// Return n || x with n as a byte and x an n bytes in big-endian order.
+	b := make([]byte, 9)
+	binary.BigEndian.PutUint64(b[1:], x)
+	b = b[9-n-1:]
+	b[0] = byte(n)
+	return b
 }
 
 func newCShake(N, S []byte, rate, outputLen int, dsbyte byte) ShakeHash {
 	c := cshakeState{state: &state{rate: rate, outputLen: outputLen, dsbyte: dsbyte}}
-
-	// leftEncode returns max 9 bytes
-	c.initBlock = make([]byte, 0, 9*2+len(N)+len(S))
+	c.initBlock = make([]byte, 0, 9+len(N)+9+len(S)) // leftEncode returns max 9 bytes
 	c.initBlock = append(c.initBlock, leftEncode(uint64(len(N))*8)...)
 	c.initBlock = append(c.initBlock, N...)
 	c.initBlock = append(c.initBlock, leftEncode(uint64(len(S))*8)...)
@@ -111,6 +106,30 @@ func (c *state) Clone() ShakeHash {
 	return c.clone()
 }
 
+func (c *cshakeState) MarshalBinary() ([]byte, error) {
+	return c.AppendBinary(make([]byte, 0, marshaledSize+len(c.initBlock)))
+}
+
+func (c *cshakeState) AppendBinary(b []byte) ([]byte, error) {
+	b, err := c.state.AppendBinary(b)
+	if err != nil {
+		return nil, err
+	}
+	b = append(b, c.initBlock...)
+	return b, nil
+}
+
+func (c *cshakeState) UnmarshalBinary(b []byte) error {
+	if len(b) <= marshaledSize {
+		return errors.New("sha3: invalid hash state")
+	}
+	if err := c.state.UnmarshalBinary(b[:marshaledSize]); err != nil {
+		return err
+	}
+	c.initBlock = bytes.Clone(b[marshaledSize:])
+	return nil
+}
+
 // NewShake128 creates a new SHAKE128 variable-output-length ShakeHash.
 // Its generic security strength is 128 bits against all attacks if at
 // least 32 bytes of its output are used.
@@ -126,11 +145,11 @@ func NewShake256() ShakeHash {
 }
 
 func newShake128Generic() *state {
-	return &state{rate: rate128, outputLen: 32, dsbyte: dsbyteShake}
+	return &state{rate: rateK256, outputLen: 32, dsbyte: dsbyteShake}
 }
 
 func newShake256Generic() *state {
-	return &state{rate: rate256, outputLen: 64, dsbyte: dsbyteShake}
+	return &state{rate: rateK512, outputLen: 64, dsbyte: dsbyteShake}
 }
 
 // NewCShake128 creates a new instance of cSHAKE128 variable-output-length ShakeHash,
@@ -143,7 +162,7 @@ func NewCShake128(N, S []byte) ShakeHash {
 	if len(N) == 0 && len(S) == 0 {
 		return NewShake128()
 	}
-	return newCShake(N, S, rate128, 32, dsbyteCShake)
+	return newCShake(N, S, rateK256, 32, dsbyteCShake)
 }
 
 // NewCShake256 creates a new instance of cSHAKE256 variable-output-length ShakeHash,
@@ -156,7 +175,7 @@ func NewCShake256(N, S []byte) ShakeHash {
 	if len(N) == 0 && len(S) == 0 {
 		return NewShake256()
 	}
-	return newCShake(N, S, rate256, 64, dsbyteCShake)
+	return newCShake(N, S, rateK512, 64, dsbyteCShake)
 }
 
 // ShakeSum128 writes an arbitrary-length digest of data into hash.
diff --git a/sha3/xor.go b/sha3/xor.go
deleted file mode 100644
index 6ada5c9574..0000000000
--- a/sha3/xor.go
+++ /dev/null
@@ -1,40 +0,0 @@
-// Copyright 2015 The Go Authors. All rights reserved.
-// Use of this source code is governed by a BSD-style
-// license that can be found in the LICENSE file.
-
-package sha3
-
-import (
-	"crypto/subtle"
-	"encoding/binary"
-	"unsafe"
-
-	"golang.org/x/sys/cpu"
-)
-
-// xorIn xors the bytes in buf into the state.
-func xorIn(d *state, buf []byte) {
-	if cpu.IsBigEndian {
-		for i := 0; len(buf) >= 8; i++ {
-			a := binary.LittleEndian.Uint64(buf)
-			d.a[i] ^= a
-			buf = buf[8:]
-		}
-	} else {
-		ab := (*[25 * 64 / 8]byte)(unsafe.Pointer(&d.a))
-		subtle.XORBytes(ab[:], ab[:], buf)
-	}
-}
-
-// copyOut copies uint64s to a byte buffer.
-func copyOut(d *state, b []byte) {
-	if cpu.IsBigEndian {
-		for i := 0; len(b) >= 8; i++ {
-			binary.LittleEndian.PutUint64(b, d.a[i])
-			b = b[8:]
-		}
-	} else {
-		ab := (*[25 * 64 / 8]byte)(unsafe.Pointer(&d.a))
-		copy(b, ab[:])
-	}
-}
diff --git a/ssh/client_auth.go b/ssh/client_auth.go
index b93961010d..b86dde151d 100644
--- a/ssh/client_auth.go
+++ b/ssh/client_auth.go
@@ -555,6 +555,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 	}
 
 	gotMsgExtInfo := false
+	gotUserAuthInfoRequest := false
 	for {
 		packet, err := c.readPacket()
 		if err != nil {
@@ -585,6 +586,9 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 			if msg.PartialSuccess {
 				return authPartialSuccess, msg.Methods, nil
 			}
+			if !gotUserAuthInfoRequest {
+				return authFailure, msg.Methods, unexpectedMessageError(msgUserAuthInfoRequest, packet[0])
+			}
 			return authFailure, msg.Methods, nil
 		case msgUserAuthSuccess:
 			return authSuccess, nil, nil
@@ -596,6 +600,7 @@ func (cb KeyboardInteractiveChallenge) auth(session []byte, user string, c packe
 		if err := Unmarshal(packet, &msg); err != nil {
 			return authFailure, nil, err
 		}
+		gotUserAuthInfoRequest = true
 
 		// Manually unpack the prompt/echo pairs.
 		rest := msg.Prompts
diff --git a/ssh/client_auth_test.go b/ssh/client_auth_test.go
index e981cc49a6..f11eeb590b 100644
--- a/ssh/client_auth_test.go
+++ b/ssh/client_auth_test.go
@@ -1293,3 +1293,92 @@ func TestCertAuthOpenSSHCompat(t *testing.T) {
 		t.Fatalf("unable to dial remote side: %s", err)
 	}
 }
+
+func TestKeyboardInteractiveAuthEarlyFail(t *testing.T) {
+	const maxAuthTries = 2
+
+	c1, c2, err := netPipe()
+	if err != nil {
+		t.Fatalf("netPipe: %v", err)
+	}
+	defer c1.Close()
+	defer c2.Close()
+
+	// Start testserver
+	serverConfig := &ServerConfig{
+		MaxAuthTries: maxAuthTries,
+		KeyboardInteractiveCallback: func(c ConnMetadata,
+			client KeyboardInteractiveChallenge) (*Permissions, error) {
+			// Fail keyboard-interactive authentication early before
+			// any prompt is sent to client.
+			return nil, errors.New("keyboard-interactive auth failed")
+		},
+		PasswordCallback: func(c ConnMetadata,
+			pass []byte) (*Permissions, error) {
+			if string(pass) == clientPassword {
+				return nil, nil
+			}
+			return nil, errors.New("password auth failed")
+		},
+	}
+	serverConfig.AddHostKey(testSigners["rsa"])
+
+	serverDone := make(chan struct{})
+	go func() {
+		defer func() { serverDone <- struct{}{} }()
+		conn, chans, reqs, err := NewServerConn(c2, serverConfig)
+		if err != nil {
+			return
+		}
+		_ = conn.Close()
+
+		discarderDone := make(chan struct{})
+		go func() {
+			defer func() { discarderDone <- struct{}{} }()
+			DiscardRequests(reqs)
+		}()
+		for newChannel := range chans {
+			newChannel.Reject(Prohibited,
+				"testserver not accepting requests")
+		}
+
+		<-discarderDone
+	}()
+
+	// Connect to testserver, expect KeyboardInteractive() to be not called,
+	// PasswordCallback() to be called and connection to succeed.
+	passwordCallbackCalled := false
+	clientConfig := &ClientConfig{
+		User: "testuser",
+		Auth: []AuthMethod{
+			RetryableAuthMethod(KeyboardInteractive(func(name,
+				instruction string, questions []string,
+				echos []bool) ([]string, error) {
+				t.Errorf("unexpected call to KeyboardInteractive()")
+				return []string{clientPassword}, nil
+			}), maxAuthTries),
+			RetryableAuthMethod(PasswordCallback(func() (secret string,
+				err error) {
+				t.Logf("PasswordCallback()")
+				passwordCallbackCalled = true
+				return clientPassword, nil
+			}), maxAuthTries),
+		},
+		HostKeyCallback: InsecureIgnoreHostKey(),
+	}
+
+	conn, _, _, err := NewClientConn(c1, "", clientConfig)
+	if err != nil {
+		t.Errorf("unexpected NewClientConn() error: %v", err)
+	}
+	if conn != nil {
+		conn.Close()
+	}
+
+	// Wait for server to finish.
+	<-serverDone
+
+	if !passwordCallbackCalled {
+		t.Errorf("expected PasswordCallback() to be called")
+	}
+}