HEARTBLEED

Created by Dennis / @cdepillabout

問題のコード

int dtls1_process_heartbeat(SSL *s)
{
    unsigned char *p = &s->s3->rrec.data[0], *pl;
    unsigned short hbtype;
    unsigned int payload;

    hbtype = *p++;
    n2s(p, payload);
    pl = p;
    ...
    buffer = OPENSSL_malloc(1 + 2 + payload);
    bp = buffer;

    *bp++ = TLS1_HB_RESPONSE;
    s2n(payload, bp);
    memcpy(bp, pl, payload);
    bp += payload;

    r = dtls1_write_bytes(s, TLS1_RT_HEARTBEAT, buffer,
            1 + 2 + payload);
    ...
}

リクエストってどうなっている？

int dtls1_process_heartbeat(SSL *s)
{
    unsigned char *p = &s->s3->rrec.data[0], *pl;
    unsigned short hbtype;
    unsigned int payload;
}

リクエストの構成

チェック無し

    unsigned int payload;

    hbtype = *p++;
    n2s(p, payload);
    pl = p;

リクエストの構成

大きすぎるmalloc

    buffer = OPENSSL_malloc(1 + 2 + payload);
    bp = buffer;

リクエストの構成

memcpyあるある

    unsigned char *p = &s->s3->rrec.data[0], *pl;
    ...
    hbtype = *p++;
    n2s(p, payload);
    pl = p;
    ...
    *bp++ = TLS1_HB_RESPONSE;
    s2n(payload, bp);
    memcpy(bp, pl, payload);
    bp += payload;

リクエストの構成

Cが怖い

fin.