From d46de4ce483d684ecbec2aa967618f06865ae74a Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Mon, 1 Jun 2015 17:25:29 +0100 Subject: [PATCH] DTLS handshake message fragments musn't span packets It should not be possible for DTLS message fragments to span multiple packets. However previously if the message header fitted exactly into one packet, and the fragment body was in the next packet then this would work. Obviously this would fail if packets get re-ordered mid-flight. Reviewed-by: Tim Hudson --- ssl/d1_both.c | 26 ++++++++++++++++++-------- 1 file changed, 18 insertions(+), 8 deletions(-) diff --git a/ssl/d1_both.c b/ssl/d1_both.c index c5b2e99669..8dd8ea33ca 100644 --- a/ssl/d1_both.c +++ b/ssl/d1_both.c @@ -875,6 +875,20 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) /* parse the message fragment header */ dtls1_get_message_header(wire, &msg_hdr); + len = msg_hdr.msg_len; + frag_off = msg_hdr.frag_off; + frag_len = msg_hdr.frag_len; + + /* + * We must have at least frag_len bytes left in the record to be read. + * Fragments must not span records. + */ + if (frag_len > s->s3->rrec.length) { + al = SSL3_AD_ILLEGAL_PARAMETER; + SSLerr(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT, SSL_R_BAD_LENGTH); + goto f_err; + } + /* * if this is a future (or stale) message it gets buffered * (or dropped)--no further processing at this time @@ -885,10 +899,6 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) && !(s->d1->listen && msg_hdr.seq == 1)) return dtls1_process_out_of_seq_message(s, &msg_hdr, ok); - len = msg_hdr.msg_len; - frag_off = msg_hdr.frag_off; - frag_len = msg_hdr.frag_len; - if (frag_len && frag_len < len) return dtls1_reassemble_fragment(s, &msg_hdr, ok); @@ -919,17 +929,16 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) if ((al = dtls1_preprocess_fragment(s, &msg_hdr, max))) goto f_err; - /* XDTLS: ressurect this when restart is in place */ - s->state = stn; - if (frag_len > 0) { unsigned char *p = (unsigned char *)s->init_buf->data + DTLS1_HM_HEADER_LENGTH; i = s->method->ssl_read_bytes(s, SSL3_RT_HANDSHAKE, &p[frag_off], frag_len, 0); + /* - * XDTLS: fix this--message fragments cannot span multiple packets + * This shouldn't ever fail due to NBIO because we already checked + * that we have enough data in the record */ if (i <= 0) { s->rwstate = SSL_READING; @@ -950,6 +959,7 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) } *ok = 1; + s->state = stn; /* * Note that s->init_num is *not* used as current offset in -- 2.25.1