Add tests for arc4random_buf() and an implementation for those without.

MANIFEST

@@ -110,6 +110,7 @@ lib/logsrv/protobuf-c.c
 lib/util/Makefile.in
 lib/util/aix.c
 lib/util/arc4random.c
+lib/util/arc4random_buf.c
 lib/util/arc4random_uniform.c
 lib/util/cfmakeraw.c
 lib/util/chacha_private.h

config.h.in

@@ -54,6 +54,9 @@
 /* Define to 1 if you have the `arc4random' function. */
 #undef HAVE_ARC4RANDOM
 
+/* Define to 1 if you have the `arc4random_buf' function. */
+#undef HAVE_ARC4RANDOM_BUF
+
 /* Define to 1 if you have the `arc4random_uniform' function. */
 #undef HAVE_ARC4RANDOM_UNIFORM
 

configure

@@ -19911,6 +19911,32 @@ esac
     done
 
 
+fi
+done
+
+    for ac_func in arc4random_buf
+do :
+  ac_fn_c_check_func "$LINENO" "arc4random_buf" "ac_cv_func_arc4random_buf"
+if test "x$ac_cv_func_arc4random_buf" = xyes; then :
+  cat >>confdefs.h <<_ACEOF
+#define HAVE_ARC4RANDOM_BUF 1
+_ACEOF
+
+else
+
+	case " $LIBOBJS " in
+  *" arc4random_buf.$ac_objext "* ) ;;
+  *) LIBOBJS="$LIBOBJS arc4random_buf.$ac_objext"
+ ;;
+esac
+
+
+    for _sym in sudo_arc4random_buf; do
+	COMPAT_EXP="${COMPAT_EXP}${_sym}
+"
+    done
+
+
 fi
 done
 
@@ -19929,6 +19955,12 @@ esac
 "
     done
 
+
+    for _sym in sudo_arc4random_buf; do
+	COMPAT_EXP="${COMPAT_EXP}${_sym}
+"
+    done
+
     case " $LIBOBJS " in
   *" arc4random_uniform.$ac_objext "* ) ;;
   *) LIBOBJS="$LIBOBJS arc4random_uniform.$ac_objext"

configure.ac

@@ -2637,9 +2637,14 @@ AC_CHECK_FUNCS([arc4random], [
 	AC_LIBOBJ(arc4random_uniform)
 	SUDO_APPEND_COMPAT_EXP(sudo_arc4random_uniform)
     ])
+    AC_CHECK_FUNCS([arc4random_buf], [], [
+	AC_LIBOBJ(arc4random_buf)
+	SUDO_APPEND_COMPAT_EXP(sudo_arc4random_buf)
+    ])
 ], [
     AC_LIBOBJ(arc4random)
     SUDO_APPEND_COMPAT_EXP(sudo_arc4random)
+    SUDO_APPEND_COMPAT_EXP(sudo_arc4random_buf)
     AC_LIBOBJ(arc4random_uniform)
     SUDO_APPEND_COMPAT_EXP(sudo_arc4random_uniform)
     # arc4random.c needs getentropy()

include/sudo_rand.h

@@ -35,6 +35,12 @@ __dso_public uint32_t sudo_arc4random(void);
 # define arc4random() sudo_arc4random()
 #endif /* ARC4RANDOM */
 
+#ifndef HAVE_ARC4RANDOM_BUF
+__dso_public void sudo_arc4random_buf(void *buf, size_t n);
+# undef arc4random_buf
+# define arc4random_buf(a, b) sudo_arc4random_buf((a), (b))
+#endif /* ARC4RANDOM_BUF */
+
 #ifndef HAVE_ARC4RANDOM_UNIFORM
 __dso_public uint32_t sudo_arc4random_uniform(uint32_t upper_bound);
 # undef arc4random_uniform

lib/util/arc4random.c

@@ -148,7 +148,6 @@ _rs_rekey(unsigned char *dat, size_t datlen)
 	rs_have = sizeof(rs_buf) - KEYSZ - IVSZ;
 }
 
-#ifdef notdef
 static inline void
 _rs_random_buf(void *_buf, size_t n)
 {
@@ -171,7 +170,6 @@ _rs_random_buf(void *_buf, size_t n)
 			_rs_rekey(NULL, 0);
 	}
 }
-#endif
 
 static inline void
 _rs_random_u32(uint32_t *val)
@@ -198,7 +196,6 @@ sudo_arc4random(void)
 	return val;
 }
 
-#ifdef notdef
 void
 sudo_arc4random_buf(void *buf, size_t n)
 {
@@ -206,6 +203,5 @@ sudo_arc4random_buf(void *buf, size_t n)
 	_rs_random_buf(buf, n);
 	_ARC4_UNLOCK();
 }
-#endif
 
 #endif /* HAVE_ARC4RANDOM */

lib/util/arc4random_buf.c

@@ -0,0 +1,69 @@
+/*
+ * SPDX-License-Identifier: ISC
+ *
+ * Copyright (c) 2020 Todd C. Miller <Todd.Miller@sudo.ws>
+ *
+ * Permission to use, copy, modify, and distribute this software for any
+ * purpose with or without fee is hereby granted, provided that the above
+ * copyright notice and this permission notice appear in all copies.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
+ * WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
+ * MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
+ * ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
+ * WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
+ * ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
+ * OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
+ */
+
+/*
+ * This is an open source non-commercial project. Dear PVS-Studio, please check it.
+ * PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com
+ */
+
+#include <config.h>
+
+#ifndef HAVE_ARC4RANDOM_BUF
+
+#include <sys/types.h>
+#include <stdlib.h>
+#if defined(HAVE_STDINT_H)
+# include <stdint.h>
+#elif defined(HAVE_INTTYPES_H)
+# include <inttypes.h>
+#endif
+
+#include "sudo_compat.h"
+#include "sudo_rand.h"
+
+/*
+ * Call arc4random() repeatedly to fill buf with n bytes of random data.
+ */
+void
+sudo_arc4random_buf(void *buf, size_t n)
+{
+	char *cp = buf;
+
+	while (n != 0) {
+		size_t m = minimum(n, 4);
+		uint32_t val = arc4random();
+
+		switch (m) {
+		case 4:
+			*cp++ = (val >> 24) & 0xff;
+			/* FALLTHROUGH */
+		case 3:
+			*cp++ = (val >> 16) & 0xff;
+			/* FALLTHROUGH */
+		case 2:
+			*cp++ = (val >> 8) & 0xff;
+			/* FALLTHROUGH */
+		case 1:
+			*cp++ = val & 0xff;
+			break;
+		}
+		n -= m;
+	}
+}
+
+#endif /* HAVE_ARC4RANDOM_BUF */