From 2ad226e88bee97847496e542d63c67997d5beda6 Mon Sep 17 00:00:00 2001 From: Matt Caswell Date: Tue, 3 Nov 2015 14:45:07 +0000 Subject: [PATCH] Fix DTLS handshake fragment retries If using DTLS and NBIO then if a second or subsequent handshake message fragment hits a retry, then the retry attempt uses the wrong fragment offset value. This commit restores the fragment offset from the last attempt. Reviewed-by: Richard Levitte --- ssl/statem/statem_dtls.c | 64 +++++++++++++++++++++++++++------------- 1 file changed, 44 insertions(+), 20 deletions(-) diff --git a/ssl/statem/statem_dtls.c b/ssl/statem/statem_dtls.c index 6d73659df6..44c5c1322f 100644 --- a/ssl/statem/statem_dtls.c +++ b/ssl/statem/statem_dtls.c @@ -252,6 +252,40 @@ int dtls1_do_write(SSL *s, int type) frag_off = 0; /* s->init_num shouldn't ever be < 0...but just in case */ while (s->init_num > 0) { + if (type == SSL3_RT_HANDSHAKE && s->init_off != 0) { + /* We must be writing a fragment other than the first one */ + + if (frag_off > 0) { + /* This is the first attempt at writing out this fragment */ + + if (s->init_off <= DTLS1_HM_HEADER_LENGTH) { + /* + * Each fragment that was already sent must at least have + * contained the message header plus one other byte. + * Therefore |init_off| must have progressed by at least + * |DTLS1_HM_HEADER_LENGTH + 1| bytes. If not something went + * wrong. + */ + return -1; + } + + /* + * Adjust |init_off| and |init_num| to allow room for a new + * message header for this fragment. + */ + s->init_off -= DTLS1_HM_HEADER_LENGTH; + s->init_num += DTLS1_HM_HEADER_LENGTH; + } else { + /* + * We must have been called again after a retry so use the + * fragment offset from our last attempt. We do not need + * to adjust |init_off| and |init_num| as above, because + * that should already have been done before the retry. + */ + frag_off = s->d1->w_msg_hdr.frag_off; + } + } + used_len = BIO_wpending(SSL_get_wbio(s)) + DTLS1_RT_HEADER_LENGTH + mac_size + blocksize; if (s->d1->mtu > used_len) @@ -291,25 +325,6 @@ int dtls1_do_write(SSL *s, int type) * XDTLS: this function is too long. split out the CCS part */ if (type == SSL3_RT_HANDSHAKE) { - if (s->init_off != 0) { - OPENSSL_assert(s->init_off > DTLS1_HM_HEADER_LENGTH); - s->init_off -= DTLS1_HM_HEADER_LENGTH; - s->init_num += DTLS1_HM_HEADER_LENGTH; - - /* - * We just checked that s->init_num > 0 so this cast should - * be safe - */ - if (((unsigned int)s->init_num) > curr_mtu) - len = curr_mtu; - else - len = s->init_num; - } - - /* Shouldn't ever happen */ - if (len > INT_MAX) - len = INT_MAX; - if (len < DTLS1_HM_HEADER_LENGTH) { /* * len is so small that we really can't do anything sensible @@ -397,7 +412,16 @@ int dtls1_do_write(SSL *s, int type) } s->init_off += ret; s->init_num -= ret; - frag_off += (ret -= DTLS1_HM_HEADER_LENGTH); + ret -= DTLS1_HM_HEADER_LENGTH; + frag_off += ret; + + /* + * We save the fragment offset for the next fragment so we have it + * available in case of an IO retry. We don't know the length of the + * next fragment yet so just set that to 0 for now. It will be + * updated again later. + */ + dtls1_fix_message_header(s, frag_off, 0); } } return (0); -- 2.25.1