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When reading data from various spots in /proc to initialize the random

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number generator:
 * reduce timeout from 2s to 1ms
 * if timeout, abort
 * only read first 4096 bytes
this is to work around the fact that on Samsung Tab 4, /proc/timer_list
is apparently 167MB!
This commit is contained in:
Greg Alexander 2016-08-08 14:08:49 -04:00
parent 3d9a5b5ced
commit 60fcaa6ec9
1 changed files with 9 additions and 7 deletions
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16
dropbear/dbrandom.c
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@ -85,8 +85,8 @@ process_file(hash_state *hs, const char *filename,
struct timeval timeout;
fd_set read_fds;
timeout.tv_sec = 2;
timeout.tv_usec = 0;
timeout.tv_sec = 0;
timeout.tv_usec = 1000;
FD_ZERO(&read_fds);
FD_SET(readfd, &read_fds);
@ -98,6 +98,8 @@ process_file(hash_state *hs, const char *filename,
}
}
if (already_blocked) break;
if (len == 0)
{
wantread = sizeof(readbuf);
@ -205,12 +207,12 @@ void seedrandom() {
#ifdef __linux__
/* Seems to be a reasonable source of entropy from timers. Possibly hard
* for even local attackers to reproduce */
process_file(&hs, "/proc/timer_list", 0, 0);
process_file(&hs, "/proc/timer_list", 4096, 0);
/* Might help on systems with wireless */
process_file(&hs, "/proc/interrupts", 0, 0);
process_file(&hs, "/proc/interrupts", 4096, 0);
process_file(&hs, "/proc/loadavg", 0, 0);
process_file(&hs, "/proc/sys/kernel/random/entropy_avail", 0, 0);
process_file(&hs, "/proc/loadavg", 4096, 0);
process_file(&hs, "/proc/sys/kernel/random/entropy_avail", 4096, 0);
/* Mostly network visible but useful in some situations.
* Limit size to avoid slowdowns on systems with lots of routes */
@ -219,7 +221,7 @@ void seedrandom() {
process_file(&hs, "/proc/net/tcp", 4096, 0);
/* Also includes interface lo */
process_file(&hs, "/proc/net/rt_cache", 4096, 0);
process_file(&hs, "/proc/vmstat", 0, 0);
process_file(&hs, "/proc/vmstat", 4096, 0);
#endif
pid = getpid();