stdlib: Add arc4random, arc4random_buf, and arc4random_uniform (BZ #4417)

The implementation is based on scalar Chacha20 with per-thread cache.
It uses getrandom or /dev/urandom as fallback to get the initial entropy,
and reseeds the internal state on every 16MB of consumed buffer.

To improve performance and lower memory consumption the per-thread cache
is allocated lazily on first arc4random functions call, and if the
memory allocation fails getentropy or /dev/urandom is used as fallback.
The cache is also cleared on thread exit iff it was initialized (so if
arc4random is not called it is not touched).

Although it is lock-free, arc4random is still not async-signal-safe
(the per thread state is not updated atomically).

The ChaCha20 implementation is based on RFC8439 [1], omitting the final
XOR of the keystream with the plaintext because the plaintext is a
stream of zeros.  This strategy is similar to what OpenBSD arc4random
does.

The arc4random_uniform is based on previous work by Florian Weimer,
where the algorithm is based on Jérémie Lumbroso paper Optimal Discrete
Uniform Generation from Coin Flips, and Applications (2013) [2], who
credits Donald E. Knuth and Andrew C. Yao, The complexity of nonuniform
random number generation (1976), for solving the general case.

The main advantage of this method is the that the unit of randomness is not
the uniform random variable (uint32_t), but a random bit.  It optimizes the
internal buffer sampling by initially consuming a 32-bit random variable
and then sampling byte per byte.  Depending of the upper bound requested,
it might lead to better CPU utilization.

Checked on x86_64-linux-gnu, aarch64-linux, and powerpc64le-linux-gnu.

Co-authored-by: Florian Weimer <fweimer@redhat.com>
Reviewed-by: Yann Droneaud <ydroneaud@opteya.com>

[1] https://datatracker.ietf.org/doc/html/rfc8439
[2] https://arxiv.org/pdf/1304.1916.pdf

55 files changed, 800 insertions, 15 deletions

diff --git a/NEWS b/NEWS
index df882ec..8420a65 100644
--- a/NEWS
+++ b/NEWS
@@ -60,6 +60,10 @@ Major new features:
   _GNU_SOURCE macro is defined and the C++20 __cpp_char8_t feature test macro
   is not defined (if __cpp_char8_t is defined, then char8_t is a builtin type).
 
+* The functions arc4random, arc4random_buf, and arc4random_uniform have been
+  added.  The functions use a pseudo-random number generator along with
+  entropy from the kernel.
+
 Deprecated and removed features, and other changes affecting compatibility:
 
 * Support for prelink will be removed in the next release; this includes
diff --git a/include/stdlib.h b/include/stdlib.h
index 1c6f70b..cae7f7c 100644
--- a/include/stdlib.h
+++ b/include/stdlib.h
@@ -144,6 +144,18 @@ libc_hidden_proto (__ptsname_r)
 libc_hidden_proto (grantpt)
 libc_hidden_proto (unlockpt)
 
+__typeof (arc4random) __arc4random;
+libc_hidden_proto (__arc4random);
+__typeof (arc4random_buf) __arc4random_buf;
+libc_hidden_proto (__arc4random_buf);
+__typeof (arc4random_uniform) __arc4random_uniform;
+libc_hidden_proto (__arc4random_uniform);
+extern void __arc4random_buf_internal (void *buffer, size_t len)
+     attribute_hidden;
+/* Called from the fork function to reinitialize the internal cipher state
+   in child process.  */
+extern void __arc4random_fork_subprocess (void) attribute_hidden;
+
 extern double __strtod_internal (const char *__restrict __nptr,
 				 char **__restrict __endptr, int __group)
      __THROW __nonnull ((1)) __wur;
diff --git a/malloc/thread-freeres.c b/malloc/thread-freeres.c
index 3894652..b22e1d7 100644
--- a/malloc/thread-freeres.c
+++ b/malloc/thread-freeres.c
@@ -36,7 +36,7 @@ __libc_thread_freeres (void)
   __rpc_thread_destroy ();
 #endif
   call_function_static_weak (__res_thread_freeres);
-  __glibc_tls_internal_free ();
+  call_function_static_weak (__glibc_tls_internal_free);
   call_function_static_weak (__libc_dlerror_result_free);
 
   /* This should come last because it shuts down malloc for this
diff --git a/nptl/allocatestack.c b/nptl/allocatestack.c
index 98f5f6d..219854f 100644
--- a/nptl/allocatestack.c
+++ b/nptl/allocatestack.c
@@ -32,6 +32,7 @@
 #include <kernel-features.h>
 #include <nptl-stack.h>
 #include <libc-lock.h>
+#include <tls-internal.h>
 
 /* Default alignment of stack.  */
 #ifndef STACK_ALIGN
@@ -127,7 +128,7 @@ get_cached_stack (size_t *sizep, void **memp)
 
   result->exiting = false;
   __libc_lock_init (result->exit_lock);
-  result->tls_state = (struct tls_internal_t) { 0 };
+  memset (&result->tls_state, 0, sizeof result->tls_state);
 
   /* Clear the DTV.  */
   dtv_t *dtv = GET_DTV (TLS_TPADJ (result));
diff --git a/stdlib/Makefile b/stdlib/Makefile
index d4a4d56..62f8253 100644
--- a/stdlib/Makefile
+++ b/stdlib/Makefile
@@ -53,6 +53,8 @@ routines := \
   a64l \
   abort \
   abs \
+  arc4random \
+  arc4random_uniform \
   at_quick_exit \
   atof \
   atoi \
diff --git a/stdlib/Versions b/stdlib/Versions
index 5e9099a..d09a308 100644
--- a/stdlib/Versions
+++ b/stdlib/Versions
@@ -136,6 +136,11 @@ libc {
     strtof32; strtof64; strtof32x;
     strtof32_l; strtof64_l; strtof32x_l;
   }
+  GLIBC_2.36 {
+    arc4random;
+    arc4random_buf;
+    arc4random_uniform;
+  }
   GLIBC_PRIVATE {
     # functions which have an additional interface since they are
     # are cancelable.
diff --git a/stdlib/arc4random.c b/stdlib/arc4random.c
new file mode 100644
index 0000000..65547e7
--- /dev/null
+++ b/stdlib/arc4random.c
@@ -0,0 +1,208 @@
+/* Pseudo Random Number Generator based on ChaCha20.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <arc4random.h>
+#include <errno.h>
+#include <not-cancel.h>
+#include <stdio.h>
+#include <stdlib.h>
+#include <sys/mman.h>
+#include <sys/param.h>
+#include <sys/random.h>
+#include <tls-internal.h>
+
+/* arc4random keeps two counters: 'have' is the current valid bytes not yet
+   consumed in 'buf' while 'count' is the maximum number of bytes until a
+   reseed.
+
+   Both the initial seed and reseed try to obtain entropy from the kernel
+   and abort the process if none could be obtained.
+
+   The state 'buf' improves the usage of the cipher calls, allowing to call
+   optimized implementations (if the architecture provides it) and minimize
+   function call overhead.  */
+
+#include <chacha20.c>
+
+/* Called from the fork function to reset the state.  */
+void
+__arc4random_fork_subprocess (void)
+{
+  struct arc4random_state_t *state = __glibc_tls_internal ()->rand_state;
+  if (state != NULL)
+    {
+      explicit_bzero (state, sizeof (*state));
+      /* Force key init.  */
+      state->count = -1;
+    }
+}
+
+/* Return the current thread random state or try to create one if there is
+   none available.  In the case malloc can not allocate a state, arc4random
+   will try to get entropy with arc4random_getentropy.  */
+static struct arc4random_state_t *
+arc4random_get_state (void)
+{
+  struct arc4random_state_t *state = __glibc_tls_internal ()->rand_state;
+  if (state == NULL)
+    {
+      state = malloc (sizeof (struct arc4random_state_t));
+      if (state != NULL)
+	{
+	  /* Force key initialization on first call.  */
+	  state->count = -1;
+	  __glibc_tls_internal ()->rand_state = state;
+	}
+    }
+  return state;
+}
+
+static void
+arc4random_getrandom_failure (void)
+{
+  __libc_fatal ("Fatal glibc error: cannot get entropy for arc4random\n");
+}
+
+static void
+arc4random_rekey (struct arc4random_state_t *state, uint8_t *rnd, size_t rndlen)
+{
+  chacha20_crypt (state->ctx, state->buf, state->buf, sizeof state->buf);
+
+  /* Mix optional user provided data.  */
+  if (rnd != NULL)
+    {
+      size_t m = MIN (rndlen, CHACHA20_KEY_SIZE + CHACHA20_IV_SIZE);
+      for (size_t i = 0; i < m; i++)
+	state->buf[i] ^= rnd[i];
+    }
+
+  /* Immediately reinit for backtracking resistance.  */
+  chacha20_init (state->ctx, state->buf, state->buf + CHACHA20_KEY_SIZE);
+  explicit_bzero (state->buf, CHACHA20_KEY_SIZE + CHACHA20_IV_SIZE);
+  state->have = sizeof (state->buf) - (CHACHA20_KEY_SIZE + CHACHA20_IV_SIZE);
+}
+
+static void
+arc4random_getentropy (void *rnd, size_t len)
+{
+  if (__getrandom_nocancel (rnd, len, GRND_NONBLOCK) == len)
+    return;
+
+  int fd = TEMP_FAILURE_RETRY (__open64_nocancel ("/dev/urandom",
+						  O_RDONLY | O_CLOEXEC));
+  if (fd != -1)
+    {
+      uint8_t *p = rnd;
+      uint8_t *end = p + len;
+      do
+	{
+	  ssize_t ret = TEMP_FAILURE_RETRY (__read_nocancel (fd, p, end - p));
+	  if (ret <= 0)
+	    arc4random_getrandom_failure ();
+	  p += ret;
+	}
+      while (p < end);
+
+      if (__close_nocancel (fd) == 0)
+	return;
+    }
+  arc4random_getrandom_failure ();
+}
+
+/* Check if the thread context STATE should be reseed with kernel entropy
+   depending of requested LEN bytes.  If there is less than requested,
+   the state is either initialized or reseeded, otherwise the internal
+   counter subtract the requested length.  */
+static void
+arc4random_check_stir (struct arc4random_state_t *state, size_t len)
+{
+  if (state->count <= len || state->count == -1)
+    {
+      uint8_t rnd[CHACHA20_KEY_SIZE + CHACHA20_IV_SIZE];
+      arc4random_getentropy (rnd, sizeof rnd);
+
+      if (state->count == -1)
+	chacha20_init (state->ctx, rnd, rnd + CHACHA20_KEY_SIZE);
+      else
+	arc4random_rekey (state, rnd, sizeof rnd);
+
+      explicit_bzero (rnd, sizeof rnd);
+
+      /* Invalidate the buf.  */
+      state->have = 0;
+      memset (state->buf, 0, sizeof state->buf);
+      state->count = CHACHA20_RESEED_SIZE;
+    }
+  else
+    state->count -= len;
+}
+
+void
+__arc4random_buf (void *buffer, size_t len)
+{
+  struct arc4random_state_t *state = arc4random_get_state ();
+  if (__glibc_unlikely (state == NULL))
+    {
+      arc4random_getentropy (buffer, len);
+      return;
+    }
+
+  arc4random_check_stir (state, len);
+  while (len > 0)
+    {
+      if (state->have > 0)
+	{
+	  size_t m = MIN (len, state->have);
+	  uint8_t *ks = state->buf + sizeof (state->buf) - state->have;
+	  memcpy (buffer, ks, m);
+	  explicit_bzero (ks, m);
+	  buffer += m;
+	  len -= m;
+	  state->have -= m;
+	}
+      if (state->have == 0)
+	arc4random_rekey (state, NULL, 0);
+    }
+}
+libc_hidden_def (__arc4random_buf)
+weak_alias (__arc4random_buf, arc4random_buf)
+
+uint32_t
+__arc4random (void)
+{
+  uint32_t r;
+
+  struct arc4random_state_t *state = arc4random_get_state ();
+  if (__glibc_unlikely (state == NULL))
+    {
+      arc4random_getentropy (&r, sizeof (uint32_t));
+      return r;
+    }
+
+  arc4random_check_stir (state, sizeof (uint32_t));
+  if (state->have < sizeof (uint32_t))
+    arc4random_rekey (state, NULL, 0);
+  uint8_t *ks = state->buf + sizeof (state->buf) - state->have;
+  memcpy (&r, ks, sizeof (uint32_t));
+  memset (ks, 0, sizeof (uint32_t));
+  state->have -= sizeof (uint32_t);
+
+  return r;
+}
+libc_hidden_def (__arc4random)
+weak_alias (__arc4random, arc4random)
diff --git a/stdlib/arc4random.h b/stdlib/arc4random.h
new file mode 100644
index 0000000..cd39389
--- /dev/null
+++ b/stdlib/arc4random.h
@@ -0,0 +1,48 @@
+/* Arc4random definition used on TLS.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#ifndef _CHACHA20_H
+#define _CHACHA20_H
+
+#include <stddef.h>
+#include <stdint.h>
+
+/* Internal ChaCha20 state.  */
+#define CHACHA20_STATE_LEN	16
+#define CHACHA20_BLOCK_SIZE	64
+
+/* Maximum number bytes until reseed (16 MB).  */
+#define CHACHA20_RESEED_SIZE	(16 * 1024 * 1024)
+
+/* Internal arc4random buffer, used on each feedback step so offer some
+   backtracking protection and to allow better used of vectorized
+   chacha20 implementations.  */
+#define CHACHA20_BUFSIZE        (8 * CHACHA20_BLOCK_SIZE)
+
+_Static_assert (CHACHA20_BUFSIZE >= CHACHA20_BLOCK_SIZE + CHACHA20_BLOCK_SIZE,
+		"CHACHA20_BUFSIZE < CHACHA20_BLOCK_SIZE + CHACHA20_BLOCK_SIZE");
+
+struct arc4random_state_t
+{
+  uint32_t ctx[CHACHA20_STATE_LEN];
+  size_t have;
+  size_t count;
+  uint8_t buf[CHACHA20_BUFSIZE];
+};
+
+#endif
diff --git a/stdlib/arc4random_uniform.c b/stdlib/arc4random_uniform.c
new file mode 100644
index 0000000..1326dfa
--- /dev/null
+++ b/stdlib/arc4random_uniform.c
@@ -0,0 +1,140 @@
+/* Random pseudo generator number which returns a single 32 bit value
+   uniformly distributed but with an upper_bound.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <endian.h>
+#include <libc-lock.h>
+#include <stdlib.h>
+#include <sys/param.h>
+
+/* Return the number of bytes which cover values up to the limit.  */
+__attribute__ ((const))
+static uint32_t
+byte_count (uint32_t n)
+{
+  if (n < (1U << 8))
+    return 1;
+  else if (n < (1U << 16))
+    return 2;
+  else if (n < (1U << 24))
+    return 3;
+  else
+    return 4;
+}
+
+/* Fill the lower bits of the result with randomness, according to the
+   number of bytes requested.  */
+static void
+random_bytes (uint32_t *result, uint32_t byte_count)
+{
+  *result = 0;
+  unsigned char *ptr = (unsigned char *) result;
+  if (__BYTE_ORDER == __BIG_ENDIAN)
+    ptr += 4 - byte_count;
+  __arc4random_buf (ptr, byte_count);
+}
+
+uint32_t
+__arc4random_uniform (uint32_t n)
+{
+  if (n <= 1)
+    /* There is no valid return value for a zero limit, and 0 is the
+       only possible result for limit 1.  */
+    return 0;
+
+  /* The bits variable serves as a source for bits.  Prefetch the
+     minimum number of bytes needed.  */
+  uint32_t count = byte_count (n);
+  uint32_t bits_length = count * CHAR_BIT;
+  uint32_t bits;
+  random_bytes (&bits, count);
+
+  /* Powers of two are easy.  */
+  if (powerof2 (n))
+    return bits & (n - 1);
+
+  /* The general case.  This algorithm follows Jérémie Lumbroso,
+     Optimal Discrete Uniform Generation from Coin Flips, and
+     Applications (2013), who credits Donald E. Knuth and Andrew
+     C. Yao, The complexity of nonuniform random number generation
+     (1976), for solving the general case.
+
+     The implementation below unrolls the initialization stage of the
+     loop, where v is less than n.  */
+
+  /* Use 64-bit variables even though the intermediate results are
+     never larger than 33 bits.  This ensures the code is easier to
+     compile on 64-bit architectures.  */
+  uint64_t v;
+  uint64_t c;
+
+  /* Initialize v and c.  v is the smallest power of 2 which is larger
+     than n.*/
+  {
+    uint32_t log2p1 = 32 - __builtin_clz (n);
+    v = 1ULL << log2p1;
+    c = bits & (v - 1);
+    bits >>= log2p1;
+    bits_length -= log2p1;
+  }
+
+  /* At the start of the loop, c is uniformly distributed within the
+     half-open interval [0, v), and v < 2n < 2**33.  */
+  while (true)
+    {
+      if (v >= n)
+        {
+          /* If the candidate is less than n, accept it.  */
+          if (c < n)
+            /* c is uniformly distributed on [0, n).  */
+            return c;
+          else
+            {
+              /* c is uniformly distributed on [n, v).  */
+              v -= n;
+              c -= n;
+              /* The distribution was shifted, so c is uniformly
+                 distributed on [0, v) again.  */
+            }
+        }
+      /* v < n here.  */
+
+      /* Replenish the bit source if necessary.  */
+      if (bits_length == 0)
+        {
+          /* Overwrite the least significant byte.  */
+	  random_bytes (&bits, 1);
+	  bits_length = CHAR_BIT;
+        }
+
+      /* Double the range.  No overflow because v < n < 2**32.  */
+      v *= 2;
+      /* v < 2n here.  */
+
+      /* Extract a bit and append it to c.  c remains less than v and
+         thus 2**33.  */
+      c = (c << 1) | (bits & 1);
+      bits >>= 1;
+      --bits_length;
+
+      /* At this point, c is uniformly distributed on [0, v) again,
+         and v < 2n < 2**33.  */
+    }
+}
+libc_hidden_def (__arc4random_uniform)
+weak_alias (__arc4random_uniform, arc4random_uniform)
diff --git a/stdlib/chacha20.c b/stdlib/chacha20.c
new file mode 100644
index 0000000..c47b841
--- /dev/null
+++ b/stdlib/chacha20.c
@@ -0,0 +1,187 @@
+/* Generic ChaCha20 implementation (used on arc4random).
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <array_length.h>
+#include <endian.h>
+#include <stddef.h>
+#include <stdint.h>
+#include <string.h>
+
+/* 32-bit stream position, then 96-bit nonce.  */
+#define CHACHA20_IV_SIZE	16
+#define CHACHA20_KEY_SIZE	32
+
+#define CHACHA20_STATE_LEN	16
+
+/* The ChaCha20 implementation is based on RFC8439 [1], omitting the final
+   XOR of the keystream with the plaintext because the plaintext is a
+   stream of zeros.  */
+
+enum chacha20_constants
+{
+  CHACHA20_CONSTANT_EXPA = 0x61707865U,
+  CHACHA20_CONSTANT_ND_3 = 0x3320646eU,
+  CHACHA20_CONSTANT_2_BY = 0x79622d32U,
+  CHACHA20_CONSTANT_TE_K = 0x6b206574U
+};
+
+static inline uint32_t
+read_unaligned_32 (const uint8_t *p)
+{
+  uint32_t r;
+  memcpy (&r, p, sizeof (r));
+  return r;
+}
+
+static inline void
+write_unaligned_32 (uint8_t *p, uint32_t v)
+{
+  memcpy (p, &v, sizeof (v));
+}
+
+#if __BYTE_ORDER == __BIG_ENDIAN
+# define read_unaligned_le32(p) __builtin_bswap32 (read_unaligned_32 (p))
+# define set_state(v)		__builtin_bswap32 ((v))
+#else
+# define read_unaligned_le32(p) read_unaligned_32 ((p))
+# define set_state(v)		(v)
+#endif
+
+static inline void
+chacha20_init (uint32_t *state, const uint8_t *key, const uint8_t *iv)
+{
+  state[0]  = CHACHA20_CONSTANT_EXPA;
+  state[1]  = CHACHA20_CONSTANT_ND_3;
+  state[2]  = CHACHA20_CONSTANT_2_BY;
+  state[3]  = CHACHA20_CONSTANT_TE_K;
+
+  state[4]  = read_unaligned_le32 (key + 0 * sizeof (uint32_t));
+  state[5]  = read_unaligned_le32 (key + 1 * sizeof (uint32_t));
+  state[6]  = read_unaligned_le32 (key + 2 * sizeof (uint32_t));
+  state[7]  = read_unaligned_le32 (key + 3 * sizeof (uint32_t));
+  state[8]  = read_unaligned_le32 (key + 4 * sizeof (uint32_t));
+  state[9]  = read_unaligned_le32 (key + 5 * sizeof (uint32_t));
+  state[10] = read_unaligned_le32 (key + 6 * sizeof (uint32_t));
+  state[11] = read_unaligned_le32 (key + 7 * sizeof (uint32_t));
+
+  state[12] = read_unaligned_le32 (iv + 0 * sizeof (uint32_t));
+  state[13] = read_unaligned_le32 (iv + 1 * sizeof (uint32_t));
+  state[14] = read_unaligned_le32 (iv + 2 * sizeof (uint32_t));
+  state[15] = read_unaligned_le32 (iv + 3 * sizeof (uint32_t));
+}
+
+static inline uint32_t
+rotl32 (unsigned int shift, uint32_t word)
+{
+  return (word << (shift & 31)) | (word >> ((-shift) & 31));
+}
+
+static void
+state_final (const uint8_t *src, uint8_t *dst, uint32_t v)
+{
+#ifdef CHACHA20_XOR_FINAL
+  v ^= read_unaligned_32 (src);
+#endif
+  write_unaligned_32 (dst, v);
+}
+
+static inline void
+chacha20_block (uint32_t *state, uint8_t *dst, const uint8_t *src)
+{
+  uint32_t x0, x1, x2, x3, x4, x5, x6, x7;
+  uint32_t x8, x9, x10, x11, x12, x13, x14, x15;
+
+  x0 = state[0];
+  x1 = state[1];
+  x2 = state[2];
+  x3 = state[3];
+  x4 = state[4];
+  x5 = state[5];
+  x6 = state[6];
+  x7 = state[7];
+  x8 = state[8];
+  x9 = state[9];
+  x10 = state[10];
+  x11 = state[11];
+  x12 = state[12];
+  x13 = state[13];
+  x14 = state[14];
+  x15 = state[15];
+
+  for (int i = 0; i < 20; i += 2)
+    {
+#define QROUND(_x0, _x1, _x2, _x3) 			\
+  do {							\
+   _x0 = _x0 + _x1; _x3 = rotl32 (16, (_x0 ^ _x3)); 	\
+   _x2 = _x2 + _x3; _x1 = rotl32 (12, (_x1 ^ _x2)); 	\
+   _x0 = _x0 + _x1; _x3 = rotl32 (8,  (_x0 ^ _x3));	\
+   _x2 = _x2 + _x3; _x1 = rotl32 (7,  (_x1 ^ _x2));	\
+  } while(0)
+
+      QROUND (x0, x4, x8,  x12);
+      QROUND (x1, x5, x9,  x13);
+      QROUND (x2, x6, x10, x14);
+      QROUND (x3, x7, x11, x15);
+
+      QROUND (x0, x5, x10, x15);
+      QROUND (x1, x6, x11, x12);
+      QROUND (x2, x7, x8,  x13);
+      QROUND (x3, x4, x9,  x14);
+    }
+
+  state_final (&src[0], &dst[0], set_state (x0 + state[0]));
+  state_final (&src[4], &dst[4], set_state (x1 + state[1]));
+  state_final (&src[8], &dst[8], set_state (x2 + state[2]));
+  state_final (&src[12], &dst[12], set_state (x3 + state[3]));
+  state_final (&src[16], &dst[16], set_state (x4 + state[4]));
+  state_final (&src[20], &dst[20], set_state (x5 + state[5]));
+  state_final (&src[24], &dst[24], set_state (x6 + state[6]));
+  state_final (&src[28], &dst[28], set_state (x7 + state[7]));
+  state_final (&src[32], &dst[32], set_state (x8 + state[8]));
+  state_final (&src[36], &dst[36], set_state (x9 + state[9]));
+  state_final (&src[40], &dst[40], set_state (x10 + state[10]));
+  state_final (&src[44], &dst[44], set_state (x11 + state[11]));
+  state_final (&src[48], &dst[48], set_state (x12 + state[12]));
+  state_final (&src[52], &dst[52], set_state (x13 + state[13]));
+  state_final (&src[56], &dst[56], set_state (x14 + state[14]));
+  state_final (&src[60], &dst[60], set_state (x15 + state[15]));
+
+  state[12]++;
+}
+
+static void
+chacha20_crypt (uint32_t *state, uint8_t *dst, const uint8_t *src,
+		size_t bytes)
+{
+  while (bytes >= CHACHA20_BLOCK_SIZE)
+    {
+      chacha20_block (state, dst, src);
+
+      bytes -= CHACHA20_BLOCK_SIZE;
+      dst += CHACHA20_BLOCK_SIZE;
+      src += CHACHA20_BLOCK_SIZE;
+    }
+
+  if (__glibc_unlikely (bytes != 0))
+    {
+      uint8_t stream[CHACHA20_BLOCK_SIZE];
+      chacha20_block (state, stream, src);
+      memcpy (dst, stream, bytes);
+      explicit_bzero (stream, sizeof stream);
+    }
+}
diff --git a/stdlib/stdlib.h b/stdlib/stdlib.h
index bf7cd43..3a630a0 100644
--- a/stdlib/stdlib.h
+++ b/stdlib/stdlib.h
@@ -533,6 +533,19 @@ extern int seed48_r (unsigned short int __seed16v[3],
 extern int lcong48_r (unsigned short int __param[7],
 		      struct drand48_data *__buffer)
      __THROW __nonnull ((1, 2));
+
+/* Return a random integer between zero and 2**32-1 (inclusive).  */
+extern __uint32_t arc4random (void)
+     __THROW __wur;
+
+/* Fill the buffer with random data.  */
+extern void arc4random_buf (void *__buf, size_t __size)
+     __THROW __nonnull ((1));
+
+/* Return a random number between zero (inclusive) and the specified
+   limit (exclusive).  */
+extern __uint32_t arc4random_uniform (__uint32_t __upper_bound)
+     __THROW __wur;
 # endif	/* Use misc.  */
 #endif	/* Use misc or X/Open.  */
 
diff --git a/sysdeps/generic/not-cancel.h b/sysdeps/generic/not-cancel.h
index 2104efe..acceb9b 100644
--- a/sysdeps/generic/not-cancel.h
+++ b/sysdeps/generic/not-cancel.h
@@ -48,5 +48,7 @@
   (void) __writev (fd, iov, n)
 #define __fcntl64_nocancel(fd, cmd, ...) \
   __fcntl64 (fd, cmd, __VA_ARGS__)
+#define __getrandom_nocancel(buf, size, flags) \
+  __getrandom (buf, size, flags)
 
 #endif /* NOT_CANCEL_H  */
diff --git a/sysdeps/generic/tls-internal-struct.h b/sysdeps/generic/tls-internal-struct.h
index d76c715..a919158 100644
--- a/sysdeps/generic/tls-internal-struct.h
+++ b/sysdeps/generic/tls-internal-struct.h
@@ -23,6 +23,7 @@ struct tls_internal_t
 {
   char *strsignal_buf;
   char *strerror_l_buf;
+  struct arc4random_state_t *rand_state;
 };
 
 #endif
diff --git a/sysdeps/generic/tls-internal.c b/sysdeps/generic/tls-internal.c
index 898c20b..8a0f37d 100644
--- a/sysdeps/generic/tls-internal.c
+++ b/sysdeps/generic/tls-internal.c
@@ -16,6 +16,24 @@
    License along with the GNU C Library; if not, see
    <https://www.gnu.org/licenses/>.  */
 
+#include <stdlib/arc4random.h>
+#include <string.h>
 #include <tls-internal.h>
 
 __thread struct tls_internal_t __tls_internal;
+
+void
+__glibc_tls_internal_free (void)
+{
+  free (__tls_internal.strsignal_buf);
+  free (__tls_internal.strerror_l_buf);
+
+  if (__tls_internal.rand_state != NULL)
+    {
+      /* Clear any lingering random state prior so if the thread stack is
+	 cached it won't leak any data.  */
+      explicit_bzero (__tls_internal.rand_state,
+		      sizeof (*__tls_internal.rand_state));
+      free (__tls_internal.rand_state);
+    }
+}
diff --git a/sysdeps/generic/tls-internal.h b/sysdeps/generic/tls-internal.h
index acb8ac9..3f53e4a 100644
--- a/sysdeps/generic/tls-internal.h
+++ b/sysdeps/generic/tls-internal.h
@@ -30,11 +30,6 @@ __glibc_tls_internal (void)
   return &__tls_internal;
 }
 
-static inline void
-__glibc_tls_internal_free (void)
-{
-  free (__tls_internal.strsignal_buf);
-  free (__tls_internal.strerror_l_buf);
-}
+extern void __glibc_tls_internal_free (void) attribute_hidden;
 
 #endif
diff --git a/sysdeps/mach/hurd/_Fork.c b/sysdeps/mach/hurd/_Fork.c
index e60b86f..667068c 100644
--- a/sysdeps/mach/hurd/_Fork.c
+++ b/sysdeps/mach/hurd/_Fork.c
@@ -662,6 +662,8 @@ retry:
       _hurd_malloc_fork_child ();
       call_function_static_weak (__malloc_fork_unlock_child);
 
+      call_function_static_weak (__arc4random_fork_subprocess);
+
       /* Run things that want to run in the child task to set up.  */
       RUN_HOOK (_hurd_fork_child_hook, ());
 
diff --git a/sysdeps/mach/hurd/i386/libc.abilist b/sysdeps/mach/hurd/i386/libc.abilist
index 66fb0e2..4e3200e 100644
--- a/sysdeps/mach/hurd/i386/libc.abilist
+++ b/sysdeps/mach/hurd/i386/libc.abilist
@@ -2289,6 +2289,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 close_range F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 mbrtoc8 F
 GLIBC_2.4 __confstr_chk F
diff --git a/sysdeps/mach/hurd/not-cancel.h b/sysdeps/mach/hurd/not-cancel.h
index 6ec92ce..9a3a7ed 100644
--- a/sysdeps/mach/hurd/not-cancel.h
+++ b/sysdeps/mach/hurd/not-cancel.h
@@ -74,6 +74,9 @@ __typeof (__fcntl) __fcntl_nocancel;
 #define __fcntl64_nocancel(...) \
   __fcntl_nocancel (__VA_ARGS__)
 
+#define __getrandom_nocancel(buf, size, flags) \
+  __getrandom (buf, size, flags)
+
 #if IS_IN (libc)
 hidden_proto (__close_nocancel)
 hidden_proto (__close_nocancel_nostatus)
diff --git a/sysdeps/nptl/_Fork.c b/sysdeps/nptl/_Fork.c
index dd56899..7dc0256 100644
--- a/sysdeps/nptl/_Fork.c
+++ b/sysdeps/nptl/_Fork.c
@@ -43,6 +43,8 @@ _Fork (void)
       self->robust_head.list = &self->robust_head;
       INTERNAL_SYSCALL_CALL (set_robust_list, &self->robust_head,
 			     sizeof (struct robust_list_head));
+
+      call_function_static_weak (__arc4random_fork_subprocess);
     }
   return pid;
 }
diff --git a/sysdeps/unix/sysv/linux/aarch64/libc.abilist b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
index 516b029..b66fade 100644
--- a/sysdeps/unix/sysv/linux/aarch64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/aarch64/libc.abilist
@@ -2616,6 +2616,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/alpha/libc.abilist b/sysdeps/unix/sysv/linux/alpha/libc.abilist
index dde0889..f918bb2 100644
--- a/sysdeps/unix/sysv/linux/alpha/libc.abilist
+++ b/sysdeps/unix/sysv/linux/alpha/libc.abilist
@@ -2713,6 +2713,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/arc/libc.abilist b/sysdeps/unix/sysv/linux/arc/libc.abilist
index ade44d3..093043a 100644
--- a/sysdeps/unix/sysv/linux/arc/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arc/libc.abilist
@@ -2377,6 +2377,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/arm/be/libc.abilist b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
index 98b3370..e0668a8 100644
--- a/sysdeps/unix/sysv/linux/arm/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/be/libc.abilist
@@ -496,6 +496,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/arm/le/libc.abilist b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
index 05dbbe5..d28e7c6 100644
--- a/sysdeps/unix/sysv/linux/arm/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/arm/le/libc.abilist
@@ -493,6 +493,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/csky/libc.abilist b/sysdeps/unix/sysv/linux/csky/libc.abilist
index 430a243..922b050 100644
--- a/sysdeps/unix/sysv/linux/csky/libc.abilist
+++ b/sysdeps/unix/sysv/linux/csky/libc.abilist
@@ -2652,6 +2652,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/hppa/libc.abilist b/sysdeps/unix/sysv/linux/hppa/libc.abilist
index de44616..412144f 100644
--- a/sysdeps/unix/sysv/linux/hppa/libc.abilist
+++ b/sysdeps/unix/sysv/linux/hppa/libc.abilist
@@ -2601,6 +2601,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/i386/libc.abilist b/sysdeps/unix/sysv/linux/i386/libc.abilist
index 18b4fbf..1343939 100644
--- a/sysdeps/unix/sysv/linux/i386/libc.abilist
+++ b/sysdeps/unix/sysv/linux/i386/libc.abilist
@@ -2785,6 +2785,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/ia64/libc.abilist b/sysdeps/unix/sysv/linux/ia64/libc.abilist
index a8e959d..02c65b6 100644
--- a/sysdeps/unix/sysv/linux/ia64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/ia64/libc.abilist
@@ -2551,6 +2551,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
index 3a7e4ef..0604029 100644
--- a/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/coldfire/libc.abilist
@@ -497,6 +497,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
index 864ad2c..af2be5c 100644
--- a/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
+++ b/sysdeps/unix/sysv/linux/m68k/m680x0/libc.abilist
@@ -2728,6 +2728,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
index 1630584..e090b8d 100644
--- a/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/be/libc.abilist
@@ -2701,6 +2701,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
index a6debfd..8c5b2db 100644
--- a/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/microblaze/le/libc.abilist
@@ -2698,6 +2698,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
index 2b53d88..6884713 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/fpu/libc.abilist
@@ -2693,6 +2693,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
index 849aae4..daa44e6 100644
--- a/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips32/nofpu/libc.abilist
@@ -2691,6 +2691,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
index 37f6c1b..6169188 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n32/libc.abilist
@@ -2699,6 +2699,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
index ff1eb91..2f7f1cc 100644
--- a/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/mips/mips64/n64/libc.abilist
@@ -2602,6 +2602,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/nios2/libc.abilist b/sysdeps/unix/sysv/linux/nios2/libc.abilist
index 361b91f..58e9b48 100644
--- a/sysdeps/unix/sysv/linux/nios2/libc.abilist
+++ b/sysdeps/unix/sysv/linux/nios2/libc.abilist
@@ -2740,6 +2740,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/not-cancel.h b/sysdeps/unix/sysv/linux/not-cancel.h
index 75b9e0e..2c58d5a 100644
--- a/sysdeps/unix/sysv/linux/not-cancel.h
+++ b/sysdeps/unix/sysv/linux/not-cancel.h
@@ -67,6 +67,13 @@ __writev_nocancel_nostatus (int fd, const struct iovec *iov, int iovcnt)
   INTERNAL_SYSCALL_CALL (writev, fd, iov, iovcnt);
 }
 
+static inline int
+__getrandom_nocancel (void *buf, size_t buflen, unsigned int flags)
+{
+  return INTERNAL_SYSCALL_CALL (getrandom, buf, buflen, flags);
+}
+
+
 /* Uncancelable fcntl.  */
 __typeof (__fcntl) __fcntl64_nocancel;
 
diff --git a/sysdeps/unix/sysv/linux/or1k/libc.abilist b/sysdeps/unix/sysv/linux/or1k/libc.abilist
index cb91606..ffdb881 100644
--- a/sysdeps/unix/sysv/linux/or1k/libc.abilist
+++ b/sysdeps/unix/sysv/linux/or1k/libc.abilist
@@ -2123,6 +2123,9 @@ GLIBC_2.35 wprintf F
 GLIBC_2.35 write F
 GLIBC_2.35 writev F
 GLIBC_2.35 wscanf F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
index 1264aff..8c9ca32 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/fpu/libc.abilist
@@ -2755,6 +2755,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
index f96d6e3..08a6604 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc32/nofpu/libc.abilist
@@ -2788,6 +2788,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
index e7082e1..849863e 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/be/libc.abilist
@@ -2510,6 +2510,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
index 1032c7e..b2ccee0 100644
--- a/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/powerpc/powerpc64/le/libc.abilist
@@ -2812,6 +2812,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
index f932db7..ff90d1b 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv32/libc.abilist
@@ -2379,6 +2379,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
index ccc53b0..f1017f6 100644
--- a/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/riscv/rv64/libc.abilist
@@ -2579,6 +2579,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
index dbf6501..009f229 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-32/libc.abilist
@@ -2753,6 +2753,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
index 98f08a0..0e0b3df 100644
--- a/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/s390/s390-64/libc.abilist
@@ -2547,6 +2547,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/sh/be/libc.abilist b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
index df11cc8..afb5bc3 100644
--- a/sysdeps/unix/sysv/linux/sh/be/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/be/libc.abilist
@@ -2608,6 +2608,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/sh/le/libc.abilist b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
index 4ee5513..2b53a3c 100644
--- a/sysdeps/unix/sysv/linux/sh/le/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sh/le/libc.abilist
@@ -2605,6 +2605,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
index 3cefa76..43b9844 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc32/libc.abilist
@@ -2748,6 +2748,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
index e3ea5c4..9ec4a0b 100644
--- a/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/sparc/sparc64/libc.abilist
@@ -2574,6 +2574,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/tls-internal.c b/sysdeps/unix/sysv/linux/tls-internal.c
index 6e25b02..0326ebb 100644
--- a/sysdeps/unix/sysv/linux/tls-internal.c
+++ b/sysdeps/unix/sysv/linux/tls-internal.c
@@ -1 +1,38 @@
-/* Empty.  */
+/* Per-thread state.  Linux version.
+   Copyright (C) 2022 Free Software Foundation, Inc.
+   This file is part of the GNU C Library.
+
+   The GNU C Library is free software; you can redistribute it and/or
+   modify it under the terms of the GNU Lesser General Public
+   License as published by the Free Software Foundation; either
+   version 2.1 of the License, or (at your option) any later version.
+
+   The GNU C Library is distributed in the hope that it will be useful,
+   but WITHOUT ANY WARRANTY; without even the implied warranty of
+   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
+   Lesser General Public License for more details.
+
+   You should have received a copy of the GNU Lesser General Public
+   License along with the GNU C Library; if not, see
+   <https://www.gnu.org/licenses/>.  */
+
+#include <stdlib/arc4random.h>
+#include <string.h>
+#include <tls-internal.h>
+
+void
+__glibc_tls_internal_free (void)
+{
+  struct pthread *self = THREAD_SELF;
+  free (self->tls_state.strsignal_buf);
+  free (self->tls_state.strerror_l_buf);
+
+  if (self->tls_state.rand_state != NULL)
+    {
+      /* Clear any lingering random state prior so if the thread stack is
+         cached it won't leak any data.  */
+      explicit_bzero (self->tls_state.rand_state,
+		      sizeof (*self->tls_state.rand_state));
+      free (self->tls_state.rand_state);
+    }
+}
diff --git a/sysdeps/unix/sysv/linux/tls-internal.h b/sysdeps/unix/sysv/linux/tls-internal.h
index f7a1a62..ebc65d8 100644
--- a/sysdeps/unix/sysv/linux/tls-internal.h
+++ b/sysdeps/unix/sysv/linux/tls-internal.h
@@ -28,11 +28,7 @@ __glibc_tls_internal (void)
   return &THREAD_SELF->tls_state;
 }
 
-static inline void
-__glibc_tls_internal_free (void)
-{
-  free (THREAD_SELF->tls_state.strsignal_buf);
-  free (THREAD_SELF->tls_state.strerror_l_buf);
-}
+/* Reset the arc4random TCB state on fork.  */
+extern void __glibc_tls_internal_free (void) attribute_hidden;
 
 #endif
diff --git a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
index 2944bc7..367c8d0 100644
--- a/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/64/libc.abilist
@@ -2525,6 +2525,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F
diff --git a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
index 4729619..6a614ef 100644
--- a/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
+++ b/sysdeps/unix/sysv/linux/x86_64/x32/libc.abilist
@@ -2631,6 +2631,9 @@ GLIBC_2.35 __memcmpeq F
 GLIBC_2.35 _dl_find_object F
 GLIBC_2.35 epoll_pwait2 F
 GLIBC_2.35 posix_spawn_file_actions_addtcsetpgrp_np F
+GLIBC_2.36 arc4random F
+GLIBC_2.36 arc4random_buf F
+GLIBC_2.36 arc4random_uniform F
 GLIBC_2.36 c8rtomb F
 GLIBC_2.36 fsconfig F
 GLIBC_2.36 fsmount F