Add sudo_uuid_from_string() to parse uuid string into a uid.

Also fixes a bug in sudo_uuid_to_string() where the '-' were
misplaced.  The uuid tests now verify that the generated uuid
round-trips from binary -> string -> binary.

Author: millert

include/sudo_util.h

@@ -375,5 +375,7 @@ sudo_dso_public void sudo_uuid_create_v1(unsigned char uuid_out[restrict static
 #define sudo_uuid_create(_a) sudo_uuid_create_v1((_a))
 sudo_dso_public char *sudo_uuid_to_string_v1(const unsigned char uuid[restrict static 16], char * restrict dst, size_t dstsiz);
 #define sudo_uuid_to_string(_a, _b, _c) sudo_uuid_to_string_v1((_a), (_b), (_c))
+sudo_dso_public int sudo_uuid_from_string_v1(const char *str, unsigned char uuid[restrict static 16]);
+#define sudo_uuid_from_string(_a, _b) sudo_uuid_from_string_v1((_a), (_b))
 
 #endif /* SUDO_UTIL_H */

lib/util/regress/uuid/uuid_test.c

@@ -1,7 +1,7 @@
 /*
  * SPDX-License-Identifier: ISC
  *
- * Copyright (c) 2021 Todd C. Miller <[email protected]>
+ * Copyright (c) 2021, 2025 Todd C. Miller <[email protected]>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -75,6 +75,8 @@ main(int argc, char *argv[])
 
     /* Do 16 passes. */
     for (ntests = 0; ntests < 16; ntests++) {
+	char uuid_buf[16], uuid_str[37];
+
 	sudo_uuid_create(uuid.u8);
 
 	/* Variant: two most significant bits (6 and 7) are 0 and 1. */
@@ -95,6 +97,24 @@ main(int argc, char *argv[])
 	    errors++;
 	    continue;
 	}
+
+	/* Test round-tripping uuid -> string -> uuid */
+	if (sudo_uuid_to_string(uuid.u8, uuid_str, sizeof(uuid_str)) == NULL) {
+	    sudo_warnx("unable to convert uuid to string form");
+	    errors++;
+	    continue;
+	}
+	if (sudo_uuid_from_string(uuid_str, uuid_buf) != 0) {
+	    sudo_warnx("unable to parse uuid string \"%s\" to binary",
+		uuid_str);
+	    errors++;
+	    continue;
+	}
+	if (memcmp(uuid.u8, uuid_buf, sizeof(uuid_buf)) != 0) {
+	    sudo_warnx("binary uuid mismatch");
+	    errors++;
+	    continue;
+	}
     }
 
     if (ntests != 0) {

lib/util/util.exp.in

@@ -172,6 +172,7 @@ sudo_term_raw_v1
 sudo_term_restore_v1
 sudo_ttyname_dev_v1
 sudo_uuid_create_v1
+sudo_uuid_from_string_v1
 sudo_uuid_to_string_v1
 sudo_vfatal_nodebug_v1
 sudo_vfatalx_nodebug_v1

lib/util/uuid.c

@@ -1,7 +1,7 @@
 /*
  * SPDX-License-Identifier: ISC
  *
- * Copyright (c) 2020 Todd C. Miller <[email protected]>
+ * Copyright (c) 2020-2021, 2025 Todd C. Miller <[email protected]>
  *
  * Permission to use, copy, modify, and distribute this software for any
  * purpose with or without fee is hereby granted, provided that the above
@@ -80,10 +80,7 @@ sudo_uuid_to_string_v1(const unsigned char uuid[restrict static 16], char * rest
 	*cp++ = hex[uuid[i] & 0x0f];
 
 	switch (i) {
-	case 4:
-	case 6:
-	case 8:
-	case 10:
+	case 3: case 5: case 7: case 9:
 	    *cp++ = '-';
 	    break;
 	}
@@ -92,3 +89,36 @@ sudo_uuid_to_string_v1(const unsigned char uuid[restrict static 16], char * rest
 
     return dst;
 }
+
+/*
+ * Parse 36-byte uuid string into a 16-byte binary uuid.
+ * Returns 0 on success, -1 if str is not a valid uuid.
+ */
+int
+sudo_uuid_from_string_v1(const char *str, unsigned char uuid[static 16])
+{
+    unsigned int i = 0, j = 0;
+    int ch;
+
+    if (strlen(str) != 36)
+	return -1;
+
+    /* Parse a uuid in the format 123e4567-e89b-12d3-a456-426655440000 */
+    while (i < 36) {
+	switch (i) {
+	case 8: case 13: case 18: case 23:
+	    if (str[i] != '-')
+		return -1;
+	    i++;
+	    FALLTHROUGH;
+	default:
+	    ch = sudo_hexchar(str + i);
+	    if (ch == -1)
+		return -1;
+	    uuid[j++] = ch;
+	    i += 2;
+	}
+    }
+
+    return 0;
+}