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start code: overwrite AT_RANDOM after we use it

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Andrew Kelley 2020-12-17 20:35:29 -07:00
parent 013efaf139
commit 4dcd1e6059
1 changed files with 7 additions and 1 deletions
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8
lib/std/start.zig
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@ -226,11 +226,17 @@ fn posixCallMainAndExit() noreturn {
// "The address of sixteen bytes containing a random value."
const addr = auxv[i].a_un.a_val;
if (addr == 0) break;
const ptr = @intToPtr(*const [16]u8, addr);
const ptr = @intToPtr(*[16]u8, addr);
var seed: [32]u8 = undefined;
seed[0..16].* = ptr.*;
seed[16..].* = ptr.*;
tlcsprng.init(seed);
// Overwrite AT_RANDOM after we use it, otherwise our secure
// seed is sitting in memory ready for some other code in the
// program to reuse, and hence break our security.
// We play nice by refreshing it with fresh random bytes
// rather than clearing it.
std.crypto.random.bytes(ptr);
break;
},
else => continue,