Update to FreeBSD head 2019-09-24

Git mirror commit 6b0307a0a5184339393f555d5d424190d8a8277a.

1 files changed, 57 insertions, 48 deletions

diff --git a/freebsd/crypto/openssl/crypto/rsa/rsa_pk1.c b/freebsd/crypto/openssl/crypto/rsa/rsa_pk1.c
index 1b285786..429be508 100644
--- a/freebsd/crypto/openssl/crypto/rsa/rsa_pk1.c
+++ b/freebsd/crypto/openssl/crypto/rsa/rsa_pk1.c
@@ -1,7 +1,7 @@
 #include <machine/rtems-bsd-user-space.h>
 
 /*
- * Copyright 1995-2018 The OpenSSL Project Authors. All Rights Reserved.
+ * Copyright 1995-2019 The OpenSSL Project Authors. All Rights Reserved.
  *
  * Licensed under the OpenSSL license (the "License").  You may not use
  * this file except in compliance with the License.  You can obtain a copy
@@ -160,10 +160,10 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
     int i;
     /* |em| is the encoded message, zero-padded to exactly |num| bytes */
     unsigned char *em = NULL;
-    unsigned int good, found_zero_byte;
+    unsigned int good, found_zero_byte, mask;
     int zero_index = 0, msg_index, mlen = -1;
 
-    if (tlen < 0 || flen < 0)
+    if (tlen <= 0 || flen <= 0)
         return -1;
 
     /*
@@ -171,48 +171,49 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
      * section 7.2.2.
      */
 
-    if (flen > num)
-        goto err;
-
-    if (num < 11)
-        goto err;
+    if (flen > num || num < 11) {
+        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
+               RSA_R_PKCS_DECODING_ERROR);
+        return -1;
+    }
 
-    if (flen != num) {
-        em = OPENSSL_zalloc(num);
-        if (em == NULL) {
-            RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE);
-            return -1;
-        }
-        /*
-         * Caller is encouraged to pass zero-padded message created with
-         * BN_bn2binpad, but if it doesn't, we do this zero-padding copy
-         * to avoid leaking that information. The copy still leaks some
-         * side-channel information, but it's impossible to have a fixed
-         * memory access pattern since we can't read out of the bounds of
-         * |from|.
-         */
-        memcpy(em + num - flen, from, flen);
-        from = em;
+    em = OPENSSL_malloc(num);
+    if (em == NULL) {
+        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, ERR_R_MALLOC_FAILURE);
+        return -1;
+    }
+    /*
+     * Caller is encouraged to pass zero-padded message created with
+     * BN_bn2binpad. Trouble is that since we can't read out of |from|'s
+     * bounds, it's impossible to have an invariant memory access pattern
+     * in case |from| was not zero-padded in advance.
+     */
+    for (from += flen, em += num, i = 0; i < num; i++) {
+        mask = ~constant_time_is_zero(flen);
+        flen -= 1 & mask;
+        from -= 1 & mask;
+        *--em = *from & mask;
     }
 
-    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]);
-        zero_index =
-            constant_time_select_int(~found_zero_byte & equals0, i,
-                                     zero_index);
+        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;
     }
 
     /*
-     * 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.
      */
-    good &= constant_time_ge((unsigned int)(zero_index), 2 + 8);
+    good &= constant_time_ge(zero_index, 2 + 8);
 
     /*
      * Skip the zero byte. This is incorrect if we never found a zero-byte
@@ -222,27 +223,35 @@ int RSA_padding_check_PKCS1_type_2(unsigned char *to, int tlen,
     mlen = num - msg_index;
 
     /*
-     * For good measure, do this check in constant time as well; it could
-     * leak something if |tlen| was assuming valid padding.
+     * For good measure, do this check in constant time as well.
      */
-    good &= constant_time_ge((unsigned int)(tlen), (unsigned int)(mlen));
+    good &= constant_time_ge(tlen, mlen);
 
     /*
-     * We can't continue in constant-time because we need to copy the result
-     * and we cannot fake its length. This unavoidably leaks timing
-     * information at the API boundary.
+     * Move the result in-place by |num|-11-|mlen| bytes to the left.
+     * Then if |good| move |mlen| bytes from |em|+11 to |to|.
+     * Otherwise leave |to| unchanged.
+     * Copy the memory back in a way that does not reveal the size of
+     * the data being copied via a timing side channel. This requires copying
+     * parts of the buffer multiple times based on the bits set in the real
+     * length. Clear bits do a non-copy with identical access pattern.
+     * The loop below has overall complexity of O(N*log(N)).
      */
-    if (!good) {
-        mlen = -1;
-        goto err;
+    tlen = constant_time_select_int(constant_time_lt(num - 11, tlen),
+                                    num - 11, tlen);
+    for (msg_index = 1; msg_index < num - 11; msg_index <<= 1) {
+        mask = ~constant_time_eq(msg_index & (num - 11 - mlen), 0);
+        for (i = 11; i < num - msg_index; i++)
+            em[i] = constant_time_select_8(mask, em[i + msg_index], em[i]);
+    }
+    for (i = 0; i < tlen; i++) {
+        mask = good & constant_time_lt(i, mlen);
+        to[i] = constant_time_select_8(mask, em[i + 11], to[i]);
     }
 
-    memcpy(to, from + msg_index, mlen);
-
- err:
     OPENSSL_clear_free(em, num);
-    if (mlen == -1)
-        RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2,
-               RSA_R_PKCS_DECODING_ERROR);
-    return mlen;
+    RSAerr(RSA_F_RSA_PADDING_CHECK_PKCS1_TYPE_2, RSA_R_PKCS_DECODING_ERROR);
+    err_clear_last_constant_time(1 & good);
+
+    return constant_time_select_int(good, mlen, -1);
 }