Adding upstream version 241.upstream/241upstream

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

1 files changed, 265 insertions, 0 deletions

diff --git a/src/basic/random-util.c b/src/basic/random-util.c
new file mode 100644
index 0000000..f7decf6
--- /dev/null
+++ b/src/basic/random-util.c
@@ -0,0 +1,265 @@
+/* SPDX-License-Identifier: LGPL-2.1+ */
+
+#if defined(__i386__) || defined(__x86_64__)
+#include <cpuid.h>
+#endif
+
+#include <elf.h>
+#include <errno.h>
+#include <fcntl.h>
+#include <stdbool.h>
+#include <stdint.h>
+#include <stdlib.h>
+#include <string.h>
+#include <sys/time.h>
+
+#if HAVE_SYS_AUXV_H
+#  include <sys/auxv.h>
+#endif
+
+#if USE_SYS_RANDOM_H
+#  include <sys/random.h>
+#else
+#  include <linux/random.h>
+#endif
+
+#include "fd-util.h"
+#include "io-util.h"
+#include "missing.h"
+#include "random-util.h"
+#include "time-util.h"
+
+#if HAS_FEATURE_MEMORY_SANITIZER
+#include <sanitizer/msan_interface.h>
+#endif
+
+int rdrand(unsigned long *ret) {
+
+#if defined(__i386__) || defined(__x86_64__)
+        static int have_rdrand = -1;
+        unsigned char err;
+
+        if (have_rdrand < 0) {
+                uint32_t eax, ebx, ecx, edx;
+
+                /* Check if RDRAND is supported by the CPU */
+                if (__get_cpuid(1, &eax, &ebx, &ecx, &edx) == 0) {
+                        have_rdrand = false;
+                        return -EOPNOTSUPP;
+                }
+
+                have_rdrand = !!(ecx & (1U << 30));
+        }
+
+        if (have_rdrand == 0)
+                return -EOPNOTSUPP;
+
+        asm volatile("rdrand %0;"
+                     "setc %1"
+                     : "=r" (*ret),
+                       "=qm" (err));
+
+#if HAS_FEATURE_MEMORY_SANITIZER
+        __msan_unpoison(&err, sizeof(err));
+#endif
+
+        if (!err)
+                return -EAGAIN;
+
+        return 0;
+#else
+        return -EOPNOTSUPP;
+#endif
+}
+
+int genuine_random_bytes(void *p, size_t n, RandomFlags flags) {
+        static int have_syscall = -1;
+        _cleanup_close_ int fd = -1;
+        bool got_some = false;
+        int r;
+
+        /* Gathers some randomness from the kernel (or the CPU if the RANDOM_ALLOW_RDRAND flag is set). This call won't
+         * block, unless the RANDOM_BLOCK flag is set. If RANDOM_DONT_DRAIN is set, an error is returned if the random
+         * pool is not initialized. Otherwise it will always return some data from the kernel, regardless of whether
+         * the random pool is fully initialized or not. */
+
+        if (n == 0)
+                return 0;
+
+        if (FLAGS_SET(flags, RANDOM_ALLOW_RDRAND))
+                /* Try x86-64' RDRAND intrinsic if we have it. We only use it if high quality randomness is not
+                 * required, as we don't trust it (who does?). Note that we only do a single iteration of RDRAND here,
+                 * even though the Intel docs suggest calling this in a tight loop of 10 invocations or so. That's
+                 * because we don't really care about the quality here. We generally prefer using RDRAND if the caller
+                 * allows us too, since this way we won't drain the kernel randomness pool if we don't need it, as the
+                 * pool's entropy is scarce. */
+                for (;;) {
+                        unsigned long u;
+                        size_t m;
+
+                        if (rdrand(&u) < 0) {
+                                if (got_some && FLAGS_SET(flags, RANDOM_EXTEND_WITH_PSEUDO)) {
+                                        /* Fill in the remaining bytes using pseudo-random values */
+                                        pseudo_random_bytes(p, n);
+                                        return 0;
+                                }
+
+                                /* OK, this didn't work, let's go to getrandom() + /dev/urandom instead */
+                                break;
+                        }
+
+                        m = MIN(sizeof(u), n);
+                        memcpy(p, &u, m);
+
+                        p = (uint8_t*) p + m;
+                        n -= m;
+
+                        if (n == 0)
+                                return 0; /* Yay, success! */
+
+                        got_some = true;
+                }
+
+        /* Use the getrandom() syscall unless we know we don't have it. */
+        if (have_syscall != 0 && !HAS_FEATURE_MEMORY_SANITIZER) {
+
+                for (;;) {
+                        r = getrandom(p, n, FLAGS_SET(flags, RANDOM_BLOCK) ? 0 : GRND_NONBLOCK);
+                        if (r > 0) {
+                                have_syscall = true;
+
+                                if ((size_t) r == n)
+                                        return 0; /* Yay, success! */
+
+                                assert((size_t) r < n);
+                                p = (uint8_t*) p + r;
+                                n -= r;
+
+                                if (FLAGS_SET(flags, RANDOM_EXTEND_WITH_PSEUDO)) {
+                                        /* Fill in the remaining bytes using pseudo-random values */
+                                        pseudo_random_bytes(p, n);
+                                        return 0;
+                                }
+
+                                got_some = true;
+
+                                /* Hmm, we didn't get enough good data but the caller insists on good data? Then try again */
+                                if (FLAGS_SET(flags, RANDOM_BLOCK))
+                                        continue;
+
+                                /* Fill in the rest with /dev/urandom */
+                                break;
+
+                        } else if (r == 0) {
+                                have_syscall = true;
+                                return -EIO;
+
+                        } else if (errno == ENOSYS) {
+                                /* We lack the syscall, continue with reading from /dev/urandom. */
+                                have_syscall = false;
+                                break;
+
+                        } else if (errno == EAGAIN) {
+                                /* The kernel has no entropy whatsoever. Let's remember to use the syscall the next
+                                 * time again though.
+                                 *
+                                 * If RANDOM_DONT_DRAIN is set, return an error so that random_bytes() can produce some
+                                 * pseudo-random bytes instead. Otherwise, fall back to /dev/urandom, which we know is empty,
+                                 * but the kernel will produce some bytes for us on a best-effort basis. */
+                                have_syscall = true;
+
+                                if (got_some && FLAGS_SET(flags, RANDOM_EXTEND_WITH_PSEUDO)) {
+                                        /* Fill in the remaining bytes using pseudorandom values */
+                                        pseudo_random_bytes(p, n);
+                                        return 0;
+                                }
+
+                                if (FLAGS_SET(flags, RANDOM_DONT_DRAIN))
+                                        return -ENODATA;
+
+                                /* Use /dev/urandom instead */
+                                break;
+                        } else
+                                return -errno;
+                }
+        }
+
+        fd = open("/dev/urandom", O_RDONLY|O_CLOEXEC|O_NOCTTY);
+        if (fd < 0)
+                return errno == ENOENT ? -ENOSYS : -errno;
+
+        return loop_read_exact(fd, p, n, true);
+}
+
+void initialize_srand(void) {
+        static bool srand_called = false;
+        unsigned x;
+#if HAVE_SYS_AUXV_H
+        const void *auxv;
+#endif
+        unsigned long k;
+
+        if (srand_called)
+                return;
+
+#if HAVE_SYS_AUXV_H
+        /* The kernel provides us with 16 bytes of entropy in auxv, so let's
+         * try to make use of that to seed the pseudo-random generator. It's
+         * better than nothing... */
+
+        auxv = (const void*) getauxval(AT_RANDOM);
+        if (auxv) {
+                assert_cc(sizeof(x) <= 16);
+                memcpy(&x, auxv, sizeof(x));
+        } else
+#endif
+                x = 0;
+
+        x ^= (unsigned) now(CLOCK_REALTIME);
+        x ^= (unsigned) gettid();
+
+        if (rdrand(&k) >= 0)
+                x ^= (unsigned) k;
+
+        srand(x);
+        srand_called = true;
+}
+
+/* INT_MAX gives us only 31 bits, so use 24 out of that. */
+#if RAND_MAX >= INT_MAX
+#  define RAND_STEP 3
+#else
+/* SHORT_INT_MAX or lower gives at most 15 bits, we just just 8 out of that. */
+#  define RAND_STEP 1
+#endif
+
+void pseudo_random_bytes(void *p, size_t n) {
+        uint8_t *q;
+
+        initialize_srand();
+
+        for (q = p; q < (uint8_t*) p + n; q += RAND_STEP) {
+                unsigned rr;
+
+                rr = (unsigned) rand();
+
+#if RAND_STEP >= 3
+                if ((size_t) (q - (uint8_t*) p + 2) < n)
+                        q[2] = rr >> 16;
+#endif
+#if RAND_STEP >= 2
+                if ((size_t) (q - (uint8_t*) p + 1) < n)
+                        q[1] = rr >> 8;
+#endif
+                q[0] = rr;
+        }
+}
+
+void random_bytes(void *p, size_t n) {
+
+        if (genuine_random_bytes(p, n, RANDOM_EXTEND_WITH_PSEUDO|RANDOM_DONT_DRAIN|RANDOM_ALLOW_RDRAND) >= 0)
+                return;
+
+        /* If for some reason some user made /dev/urandom unavailable to us, or the kernel has no entropy, use a PRNG instead. */
+        pseudo_random_bytes(p, n);
+}