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Fix potential stack smash in getsyshwaddr on OS X

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getsyshwaddr assumed that the first ifaddr it came across was the MAC
address, and as such assumes that it has the right length. After
upgrading to OS X 10.13.4, this causes minidlnad to crash on startup due
to tripping stack smash protection -- I'm not sure if the order of
addresses returned previously happened to accidentally hit this
invariant, or if this was always an issue and the stack smash protection
got smarter.

In any event, we just need to look for the AF_LINK address and use that.
As an extra check, we make sure the length is the length we expect to
copy into the target buffer.
This commit is contained in:
Josh Watzman 2018-04-10 23:17:22 +01:00 committed by Justin Maggard
parent 138d03db19
commit ade51e9c94
1 changed files with 5 additions and 1 deletions
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6
getifaddr.c
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@ -205,9 +205,13 @@ getsyshwaddr(char *buf, int len)
continue; continue;
memcpy(mac, ifr.ifr_hwaddr.sa_data, 6); memcpy(mac, ifr.ifr_hwaddr.sa_data, 6);
#else #else
if (p->ifa_addr->sa_family != AF_LINK)
continue;
struct sockaddr_dl *sdl; struct sockaddr_dl *sdl;
sdl = (struct sockaddr_dl*)p->ifa_addr; sdl = (struct sockaddr_dl*)p->ifa_addr;
memcpy(mac, LLADDR(sdl), sdl->sdl_alen); if (sdl->sdl_alen != 6)
continue;
memcpy(mac, LLADDR(sdl), 6);
#endif #endif
if (MACADDR_IS_ZERO(mac)) if (MACADDR_IS_ZERO(mac))
continue; continue;