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Fix dtls_query_mtu so that it will always either complete with an mtu that is

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at least the minimum or it will fail.
There were some instances in dtls1_query_mtu where the final mtu can end up
being less than the minimum, i.e. where the user has set an mtu manually. This
shouldn't be allowed. Also remove dtls1_guess_mtu that, despite having
logic for guessing an mtu, was actually only ever used to work out the minimum
mtu to use.

Reviewed-by: Tim Hudson <tjh@openssl.org>
(cherry picked from commit 1620a2e49c777f31f2ce57966ae74006b48ad759)
This commit is contained in:
Matt Caswell 2014-12-01 22:18:18 +00:00
parent 05e769f269
commit 1872083ca1
1 changed files with 24 additions and 37 deletions

61
ssl/d1_both.c

@ -158,7 +158,6 @@ static unsigned char bitmask_end_values[] = {0xff, 0x01, 0x03, 0x07, 0x0f, 0x1
/* XDTLS: figure out the right values */ /* XDTLS: figure out the right values */
static const unsigned int g_probable_mtu[] = {1500, 512, 256}; static const unsigned int g_probable_mtu[] = {1500, 512, 256};
static void dtls1_guess_mtu(SSL *s);
static void dtls1_fix_message_header(SSL *s, unsigned long frag_off, static void dtls1_fix_message_header(SSL *s, unsigned long frag_off,
unsigned long frag_len); unsigned long frag_len);
static unsigned char *dtls1_write_message_header(SSL *s, static unsigned char *dtls1_write_message_header(SSL *s,
@ -224,7 +223,7 @@ void dtls1_hm_fragment_free(hm_fragment *frag)
OPENSSL_free(frag); OPENSSL_free(frag);
} }
static void dtls1_query_mtu(SSL *s) static int dtls1_query_mtu(SSL *s)
{ {
if(s->d1->link_mtu) if(s->d1->link_mtu)
{ {
@ -233,21 +232,27 @@ static void dtls1_query_mtu(SSL *s)
} }
/* AHA! Figure out the MTU, and stick to the right size */ /* AHA! Figure out the MTU, and stick to the right size */
if (s->d1->mtu < dtls1_min_mtu(s) && !(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) if (s->d1->mtu < dtls1_min_mtu(s))
{ {
s->d1->mtu = if(!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU))
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
/* I've seen the kernel return bogus numbers when it doesn't know
* (initial write), so just make sure we have a reasonable number */
if (s->d1->mtu < dtls1_min_mtu(s))
{ {
s->d1->mtu = 0; s->d1->mtu =
dtls1_guess_mtu(s); BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_QUERY_MTU, 0, NULL);
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
s->d1->mtu, NULL); /* I've seen the kernel return bogus numbers when it doesn't know
* (initial write), so just make sure we have a reasonable number */
if (s->d1->mtu < dtls1_min_mtu(s))
{
/* Set to min mtu */
s->d1->mtu = dtls1_min_mtu(s);
BIO_ctrl(SSL_get_wbio(s), BIO_CTRL_DGRAM_SET_MTU,
s->d1->mtu, NULL);
}
} }
else
return 0;
} }
return 1;
} }
/* send s->init_buf in records of type 'type' (SSL3_RT_HANDSHAKE or SSL3_RT_CHANGE_CIPHER_SPEC) */ /* send s->init_buf in records of type 'type' (SSL3_RT_HANDSHAKE or SSL3_RT_CHANGE_CIPHER_SPEC) */
@ -257,7 +262,8 @@ int dtls1_do_write(SSL *s, int type)
int curr_mtu; int curr_mtu;
unsigned int len, frag_off, mac_size, blocksize; unsigned int len, frag_off, mac_size, blocksize;
dtls1_query_mtu(s); if(!dtls1_query_mtu(s))
return -1;
#if 0 #if 0
mtu = s->d1->mtu; mtu = s->d1->mtu;
@ -368,7 +374,10 @@ int dtls1_do_write(SSL *s, int type)
BIO_CTRL_DGRAM_MTU_EXCEEDED, 0, NULL) > 0 ) BIO_CTRL_DGRAM_MTU_EXCEEDED, 0, NULL) > 0 )
{ {
if(!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU)) if(!(SSL_get_options(s) & SSL_OP_NO_QUERY_MTU))
dtls1_query_mtu(s); {
if(!dtls1_query_mtu(s))
return -1;
}
else else
return -1; return -1;
} }
@ -1318,28 +1327,6 @@ dtls1_min_mtu(SSL *s)
return dtls1_link_min_mtu()-BIO_dgram_get_mtu_overhead(SSL_get_wbio(s)); return dtls1_link_min_mtu()-BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
} }
static void
dtls1_guess_mtu(SSL *s)
{
unsigned int curr_mtu;
unsigned int i;
unsigned int mtu_ovr;
curr_mtu = s->d1->mtu;
mtu_ovr = BIO_dgram_get_mtu_overhead(SSL_get_wbio(s));
if ( curr_mtu == 0 )
{
curr_mtu = g_probable_mtu[0] - mtu_ovr;
}
else
{
for ( i = 0; i < sizeof(g_probable_mtu)/sizeof(g_probable_mtu[0]); i++)
if ( curr_mtu > g_probable_mtu[i] - mtu_ovr)
return g_probable_mtu[i] - mtu_ovr;
}
s->d1->mtu = curr_mtu;
}
void void
dtls1_get_message_header(unsigned char *data, struct hm_header_st *msg_hdr) dtls1_get_message_header(unsigned char *data, struct hm_header_st *msg_hdr)