Commit 533814c6 authored by Emilia Kasper's avatar Emilia Kasper
Browse files

Add extra checks for odd-length EC curve lists. 



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: default avatarMatt Caswell <matt@openssl.org>
parent b32474a4

ssl/ssl.h

+1 −0
Original line number Diff line number Diff line
@@ -2688,6 +2688,7 @@ 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

ssl/ssl_err.c

+1 −0
Original line number Diff line number Diff line
@@ -292,6 +292,7 @@ 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"},

ssl/t1_lib.c

+114 −79
Original line number Diff line number Diff line
@@ -429,39 +429,50 @@ 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;

		}

	else

		{

		/* 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);

			pcurveslen = sizeof(suiteb_curves);

			break;



		case SSL_CERT_FLAG_SUITEB_128_LOS_ONLY:

			*pcurves = suiteb_curves;

		*pcurveslen = 2;

			pcurveslen = 2;

			break;



		case SSL_CERT_FLAG_SUITEB_192_LOS:

			*pcurves = suiteb_curves + 2;

		*pcurveslen = 2;

			pcurveslen = 2;

			break;

		default:

			*pcurves = s->tlsext_ellipticcurvelist;

		*pcurveslen = s->tlsext_ellipticcurvelist_length;

			pcurveslen = s->tlsext_ellipticcurvelist_length;

			}

		if (!*pcurves)

			{
@@ -470,18 +481,33 @@ static void tls1_get_curvelist(SSL *s, int sess, 
				{

				*pcurves = fips_curves_default;

				*pcurveslen = sizeof(fips_curves_default);

			return;

				}

			else

#endif

				{

				*pcurves = eccurves_default;

		*pcurveslen = sizeof(eccurves_default);

				pcurveslen = sizeof(eccurves_default);

				}

			}

		}

	/* We do not allow odd length arrays to enter the system. */

	if (pcurveslen & 1)

		{

		SSLerr(SSL_F_TLS1_GET_CURVELIST, ERR_R_INTERNAL_ERROR);

		*num_curves = 0;

		return 0;

		}

	else

		{

		*num_curves = pcurveslen / 2;

		return 1;

		}

	}

/* Check a curve is one of our preferences */

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;
@@ -504,8 +530,9 @@ 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 1;
@@ -521,7 +548,7 @@ 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)
@@ -545,17 +572,21 @@ 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])

				{
@@ -733,22 +764,22 @@ 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)
@@ -756,13 +787,15 @@ 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)
@@ -772,23 +805,23 @@ 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);

		}

	}
@@ -1317,42 +1350,44 @@ 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;



		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;

			}

		

		curves_list_len = 2*num_curves;

		s2n(TLSEXT_TYPE_elliptic_curves,ret);

		s2n(plistlen + 2, ret);

		s2n(plistlen, ret);

		memcpy(ret, plist, plistlen);

		ret+=plistlen;

		s2n(curves_list_len + 2, ret);

		s2n(curves_list_len, ret);

		memcpy(ret, pcurves, curves_list_len);

		ret+=curves_list_len;

		}

#endif /* OPENSSL_NO_EC */