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Linux/MacOSX: Read at least 32 bytes from /dev/random before allowing it to fail gracefully

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This commit is contained in:
Mounir IDRASSI
2020-06-21 17:37:11 +02:00
parent e97114e7a0
commit a4c5f03bee
2 changed files with 11 additions and 3 deletions
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13
src/Core/RandomNumberGenerator.cpp
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@@ -44,12 +44,12 @@ namespace VeraCrypt
throw_sys_sub_if (random == -1, L"/dev/random"); throw_sys_sub_if (random == -1, L"/dev/random");
finally_do_arg (int, random, { close (finally_arg); }); finally_do_arg (int, random, { close (finally_arg); });
// ensure that we have read /dev/random successfully at least once before continuing // ensure that we have read at least 32 bytes from /dev/random before allowing it to fail gracefully
while (true) while (true)
{ {
int rndCount = read (random, buffer, buffer.Size()); int rndCount = read (random, buffer, buffer.Size());
throw_sys_sub_if ((rndCount == -1) && errno != EAGAIN, L"/dev/random"); throw_sys_sub_if ((rndCount == -1) && errno != EAGAIN && errno != ERESTART && errno != EINTR, L"/dev/random");
if (rndCount == -1 && !DevRandomSucceeded) if (rndCount == -1 && (!DevRandomSucceeded || (DevRandomBytesCount < 32)))
{ {
// wait 250ms before querying /dev/random again // wait 250ms before querying /dev/random again
::usleep (250 * 1000); ::usleep (250 * 1000);
@@ -57,7 +57,12 @@ namespace VeraCrypt
else else
{ {
if (rndCount != -1) if (rndCount != -1)
{
// We count returned bytes untill 32-bytes treshold reached
if (DevRandomBytesCount < 32)
DevRandomBytesCount += rndCount;
DevRandomSucceeded = true; DevRandomSucceeded = true;
}
break; break;
} }
} }
@@ -236,6 +241,7 @@ namespace VeraCrypt
EnrichedByUser = false; EnrichedByUser = false;
Running = false; Running = false;
DevRandomSucceeded = false; DevRandomSucceeded = false;
DevRandomBytesCount = 0;
} }
void RandomNumberGenerator::Test () void RandomNumberGenerator::Test ()
@@ -274,4 +280,5 @@ namespace VeraCrypt
size_t RandomNumberGenerator::WriteOffset; size_t RandomNumberGenerator::WriteOffset;
struct rand_data *RandomNumberGenerator::JitterRngCtx = NULL; struct rand_data *RandomNumberGenerator::JitterRngCtx = NULL;
bool RandomNumberGenerator::DevRandomSucceeded = false; bool RandomNumberGenerator::DevRandomSucceeded = false;
int RandomNumberGenerator::DevRandomBytesCount = 0;
} }

1
src/Core/RandomNumberGenerator.h
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@@ -56,6 +56,7 @@ namespace VeraCrypt
static size_t WriteOffset; static size_t WriteOffset;
static struct rand_data *JitterRngCtx; static struct rand_data *JitterRngCtx;
static bool DevRandomSucceeded; static bool DevRandomSucceeded;
static int DevRandomBytesCount;
}; };
} }