Commit eeda9661 authored by Matt Caswell's avatar Matt Caswell
Browse files

Check for ClientHello message overruns 



The ClientHello processing is insufficiently rigorous in its checks to make
sure that we don't read past the end of the message. This does not have
security implications due to the size of the underlying buffer - but still
needs to be fixed.

With thanks to Qinghao Tang for reporting this issue.

Reviewed-by: default avatarRich Salz <rsalz@openssl.org>
(cherry picked from commit c9642eb1ff79a30e2c7632ef8267cc34cc2b0d79)
parent c5b0f5c4

ssl/s3_srvr.c

+41 −1
Original line number Diff line number Diff line
@@ -778,6 +778,16 @@ int ssl3_get_client_hello(SSL *s) 
    s->first_packet = 0;

    d = p = (unsigned char *)s->init_msg;



    /*

     * 2 bytes for client version, SSL3_RANDOM_SIZE bytes for random, 1 byte

     * for session id length

     */

    if (n < 2 + SSL3_RANDOM_SIZE + 1) {

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

        goto f_err;

    }



    /*

     * use version from inside client hello, not from record header (may

     * differ: see RFC 2246, Appendix E, second paragraph)
@@ -808,6 +818,12 @@ int ssl3_get_client_hello(SSL *s) 
        unsigned int session_length, cookie_length;



        session_length = *(p + SSL3_RANDOM_SIZE);



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

            al = SSL_AD_DECODE_ERROR;

            SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

            goto f_err;

        }

        cookie_length = *(p + SSL3_RANDOM_SIZE + session_length + 1);



        if (cookie_length == 0)
@@ -821,6 +837,12 @@ int ssl3_get_client_hello(SSL *s) 
    /* get the session-id */

    j = *(p++);



    if (p + j > d + n) {

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

        goto f_err;

    }



    s->hit = 0;

    /*

     * Versions before 0.9.7 always allow session reuse during renegotiation
@@ -852,8 +874,19 @@ int ssl3_get_client_hello(SSL *s) 


    if (s->version == DTLS1_VERSION || s->version == DTLS1_BAD_VER) {

        /* cookie stuff */

        if (p + 1 > d + n) {

            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) {

            al = SSL_AD_DECODE_ERROR;

            SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

            goto f_err;

        }



        /*

         * The ClientHello may contain a cookie even if the

         * HelloVerify message has not been sent--make sure that it
@@ -894,6 +927,11 @@ int ssl3_get_client_hello(SSL *s) 
        p += cookie_len;

    }



    if (p + 2 > d + n) {

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_TOO_SHORT);

        goto f_err;

    }

    n2s(p, i);

    if ((i == 0) && (j != 0)) {

        /* we need a cipher if we are not resuming a session */
@@ -901,7 +939,9 @@ int ssl3_get_client_hello(SSL *s) 
        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_NO_CIPHERS_SPECIFIED);

        goto f_err;

    }

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



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

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

        /* not enough data */

        al = SSL_AD_DECODE_ERROR;

        SSLerr(SSL_F_SSL3_GET_CLIENT_HELLO, SSL_R_LENGTH_MISMATCH);