bin/uuidgen: add support for v4 uuids

The version 4 UUID is meant for generating UUIDs from truly-random or
pseudo-random numbers. [1]

bin/uuidgen gained the new flag '-r' to create version 4 UUID.

[1] RFC 4122, https://www.rfc-editor.org/rfc/rfc4122#section-4.4

Reviewed by:		pstef
Approved by:		bapt
MFC after:		1 week
Differential Revision:	https://reviews.freebsd.org/D37695

bin/uuidgen/uuidgen.1

@@ -33,6 +33,7 @@
 .Sh SYNOPSIS
 .Nm
 .Op Fl 1
+.Op Fl r
 .Op Fl n Ar count
 .Op Fl o Ar filename
 .Sh DESCRIPTION
@@ -50,6 +51,8 @@ This option only has effect if multiple identifiers are to be generated and
 instructs
 .Nm
 to not generate them in batch, but one at a time.
+.It Fl r
+This option controls creation of random UUID (version 4).
 .It Fl n
 This option controls the number of identifiers generated.
 By default, multiple identifiers are generated in batch.

bin/uuidgen/uuidgen.c

@@ -1,5 +1,6 @@
 /*
  * Copyright (c) 2002 Marcel Moolenaar
+ * Copyright (c) 2022 Tobias C. Berner
  * All rights reserved.
  *
  * Redistribution and use in source and binary forms, with or without
@@ -40,26 +41,63 @@ __FBSDID("$FreeBSD$");
 static void
 usage(void)
 {
-	(void)fprintf(stderr, "usage: uuidgen [-1] [-n count] [-o filename]\n");
+	(void)fprintf(stderr,
+	    "usage: uuidgen [-1] [-r] [-n count] [-o filename]\n");
 	exit(1);
 }
 
+static int
+uuidgen_v4(struct uuid *store, int count)
+{
+	int size;
+	struct uuid *item;
+
+	if (count < 1) {
+		errno = EINVAL;
+		return (-1);
+	}
+	size = sizeof(struct uuid) * count;
+	arc4random_buf(store, size);
+	item = store;
+	for (int i = 0; i < count; ++i) {
+		/*
+		 * Set the two most significant bits (bits 6 and 7) of the
+		 * clock_seq_hi_and_reserved to zero and one, respectively.
+		 */
+		item->clock_seq_hi_and_reserved &= ~(3 << 6);
+		item->clock_seq_hi_and_reserved |= (2 << 6);
+		/*
+		 * Set the four most significant bits (bits 12 through 15) of
+		 * the time_hi_and_version field to the 4-bit version number
+		 * from  Section 4.1.3.
+		 */
+		item->time_hi_and_version &= ~(15 << 12);
+		item->time_hi_and_version |= (4 << 12);
+		item++;
+	};
+	return (0);
+}
+
 int
 main(int argc, char *argv[])
 {
 	FILE *fp;
 	uuid_t *store, *uuid;
 	char *p;
-	int ch, count, i, iterate, status;
+	int ch, count, i, iterate, status, version;
 
-	count = -1;	/* no count yet */
+	count = -1;  /* no count yet */
-	fp = stdout;	/* default output file */
+	fp = stdout; /* default output file */
-	iterate = 0;	/* not one at a time */
+	iterate = 0; /* not one at a time */
-	while ((ch = getopt(argc, argv, "1n:o:")) != -1)
+	version = 1; /* create uuid v1 by default */
+	while ((ch = getopt(argc, argv, "1rn:o:")) != -1)
 		switch (ch) {
 		case '1':
 			iterate = 1;
 			break;
+		case 'r':
+			version = 4;
+			break;
 		case 'n':
 			if (count > 0)
 				usage();
@@ -92,19 +130,33 @@ main(int argc, char *argv[])
 	if (count == -1)
 		count = 1;
 
-	store = (uuid_t*)malloc(sizeof(uuid_t) * count);
+	store = (uuid_t *)malloc(sizeof(uuid_t) * count);
 	if (store == NULL)
 		err(1, "malloc()");
 
 	if (!iterate) {
 		/* Get them all in a single batch */
-		if (uuidgen(store, count) != 0)
+		if (version == 1) {
-			err(1, "uuidgen()");
+			if (uuidgen(store, count) != 0)
+				err(1, "uuidgen()");
+		} else if (version == 4) {
+			if (uuidgen_v4(store, count) != 0)
+				err(1, "uuidgen_v4()");
+		} else {
+			err(1, "unsupported version");
+		}
 	} else {
 		uuid = store;
 		for (i = 0; i < count; i++) {
-			if (uuidgen(uuid++, 1) != 0)
+			if (version == 1) {
-				err(1, "uuidgen()");
+				if (uuidgen(uuid++, 1) != 0)
+					err(1, "uuidgen()");
+			} else if (version == 4) {
+				if (uuidgen_v4(uuid++, 1) != 0)
+					err(1, "uuidgen_v4()");
+			} else {
+				err(1, "unsupported version");
+			}
 		}
 	}
 
@@ -112,7 +164,7 @@ main(int argc, char *argv[])
 	while (count--) {
 		uuid_to_string(uuid++, &p, &status);
 		if (status != uuid_s_ok)
-		     err(1, "cannot stringify a UUID");
+			err(1, "cannot stringify a UUID");
 		fprintf(fp, "%s\n", p);
 		free(p);
 	}