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Code Issues Releases Wiki Activity

token generation was not uniformly distributed

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This commit is contained in:
Nicolas Viennot 2016-01-22 23:12:02 -05:00
parent 23bbaab3d2
commit d687e486da
1 changed files with 45 additions and 4 deletions
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49
tmate-slave.c
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@ -61,6 +61,38 @@ long tmate_get_random_long(void)
return val;
}
#define RS_BUF_SIZE 256
struct random_stream {
char bytes[RS_BUF_SIZE];
off_t pos;
};
static void random_stream_init(struct random_stream *rs)
{
rs->pos = RS_BUF_SIZE;
}
static char *random_stream_get(struct random_stream *rs, size_t count)
{
char *ret;
if (count > RS_BUF_SIZE) {
tmate_fatal("buffer too small");
}
if (rs->pos + count > RS_BUF_SIZE) {
tmate_get_random_bytes(rs->bytes, RS_BUF_SIZE);
rs->pos = 0;
}
ret = &rs->bytes[rs->pos];
rs->pos += count;
return ret;
}
extern int server_fd;
extern void server_send_exit(void);
void request_server_termination(void)
@ -139,12 +171,21 @@ static char tmate_token_digits[] = "abcdefghijklmnopqrstuvwxyz"
static char *get_random_token(void)
{
int i;
struct random_stream rs;
char *token = xmalloc(TMATE_TOKEN_LEN + 1);
int i;
unsigned char c;
random_stream_init(&rs);
for (i = 0; i < TMATE_TOKEN_LEN; i++) {
do {
c = *random_stream_get(&rs, 1);
} while (c >= NUM_DIGITS);
token[i] = tmate_token_digits[c];
}
tmate_get_random_bytes(token, TMATE_TOKEN_LEN);
for (i = 0; i < TMATE_TOKEN_LEN; i++)
token[i] = tmate_token_digits[token[i] % NUM_DIGITS];
token[i] = 0;
return token;