Remove memory shielding

That was a great idea to protect against information leak through
speculative loads.

Realistically, nobody is going to use this.

dist-build/emscripten-symbols.def

@@ -609,9 +609,7 @@ _sodium_mlock 0 0
 _sodium_mprotect_noaccess 0 0
 _sodium_mprotect_readonly 0 0
 _sodium_mprotect_readwrite 0 0
-_sodium_mshield 1 1
 _sodium_munlock 0 0
-_sodium_munshield 1 1
 _sodium_pad 1 1
 _sodium_runtime_has_aesni 0 0
 _sodium_runtime_has_armcrypto 0 0

src/libsodium/include/sodium/utils.h

@@ -158,12 +158,6 @@ int sodium_mprotect_readonly(void *ptr) __attribute__ ((nonnull));
 SODIUM_EXPORT
 int sodium_mprotect_readwrite(void *ptr) __attribute__ ((nonnull));
 
-SODIUM_EXPORT
-int sodium_mshield(void *ptr) __attribute__ ((nonnull));
-
-SODIUM_EXPORT
-int sodium_munshield(void *ptr) __attribute__ ((nonnull));
-
 SODIUM_EXPORT
 int sodium_pad(size_t *padded_buflen_p, unsigned char *buf,
                size_t unpadded_buflen, size_t blocksize, size_t max_buflen)

src/libsodium/sodium/utils.c

@@ -61,8 +61,6 @@ void *alloca (size_t);
 #define CANARY_SIZE 16U
 #define GARBAGE_VALUE 0xdb
 
-#define SHIELDING_PREKEY_SIZE 16384U
-
 #ifndef MAP_NOCORE
 # ifdef MAP_CONCEAL
 #  define MAP_NOCORE MAP_CONCEAL
@@ -100,7 +98,6 @@ void *alloca (size_t);
 
 static size_t        page_size = DEFAULT_PAGE_SIZE;
 static unsigned char canary[CANARY_SIZE];
-static unsigned char shielding_prekey[SHIELDING_PREKEY_SIZE];
 
 /* LCOV_EXCL_START */
 #ifdef HAVE_WEAK_SYMBOLS
@@ -418,11 +415,7 @@ _sodium_alloc_init(void)
         sodium_misuse(); /* LCOV_EXCL_LINE */
     }
 #endif
-    COMPILER_ASSERT(sizeof shielding_prekey >= randombytes_SEEDBYTES);
-    randombytes_buf(shielding_prekey, randombytes_SEEDBYTES);
-    randombytes_buf_deterministic(canary, sizeof canary, shielding_prekey);
-    shielding_prekey[0] ^= 0x01;
-    randombytes_buf_deterministic(shielding_prekey, sizeof shielding_prekey, shielding_prekey);
+    randombytes_buf(canary, CANARY_SIZE);
 
     return 0;
 }
@@ -735,48 +728,6 @@ sodium_mprotect_readwrite(void *ptr)
     return _sodium_mprotect(ptr, _mprotect_readwrite);
 }
 
-#ifndef HAVE_PAGE_PROTECTION
-int
-sodium_mshield(void *ptr)
-{
-    (void) ptr;
-    errno = ENOSYS;
-    return -1;
-}
-#else
-int
-sodium_mshield(void *ptr)
-{
-    unsigned char  shielding_key[crypto_stream_KEYBYTES];
-    unsigned char  nonce[crypto_stream_NONCEBYTES];
-    unsigned char *base_ptr;
-    unsigned char *unprotected_ptr;
-    size_t         unprotected_size;
-
-    unprotected_ptr = _unprotected_ptr_from_user_ptr(ptr);
-    base_ptr        = unprotected_ptr - page_size * 2U;
-    memcpy(&unprotected_size, base_ptr, sizeof unprotected_size);
-
-    crypto_generichash(shielding_key, sizeof shielding_key,
-                       shielding_prekey, sizeof shielding_prekey, NULL, 0);
-    COMPILER_ASSERT(sizeof nonce >= (sizeof unprotected_ptr) + (sizeof unprotected_size));
-    memset(nonce, 0, sizeof nonce);
-    memcpy(nonce, &unprotected_ptr, sizeof unprotected_ptr);
-    memcpy(nonce + sizeof unprotected_ptr, &unprotected_size, sizeof unprotected_size);
-    crypto_stream_xor(unprotected_ptr, unprotected_ptr, unprotected_size, nonce, shielding_key);
-    sodium_memzero(shielding_key, sizeof shielding_key);
-    sodium_memzero(nonce, sizeof nonce);
-
-    return 0;
-}
-#endif
-
-int
-sodium_munshield(void *ptr)
-{
-    return sodium_mshield(ptr);
-}
-
 int
 sodium_pad(size_t *padded_buflen_p, unsigned char *buf,
            size_t unpadded_buflen, size_t blocksize, size_t max_buflen)

test/default/sodium_utils2.c

@@ -41,32 +41,9 @@ int
 main(void)
 {
     void         *buf;
-    void         *buf2;
     size_t        size;
     unsigned int  i;
 
-    size = randombytes_uniform(100U);
-    if ((buf = sodium_malloc(size)) == NULL ||
-        (buf2 = sodium_malloc(size)) == NULL) {
-        return 1;
-    }
-    randombytes_buf(buf, size);
-    memcpy(buf2, buf, size);
-    errno = EINVAL;
-    if (sodium_mshield(buf) != 0) {
-        assert(errno == ENOSYS);
-    } else {
-        assert(size == 0U || memcmp(buf, buf2, size) != 0);
-    }
-    errno = EINVAL;
-    if (sodium_munshield(buf) != 0) {
-        assert(errno == ENOSYS);
-    } else {
-        assert(size == 0U || memcmp(buf, buf2, size) == 0);
-    }
-    sodium_free(buf2);
-    sodium_free(buf);
-
     if (sodium_malloc(SIZE_MAX - 1U) != NULL) {
         return 1;
     }

test/symbols/all-symbols.txt

@@ -685,9 +685,7 @@ sodium_mlock
 sodium_mprotect_noaccess
 sodium_mprotect_readonly
 sodium_mprotect_readwrite
-sodium_mshield
 sodium_munlock
-sodium_munshield
 sodium_pad
 sodium_runtime_has_aesni
 sodium_runtime_has_armcrypto