Adding upstream version 255.4.upstream/255.4

Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>

1 files changed, 251 insertions, 0 deletions

diff --git a/src/basic/random-util.c b/src/basic/random-util.c
new file mode 100644
index 0000000..c7277ad
--- /dev/null
+++ b/src/basic/random-util.c
@@ -0,0 +1,251 @@
+/* SPDX-License-Identifier: LGPL-2.1-or-later */
+
+#include <elf.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <linux/random.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/ioctl.h>
+#include <sys/time.h>
+
+#if HAVE_SYS_AUXV_H
+#  include <sys/auxv.h>
+#endif
+
+#include "alloc-util.h"
+#include "env-util.h"
+#include "errno-util.h"
+#include "fd-util.h"
+#include "fileio.h"
+#include "io-util.h"
+#include "missing_random.h"
+#include "missing_syscall.h"
+#include "missing_threads.h"
+#include "parse-util.h"
+#include "process-util.h"
+#include "random-util.h"
+#include "sha256.h"
+#include "time-util.h"
+
+/* This is a "best effort" kind of thing, but has no real security value.  So, this should only be used by
+ * random_bytes(), which is not meant for crypto. This could be made better, but we're *not* trying to roll a
+ * userspace prng here, or even have forward secrecy, but rather just do the shortest thing that is at least
+ * better than libc rand(). */
+static void fallback_random_bytes(void *p, size_t n) {
+        static thread_local uint64_t fallback_counter = 0;
+        struct {
+                char label[32];
+                uint64_t call_id, block_id;
+                usec_t stamp_mono, stamp_real;
+                pid_t pid, tid;
+                uint8_t auxval[16];
+        } state = {
+                /* Arbitrary domain separation to prevent other usage of AT_RANDOM from clashing. */
+                .label = "systemd fallback random bytes v1",
+                .call_id = fallback_counter++,
+                .stamp_mono = now(CLOCK_MONOTONIC),
+                .stamp_real = now(CLOCK_REALTIME),
+                .pid = getpid_cached(),
+                .tid = gettid(),
+        };
+
+#if HAVE_SYS_AUXV_H
+        memcpy(state.auxval, ULONG_TO_PTR(getauxval(AT_RANDOM)), sizeof(state.auxval));
+#endif
+
+        while (n > 0) {
+                struct sha256_ctx ctx;
+
+                sha256_init_ctx(&ctx);
+                sha256_process_bytes(&state, sizeof(state), &ctx);
+                if (n < SHA256_DIGEST_SIZE) {
+                        uint8_t partial[SHA256_DIGEST_SIZE];
+                        sha256_finish_ctx(&ctx, partial);
+                        memcpy(p, partial, n);
+                        break;
+                }
+                sha256_finish_ctx(&ctx, p);
+                p = (uint8_t *) p + SHA256_DIGEST_SIZE;
+                n -= SHA256_DIGEST_SIZE;
+                ++state.block_id;
+        }
+}
+
+void random_bytes(void *p, size_t n) {
+        static bool have_getrandom = true, have_grndinsecure = true;
+        _cleanup_close_ int fd = -EBADF;
+
+        if (n == 0)
+                return;
+
+        for (;;) {
+                ssize_t l;
+
+                if (!have_getrandom)
+                        break;
+
+                l = getrandom(p, n, have_grndinsecure ? GRND_INSECURE : GRND_NONBLOCK);
+                if (l > 0) {
+                        if ((size_t) l == n)
+                                return; /* Done reading, success. */
+                        p = (uint8_t *) p + l;
+                        n -= l;
+                        continue; /* Interrupted by a signal; keep going. */
+                } else if (l == 0)
+                        break; /* Weird, so fallback to /dev/urandom. */
+                else if (ERRNO_IS_NOT_SUPPORTED(errno)) {
+                        have_getrandom = false;
+                        break; /* No syscall, so fallback to /dev/urandom. */
+                } else if (errno == EINVAL && have_grndinsecure) {
+                        have_grndinsecure = false;
+                        continue; /* No GRND_INSECURE; fallback to GRND_NONBLOCK. */
+                } else if (errno == EAGAIN && !have_grndinsecure)
+                        break; /* Will block, but no GRND_INSECURE, so fallback to /dev/urandom. */
+
+                break; /* Unexpected, so just give up and fallback to /dev/urandom. */
+        }
+
+        fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd >= 0 && loop_read_exact(fd, p, n, false) == 0)
+                return;
+
+        /* This is a terrible fallback. Oh well. */
+        fallback_random_bytes(p, n);
+}
+
+int crypto_random_bytes(void *p, size_t n) {
+        static bool have_getrandom = true, seen_initialized = false;
+        _cleanup_close_ int fd = -EBADF;
+
+        if (n == 0)
+                return 0;
+
+        for (;;) {
+                ssize_t l;
+
+                if (!have_getrandom)
+                        break;
+
+                l = getrandom(p, n, 0);
+                if (l > 0) {
+                        if ((size_t) l == n)
+                                return 0; /* Done reading, success. */
+                        p = (uint8_t *) p + l;
+                        n -= l;
+                        continue; /* Interrupted by a signal; keep going. */
+                } else if (l == 0)
+                        return -EIO; /* Weird, should never happen. */
+                else if (ERRNO_IS_NOT_SUPPORTED(errno)) {
+                        have_getrandom = false;
+                        break; /* No syscall, so fallback to /dev/urandom. */
+                }
+                return -errno;
+        }
+
+        if (!seen_initialized) {
+                _cleanup_close_ int ready_fd = -EBADF;
+                int r;
+
+                ready_fd = open("/dev/random", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+                if (ready_fd < 0)
+                        return -errno;
+                r = fd_wait_for_event(ready_fd, POLLIN, USEC_INFINITY);
+                if (r < 0)
+                        return r;
+                seen_initialized = true;
+        }
+
+        fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0)
+                return -errno;
+        return loop_read_exact(fd, p, n, false);
+}
+
+size_t random_pool_size(void) {
+        _cleanup_free_ char *s = NULL;
+        int r;
+
+        /* Read pool size, if possible */
+        r = read_one_line_file("/proc/sys/kernel/random/poolsize", &s);
+        if (r < 0)
+                log_debug_errno(r, "Failed to read pool size from kernel: %m");
+        else {
+                unsigned sz;
+
+                r = safe_atou(s, &sz);
+                if (r < 0)
+                        log_debug_errno(r, "Failed to parse pool size: %s", s);
+                else
+                        /* poolsize is in bits on 2.6, but we want bytes */
+                        return CLAMP(sz / 8, RANDOM_POOL_SIZE_MIN, RANDOM_POOL_SIZE_MAX);
+        }
+
+        /* Use the minimum as default, if we can't retrieve the correct value */
+        return RANDOM_POOL_SIZE_MIN;
+}
+
+int random_write_entropy(int fd, const void *seed, size_t size, bool credit) {
+        _cleanup_close_ int opened_fd = -EBADF;
+        int r;
+
+        assert(seed || size == 0);
+
+        if (size == 0)
+                return 0;
+
+        if (fd < 0) {
+                opened_fd = open("/dev/urandom", O_WRONLY|O_CLOEXEC|O_NOCTTY);
+                if (opened_fd < 0)
+                        return -errno;
+
+                fd = opened_fd;
+        }
+
+        if (credit) {
+                _cleanup_free_ struct rand_pool_info *info = NULL;
+
+                /* The kernel API only accepts "int" as entropy count (which is in bits), let's avoid any
+                 * chance for confusion here. */
+                if (size > INT_MAX / 8)
+                        return -EOVERFLOW;
+
+                info = malloc(offsetof(struct rand_pool_info, buf) + size);
+                if (!info)
+                        return -ENOMEM;
+
+                info->entropy_count = size * 8;
+                info->buf_size = size;
+                memcpy(info->buf, seed, size);
+
+                if (ioctl(fd, RNDADDENTROPY, info) < 0)
+                        return -errno;
+        } else {
+                r = loop_write(fd, seed, size);
+                if (r < 0)
+                        return r;
+        }
+
+        return 1;
+}
+
+uint64_t random_u64_range(uint64_t m) {
+        uint64_t x, remainder;
+
+        /* Generates a random number in the range 0…m-1, unbiased. (Java's algorithm) */
+
+        if (m == 0) /* Let's take m == 0 as special case to return an integer from the full range */
+                return random_u64();
+        if (m == 1)
+                return 0;
+
+        remainder = UINT64_MAX % m;
+
+        do {
+                x = random_u64();
+        } while (x >= UINT64_MAX - remainder);
+
+        return x % m;
+}