kern: ether_gen_addr: randomize on default hostuuid, too
Currently, this will still hash the default (all zero) hostuuid and potentially arrive at a MAC address that has a high chance of collision if another interface of the same name appears in the same broadcast domain on another host without a hostuuid, e.g., some virtual machine setups. Instead of using the default hostuuid, just treat it as a failure and generate a random LA unicast MAC address. Reviewed by: bz, gbe, imp, kbowling, kp MFC after: 1 week Differential Revision: https://reviews.freebsd.org/D29788
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@ -61,8 +61,9 @@ or on machines that do not use
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.Xr loader 8 .
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.Pp
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.Nm
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can fail to derive a MAC address due to memory allocation failure.
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In this case, a locally-administered unicast MAC address will be randomly
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can fail to derive a MAC address due to memory allocation failure, or because
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the hostid has not been populated.
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In these cases, a locally-administered unicast MAC address will be randomly
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generated and returned via the
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.Ar hwaddr
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parameter.
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@ -76,7 +76,6 @@ __FBSDID("$FreeBSD$");
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#include <security/mac/mac_framework.h>
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#define DEFAULT_HOSTUUID "00000000-0000-0000-0000-000000000000"
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#define PRISON0_HOSTUUID_MODULE "hostuuid"
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MALLOC_DEFINE(M_PRISON, "prison", "Prison structures");
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@ -1443,6 +1443,11 @@ ether_gen_addr(struct ifnet *ifp, struct ether_addr *hwaddr)
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char jailname[MAXHOSTNAMELEN];
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getcredhostuuid(curthread->td_ucred, uuid, sizeof(uuid));
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if (strncmp(uuid, DEFAULT_HOSTUUID, sizeof(uuid)) == 0) {
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/* Fall back to a random mac address. */
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goto rando;
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}
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/* If each (vnet) jail would also have a unique hostuuid this would not
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* be necessary. */
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getjailname(curthread->td_ucred, jailname, sizeof(jailname));
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@ -1450,9 +1455,7 @@ ether_gen_addr(struct ifnet *ifp, struct ether_addr *hwaddr)
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jailname);
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if (sz < 0) {
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/* Fall back to a random mac address. */
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arc4rand(hwaddr, sizeof(*hwaddr), 0);
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hwaddr->octet[0] = 0x02;
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return;
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goto rando;
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}
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SHA1Init(&ctx);
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@ -1467,6 +1470,14 @@ ether_gen_addr(struct ifnet *ifp, struct ether_addr *hwaddr)
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hwaddr->octet[i] = addr >> ((ETHER_ADDR_LEN - i - 1) * 8) &
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0xFF;
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}
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return;
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rando:
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arc4rand(hwaddr, sizeof(*hwaddr), 0);
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/* Unicast */
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hwaddr->octet[0] &= 0xFE;
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/* Locally administered. */
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hwaddr->octet[0] |= 0x02;
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}
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DECLARE_MODULE(ether, ether_mod, SI_SUB_INIT_IF, SI_ORDER_ANY);
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@ -140,6 +140,7 @@ MALLOC_DECLARE(M_PRISON);
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#include <sys/osd.h>
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#define HOSTUUIDLEN 64
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#define DEFAULT_HOSTUUID "00000000-0000-0000-0000-000000000000"
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#define OSRELEASELEN 32
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struct racct;
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