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Add extra checks for odd-length EC curve lists.

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Odd-length lists should be rejected everywhere upon parsing. Nevertheless,
be extra careful and add guards against off-by-one reads.

Also, drive-by replace inexplicable double-negation with an explicit comparison.

Reviewed-by: Matt Caswell <matt@openssl.org>
This commit is contained in:
Emilia Kasper 2014-12-01 16:55:55 +01:00
parent 33d5ba8629
commit 740580c2b2
3 changed files with 111 additions and 74 deletions
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1
ssl/ssl.h
View File

@ -2727,6 +2727,7 @@ void ERR_load_SSL_strings(void);
#define SSL_F_TLS1_CHECK_SERVERHELLO_TLSEXT 274
#define SSL_F_TLS1_ENC 210
#define SSL_F_TLS1_EXPORT_KEYING_MATERIAL 314
#define SSL_F_TLS1_GET_CURVELIST 338
#define SSL_F_TLS1_HEARTBEAT 315
#define SSL_F_TLS1_PREPARE_CLIENTHELLO_TLSEXT 275
#define SSL_F_TLS1_PREPARE_SERVERHELLO_TLSEXT 276

2
ssl/ssl_err.c
View File

@ -80,6 +80,7 @@ static ERR_STRING_DATA SSL_str_functs[]=
{ERR_FUNC(SSL_F_DTLS1_CHECK_TIMEOUT_NUM), "dtls1_check_timeout_num"},
{ERR_FUNC(SSL_F_DTLS1_CLIENT_HELLO), "dtls1_client_hello"},
{ERR_FUNC(SSL_F_DTLS1_CONNECT), "dtls1_connect"},
{ERR_FUNC(SSL_F_DTLS1_ENC), "DTLS1_ENC"},
{ERR_FUNC(SSL_F_DTLS1_GET_HELLO_VERIFY), "DTLS1_GET_HELLO_VERIFY"},
{ERR_FUNC(SSL_F_DTLS1_GET_MESSAGE), "dtls1_get_message"},
{ERR_FUNC(SSL_F_DTLS1_GET_MESSAGE_FRAGMENT), "DTLS1_GET_MESSAGE_FRAGMENT"},
@ -267,6 +268,7 @@ static ERR_STRING_DATA SSL_str_functs[]=
{ERR_FUNC(SSL_F_TLS1_CHECK_SERVERHELLO_TLSEXT), "TLS1_CHECK_SERVERHELLO_TLSEXT"},
{ERR_FUNC(SSL_F_TLS1_ENC), "tls1_enc"},
{ERR_FUNC(SSL_F_TLS1_EXPORT_KEYING_MATERIAL), "tls1_export_keying_material"},
{ERR_FUNC(SSL_F_TLS1_GET_CURVELIST), "TLS1_GET_CURVELIST"},
{ERR_FUNC(SSL_F_TLS1_HEARTBEAT), "tls1_heartbeat"},
{ERR_FUNC(SSL_F_TLS1_PREPARE_CLIENTHELLO_TLSEXT), "TLS1_PREPARE_CLIENTHELLO_TLSEXT"},
{ERR_FUNC(SSL_F_TLS1_PREPARE_SERVERHELLO_TLSEXT), "TLS1_PREPARE_SERVERHELLO_TLSEXT"},

182
ssl/t1_lib.c
View File

@ -384,44 +384,69 @@ int tls1_ec_nid2curve_id(int nid)
return 0;
}
}
/* Get curves list, if "sess" is set return client curves otherwise
* preferred list
/*
* Get curves list, if "sess" is set return client curves otherwise
* preferred list.
* Sets |num_curves| to the number of curves in the list, i.e.,
* the length of |pcurves| is 2 * num_curves.
* Returns 1 on success and 0 if the client curves list has invalid format.
* The latter indicates an internal error: we should not be accepting such
* lists in the first place.
* TODO(emilia): we should really be storing the curves list in explicitly
* parsed form instead. (However, this would affect binary compatibility
* so cannot happen in the 1.0.x series.)
*/
static void tls1_get_curvelist(SSL *s, int sess,
static int tls1_get_curvelist(SSL *s, int sess,
const unsigned char **pcurves,
size_t *pcurveslen)
size_t *num_curves)
{
size_t pcurveslen = 0;
if (sess)
{
*pcurves = s->session->tlsext_ellipticcurvelist;
*pcurveslen = s->session->tlsext_ellipticcurvelist_length;
return;
pcurveslen = s->session->tlsext_ellipticcurvelist_length;
}
/* For Suite B mode only include P-256, P-384 */
switch (tls1_suiteb(s))
else
{
case SSL_CERT_FLAG_SUITEB_128_LOS:
*pcurves = suiteb_curves;
*pcurveslen = sizeof(suiteb_curves);
break;
/* For Suite B mode only include P-256, P-384 */
switch (tls1_suiteb(s))
{
case SSL_CERT_FLAG_SUITEB_128_LOS:
*pcurves = suiteb_curves;
pcurveslen = sizeof(suiteb_curves);
break;
case SSL_CERT_FLAG_SUITEB_128_LOS_ONLY:
*pcurves = suiteb_curves;
*pcurveslen = 2;
break;
case SSL_CERT_FLAG_SUITEB_128_LOS_ONLY:
*pcurves = suiteb_curves;
pcurveslen = 2;
break;
case SSL_CERT_FLAG_SUITEB_192_LOS:
*pcurves = suiteb_curves + 2;
*pcurveslen = 2;
break;
default:
*pcurves = s->tlsext_ellipticcurvelist;
*pcurveslen = s->tlsext_ellipticcurvelist_length;
case SSL_CERT_FLAG_SUITEB_192_LOS:
*pcurves = suiteb_curves + 2;
pcurveslen = 2;
break;
default:
*pcurves = s->tlsext_ellipticcurvelist;
pcurveslen = s->tlsext_ellipticcurvelist_length;
}
if (!*pcurves)
{
*pcurves = eccurves_default;
pcurveslen = sizeof(eccurves_default);
}
}
if (!*pcurves)
/* We do not allow odd length arrays to enter the system. */
if (pcurveslen & 1)
{
*pcurves = eccurves_default;
*pcurveslen = sizeof(eccurves_default);
SSLerr(SSL_F_TLS1_GET_CURVELIST, ERR_R_INTERNAL_ERROR);
*num_curves = 0;
return 0;
}
else
{
*num_curves = pcurveslen / 2;
return 1;
}
}
@ -446,7 +471,7 @@ static int tls_curve_allowed(SSL *s, const unsigned char *curve, int op)
int tls1_check_curve(SSL *s, const unsigned char *p, size_t len)
{
const unsigned char *curves;
size_t curveslen, i;
size_t num_curves, i;
unsigned int suiteb_flags = tls1_suiteb(s);
if (len != 3 || p[0] != NAMED_CURVE_TYPE)
return 0;
@ -469,8 +494,9 @@ int tls1_check_curve(SSL *s, const unsigned char *p, size_t len)
else /* Should never happen */
return 0;
}
tls1_get_curvelist(s, 0, &curves, &curveslen);
for (i = 0; i < curveslen; i += 2, curves += 2)
if (!tls1_get_curvelist(s, 0, &curves, &num_curves))
return 0;
for (i = 0; i < num_curves; i++, curves += 2)
{
if (p[1] == curves[0] && p[2] == curves[1])
return tls_curve_allowed(s, p + 1, SSL_SECOP_CURVE_CHECK);
@ -486,7 +512,7 @@ int tls1_check_curve(SSL *s, const unsigned char *p, size_t len)
int tls1_shared_curve(SSL *s, int nmatch)
{
const unsigned char *pref, *supp;
size_t preflen, supplen, i, j;
size_t num_pref, num_supp, i, j;
int k;
/* Can't do anything on client side */
if (s->server == 0)
@ -510,17 +536,21 @@ int tls1_shared_curve(SSL *s, int nmatch)
/* If not Suite B just return first preference shared curve */
nmatch = 0;
}
tls1_get_curvelist(s, !!(s->options & SSL_OP_CIPHER_SERVER_PREFERENCE),
&supp, &supplen);
tls1_get_curvelist(s, !(s->options & SSL_OP_CIPHER_SERVER_PREFERENCE),
&pref, &preflen);
preflen /= 2;
supplen /= 2;
/*
* Avoid truncation. tls1_get_curvelist takes an int
* but s->options is a long...
*/
if (!tls1_get_curvelist(s, (s->options & SSL_OP_CIPHER_SERVER_PREFERENCE) != 0,
&supp, &num_supp))
return 0;
if(!tls1_get_curvelist(s, !(s->options & SSL_OP_CIPHER_SERVER_PREFERENCE),
&pref, &num_pref))
return 0;
k = 0;
for (i = 0; i < preflen; i++, pref+=2)
for (i = 0; i < num_pref; i++, pref+=2)
{
const unsigned char *tsupp = supp;
for (j = 0; j < supplen; j++, tsupp+=2)
for (j = 0; j < num_supp; j++, tsupp+=2)
{
if (pref[0] == tsupp[0] && pref[1] == tsupp[1])
{
@ -675,22 +705,22 @@ static int tls1_set_ec_id(unsigned char *curve_id, unsigned char *comp_id,
static int tls1_check_ec_key(SSL *s,
unsigned char *curve_id, unsigned char *comp_id)
{
const unsigned char *p;
size_t plen, i;
const unsigned char *pformats, *pcurves;
size_t num_formats, num_curves, i;
int j;
/* If point formats extension present check it, otherwise everything
* is supported (see RFC4492).
*/
if (comp_id && s->session->tlsext_ecpointformatlist)
{
p = s->session->tlsext_ecpointformatlist;
plen = s->session->tlsext_ecpointformatlist_length;
for (i = 0; i < plen; i++, p++)
pformats = s->session->tlsext_ecpointformatlist;
num_formats = s->session->tlsext_ecpointformatlist_length;
for (i = 0; i < num_formats; i++, pformats++)
{
if (*comp_id == *p)
if (*comp_id == *pformats)
break;
}
if (i == plen)
if (i == num_formats)
return 0;
}
if (!curve_id)
@ -698,13 +728,15 @@ static int tls1_check_ec_key(SSL *s,
/* Check curve is consistent with client and server preferences */
for (j = 0; j <= 1; j++)
{
tls1_get_curvelist(s, j, &p, &plen);
for (i = 0; i < plen; i+=2, p+=2)
if (!tls1_get_curvelist(s, j, &pcurves, &num_curves))
return 0;
for (i = 0; i < num_curves; i++, pcurves += 2)
{
if (p[0] == curve_id[0] && p[1] == curve_id[1])
if (pcurves[0] == curve_id[0] &&
pcurves[1] == curve_id[1])
break;
}
if (i == plen)
if (i == num_curves)
return 0;
/* For clients can only check sent curve list */
if (!s->server)
@ -714,23 +746,23 @@ static int tls1_check_ec_key(SSL *s,
}
static void tls1_get_formatlist(SSL *s, const unsigned char **pformats,
size_t *pformatslen)
size_t *num_formats)
{
/* If we have a custom point format list use it otherwise
* use default */
if (s->tlsext_ecpointformatlist)
{
*pformats = s->tlsext_ecpointformatlist;
*pformatslen = s->tlsext_ecpointformatlist_length;
*num_formats = s->tlsext_ecpointformatlist_length;
}
else
{
*pformats = ecformats_default;
/* For Suite B we don't support char2 fields */
if (tls1_suiteb(s))
*pformatslen = sizeof(ecformats_default) - 1;
*num_formats = sizeof(ecformats_default) - 1;
else
*pformatslen = sizeof(ecformats_default);
*num_formats = sizeof(ecformats_default);
}
}
@ -1244,34 +1276,36 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf, unsigned c
{
/* Add TLS extension ECPointFormats to the ClientHello message */
long lenmax;
const unsigned char *plist;
size_t plistlen;
const unsigned char *pcurves, *pformats;
size_t num_curves, num_formats, curves_list_len;
size_t i;
unsigned char *etmp;
tls1_get_formatlist(s, &plist, &plistlen);
tls1_get_formatlist(s, &pformats, &num_formats);
if ((lenmax = limit - ret - 5) < 0) return NULL;
if (plistlen > (size_t)lenmax) return NULL;
if (plistlen > 255)
if (num_formats > (size_t)lenmax) return NULL;
if (num_formats > 255)
{
SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
return NULL;
}
s2n(TLSEXT_TYPE_ec_point_formats,ret);
s2n(plistlen + 1,ret);
*(ret++) = (unsigned char)plistlen ;
memcpy(ret, plist, plistlen);
ret+=plistlen;
/* The point format list has 1-byte length. */
s2n(num_formats + 1,ret);
*(ret++) = (unsigned char)num_formats ;
memcpy(ret, pformats, num_formats);
ret+=num_formats;
/* Add TLS extension EllipticCurves to the ClientHello message */
plist = s->tlsext_ellipticcurvelist;
tls1_get_curvelist(s, 0, &plist, &plistlen);
pcurves = s->tlsext_ellipticcurvelist;
if (!tls1_get_curvelist(s, 0, &pcurves, &num_curves))
return NULL;
if ((lenmax = limit - ret - 6) < 0) return NULL;
if (plistlen > (size_t)lenmax) return NULL;
if (plistlen > 65532)
if (num_curves > (size_t)lenmax / 2) return NULL;
if (num_curves > 65532 / 2)
{
SSLerr(SSL_F_SSL_ADD_CLIENTHELLO_TLSEXT, ERR_R_INTERNAL_ERROR);
return NULL;
@ -1281,20 +1315,20 @@ unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf, unsigned c
s2n(TLSEXT_TYPE_elliptic_curves,ret);
etmp = ret + 4;
/* Copy curve ID if supported */
for (i = 0; i < plistlen; i += 2, plist += 2)
for (i = 0; i < num_curves; i++, pcurves += 2)
{
if (tls_curve_allowed(s, plist, SSL_SECOP_CURVE_SUPPORTED))
if (tls_curve_allowed(s, pcurves, SSL_SECOP_CURVE_SUPPORTED))
{
*etmp++ = plist[0];
*etmp++ = plist[1];
*etmp++ = pcurves[0];
*etmp++ = pcurves[1];
}
}
plistlen = etmp - ret - 4;
curves_list_len = etmp - ret - 4;
s2n(plistlen + 2, ret);
s2n(plistlen, ret);
ret+=plistlen;
s2n(curves_list_len + 2, ret);
s2n(curves_list_len, ret);
ret += curves_list_len;
}
#endif /* OPENSSL_NO_EC */