apr_strings: Provide apr_memzero_explicit() in APR.

This function is handy outside apu_crypto usage, don't require users to link
to APU for the feature.

This commit moves the apr_crypto_memzero() implementation to apr_strings under
the apr_memzero_explicit() name, and replaces the calls to the former with the
latter, and apr_crypto_memzero() now calls apr_memzero_explicit() directly.

* include/apr_strings.h():
  Declare apr_memzero_explicit().

* strings/apr_strings.c():
  Implement apr_memzero_explicit() by moving/renaming the code from apu_crypto.

* crypto/apr_crypto.c(apr_crypto_memzero):
  Fall back to apr_memzero_explicit().

* crypto/apr_crypto.c(crypto_clear):
  Use apr_memzero_explicit() instead of apr_crypto_memzero().

* crypto/apr_crypto_prng.c(cprng_cleanup, cprng_stream_bytes,
                           apr_crypto_prng_reseed, cprng_bytes,
                           apr_crypto_prng_rekey, apr_crypto_prng_after_fork):
  Use apr_memzero_explicit() instead of apr_crypto_memzero().

* crypto/apr_md4.c(MD4Transform):
  Use apr_memzero_explicit() instead of apr_crypto_memzero().



git-svn-id: https://svn.apache.org/repos/asf/apr/apr/trunk@1902323 13f79535-47bb-0310-9956-ffa450edef68

1 files changed, 32 insertions, 0 deletions

diff --git a/strings/apr_strings.c b/strings/apr_strings.c
index beca6d480..2519f95b9 100644
--- a/strings/apr_strings.c
+++ b/strings/apr_strings.c
@@ -212,6 +212,38 @@ APR_DECLARE(char *) apr_pstrcatv(apr_pool_t *a, const struct iovec *vec,
     return res;
 }
 
+#if defined(HAVE_WEAK_SYMBOLS)
+void apr__memzero_explicit(void *buffer, apr_size_t size);
+
+__attribute__ ((weak))
+void apr__memzero_explicit(void *buffer, apr_size_t size)
+{
+    memset(buffer, 0, size);
+}
+#endif
+
+APR_DECLARE(apr_status_t) apr_memzero_explicit(void *buffer, apr_size_t size)
+{
+#if defined(WIN32)
+    SecureZeroMemory(buffer, size);
+#elif defined(HAVE_EXPLICIT_BZERO)
+    explicit_bzero(buffer, size);
+#elif defined(HAVE_MEMSET_S)
+    if (size) {
+        return memset_s(buffer, (rsize_t)size, 0, (rsize_t)size);
+    }
+#elif defined(HAVE_WEAK_SYMBOLS)
+    apr__memzero_explicit(buffer, size);
+#else
+    apr_size_t i;
+    volatile unsigned char *volatile ptr = buffer;
+    for (i = 0; i < size; ++i) {
+        ptr[i] = 0;
+    }
+#endif
+    return APR_SUCCESS;
+}
+
 #if (!APR_HAVE_MEMCHR)
 void *memchr(const void *s, int c, size_t n)
 {