53056: new zsh/random module defining an SRANDOM parameter and zrand_float() and zrand_int() math functions

1 files changed, 322 insertions, 0 deletions

diff --git a/Src/Modules/random.c b/Src/Modules/random.c
new file mode 100644
index 000000000..a153d8f64
--- /dev/null
+++ b/Src/Modules/random.c
@@ -0,0 +1,322 @@
+/*
+ * random.c - module to access kernel random sources.
+ *
+ * This file is part of zsh, the Z shell.
+ *
+ * Copyright (c) 2022 Clinton Bunch
+ * All rights reserved.
+ *
+ * Permission is hereby granted, without written agreement and without
+ * license or royalty fees, to use, copy, modify, and distribute this
+ * software and to distribute modified versions of this software for any
+ * purpose, provided that the above copyright notice and the following
+ * two paragraphs appear in all copies of this software.
+ *
+ * In no event shall Clinton Bunch or the Zsh Development Group be liable
+ * to any party for direct, indirect, special, incidental, or consequential
+ * damages arising out of the use of this software and its documentation,
+ * even if Clinton Bunch and the Zsh Development Group have been advised of
+ * the possibility of such damage.
+ *
+ * Clinton Bunch and the Zsh Development Group specifically disclaim any
+ * warranties, including, but not limited to, the implied warranties of
+ * merchantability and fitness for a particular purpose.  The software
+ * provided hereunder is on an "as is" basis, and Clinton Bunch and the
+ * Zsh Development Group have no obligation to provide maintenance,
+ * support, updates, enhancements, or modifications.
+ *
+ */
+
+#include "random.mdh"
+
+#include <sys/types.h>
+#include <sys/stat.h>
+#include <fcntl.h>
+#include <unistd.h>
+#include <stdio.h>
+
+#include <stdint.h>
+
+#ifdef HAVE_SYS_RANDOM_H
+#include <sys/random.h>
+#endif
+
+/* Simplify select URANDOM specific code */
+#if !defined(HAVE_ARC4RANDOM_BUF) && !defined(HAVE_GETRANDOM)
+#define USE_URANDOM
+#endif
+
+/* buffer to pre-load integers for SRANDOM to lessen the context switches */
+static uint32_t rand_buff[8];
+static int buf_cnt = -1;
+
+#ifdef USE_URANDOM
+/* File descriptor for /dev/urandom */
+int randfd = -1;
+#endif /* USE_URANDOM */
+
+static zlong get_srandom(UNUSED(Param p));
+
+/**/
+ssize_t
+getrandom_buffer(void *buf, size_t len)
+{
+    ssize_t ret;
+    size_t  val     = 0;
+    uint8_t *bufptr = buf;
+
+    do {
+	errno = 0;
+#ifdef HAVE_ARC4RANDOM_BUF
+	arc4random_buf(buf,len);
+	ret = len;
+#elif defined(HAVE_GETRANDOM)
+	ret=getrandom(bufptr,(len - val),0);
+#else
+	ret=read(randfd,bufptr,(len - val));
+#endif
+	if (ret < 0) {
+	    if (errno != EINTR || errflag || retflag || breaks || contflag) {
+		zwarn("Unable to get random data: %e.", errno);
+		return -1;
+	    }
+	}
+	bufptr += ret;
+	val    += ret;
+    } while (ret < len);
+    return ret;
+}
+
+/*
+ * Generate count number of random 32-bit integers between 0 and max-1
+ * Got this algorithm from
+ *https://lemire.me/blog/2016/06/30/fast-random-shuffling/
+ * adapting the public domain code.
+ *
+ */
+
+/**/
+void
+get_bound_random_buffer(uint32_t *buffer, size_t count, uint32_t max)
+{
+    uint64_t multi_result;
+    uint32_t threshold;
+    uint32_t leftover;
+
+    size_t i; /* loop counter */
+
+    getrandom_buffer((void*) buffer, count*sizeof(uint32_t));
+    if (max == UINT32_MAX)
+	return;
+
+    for(i=0;i<count;i++) {
+	multi_result = ((uint64_t) buffer[i]) * (uint64_t) max;
+	leftover = (uint32_t) multi_result;
+
+	/*
+	 * The following if statement should (according to Google's Gemini)
+	 * only be executed with a probability of 1/2**32 or 2.33e-10
+	 */
+	if(leftover < max) {
+	    threshold= -max % max;
+	    while (leftover < threshold) {
+		uint32_t j=get_srandom(NULL);
+		multi_result=(uint64_t) j * (uint64_t) max;
+		leftover= (uint32_t) multi_result;
+	    }
+	}
+	buffer[i]=multi_result >> 32;
+    }
+}
+
+/*
+ * Provides for the SRANDOM parameter and returns an unsigned 32-bit random
+ * integer.
+ */
+
+/**/
+static zlong
+get_srandom(UNUSED(Param pm)) {
+
+    if(buf_cnt <= 0) {
+	getrandom_buffer((void*) rand_buff,sizeof(rand_buff));
+	buf_cnt=sizeof(rand_buff)/sizeof(rand_buff[0]);
+    }
+    return rand_buff[--buf_cnt];
+}
+
+/*
+ * Implements math function zrand_int takes 0 to 3 arguments an upper bound,
+ * a lower bound and a flag as to whether the range is inclusive or not.  The
+ * default is exclusive.  If neither upper or lower is specified this is no
+ * different than SRANDOM.
+ */
+
+/**/
+static mnumber
+math_zrand_int(UNUSED(char *name), int argc, mnumber *argv, UNUSED(int id))
+{
+    mnumber ret;
+    uint32_t i;
+    zlong lower=0, upper=UINT32_MAX,incl=0, diff;
+
+    ret.type = MN_INTEGER;
+
+    switch (argc) {
+	case 0: ret.u.l=get_srandom(NULL);
+		return ret;
+		break;
+	case 3: incl = (argv[2].u.l != 0)?1:0;
+	case 2: lower = argv[1].u.l;
+	case 1: upper = argv[0].u.l;
+	default: diff = upper-lower+incl;
+    }
+
+    if (lower < 0 || lower >= UINT32_MAX) {
+	zwarn("Lower bound (%z) out of range: 0-4294967295",lower);
+    } else if (upper < lower) {
+	zwarn("Upper bound (%z) must be greater than Lower Bound (%z)",upper,lower);
+    } else if (upper < 0 || upper >= UINT32_MAX) {
+	zwarn("Upper bound (%z) out of range: 0-4294967295",upper);
+    }
+
+    if ( diff == 0 ) {
+	ret.u.l=upper; /* still not convinced this shouldn't be an error. */
+    } else {
+	get_bound_random_buffer(&i,1,(uint32_t) diff);
+	ret.u.l=i+lower;
+    }
+    return ret;
+}
+
+/*
+ * Implements the mathfunc zrand_float and returns a random floating-point
+ * number between 0 and 1.
+ *
+ */
+
+/**/
+static mnumber
+math_zrand_float(UNUSED(char *name), UNUSED(int argc), UNUSED(mnumber *argv),
+	     UNUSED(int id))
+{
+    mnumber ret;
+    double r;
+
+    r = random_real();
+    if (r < 0) {
+	zwarnnam(name, "Failed to get sufficient random data.");
+    }
+    ret.type = MN_FLOAT;
+    ret.u.d = r;
+
+    return ret;
+}
+
+static const struct gsu_integer srandom_gsu =
+{ get_srandom, nullintsetfn, stdunsetfn };
+
+static struct paramdef patab[] = {
+    {"SRANDOM", PM_INTEGER | PM_READONLY_SPECIAL | PM_HIDEVAL, NULL,
+	    &srandom_gsu, NULL, NULL, NULL},
+};
+
+static struct mathfunc mftab[] = {
+    NUMMATHFUNC("zrand_float", math_zrand_float, 0, 0, 0),
+    NUMMATHFUNC("zrand_int", math_zrand_int, 0, 3, 0),
+};
+
+static struct features module_features = {
+    NULL, 0,
+    NULL, 0,
+    mftab, sizeof(mftab)/sizeof(*mftab),
+    patab, sizeof(patab)/sizeof(*patab),
+    0
+};
+
+/**/
+int
+setup_(UNUSED(Module m))
+{
+#ifdef USE_URANDOM
+    /* Check for the existence of /dev/urandom */
+
+    struct stat st;
+
+    errno=0;
+    if (stat("/dev/urandom",&st) < 0) {
+	zwarn("Error getting kernel random pool: %e.", errno);
+	return 1;
+    }
+
+    errno=0;
+    if (!(S_ISCHR(st.st_mode)) ) {
+	zwarn("Error getting kernel random pool: %e.", errno);
+	return 1;
+    }
+#endif /* USE_URANDOM */
+    return 0;
+}
+
+/**/
+int
+features_(Module m, char ***features)
+{
+    *features = featuresarray(m, &module_features);
+    return 0;
+}
+
+/**/
+int
+enables_(Module m, int **enables)
+{
+    return handlefeatures(m, &module_features, enables);
+}
+
+/**/
+int
+boot_(UNUSED(Module m))
+{
+#ifdef USE_URANDOM
+    /*
+     * Open /dev/urandom.  Here because of a weird issue on HP-UX 11.31
+     * When opening in setup_ open returned 0.  In boot_, it returns
+     * an unused file descriptor. Decided against ifdef HPUX as it works
+     * here just as well for other platforms.
+     *
+     */
+
+    int tmpfd=-1;
+
+    errno=0;
+    if ((tmpfd = open("/dev/urandom", O_RDONLY)) < 0) {
+	zwarn("Could not access kernel random pool: %e.",errno);
+	return 1;
+    }
+    randfd = movefd(tmpfd);
+    addmodulefd(randfd,FDT_MODULE);
+    if (randfd < 0) {
+	zwarn("Could not access kernel random pool.");
+	return 1;
+    }
+#endif /* USE_URANDOM */
+    return 0;
+}
+
+/**/
+int
+cleanup_(Module m)
+{
+    return setfeatureenables(m, &module_features, NULL);
+}
+
+/**/
+int
+finish_(UNUSED(Module m))
+{
+#ifdef USE_URANDOM
+    if (randfd >= 0)
+	zclose(randfd);
+#endif /* USE_URANDOM */
+    return 0;
+}