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![Eugeniu Rosca](/assets/img/avatar_default.png)
The random uuid values (enabled via CONFIG_RANDOM_UUID=y) on our
platform are always the same. Below is consistent on each cold boot:
=> ### interrupt autoboot
=> env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc
...
uuid_gpt_misc=d117f98e-6f2c-d04b-a5b2-331a19f91cb2
=> env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc
...
uuid_gpt_misc=ad5ec4b6-2d9f-8544-9417-fe3bd1c9b1b3
=> env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc
...
uuid_gpt_misc=cceb0b18-39cb-d547-9db7-03b405fa77d4
=> env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc
...
uuid_gpt_misc=d4981a2b-0478-544e-9607-7fd3c651068d
=> env default -a; gpt write mmc 1 $partitions; print uuid_gpt_misc
...
uuid_gpt_misc=6d6c9a36-e919-264d-a9ee-bd00379686c7
While the uuids do change on every 'gpt write' command, the values
appear to be taken from the same pool, in the same order.
Assuming U-Boot with RANDOM_UUID=y is deployed on a large number of
devices, all those devices would essentially expose the same UUID,
breaking the assumption of system/RFS/application designers who rely
on UUID as being globally unique (e.g. a database using UUID as key
would alias/mix up entries/records due to duplicated UUID).
The root cause seems to be simply _not_ seeding PRNG before generating
a random value. It turns out this belongs to an established class of
PRNG-specific problems, commonly known as "unseeded randomness", for
which I am able to find below bugs/CVE/CWE:
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2015-0285
("CVE-2015-0285 openssl: handshake with unseeded PRNG")
- https://bugzilla.redhat.com/show_bug.cgi?id=CVE-2015-9019
("CVE-2015-9019 libxslt: math.random() in xslt uses unseeded
randomness")
- https://cwe.mitre.org/data/definitions/336.html
("CWE-336: Same Seed in Pseudo-Random Number Generator (PRNG)")
The first revision [1] of this patch updated the seed based on the
output of get_timer(), similar to [4].
There are two problems with this approach:
- get_timer() has a poor _ms_ resolution
- when gen_rand_uuid() is called in a loop, get_timer() returns the
same result, leading to the same seed being passed to srand(),
leading to the same uuid being generated for several partitions
with different names
The above drawbacks have been addressed in the second version [2].
In its third revision (current), the patch reworded the description
and summary line to emphasize it is a *fix* rather than an improvement.
Testing [3] consisted of running 'gpt write mmc 1 $partitions' in a
loop on R-Car3 for several minutes, collecting 8844 randomly generated
UUIDS. Two consecutive cold boots are concatenated in the log.
As a result, all uuid values are unique (scripted check).
Thanks to Roman, who reported the issue and provided support in fixing.
[1] https://patchwork.ozlabs.org/patch/1091802/
[2] https://patchwork.ozlabs.org/patch/1092945/
[3] https://gist.github.com/erosca/2820be9d554f76b982edd48474d0e7ca
[4] commit da384a9d76
("net: rename and refactor eth_rand_ethaddr() function")
Reported-by: Roman Stratiienko <roman.stratiienko@globallogic.com>
Signed-off-by: Eugeniu Rosca <erosca@de.adit-jv.com>
Reviewed-by: Heinrich Schuchardt <xypron.glpk@gmx.de>
317 lines
8.3 KiB
C
317 lines
8.3 KiB
C
// SPDX-License-Identifier: GPL-2.0+
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/*
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* Copyright 2011 Calxeda, Inc.
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*/
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#include <common.h>
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#include <linux/ctype.h>
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#include <errno.h>
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#include <common.h>
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#include <asm/io.h>
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#include <part_efi.h>
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#include <malloc.h>
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/*
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* UUID - Universally Unique IDentifier - 128 bits unique number.
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* There are 5 versions and one variant of UUID defined by RFC4122
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* specification. A UUID contains a set of fields. The set varies
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* depending on the version of the UUID, as shown below:
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* - time, MAC address(v1),
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* - user ID(v2),
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* - MD5 of name or URL(v3),
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* - random data(v4),
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* - SHA-1 of name or URL(v5),
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*
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* Layout of UUID:
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* timestamp - 60-bit: time_low, time_mid, time_hi_and_version
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* version - 4 bit (bit 4 through 7 of the time_hi_and_version)
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* clock seq - 14 bit: clock_seq_hi_and_reserved, clock_seq_low
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* variant: - bit 6 and 7 of clock_seq_hi_and_reserved
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* node - 48 bit
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*
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* source: https://www.ietf.org/rfc/rfc4122.txt
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*
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* UUID binary format (16 bytes):
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*
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* 4B-2B-2B-2B-6B (big endian - network byte order)
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*
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* UUID string is 36 length of characters (36 bytes):
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*
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* 0 9 14 19 24
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* xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
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* be be be be be
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*
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* where x is a hexadecimal character. Fields are separated by '-'s.
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* When converting to a binary UUID, le means the field should be converted
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* to little endian and be means it should be converted to big endian.
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*
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* UUID is also used as GUID (Globally Unique Identifier) with the same binary
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* format but it differs in string format like below.
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*
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* GUID:
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* 0 9 14 19 24
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* xxxxxxxx-xxxx-xxxx-xxxx-xxxxxxxxxxxx
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* le le le be be
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*
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* GUID is used e.g. in GPT (GUID Partition Table) as a partiions unique id.
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*/
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int uuid_str_valid(const char *uuid)
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{
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int i, valid;
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if (uuid == NULL)
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return 0;
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for (i = 0, valid = 1; uuid[i] && valid; i++) {
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switch (i) {
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case 8: case 13: case 18: case 23:
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valid = (uuid[i] == '-');
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break;
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default:
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valid = isxdigit(uuid[i]);
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break;
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}
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}
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if (i != UUID_STR_LEN || !valid)
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return 0;
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return 1;
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}
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#ifdef CONFIG_PARTITION_TYPE_GUID
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static const struct {
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const char *string;
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efi_guid_t guid;
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} list_guid[] = {
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{"system", PARTITION_SYSTEM_GUID},
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{"mbr", LEGACY_MBR_PARTITION_GUID},
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{"msft", PARTITION_MSFT_RESERVED_GUID},
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{"data", PARTITION_BASIC_DATA_GUID},
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{"linux", PARTITION_LINUX_FILE_SYSTEM_DATA_GUID},
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{"raid", PARTITION_LINUX_RAID_GUID},
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{"swap", PARTITION_LINUX_SWAP_GUID},
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{"lvm", PARTITION_LINUX_LVM_GUID}
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};
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/*
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* uuid_guid_get_bin() - this function get GUID bin for string
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*
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* @param guid_str - pointer to partition type string
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* @param guid_bin - pointer to allocated array for big endian output [16B]
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*/
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int uuid_guid_get_bin(const char *guid_str, unsigned char *guid_bin)
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{
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int i;
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for (i = 0; i < ARRAY_SIZE(list_guid); i++) {
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if (!strcmp(list_guid[i].string, guid_str)) {
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memcpy(guid_bin, &list_guid[i].guid, 16);
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return 0;
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}
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}
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return -ENODEV;
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}
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/*
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* uuid_guid_get_str() - this function get string for GUID.
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*
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* @param guid_bin - pointer to string with partition type guid [16B]
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* @param guid_str - pointer to allocated partition type string [7B]
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*/
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int uuid_guid_get_str(unsigned char *guid_bin, char *guid_str)
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{
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int i;
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*guid_str = 0;
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for (i = 0; i < ARRAY_SIZE(list_guid); i++) {
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if (!memcmp(list_guid[i].guid.b, guid_bin, 16)) {
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strcpy(guid_str, list_guid[i].string);
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return 0;
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}
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}
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return -ENODEV;
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}
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#endif
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/*
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* uuid_str_to_bin() - convert string UUID or GUID to big endian binary data.
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*
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* @param uuid_str - pointer to UUID or GUID string [37B] or GUID shorcut
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* @param uuid_bin - pointer to allocated array for big endian output [16B]
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* @str_format - UUID string format: 0 - UUID; 1 - GUID
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*/
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int uuid_str_to_bin(char *uuid_str, unsigned char *uuid_bin, int str_format)
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{
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uint16_t tmp16;
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uint32_t tmp32;
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uint64_t tmp64;
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if (!uuid_str_valid(uuid_str)) {
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#ifdef CONFIG_PARTITION_TYPE_GUID
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if (!uuid_guid_get_bin(uuid_str, uuid_bin))
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return 0;
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#endif
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return -EINVAL;
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}
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if (str_format == UUID_STR_FORMAT_STD) {
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tmp32 = cpu_to_be32(simple_strtoul(uuid_str, NULL, 16));
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memcpy(uuid_bin, &tmp32, 4);
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tmp16 = cpu_to_be16(simple_strtoul(uuid_str + 9, NULL, 16));
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memcpy(uuid_bin + 4, &tmp16, 2);
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tmp16 = cpu_to_be16(simple_strtoul(uuid_str + 14, NULL, 16));
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memcpy(uuid_bin + 6, &tmp16, 2);
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} else {
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tmp32 = cpu_to_le32(simple_strtoul(uuid_str, NULL, 16));
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memcpy(uuid_bin, &tmp32, 4);
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tmp16 = cpu_to_le16(simple_strtoul(uuid_str + 9, NULL, 16));
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memcpy(uuid_bin + 4, &tmp16, 2);
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tmp16 = cpu_to_le16(simple_strtoul(uuid_str + 14, NULL, 16));
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memcpy(uuid_bin + 6, &tmp16, 2);
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}
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tmp16 = cpu_to_be16(simple_strtoul(uuid_str + 19, NULL, 16));
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memcpy(uuid_bin + 8, &tmp16, 2);
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tmp64 = cpu_to_be64(simple_strtoull(uuid_str + 24, NULL, 16));
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memcpy(uuid_bin + 10, (char *)&tmp64 + 2, 6);
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return 0;
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}
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/*
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* uuid_bin_to_str() - convert big endian binary data to string UUID or GUID.
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*
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* @param uuid_bin - pointer to binary data of UUID (big endian) [16B]
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* @param uuid_str - pointer to allocated array for output string [37B]
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* @str_format - UUID string format: 0 - UUID; 1 - GUID
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*/
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void uuid_bin_to_str(unsigned char *uuid_bin, char *uuid_str, int str_format)
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{
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const u8 uuid_char_order[UUID_BIN_LEN] = {0, 1, 2, 3, 4, 5, 6, 7, 8,
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9, 10, 11, 12, 13, 14, 15};
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const u8 guid_char_order[UUID_BIN_LEN] = {3, 2, 1, 0, 5, 4, 7, 6, 8,
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9, 10, 11, 12, 13, 14, 15};
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const u8 *char_order;
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int i;
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/*
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* UUID and GUID bin data - always in big endian:
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* 4B-2B-2B-2B-6B
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* be be be be be
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*/
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if (str_format == UUID_STR_FORMAT_STD)
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char_order = uuid_char_order;
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else
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char_order = guid_char_order;
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for (i = 0; i < 16; i++) {
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sprintf(uuid_str, "%02x", uuid_bin[char_order[i]]);
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uuid_str += 2;
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switch (i) {
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case 3:
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case 5:
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case 7:
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case 9:
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*uuid_str++ = '-';
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break;
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}
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}
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}
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/*
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* gen_rand_uuid() - this function generates a random binary UUID version 4.
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* In this version all fields beside 4 bits of version and
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* 2 bits of variant are randomly generated.
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*
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* @param uuid_bin - pointer to allocated array [16B]. Output is in big endian.
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*/
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#if defined(CONFIG_RANDOM_UUID) || defined(CONFIG_CMD_UUID)
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void gen_rand_uuid(unsigned char *uuid_bin)
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{
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struct uuid uuid;
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unsigned int *ptr = (unsigned int *)&uuid;
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int i;
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srand(get_ticks() + rand());
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/* Set all fields randomly */
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for (i = 0; i < sizeof(struct uuid) / sizeof(*ptr); i++)
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*(ptr + i) = cpu_to_be32(rand());
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clrsetbits_be16(&uuid.time_hi_and_version,
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UUID_VERSION_MASK,
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UUID_VERSION << UUID_VERSION_SHIFT);
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clrsetbits_8(&uuid.clock_seq_hi_and_reserved,
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UUID_VARIANT_MASK,
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UUID_VARIANT << UUID_VARIANT_SHIFT);
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memcpy(uuid_bin, &uuid, sizeof(struct uuid));
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}
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/*
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* gen_rand_uuid_str() - this function generates UUID v4 (random) in two string
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* formats UUID or GUID.
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*
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* @param uuid_str - pointer to allocated array [37B].
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* @param - uuid output type: UUID - 0, GUID - 1
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*/
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void gen_rand_uuid_str(char *uuid_str, int str_format)
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{
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unsigned char uuid_bin[UUID_BIN_LEN];
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/* Generate UUID (big endian) */
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gen_rand_uuid(uuid_bin);
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/* Convert UUID bin to UUID or GUID formated STRING */
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uuid_bin_to_str(uuid_bin, uuid_str, str_format);
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}
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#if !defined(CONFIG_SPL_BUILD) && defined(CONFIG_CMD_UUID)
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int do_uuid(cmd_tbl_t *cmdtp, int flag, int argc, char * const argv[])
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{
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char uuid[UUID_STR_LEN + 1];
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int str_format;
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if (!strcmp(argv[0], "uuid"))
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str_format = UUID_STR_FORMAT_STD;
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else
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str_format = UUID_STR_FORMAT_GUID;
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if (argc > 2)
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return CMD_RET_USAGE;
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gen_rand_uuid_str(uuid, str_format);
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if (argc == 1)
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printf("%s\n", uuid);
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else
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env_set(argv[1], uuid);
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return CMD_RET_SUCCESS;
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}
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U_BOOT_CMD(uuid, CONFIG_SYS_MAXARGS, 1, do_uuid,
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"UUID - generate random Universally Unique Identifier",
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"[<varname>]\n"
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"Argument:\n"
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"varname: for set result in a environment variable\n"
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"e.g. uuid uuid_env"
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);
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U_BOOT_CMD(guid, CONFIG_SYS_MAXARGS, 1, do_uuid,
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"GUID - generate Globally Unique Identifier based on random UUID",
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"[<varname>]\n"
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"Argument:\n"
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"varname: for set result in a environment variable\n"
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"e.g. guid guid_env"
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);
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#endif /* CONFIG_CMD_UUID */
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#endif /* CONFIG_RANDOM_UUID || CONFIG_CMD_UUID */
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