* [PATCH v2 1/2] common: machine_id: support deriving app specific UUIDs
2023-11-15 9:02 [PATCH v2 0/2] Allow generating MAC addresses from machine ID Uwe Kleine-König
@ 2023-11-15 9:02 ` Uwe Kleine-König
2023-11-15 9:02 ` [PATCH v2 2/2] net: add generic MAC address derivation from machine ID Uwe Kleine-König
2023-11-21 8:33 ` [PATCH v2 0/2] Allow generating MAC addresses " Sascha Hauer
2 siblings, 0 replies; 4+ messages in thread
From: Uwe Kleine-König @ 2023-11-15 9:02 UTC (permalink / raw)
To: Sascha Hauer; +Cc: Ahmad Fatoum, Alexander Shiyan, Thorsten Scherer, barebox
From: Ahmad Fatoum <a.fatoum@pengutronix.de>
libsystemd provides a sd_id128_get_machine_app_specific() function that
allows deriving an application specific UUID without directly leaking
the machine ID.
Let's provide an equivalent for barebox that will be used in a following
commit to generate a stable MAC instead of randomizing it.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
common/machine_id.c | 84 ++++++++++++++++++++++++++++++++++++++++++--
include/linux/uuid.h | 8 +++++
include/machine_id.h | 11 ++++++
3 files changed, 101 insertions(+), 2 deletions(-)
diff --git a/common/machine_id.c b/common/machine_id.c
index 8c273b934989..edc8ad0ac156 100644
--- a/common/machine_id.c
+++ b/common/machine_id.c
@@ -13,17 +13,96 @@
#define MACHINE_ID_LENGTH 32
+static bool __machine_id_initialized;
static void *__machine_id_hashable;
static size_t __machine_id_hashable_length;
-
+/**
+ * machine_id_set_hashable - Provide per-board unique data
+ * @hashable: Buffer
+ * @len: size of buffer
+ *
+ * The data supplied to the last call of this function prior to
+ * late_initcall will be hashed and stored into global.machine_id,
+ * which can be later used for fixup into the kernel command line
+ * or for deriving application specific unique IDs via
+ * machine_id_get_app_specific().
+ */
void machine_id_set_hashable(const void *hashable, size_t len)
{
-
__machine_id_hashable = xmemdup(hashable, len);
__machine_id_hashable_length = len;
}
+/**
+ * machine_id_get_app_specific - Generates an application-specific UUID
+ * @result: UUID output of the function
+ * @...: pairs of (const void *, size_t) arguments of data to factor
+ * into the UUID followed by a NULL sentinel value.
+ *
+ * Combines the machine ID with the application specific varargs data
+ * to arrive at an application-specific and board-specific UUID that is
+ * stable and unique.
+ *
+ * The function returns 0 if a UUID was successfully written into @result
+ * and a negative error code otherwise.
+ */
+int machine_id_get_app_specific(uuid_t *result, ...)
+{
+ static u8 hmac[SHA256_DIGEST_SIZE];
+ const void *data;
+ size_t size;
+ va_list args;
+ struct digest *d;
+ int ret;
+
+ if (!__machine_id_initialized)
+ return -ENODATA;
+
+ d = digest_alloc("hmac(sha256)");
+ if (!d)
+ return -ENOSYS;
+
+ ret = digest_set_key(d, __machine_id_hashable, __machine_id_hashable_length);
+ if (ret)
+ goto out;
+
+ ret = digest_init(d);
+ if (ret)
+ goto out;
+
+ ret = -ENODATA;
+
+ va_start(args, result);
+
+ while ((data = va_arg(args, const void *))) {
+ size = va_arg(args, size_t);
+
+ ret = digest_update(d, data, size);
+ if (ret)
+ break;
+ }
+
+ va_end(args);
+
+ if (ret)
+ goto out;
+
+ ret = digest_final(d, hmac);
+ if (ret)
+ goto out;
+
+ /* Take only the first half. */
+ memcpy(result, hmac, min(sizeof(hmac), sizeof(*result)));
+
+ uuid_make_v4(result);
+
+out:
+ digest_free(d);
+
+ return ret;
+}
+
static int machine_id_set_globalvar(void)
{
struct digest *digest = NULL;
@@ -61,6 +140,7 @@ static int machine_id_set_globalvar(void)
env_machine_id = basprintf("%.*s", MACHINE_ID_LENGTH, hex_machine_id);
globalvar_add_simple("machine_id", env_machine_id);
free(env_machine_id);
+ __machine_id_initialized = true;
out:
digest_free(digest);
diff --git a/include/linux/uuid.h b/include/linux/uuid.h
index 6b1a3efa1e0b..1e4ffb343452 100644
--- a/include/linux/uuid.h
+++ b/include/linux/uuid.h
@@ -107,6 +107,14 @@ extern const u8 uuid_index[16];
int guid_parse(const char *uuid, guid_t *u);
int uuid_parse(const char *uuid, uuid_t *u);
+static inline void uuid_make_v4(uuid_t *u) {
+ /* Set UUID version to 4 --- truly random generation */
+ u->b[6] = (u->b[6] & 0x0F) | 0x40;
+
+ /* Set the UUID variant to DCE */
+ u->b[8] = (u->b[8] & 0x3F) | 0x80;
+}
+
/* MEI UUID type, don't use anywhere else */
#include <uapi/linux/uuid.h>
diff --git a/include/machine_id.h b/include/machine_id.h
index e30bbada1acd..9245a5412770 100644
--- a/include/machine_id.h
+++ b/include/machine_id.h
@@ -3,9 +3,13 @@
#ifndef __MACHINE_ID_H__
#define __MACHINE_ID_H__
+#include <linux/types.h>
+#include <linux/uuid.h>
+
#if IS_ENABLED(CONFIG_MACHINE_ID)
void machine_id_set_hashable(const void *hashable, size_t len);
+int machine_id_get_app_specific(uuid_t *result, ...) __attribute__((__sentinel__));
#else
@@ -13,6 +17,13 @@ static inline void machine_id_set_hashable(const void *hashable, size_t len)
{
}
+static inline int machine_id_get_app_specific(uuid_t *result, ...)
+ __attribute__((__sentinel__));
+static inline int machine_id_get_app_specific(uuid_t *result, ...)
+{
+ return -ENOSYS;
+}
+
#endif /* CONFIG_MACHINE_ID */
#endif /* __MACHINE_ID_H__ */
--
2.42.0.586.gbc5204569f7d.dirty
^ permalink raw reply [flat|nested] 4+ messages in thread* [PATCH v2 2/2] net: add generic MAC address derivation from machine ID
2023-11-15 9:02 [PATCH v2 0/2] Allow generating MAC addresses from machine ID Uwe Kleine-König
2023-11-15 9:02 ` [PATCH v2 1/2] common: machine_id: support deriving app specific UUIDs Uwe Kleine-König
@ 2023-11-15 9:02 ` Uwe Kleine-König
2023-11-21 8:33 ` [PATCH v2 0/2] Allow generating MAC addresses " Sascha Hauer
2 siblings, 0 replies; 4+ messages in thread
From: Uwe Kleine-König @ 2023-11-15 9:02 UTC (permalink / raw)
To: Sascha Hauer
Cc: Ahmad Fatoum, Alexander Shiyan, Thorsten Scherer, Ahmad Fatoum, barebox
From: Ahmad Fatoum <ahmad@a3f.at>
Especially during development, devices often lack a MAC address. While a
MAC address can be easily added to the environment:
nv dev.eth0.ethaddr="aa:bb:cc:dd:ee:ff"
It's easily lost when flashing complete new images, e.g. from CI.
Make the development experience neater by deriving a stable MAC address
if possible.
Signed-off-by: Ahmad Fatoum <a.fatoum@pengutronix.de>
---
include/net.h | 2 ++
net/Kconfig | 17 +++++++++++++++++
net/eth.c | 15 ++++++++++++---
net/net.c | 49 +++++++++++++++++++++++++++++++++++++++++++++++--
4 files changed, 78 insertions(+), 5 deletions(-)
diff --git a/include/net.h b/include/net.h
index a0ef8bee0404..de43c29f74ac 100644
--- a/include/net.h
+++ b/include/net.h
@@ -418,6 +418,8 @@ static inline int is_broadcast_ether_addr(const u8 *addr)
#define ETH_ALEN 6 /* Octets in an Ethernet address */
#define ETH_HLEN 14 /* Total octets in header.*/
+int generate_ether_addr(u8 *addr, int ethid);
+
/**
* random_ether_addr - Generate software assigned random Ethernet address
* @addr: Pointer to a six-byte array containing the Ethernet address
diff --git a/net/Kconfig b/net/Kconfig
index 59f14c23cba2..07e623670e22 100644
--- a/net/Kconfig
+++ b/net/Kconfig
@@ -6,6 +6,23 @@ menuconfig NET
if NET
+config NET_ETHADDR_FROM_MACHINE_ID
+ bool
+ prompt "generate stable Ethernet address"
+ depends on MACHINE_ID && HAVE_DIGEST_SHA256 && HAVE_DIGEST_HMAC
+ help
+ By default, barebox will generate random Ethernet addresses for
+ interfaces that had no explicit Ethernet address set via
+ either board code or NVMEM properties in device tree.
+
+ Say y here, to randomize Ethernet addresses only if no machine ID
+ is available. Should barebox have a machine ID, it will be used
+ alongside the hostname to generate MAC addresses that are unlikely
+ to change between subsequent runs of barebox.
+
+ This is not recommended for use in production as it may leak
+ information about the machine ID.
+
config NET_NFS
bool
prompt "nfs support"
diff --git a/net/eth.c b/net/eth.c
index ccac5e2a6488..d1474ec57df3 100644
--- a/net/eth.c
+++ b/net/eth.c
@@ -10,6 +10,7 @@
#include <dhcp.h>
#include <net.h>
#include <dma.h>
+#include <machine_id.h>
#include <of.h>
#include <of_net.h>
#include <linux/phy.h>
@@ -554,10 +555,11 @@ void eth_open_all(void)
}
}
-static int of_populate_ethaddr(void)
+static int populate_ethaddr(void)
{
char str[sizeof("xx:xx:xx:xx:xx:xx")];
struct eth_device *edev;
+ bool generated = false;
int ret;
list_for_each_entry(edev, &netdev_list, list) {
@@ -566,14 +568,21 @@ static int of_populate_ethaddr(void)
ret = of_get_mac_addr_nvmem(edev->parent->of_node,
edev->ethaddr);
+ if (IS_ENABLED(CONFIG_NET_ETHADDR_FROM_MACHINE_ID) && ret) {
+ ret = generate_ether_addr(edev->ethaddr, edev->dev.id);
+ generated = true;
+ }
if (ret)
continue;
ethaddr_to_string(edev->ethaddr, str);
- dev_info(&edev->dev, "Got preset MAC address from device tree: %s\n", str);
+ if (generated)
+ dev_notice(&edev->dev, "Generated MAC address from unique id: %s\n", str);
+ else
+ dev_info(&edev->dev, "Got preset MAC address from NVMEM: %s\n", str);
eth_set_ethaddr(edev, edev->ethaddr);
}
return 0;
}
-postenvironment_initcall(of_populate_ethaddr);
+postenvironment_initcall(populate_ethaddr);
diff --git a/net/net.c b/net/net.c
index bf2117ff7ec2..e38179491d7a 100644
--- a/net/net.c
+++ b/net/net.c
@@ -25,6 +25,7 @@
#include <init.h>
#include <globalvar.h>
#include <magicvar.h>
+#include <machine_id.h>
#include <linux/ctype.h>
#include <linux/err.h>
@@ -365,6 +366,43 @@ IPaddr_t net_get_gateway(void)
static LIST_HEAD(connection_list);
+/**
+ * generate_ether_addr - Generates stable software assigned Ethernet address
+ * @addr: Pointer to a six-byte array to contain the Ethernet address
+ * @ethid: index of the Ethernet interface
+ *
+ * Derives an Ethernet address (MAC) from the machine ID, that's stable
+ * per board that is not multicast and has the local assigned bit set.
+ *
+ * Return 0 if an address could be generated or a negative error code otherwise.
+ */
+int generate_ether_addr(u8 *ethaddr, int ethid)
+{
+ const char *hostname;
+ uuid_t id;
+ int ret;
+
+ if (!IS_ENABLED(CONFIG_NET_ETHADDR_FROM_MACHINE_ID))
+ return -ENOSYS;
+
+ hostname = barebox_get_hostname();
+ if (!hostname)
+ return -EINVAL;
+
+ ret = machine_id_get_app_specific(&id, ARRAY_AND_SIZE("barebox-macaddr:"),
+ hostname, strlen(hostname), NULL);
+ if (ret)
+ return ret;
+
+ memcpy(ethaddr, &id.b, ETH_ALEN);
+ eth_addr_add(ethaddr, ethid);
+
+ ethaddr[0] &= 0xfe; /* clear multicast bit */
+ ethaddr[0] |= 0x02; /* set local assignment bit (IEEE802) */
+
+ return 0;
+}
+
static struct net_connection *net_new(struct eth_device *edev, IPaddr_t dest,
rx_handler_f *handler, void *ctx)
{
@@ -381,9 +419,16 @@ static struct net_connection *net_new(struct eth_device *edev, IPaddr_t dest,
if (!is_valid_ether_addr(edev->ethaddr)) {
char str[sizeof("xx:xx:xx:xx:xx:xx")];
- random_ether_addr(edev->ethaddr);
+
+ ret = generate_ether_addr(edev->ethaddr, edev->dev.id);
+ if (ret)
+ random_ether_addr(edev->ethaddr);
+
ethaddr_to_string(edev->ethaddr, str);
- dev_warn(&edev->dev, "No MAC address set. Using random address %s\n", str);
+
+ dev_warn(&edev->dev, "No MAC address set. Using %s %s\n",
+ ret == 1 ? "address computed from unique ID" : "random address",
+ str);
eth_set_ethaddr(edev, edev->ethaddr);
}
--
2.42.0.586.gbc5204569f7d.dirty
^ permalink raw reply [flat|nested] 4+ messages in thread* Re: [PATCH v2 0/2] Allow generating MAC addresses from machine ID
2023-11-15 9:02 [PATCH v2 0/2] Allow generating MAC addresses from machine ID Uwe Kleine-König
2023-11-15 9:02 ` [PATCH v2 1/2] common: machine_id: support deriving app specific UUIDs Uwe Kleine-König
2023-11-15 9:02 ` [PATCH v2 2/2] net: add generic MAC address derivation from machine ID Uwe Kleine-König
@ 2023-11-21 8:33 ` Sascha Hauer
2 siblings, 0 replies; 4+ messages in thread
From: Sascha Hauer @ 2023-11-21 8:33 UTC (permalink / raw)
To: Uwe Kleine-König
Cc: Alexander Shiyan, Thorsten Scherer, Ahmad Fatoum, barebox
On Wed, Nov 15, 2023 at 10:02:39AM +0100, Uwe Kleine-König wrote:
> Hello,
>
> this series contains two patches by Ahmad that he send earlier starting
> with Message-Id: <20230911155927.3786335-1-a.fatoum@pengutronix.de>.
>
> Patch #1 was already applied back then as 9831b2e5fed8 ("common:
> machine_id: support deriving app specific UUIDs").
>
> Changes since (implicit) v1:
>
> - fix compilation with MACHINE_ID=n (Sascha)
> - fix typo in NET_ETHADDR_FROM_MACHINE_ID helptext (Thorsten)
> - rename of_populate_ethaddr -> populate_ethaddr as it's not about of any more (Sascha)
This series neither applies to master nor to next, please resend
Sascha
>
> On Tue, Sep 12, 2023 at 12:49:03PM +0200, Sascha Hauer wrote:
> > On Mon, Sep 11, 2023 at 05:59:27PM +0200, Ahmad Fatoum wrote:
> > > @@ -566,11 +568,18 @@ static int of_populate_ethaddr(void)
> > >
> > > ret = of_get_mac_addr_nvmem(edev->parent->of_node,
> > > edev->ethaddr);
> > > + if (ret && IS_ENABLED(CONFIG_NET_ETHADDR_FROM_MACHINE_ID)) {
> >
> > This check doesn't seem to be needed, generate_ether_addr() already
> > returns -ENOSYS when this option is not enabled.
>
> I kept this check, Ahmad already argued that is should be kept. (I only
> swapped the checks to have the static one first which is IMHO more
> natural.)
>
> Best regards
> Uwe
>
> Ahmad Fatoum (2):
> common: machine_id: support deriving app specific UUIDs
> net: add generic MAC address derivation from machine ID
>
> common/machine_id.c | 84 ++++++++++++++++++++++++++++++++++++++++++--
> include/linux/uuid.h | 8 +++++
> include/machine_id.h | 11 ++++++
> include/net.h | 2 ++
> net/Kconfig | 17 +++++++++
> net/eth.c | 15 ++++++--
> net/net.c | 49 ++++++++++++++++++++++++--
> 7 files changed, 179 insertions(+), 7 deletions(-)
>
> base-commit: bc5e49335067d0c6c6e97c082a0368fe9d86b725
> --
> 2.42.0.586.gbc5204569f7d.dirty
>
>
--
Pengutronix e.K. | |
Steuerwalder Str. 21 | http://www.pengutronix.de/ |
31137 Hildesheim, Germany | Phone: +49-5121-206917-0 |
Amtsgericht Hildesheim, HRA 2686 | Fax: +49-5121-206917-5555 |
^ permalink raw reply [flat|nested] 4+ messages in thread