Commit a004e72b authored by Matt Caswell's avatar Matt Caswell
Browse files

Avoid some undefined pointer arithmetic 



A common idiom in the codebase is:

if (p + len > limit)
{
    return; /* Too long */
}

Where "p" points to some malloc'd data of SIZE bytes and
limit == p + SIZE

"len" here could be from some externally supplied data (e.g. from a TLS
message).

The rules of C pointer arithmetic are such that "p + len" is only well
defined where len <= SIZE. Therefore the above idiom is actually
undefined behaviour.

For example this could cause problems if some malloc implementation
provides an address for "p" such that "p + len" actually overflows for
values of len that are too big and therefore p + len < limit!

Issue reported by Guido Vranken.

CVE-2016-2177

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
parent f792c663

ssl/s3_srvr.c

+7 −7
Original line number Diff line number Diff line
@@ -980,7 +980,7 @@ int ssl3_get_client_hello(SSL *s) 


        session_length = *(p + SSL3_RANDOM_SIZE);



        if (p + SSL3_RANDOM_SIZE + session_length + 1 >= d + n) {

        if (SSL3_RANDOM_SIZE + session_length + 1 >= (d + n) - p) {

            al = SSL_AD_DECODE_ERROR;

            SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

            goto f_err;
@@ -998,7 +998,7 @@ int ssl3_get_client_hello(SSL *s) 
    /* get the session-id */

    j = *(p++);



    if (p + j > d + n) {

    if ((d + n) - p < j) {

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

        goto f_err;
@@ -1054,14 +1054,14 @@ int ssl3_get_client_hello(SSL *s) 


    if (SSL_IS_DTLS(s)) {

        /* cookie stuff */

        if (p + 1 > d + n) {

        if ((d + n) - p < 1) {

            al = SSL_AD_DECODE_ERROR;

            SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

            goto f_err;

        }

        cookie_len = *(p++);



        if (p + cookie_len > d + n) {

        if ((d + n ) - p < cookie_len) {

            al = SSL_AD_DECODE_ERROR;

            SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

            goto f_err;
@@ -1131,7 +1131,7 @@ int ssl3_get_client_hello(SSL *s) 
        }

    }



    if (p + 2 > d + n) {

    if ((d + n ) - p < 2) {

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

        goto f_err;
@@ -1145,7 +1145,7 @@ int ssl3_get_client_hello(SSL *s) 
    }



    /* i bytes of cipher data + 1 byte for compression length later */

    if ((p + i + 1) > (d + n)) {

    if ((d + n) - p < i + 1) {

        /* not enough data */

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);
@@ -1211,7 +1211,7 @@ int ssl3_get_client_hello(SSL *s) 


    /* compression */

    i = *(p++);

    if ((p + i) > (d + n)) {

    if ((d + n) - p < i) {

        /* not enough data */

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);

ssl/ssl_sess.c

+1 −1
Original line number Diff line number Diff line
@@ -573,7 +573,7 @@ int ssl_get_prev_session(SSL *s, unsigned char *session_id, int len, 
    int r;

#endif



    if (session_id + len > limit) {

    if (limit - session_id < len) {

        fatal = 1;

        goto err;

    }

ssl/t1_lib.c

+30 −26
Original line number Diff line number Diff line
@@ -1867,11 +1867,11 @@ static void ssl_check_for_safari(SSL *s, const unsigned char *data, 
        0x02, 0x03,             /* SHA-1/ECDSA */

    };



    if (data >= (limit - 2))

    if (limit - data <= 2)

        return;

    data += 2;



    if (data > (limit - 4))

    if (limit - data < 4)

        return;

    n2s(data, type);

    n2s(data, size);
@@ -1879,7 +1879,7 @@ static void ssl_check_for_safari(SSL *s, const unsigned char *data, 
    if (type != TLSEXT_TYPE_server_name)

        return;



    if (data + size > limit)

    if (limit - data < size)

        return;

    data += size;
@@ -1887,7 +1887,7 @@ static void ssl_check_for_safari(SSL *s, const unsigned char *data, 
        const size_t len1 = sizeof(kSafariExtensionsBlock);

        const size_t len2 = sizeof(kSafariTLS12ExtensionsBlock);



        if (data + len1 + len2 != limit)

        if (limit - data != (int)(len1 + len2))

            return;

        if (memcmp(data, kSafariExtensionsBlock, len1) != 0)

            return;
@@ -1896,7 +1896,7 @@ static void ssl_check_for_safari(SSL *s, const unsigned char *data, 
    } else {

        const size_t len = sizeof(kSafariExtensionsBlock);



        if (data + len != limit)

        if (limit - data != (int)(len))

            return;

        if (memcmp(data, kSafariExtensionsBlock, len) != 0)

            return;
@@ -2053,19 +2053,19 @@ static int ssl_scan_clienthello_tlsext(SSL *s, unsigned char **p, 
    if (data == limit)

        goto ri_check;



    if (data > (limit - 2))

    if (limit - data < 2)

        goto err;



    n2s(data, len);



    if (data + len != limit)

    if (limit - data != len)

        goto err;



    while (data <= (limit - 4)) {

    while (limit - data >= 4) {

        n2s(data, type);

        n2s(data, size);



        if (data + size > (limit))

        if (limit - data < size)

            goto err;

# if 0

        fprintf(stderr, "Received extension type %d size %d\n", type, size);
@@ -2472,18 +2472,18 @@ static int ssl_scan_clienthello_custom_tlsext(SSL *s, 
    if (s->hit || s->cert->srv_ext.meths_count == 0)

        return 1;



    if (data >= limit - 2)

    if (limit - data <= 2)

        return 1;

    n2s(data, len);



    if (data > limit - len)

    if (limit - data < len)

        return 1;



    while (data <= limit - 4) {

    while (limit - data >= 4) {

        n2s(data, type);

        n2s(data, size);



        if (data + size > limit)

        if (limit - data < size)

            return 1;

        if (custom_ext_parse(s, 1 /* server */ , type, data, size, al) <= 0)

            return 0;
@@ -2569,20 +2569,20 @@ static int ssl_scan_serverhello_tlsext(SSL *s, unsigned char **p, 
                             SSL_TLSEXT_HB_DONT_SEND_REQUESTS);

# endif



    if (data >= (d + n - 2))

    if ((d + n) - data <= 2)

        goto ri_check;



    n2s(data, length);

    if (data + length != d + n) {

    if ((d + n) - data != length) {

        *al = SSL_AD_DECODE_ERROR;

        return 0;

    }



    while (data <= (d + n - 4)) {

    while ((d + n) - data >= 4) {

        n2s(data, type);

        n2s(data, size);



        if (data + size > (d + n))

        if ((d + n) - data < size)

            goto ri_check;



        if (s->tlsext_debug_cb)
@@ -3307,29 +3307,33 @@ int tls1_process_ticket(SSL *s, unsigned char *session_id, int len, 
    /* Skip past DTLS cookie */

    if (SSL_IS_DTLS(s)) {

        i = *(p++);

        p += i;

        if (p >= limit)



        if (limit - p <= i)

            return -1;



        p += i;

    }

    /* Skip past cipher list */

    n2s(p, i);

    p += i;

    if (p >= limit)

    if (limit - p <= i)

        return -1;

    p += i;



    /* Skip past compression algorithm list */

    i = *(p++);

    p += i;

    if (p > limit)

    if (limit - p < i)

        return -1;

    p += i;



    /* Now at start of extensions */

    if ((p + 2) >= limit)

    if (limit - p <= 2)

        return 0;

    n2s(p, i);

    while ((p + 4) <= limit) {

    while (limit - p >= 4) {

        unsigned short type, size;

        n2s(p, type);

        n2s(p, size);

        if (p + size > limit)

        if (limit - p < size)

            return 0;

        if (type == TLSEXT_TYPE_session_ticket) {

            int r;