On Fri, Jul 29, 2016 at 7:40 AM, Stephan Mueller <smueller@xxxxxxxxxx> wrote:
> And finally, you have a coding error that is very very common but fatal when
> reading from /dev/random: you do not account for short reads which implies
> that your loop continues even in the case of short reads.
>
> Fix your code with something like the following:
> int read_random(char *buf, size_t buflen)
> {
> int fd = 0;
> ssize_t ret = 0;
> size_t len = 0;
>
> fd = open("/dev/random", O_RDONLY|O_CLOEXEC);
> if(0 > fd)
> return fd;
> do {
> ret = read(fd, (buf + len), (buflen - len));
> if (0 < ret)
> len += ret;
> } while ((0 < ret || EINTR == errno || ERESTART == errno)
> && buflen > len);
Unless there is a documentation error, the same is required when using
getrandom(). It can also return short as well as to be interrupted.
regards,
Nikos
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