TLS extension limit check fixes.
Fix limit checks in ssl_add_clienthello_tlsext and
ssl_add_serverhello_tlsext.
Some of the limit checks reference p rather than ret. p is the original
buffer position, not the current one. Fix those and rename p to orig so
it's clearer.
diff --git a/ssl/s23_clnt.c b/ssl/s23_clnt.c
index e36d932..f2bbabc 100644
--- a/ssl/s23_clnt.c
+++ b/ssl/s23_clnt.c
@@ -477,7 +477,10 @@
{
/* create Client Hello in SSL 3.0/TLS 1.0 format */
- /* do the record header (5 bytes) and handshake message header (4 bytes) last */
+ /* do the record header (5 bytes) and handshake message
+ * header (4 bytes) last. Note: the final argument to
+ * ssl_add_clienthello_tlsext below depends on the size
+ * of this prefix. */
d = p = &(buf[9]);
*(p++) = version_major;
@@ -520,7 +523,11 @@
OPENSSL_PUT_ERROR(SSL, ssl23_client_hello, SSL_R_CLIENTHELLO_TLSEXT);
return -1;
}
- if ((p = ssl_add_clienthello_tlsext(s, p, buf+SSL3_RT_MAX_PLAIN_LENGTH)) == NULL)
+
+ /* The buffer includes the 5 byte record header, so
+ * subtract it to compute hlen for
+ * ssl_add_clienthello_tlsext. */
+ if ((p = ssl_add_clienthello_tlsext(s, p, buf+SSL3_RT_MAX_PLAIN_LENGTH, p-buf-5)) == NULL)
{
OPENSSL_PUT_ERROR(SSL, ssl23_client_hello, ERR_R_INTERNAL_ERROR);
return -1;
diff --git a/ssl/s3_clnt.c b/ssl/s3_clnt.c
index 48d4a55..64d3094 100644
--- a/ssl/s3_clnt.c
+++ b/ssl/s3_clnt.c
@@ -794,7 +794,9 @@
ssl_fill_hello_random(s, 0, p,
sizeof(s->s3->client_random));
- /* Do the message type and length last */
+ /* Do the message type and length last.
+ * Note: the final argument to ssl_add_clienthello_tlsext below
+ * depends on the size of this prefix. */
d=p= ssl_handshake_start(s);
/* version indicates the negotiated version: for example from
@@ -899,7 +901,7 @@
OPENSSL_PUT_ERROR(SSL, ssl3_client_hello, SSL_R_CLIENTHELLO_TLSEXT);
goto err;
}
- if ((p = ssl_add_clienthello_tlsext(s, p, buf+SSL3_RT_MAX_PLAIN_LENGTH)) == NULL)
+ if ((p = ssl_add_clienthello_tlsext(s, p, buf+SSL3_RT_MAX_PLAIN_LENGTH, p-buf)) == NULL)
{
OPENSSL_PUT_ERROR(SSL, ssl3_client_hello, ERR_R_INTERNAL_ERROR);
goto err;
diff --git a/ssl/ssl_locl.h b/ssl/ssl_locl.h
index ad938b6..d61a03c 100644
--- a/ssl/ssl_locl.h
+++ b/ssl/ssl_locl.h
@@ -1298,8 +1298,8 @@
const unsigned char *l1, size_t l1len,
const unsigned char *l2, size_t l2len,
int nmatch);
-unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned char *limit);
-unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *p, unsigned char *limit);
+unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf, unsigned char *limit, size_t header_len);
+unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf, unsigned char *limit);
int ssl_parse_clienthello_tlsext(SSL *s, unsigned char **data, unsigned char *d, int n);
int ssl_check_clienthello_tlsext_late(SSL *s);
int ssl_parse_serverhello_tlsext(SSL *s, unsigned char **data, unsigned char *d, int n);
diff --git a/ssl/t1_lib.c b/ssl/t1_lib.c
index ec4137f..726ec51 100644
--- a/ssl/t1_lib.c
+++ b/ssl/t1_lib.c
@@ -1098,10 +1098,14 @@
return 0;
}
-unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *p, unsigned char *limit)
+/* header_len is the length of the ClientHello header written so far, used to
+ * compute padding. It does not include the record header. Pass 0 if no padding
+ * is to be done. */
+unsigned char *ssl_add_clienthello_tlsext(SSL *s, unsigned char *buf, unsigned char *limit, size_t header_len)
{
int extdatalen=0;
- unsigned char *ret = p;
+ unsigned char *ret = buf;
+ unsigned char *orig = buf;
#ifndef OPENSSL_NO_EC
/* See if we support any ECC ciphersuites */
int using_ecc = 0;
@@ -1130,7 +1134,7 @@
/* don't add extensions for SSLv3 unless doing secure renegotiation */
if (s->client_version == SSL3_VERSION
&& !s->s3->send_connection_binding)
- return p;
+ return orig;
ret+=2;
@@ -1179,7 +1183,7 @@
return NULL;
}
- if((limit - p - 4 - el) < 0) return NULL;
+ if((limit - ret - 4 - el) < 0) return NULL;
s2n(TLSEXT_TYPE_renegotiate,ret);
s2n(el,ret);
@@ -1420,7 +1424,7 @@
ssl_add_clienthello_use_srtp_ext(s, 0, &el, 0);
- if((limit - p - 4 - el) < 0) return NULL;
+ if((limit - ret - 4 - el) < 0) return NULL;
s2n(TLSEXT_TYPE_use_srtp,ret);
s2n(el,ret);
@@ -1489,44 +1493,43 @@
#ifdef TLSEXT_TYPE_padding
/* Add padding to workaround bugs in F5 terminators.
- * See https://tools.ietf.org/html/draft-agl-tls-padding-02
+ * See https://tools.ietf.org/html/draft-agl-tls-padding-03
*
* NB: because this code works out the length of all existing
- * extensions it MUST always appear last.
- */
- {
- int hlen = ret - (unsigned char *)s->init_buf->data;
- /* The code in s23_clnt.c to build ClientHello messages includes the
- * 5-byte record header in the buffer, while the code in s3_clnt.c does
- * not. */
- if (s->state == SSL23_ST_CW_CLNT_HELLO_A)
- hlen -= 5;
- if (hlen > 0xff && hlen < 0x200)
+ * extensions it MUST always appear last. */
+ if (header_len > 0)
{
- hlen = 0x200 - hlen;
- if (hlen >= 4)
- hlen -= 4;
- else
- hlen = 0;
+ header_len += ret - orig;
+ if (header_len > 0xff && header_len < 0x200)
+ {
+ size_t padding_len = 0x200 - header_len;
+ if (padding_len >= 4)
+ padding_len -= 4;
+ else
+ padding_len = 0;
+ if (limit - ret - 4 - (long)padding_len < 0)
+ return NULL;
- s2n(TLSEXT_TYPE_padding, ret);
- s2n(hlen, ret);
- memset(ret, 0, hlen);
- ret += hlen;
+ s2n(TLSEXT_TYPE_padding, ret);
+ s2n(padding_len, ret);
+ memset(ret, 0, padding_len);
+ ret += padding_len;
+ }
}
#endif
- if ((extdatalen = ret-p-2) == 0)
- return p;
+ if ((extdatalen = ret-orig-2)== 0)
+ return orig;
- s2n(extdatalen,p);
+ s2n(extdatalen, orig);
return ret;
}
-unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *p, unsigned char *limit)
+unsigned char *ssl_add_serverhello_tlsext(SSL *s, unsigned char *buf, unsigned char *limit)
{
int extdatalen=0;
- unsigned char *ret = p;
+ unsigned char *orig = buf;
+ unsigned char *ret = buf;
#ifndef OPENSSL_NO_NEXTPROTONEG
int next_proto_neg_seen;
#endif
@@ -1538,7 +1541,7 @@
#endif
/* don't add extensions for SSLv3, unless doing secure renegotiation */
if (s->version == SSL3_VERSION && !s->s3->send_connection_binding)
- return p;
+ return orig;
ret+=2;
if (ret>=limit) return NULL; /* this really never occurs, but ... */
@@ -1561,7 +1564,7 @@
return NULL;
}
- if((limit - p - 4 - el) < 0) return NULL;
+ if((limit - ret - 4 - el) < 0) return NULL;
s2n(TLSEXT_TYPE_renegotiate,ret);
s2n(el,ret);
@@ -1642,7 +1645,7 @@
ssl_add_serverhello_use_srtp_ext(s, 0, &el, 0);
- if((limit - p - 4 - el) < 0) return NULL;
+ if((limit - ret - 4 - el) < 0) return NULL;
s2n(TLSEXT_TYPE_use_srtp,ret);
s2n(el,ret);
@@ -1852,10 +1855,10 @@
s2n(0,ret);
}
- if ((extdatalen = ret-p-2)== 0)
- return p;
+ if ((extdatalen = ret-orig-2) == 0)
+ return orig;
- s2n(extdatalen,p);
+ s2n(extdatalen, orig);
return ret;
}
