Commit d7f5e5ae authored by Bernd Edlinger's avatar Bernd Edlinger
Browse files

Fix memory overrun in rsa padding check functions 



Fixes #8364 and #8357

Reviewed-by: default avatarKurt Roeckx <kurt@roeckx.be>
(Merged from https://github.com/openssl/openssl/pull/8365)
parent 596521f4

crypto/rsa/rsa_oaep.c

+13 −13
Original line number Diff line number Diff line 
/*

 * Copyright 1999-2018 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright 1999-2019 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy
@@ -143,7 +143,7 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, 
     * |num| is the length of the modulus; |flen| is the length of the

     * encoded message. Therefore, for any |from| that was obtained by

     * decrypting a ciphertext, we must have |flen| <= |num|. Similarly,

     * num < 2 * mdlen + 2 must hold for the modulus irrespective of

     * |num| >= 2 * |mdlen| + 2 must hold for the modulus irrespective of

     * the ciphertext, see PKCS #1 v2.2, section 7.1.2.

     * This does not leak any side-channel information.

     */
@@ -179,17 +179,16 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, 
        from -= 1 & mask;

        *--em = *from & mask;

    }

    from = em;



    /*

     * The first byte must be zero, however we must not leak if this is

     * true. See James H. Manger, "A Chosen Ciphertext  Attack on RSA

     * Optimal Asymmetric Encryption Padding (OAEP) [...]", CRYPTO 2001).

     */

    good = constant_time_is_zero(from[0]);

    good = constant_time_is_zero(em[0]);



    maskedseed = from + 1;

    maskeddb = from + 1 + mdlen;

    maskedseed = em + 1;

    maskeddb = em + 1 + mdlen;



    if (PKCS1_MGF1(seed, mdlen, maskeddb, dblen, mgf1md))

        goto cleanup;
@@ -230,7 +229,7 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, 
    mlen = dblen - msg_index;



    /*

     * For good measure, do this check in constant tine as well.

     * For good measure, do this check in constant time as well.

     */

    good &= constant_time_ge(tlen, mlen);
@@ -244,15 +243,16 @@ int RSA_padding_check_PKCS1_OAEP_mgf1(unsigned char *to, int tlen, 
     * should be noted that failure is indistinguishable from normal

     * operation if |tlen| is fixed by protocol.

     */

    tlen = constant_time_select_int(constant_time_lt(dblen, tlen), dblen, tlen);

    tlen = constant_time_select_int(constant_time_lt(dblen - mdlen - 1, tlen),

                                    dblen - mdlen - 1, tlen);

    msg_index = constant_time_select_int(good, msg_index, dblen - tlen);

    mlen = dblen - msg_index;

    for (from = db + msg_index, mask = good, i = 0; i < tlen; i++) {

        unsigned int equals = constant_time_eq(i, mlen);

    for (mask = good, i = 0; i < tlen; i++) {

        unsigned int equals = constant_time_eq(msg_index, dblen);



        from -= dblen & equals; /* if (i == dblen) rewind   */

        mask &= mask ^ equals;  /* if (i == dblen) mask = 0 */

        to[i] = constant_time_select_8(mask, from[i], to[i]);

        msg_index -= tlen & equals;  /* rewind at EOF */

        mask &= ~equals;  /* mask = 0 at EOF */

        to[i] = constant_time_select_8(mask, db[msg_index++], to[i]);

    }



    /*

crypto/rsa/rsa_pk1.c

+12 −12
Original line number Diff line number Diff line 
/*

 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy
@@ -192,15 +192,14 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, 
        from -= 1 & mask;

        *--em = *from & mask;

    }

    from = em;



    good = constant_time_is_zero(from[0]);

    good &= constant_time_eq(from[1], 2);

    good = constant_time_is_zero(em[0]);

    good &= constant_time_eq(em[1], 2);



    /* scan over padding data */

    found_zero_byte = 0;

    for (i = 2; i < num; i++) {

        unsigned int equals0 = constant_time_is_zero(from[i]);

        unsigned int equals0 = constant_time_is_zero(em[i]);



        zero_index = constant_time_select_int(~found_zero_byte & equals0,

                                              i, zero_index);
@@ -208,7 +207,7 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, 
    }



    /*

     * PS must be at least 8 bytes long, and it starts two bytes into |from|.

     * PS must be at least 8 bytes long, and it starts two bytes into |em|.

     * If we never found a 0-byte, then |zero_index| is 0 and the check

     * also fails.

     */
@@ -236,15 +235,16 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen, 
     * should be noted that failure is indistinguishable from normal

     * operation if |tlen| is fixed by protocol.

     */

    tlen = constant_time_select_int(constant_time_lt(num, tlen), num, tlen);

    tlen = constant_time_select_int(constant_time_lt(num - 11, tlen),

                                    num - 11, tlen);

    msg_index = constant_time_select_int(good, msg_index, num - tlen);

    mlen = num - msg_index;

    for (from += msg_index, mask = good, i = 0; i < tlen; i++) {

        unsigned int equals = constant_time_eq(i, mlen);

    for (mask = good, i = 0; i < tlen; i++) {

        unsigned int equals = constant_time_eq(msg_index, num);



        from -= tlen & equals;  /* if (i == mlen) rewind   */

        mask &= mask ^ equals;  /* if (i == mlen) mask = 0 */

        to[i] = constant_time_select_8(mask, from[i], to[i]);

        msg_index -= tlen & equals;  /* rewind at EOF */

        mask &= ~equals;  /* mask = 0 at EOF */

        to[i] = constant_time_select_8(mask, em[msg_index++], to[i]);

    }



    OPENSSL_clear_free(em, num);

crypto/rsa/rsa_ssl.c

+19 −16
Original line number Diff line number Diff line 
/*

 * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.

 * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.

 *

 * Licensed under the Apache License 2.0 (the "License").  You may not use

 * this file except in compliance with the License.  You can obtain a copy
@@ -55,7 +55,7 @@ int RSA_padding_add_SSLv23(unsigned char *to, int tlen, 


/*

 * Copy of RSA_padding_check_PKCS1_type_2 with a twist that rejects padding

 * if nul delimiter is preceded by 8 consecutive 0x03 bytes. It also

 * if nul delimiter is not preceded by 8 consecutive 0x03 bytes. It also

 * preserves error code reporting for backward compatibility.

 */

int RSA_padding_check_SSLv23(unsigned char *to, int tlen,
@@ -67,7 +67,10 @@ int RSA_padding_check_SSLv23(unsigned char *to, int tlen, 
    unsigned int good, found_zero_byte, mask, threes_in_row;

    int zero_index = 0, msg_index, mlen = -1, err;



    if (flen < 10) {

    if (tlen <= 0 || flen <= 0)

        return -1;



    if (flen > num || num < 11) {

        RSAerr(RSA_F_RSA_PADDING_CHECK_SSLV23, RSA_R_DATA_TOO_SMALL);

        return -1;

    }
@@ -89,10 +92,9 @@ int RSA_padding_check_SSLv23(unsigned char *to, int tlen, 
        from -= 1 & mask;

        *--em = *from & mask;

    }

    from = em;



    good = constant_time_is_zero(from[0]);

    good &= constant_time_eq(from[1], 2);

    good = constant_time_is_zero(em[0]);

    good &= constant_time_eq(em[1], 2);

    err = constant_time_select_int(good, 0, RSA_R_BLOCK_TYPE_IS_NOT_02);

    mask = ~good;
@@ -100,18 +102,18 @@ int RSA_padding_check_SSLv23(unsigned char *to, int tlen, 
    found_zero_byte = 0;

    threes_in_row = 0;

    for (i = 2; i < num; i++) {

        unsigned int equals0 = constant_time_is_zero(from[i]);

        unsigned int equals0 = constant_time_is_zero(em[i]);



        zero_index = constant_time_select_int(~found_zero_byte & equals0,

                                              i, zero_index);

        found_zero_byte |= equals0;



        threes_in_row += 1 & ~found_zero_byte;

        threes_in_row &= found_zero_byte | constant_time_eq(from[i], 3);

        threes_in_row &= found_zero_byte | constant_time_eq(em[i], 3);

    }



    /*

     * PS must be at least 8 bytes long, and it starts two bytes into |from|.

     * PS must be at least 8 bytes long, and it starts two bytes into |em|.

     * If we never found a 0-byte, then |zero_index| is 0 and the check

     * also fails.

     */
@@ -120,7 +122,7 @@ int RSA_padding_check_SSLv23(unsigned char *to, int tlen, 
                                   RSA_R_NULL_BEFORE_BLOCK_MISSING);

    mask = ~good;



    good &= constant_time_lt(threes_in_row, 8);

    good &= constant_time_ge(threes_in_row, 8);

    err = constant_time_select_int(mask | good, err,

                                   RSA_R_SSLV3_ROLLBACK_ATTACK);

    mask = ~good;
@@ -148,15 +150,16 @@ int RSA_padding_check_SSLv23(unsigned char *to, int tlen, 
     * should be noted that failure is indistinguishable from normal

     * operation if |tlen| is fixed by protocol.

     */

    tlen = constant_time_select_int(constant_time_lt(num, tlen), num, tlen);

    tlen = constant_time_select_int(constant_time_lt(num - 11, tlen),

                                    num - 11, tlen);

    msg_index = constant_time_select_int(good, msg_index, num - tlen);

    mlen = num - msg_index;

    for (from += msg_index, mask = good, i = 0; i < tlen; i++) {

        unsigned int equals = constant_time_eq(i, mlen);

    for (mask = good, i = 0; i < tlen; i++) {

        unsigned int equals = constant_time_eq(msg_index, num);



        from -= tlen & equals;  /* if (i == mlen) rewind   */

        mask &= mask ^ equals;  /* if (i == mlen) mask = 0 */

        to[i] = constant_time_select_8(mask, from[i], to[i]);

        msg_index -= tlen & equals;  /* rewind at EOF */

        mask &= ~equals;  /* mask = 0 at EOF */

        to[i] = constant_time_select_8(mask, em[msg_index++], to[i]);

    }



    OPENSSL_clear_free(em, num);