From 934e22e81455e1e6229cbafb525a36cb6c50dbe9 Mon Sep 17 00:00:00 2001 From: "Dr. Stephen Henson" Date: Wed, 14 Apr 2010 00:17:55 +0000 Subject: [PATCH] PR: 2230 Submitted By: Robin Seggelmann Fix various DTLS fragment reassembly bugs. --- ssl/d1_both.c | 314 +++++++++++++++++++++++++++++++++++++------------- ssl/dtls1.h | 1 + 2 files changed, 232 insertions(+), 83 deletions(-) diff --git a/ssl/d1_both.c b/ssl/d1_both.c index 0242f1e4da..0855de352a 100644 --- a/ssl/d1_both.c +++ b/ssl/d1_both.c @@ -123,6 +123,36 @@ #include #include +#define RSMBLY_BITMASK_SIZE(msg_len) (((msg_len) + 7) / 8) + +#define RSMBLY_BITMASK_MARK(bitmask, start, end) { \ + if ((end) - (start) <= 8) { \ + int ii; \ + for (ii = (start); ii < (end); ii++) bitmask[((ii) >> 3)] |= (1 << ((ii) & 7)); \ + } else { \ + int ii; \ + bitmask[((start) >> 3)] |= bitmask_start_values[((start) & 7)]; \ + for (ii = (((start) >> 3) + 1); ii < ((end) >> 3); ii++) bitmask[ii] = 0xff; \ + bitmask[((end) >> 3)] |= bitmask_end_values[((end) & 7)]; \ + } } + +#define RSMBLY_BITMASK_IS_COMPLETE(bitmask, msg_len, is_complete) { \ + int ii; \ + is_complete = 1; \ + if (bitmask[((msg_len) >> 3)] != bitmask_end_values[((msg_len) & 7)]) is_complete = 0; \ + if (is_complete) for (ii = 0; ii < ((msg_len) >> 3); ii++) \ + if (bitmask[ii] != 0xff) { is_complete = 0; break; } } + +#if 0 +#define RSMBLY_BITMASK_PRINT(bitmask, msg_len) { \ + int ii; \ + printf("bitmask: "); for (ii = 0; ii < (msg_len); ii++) \ + printf("%d ", (bitmask[ii >> 3] & (1 << (ii & 7))) >> (ii & 7)); \ + printf("\n"); } +#endif + +static unsigned char bitmask_start_values[] = {0xff, 0xfe, 0xfc, 0xf8, 0xf0, 0xe0, 0xc0, 0x80}; +static unsigned char bitmask_end_values[] = {0x00, 0x01, 0x03, 0x07, 0x0f, 0x1f, 0x3f, 0x7f}; /* XDTLS: figure out the right values */ static unsigned int g_probable_mtu[] = {1500 - 28, 512 - 28, 256 - 28}; @@ -140,10 +170,11 @@ static long dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok); static hm_fragment * -dtls1_hm_fragment_new(unsigned long frag_len) +dtls1_hm_fragment_new(unsigned long frag_len, int reassembly) { hm_fragment *frag = NULL; unsigned char *buf = NULL; + unsigned char *bitmask = NULL; frag = (hm_fragment *)OPENSSL_malloc(sizeof(hm_fragment)); if ( frag == NULL) @@ -162,6 +193,21 @@ dtls1_hm_fragment_new(unsigned long frag_len) /* zero length fragment gets zero frag->fragment */ frag->fragment = buf; + /* Initialize reassembly bitmask if necessary */ + if (reassembly) + { + bitmask = (unsigned char *)OPENSSL_malloc(RSMBLY_BITMASK_SIZE(frag_len)); + if (bitmask == NULL) + { + if (buf != NULL) OPENSSL_free(buf); + OPENSSL_free(frag); + return NULL; + } + memset(bitmask, 0, RSMBLY_BITMASK_SIZE(frag_len)); + } + + frag->reassembly = bitmask; + return frag; } @@ -169,6 +215,7 @@ static void dtls1_hm_fragment_free(hm_fragment *frag) { if (frag->fragment) OPENSSL_free(frag->fragment); + if (frag->reassembly) OPENSSL_free(frag->reassembly); OPENSSL_free(frag); } @@ -363,6 +410,8 @@ long dtls1_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok) { int i, al; struct hm_header_st *msg_hdr; + unsigned char *p; + unsigned long msg_len; /* s3->tmp is used to store messages that are unexpected, caused * by the absence of an optional handshake message */ @@ -382,77 +431,55 @@ long dtls1_get_message(SSL *s, int st1, int stn, int mt, long max, int *ok) } msg_hdr = &s->d1->r_msg_hdr; - do - { - if ( msg_hdr->frag_off == 0) - { - /* s->d1->r_message_header.msg_len = 0; */ - memset(msg_hdr, 0x00, sizeof(struct hm_header_st)); - } + memset(msg_hdr, 0x00, sizeof(struct hm_header_st)); - i = dtls1_get_message_fragment(s, st1, stn, max, ok); - if ( i == DTLS1_HM_BAD_FRAGMENT || - i == DTLS1_HM_FRAGMENT_RETRY) /* bad fragment received */ - continue; - else if ( i <= 0 && !*ok) - return i; +again: + i = dtls1_get_message_fragment(s, st1, stn, max, ok); + if ( i == DTLS1_HM_BAD_FRAGMENT || + i == DTLS1_HM_FRAGMENT_RETRY) /* bad fragment received */ + goto again; + else if ( i <= 0 && !*ok) + return i; - /* Note that s->init_sum is used as a counter summing - * up fragments' lengths: as soon as they sum up to - * handshake packet length, we assume we have got all - * the fragments. Overlapping fragments would cause - * premature termination, so we don't expect overlaps. - * Well, handling overlaps would require something more - * drastic. Indeed, as it is now there is no way to - * tell if out-of-order fragment from the middle was - * the last. '>=' is the best/least we can do to control - * the potential damage caused by malformed overlaps. */ - if ((unsigned int)s->init_num >= msg_hdr->msg_len) - { - unsigned char *p = (unsigned char *)s->init_buf->data; - unsigned long msg_len = msg_hdr->msg_len; - - /* reconstruct message header as if it was - * sent in single fragment */ - *(p++) = msg_hdr->type; - l2n3(msg_len,p); - s2n (msg_hdr->seq,p); - l2n3(0,p); - l2n3(msg_len,p); - if (s->version != DTLS1_BAD_VER) { - p -= DTLS1_HM_HEADER_LENGTH; - msg_len += DTLS1_HM_HEADER_LENGTH; - } + p = (unsigned char *)s->init_buf->data; + msg_len = msg_hdr->msg_len; + + /* reconstruct message header */ + *(p++) = msg_hdr->type; + l2n3(msg_len,p); + s2n (msg_hdr->seq,p); + l2n3(0,p); + l2n3(msg_len,p); + if (s->version != DTLS1_BAD_VER) { + p -= DTLS1_HM_HEADER_LENGTH; + msg_len += DTLS1_HM_HEADER_LENGTH; + } - ssl3_finish_mac(s, p, msg_len); - if (s->msg_callback) - s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, - p, msg_len, - s, s->msg_callback_arg); - - memset(msg_hdr, 0x00, sizeof(struct hm_header_st)); - - s->d1->handshake_read_seq++; - /* we just read a handshake message from the other side: - * this means that we don't need to retransmit of the - * buffered messages. - * XDTLS: may be able clear out this - * buffer a little sooner (i.e if an out-of-order - * handshake message/record is received at the record - * layer. - * XDTLS: exception is that the server needs to - * know that change cipher spec and finished messages - * have been received by the client before clearing this - * buffer. this can simply be done by waiting for the - * first data segment, but is there a better way? */ - dtls1_clear_record_buffer(s); - - s->init_msg = s->init_buf->data + DTLS1_HM_HEADER_LENGTH; - return s->init_num; - } - else - msg_hdr->frag_off = i; - } while(1) ; + ssl3_finish_mac(s, p, msg_len); + if (s->msg_callback) + s->msg_callback(0, s->version, SSL3_RT_HANDSHAKE, + p, msg_len, + s, s->msg_callback_arg); + + memset(msg_hdr, 0x00, sizeof(struct hm_header_st)); + + s->d1->handshake_read_seq++; + /* we just read a handshake message from the other side: + * this means that we don't need to retransmit of the + * buffered messages. + * XDTLS: may be able clear out this + * buffer a little sooner (i.e if an out-of-order + * handshake message/record is received at the record + * layer. + * XDTLS: exception is that the server needs to + * know that change cipher spec and finished messages + * have been received by the client before clearing this + * buffer. this can simply be done by waiting for the + * first data segment, but is there a better way? */ + dtls1_clear_record_buffer(s); + + s->init_msg = s->init_buf->data + DTLS1_HM_HEADER_LENGTH; + return s->init_num; f_err: ssl3_send_alert(s,SSL3_AL_FATAL,al); @@ -528,6 +555,10 @@ dtls1_retrieve_buffered_fragment(SSL *s, long max, int *ok) return 0; frag = (hm_fragment *)item->data; + + /* Don't return if reassembly still in progress */ + if (frag->reassembly != NULL) + return 0; if ( s->d1->handshake_read_seq == frag->msg_header.seq) { @@ -562,6 +593,109 @@ dtls1_retrieve_buffered_fragment(SSL *s, long max, int *ok) } +static int +dtls1_reassemble_fragment(SSL *s, struct hm_header_st* msg_hdr, int *ok) + { + hm_fragment *frag = NULL; + pitem *item = NULL; + int i = -1, is_complete; + unsigned char seq64be[8]; + unsigned long frag_len = msg_hdr->frag_len, max_len; + + if ((msg_hdr->frag_off+frag_len) > msg_hdr->msg_len) + goto err; + + /* Determine maximum allowed message size. Depends on (user set) + * maximum certificate length, but 16k is minimum. + */ + if (DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH < s->max_cert_list) + max_len = s->max_cert_list; + else + max_len = DTLS1_HM_HEADER_LENGTH + SSL3_RT_MAX_ENCRYPTED_LENGTH; + + if ((msg_hdr->frag_off+frag_len) > max_len) + goto err; + + /* Try to find item in queue */ + memset(seq64be,0,sizeof(seq64be)); + seq64be[6] = (unsigned char) (msg_hdr->seq>>8); + seq64be[7] = (unsigned char) msg_hdr->seq; + item = pqueue_find(s->d1->buffered_messages, seq64be); + + if (item == NULL) + { + frag = dtls1_hm_fragment_new(msg_hdr->msg_len, 1); + if ( frag == NULL) + goto err; + memcpy(&(frag->msg_header), msg_hdr, sizeof(*msg_hdr)); + frag->msg_header.frag_len = frag->msg_header.msg_len; + frag->msg_header.frag_off = 0; + } + else + frag = (hm_fragment*) item->data; + + /* If message is already reassembled, this must be a + * retransmit and can be dropped. + */ + if (frag->reassembly == NULL) + { + unsigned char devnull [256]; + + while (frag_len) + { + i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE, + devnull, + frag_len>sizeof(devnull)?sizeof(devnull):frag_len,0); + if (i<=0) goto err; + frag_len -= i; + } + return DTLS1_HM_FRAGMENT_RETRY; + } + + /* read the body of the fragment (header has already been read */ + i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE, + frag->fragment + msg_hdr->frag_off,frag_len,0); + if (i<=0 || (unsigned long)i!=frag_len) + goto err; + + RSMBLY_BITMASK_MARK(frag->reassembly, msg_hdr->frag_off, + msg_hdr->frag_off + frag_len); + + RSMBLY_BITMASK_IS_COMPLETE(frag->reassembly, msg_hdr->msg_len, + is_complete) + + if (is_complete) + { + OPENSSL_free(frag->reassembly); + frag->reassembly = NULL; + } + + if (item == NULL) + { + memset(seq64be,0,sizeof(seq64be)); + seq64be[6] = (unsigned char)(msg_hdr->seq>>8); + seq64be[7] = (unsigned char)(msg_hdr->seq); + + item = pitem_new(seq64be, frag); + if (item == NULL) + { + goto err; + i = -1; + } + + pqueue_insert(s->d1->buffered_messages, item); + } + + return DTLS1_HM_FRAGMENT_RETRY; + +err: + if (frag != NULL) dtls1_hm_fragment_free(frag); + if (item != NULL) OPENSSL_free(item); + *ok = 0; + return i; + } + + static int dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok) { @@ -579,7 +713,13 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok) seq64be[6] = (unsigned char) (msg_hdr->seq>>8); seq64be[7] = (unsigned char) msg_hdr->seq; item = pqueue_find(s->d1->buffered_messages, seq64be); - + + /* If we already have an entry and this one is a fragment, + * don't discard it and rather try to reassemble it. + */ + if (item != NULL && frag_len < msg_hdr->msg_len) + item = NULL; + /* Discard the message if sequence number was already there, is * too far in the future, already in the queue or if we received * a FINISHED before the SERVER_HELLO, which then must be a stale @@ -600,20 +740,25 @@ dtls1_process_out_of_seq_message(SSL *s, struct hm_header_st* msg_hdr, int *ok) frag_len -= i; } } - - if (frag_len) + else { - frag = dtls1_hm_fragment_new(frag_len); + if (frag_len && frag_len < msg_hdr->msg_len) + return dtls1_reassemble_fragment(s, msg_hdr, ok); + + frag = dtls1_hm_fragment_new(frag_len, 0); if ( frag == NULL) goto err; memcpy(&(frag->msg_header), msg_hdr, sizeof(*msg_hdr)); - /* read the body of the fragment (header has already been read */ - i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE, - frag->fragment,frag_len,0); - if (i<=0 || (unsigned long)i!=frag_len) - goto err; + if (frag_len) + { + /* read the body of the fragment (header has already been read */ + i = s->method->ssl_read_bytes(s,SSL3_RT_HANDSHAKE, + frag->fragment,frag_len,0); + if (i<=0 || (unsigned long)i!=frag_len) + goto err; + } memset(seq64be,0,sizeof(seq64be)); seq64be[6] = (unsigned char)(msg_hdr->seq>>8); @@ -640,14 +785,14 @@ static long dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) { unsigned char wire[DTLS1_HM_HEADER_LENGTH]; - unsigned long l, frag_off, frag_len; + unsigned long len, frag_off, frag_len; int i,al; struct hm_header_st msg_hdr; /* see if we have the required fragment already */ if ((frag_len = dtls1_retrieve_buffered_fragment(s,max,ok)) || *ok) { - if (*ok) s->init_num += frag_len; + if (*ok) s->init_num = frag_len; return frag_len; } @@ -672,10 +817,13 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) if ( msg_hdr.seq != s->d1->handshake_read_seq) return dtls1_process_out_of_seq_message(s, &msg_hdr, ok); - l = msg_hdr.msg_len; + 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); + if (!s->server && s->d1->r_msg_hdr.frag_off == 0 && wire[0] == SSL3_MT_HELLO_REQUEST) { @@ -735,7 +883,7 @@ dtls1_get_message_fragment(SSL *s, int st1, int stn, long max, int *ok) * s->init_buf->data, but as a counter summing up fragments' * lengths: as soon as they sum up to handshake packet * length, we assume we have got all the fragments. */ - s->init_num += frag_len; + s->init_num = frag_len; return frag_len; f_err: @@ -1010,7 +1158,7 @@ dtls1_buffer_message(SSL *s, int is_ccs) * been serialized */ OPENSSL_assert(s->init_off == 0); - frag = dtls1_hm_fragment_new(s->init_num); + frag = dtls1_hm_fragment_new(s->init_num, 0); memcpy(frag->fragment, s->init_buf->data, s->init_num); diff --git a/ssl/dtls1.h b/ssl/dtls1.h index 472fe91f13..448c254be3 100644 --- a/ssl/dtls1.h +++ b/ssl/dtls1.h @@ -169,6 +169,7 @@ typedef struct hm_fragment_st { struct hm_header_st msg_header; unsigned char *fragment; + unsigned char *reassembly; } hm_fragment; typedef struct dtls1_state_st -- 2.40.0