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-rw-r--r--src/common/aes.c4
-rw-r--r--src/common/compat.c2
-rw-r--r--src/common/crypto.c89
-rw-r--r--src/common/crypto.h3
-rw-r--r--src/common/mempool.c3
-rw-r--r--src/common/tortls.c4
-rw-r--r--src/common/util.c2
7 files changed, 77 insertions, 30 deletions
diff --git a/src/common/aes.c b/src/common/aes.c
index 59d864a3d0..295a90749a 100644
--- a/src/common/aes.c
+++ b/src/common/aes.c
@@ -106,7 +106,7 @@ aes_cipher_free(aes_cnt_cipher_t *cipher)
if (!cipher)
return;
EVP_CIPHER_CTX_cleanup(&cipher->evp);
- memset(cipher, 0, sizeof(aes_cnt_cipher_t));
+ memwipe(cipher, 0, sizeof(aes_cnt_cipher_t));
tor_free(cipher);
}
void
@@ -373,7 +373,7 @@ aes_cipher_free(aes_cnt_cipher_t *cipher)
if (cipher->using_evp) {
EVP_CIPHER_CTX_cleanup(&cipher->key.evp);
}
- memset(cipher, 0, sizeof(aes_cnt_cipher_t));
+ memwipe(cipher, 0, sizeof(aes_cnt_cipher_t));
tor_free(cipher);
}
diff --git a/src/common/compat.c b/src/common/compat.c
index ca850a3038..59e3898deb 100644
--- a/src/common/compat.c
+++ b/src/common/compat.c
@@ -332,7 +332,7 @@ tor_munmap_file(tor_mmap_t *handle)
{
char *d = (char*)handle->data;
tor_free(d);
- memset(handle, 0, sizeof(tor_mmap_t));
+ memwipe(handle, 0, sizeof(tor_mmap_t));
tor_free(handle);
}
#endif
diff --git a/src/common/crypto.c b/src/common/crypto.c
index a69e6c5cb8..30990ecc8f 100644
--- a/src/common/crypto.c
+++ b/src/common/crypto.c
@@ -425,7 +425,7 @@ crypto_cipher_free(crypto_cipher_t *env)
tor_assert(env->cipher);
aes_cipher_free(env->cipher);
- memset(env, 0, sizeof(crypto_cipher_t));
+ memwipe(env, 0, sizeof(crypto_cipher_t));
tor_free(env);
}
@@ -529,7 +529,7 @@ crypto_pk_read_private_key_from_filename(crypto_pk_t *env,
/* Try to parse it. */
r = crypto_pk_read_private_key_from_string(env, contents, -1);
- memset(contents, 0, strlen(contents));
+ memwipe(contents, 0, strlen(contents));
tor_free(contents);
if (r)
return -1; /* read_private_key_from_string already warned, so we don't.*/
@@ -671,7 +671,7 @@ crypto_pk_write_private_key_to_filename(crypto_pk_t *env,
s[len]='\0';
r = write_str_to_file(fname, s, 0);
BIO_free(bio);
- memset(s, 0, strlen(s));
+ memwipe(s, 0, strlen(s));
tor_free(s);
return r;
}
@@ -981,7 +981,7 @@ crypto_pk_private_sign_digest(crypto_pk_t *env, char *to, size_t tolen,
if (crypto_digest(digest,from,fromlen)<0)
return -1;
r = crypto_pk_private_sign(env,to,tolen,digest,DIGEST_LEN);
- memset(digest, 0, sizeof(digest));
+ memwipe(digest, 0, sizeof(digest));
return r;
}
@@ -1045,14 +1045,14 @@ crypto_pk_public_hybrid_encrypt(crypto_pk_t *env,
from+pkeylen-overhead-CIPHER_KEY_LEN, symlen);
if (r<0) goto err;
- memset(buf, 0, pkeylen);
+ memwipe(buf, 0, pkeylen);
tor_free(buf);
crypto_cipher_free(cipher);
tor_assert(outlen+symlen < INT_MAX);
return (int)(outlen + symlen);
err:
- memset(buf, 0, pkeylen);
+ memwipe(buf, 0, pkeylen);
tor_free(buf);
crypto_cipher_free(cipher);
return -1;
@@ -1103,13 +1103,13 @@ crypto_pk_private_hybrid_decrypt(crypto_pk_t *env,
r = crypto_cipher_decrypt(cipher, to+outlen, from+pkeylen, fromlen-pkeylen);
if (r<0)
goto err;
- memset(buf,0,pkeylen);
+ memwipe(buf,0,pkeylen);
tor_free(buf);
crypto_cipher_free(cipher);
tor_assert(outlen + fromlen < INT_MAX);
return (int)(outlen + (fromlen-pkeylen));
err:
- memset(buf,0,pkeylen);
+ memwipe(buf,0,pkeylen);
tor_free(buf);
crypto_cipher_free(cipher);
return -1;
@@ -1509,7 +1509,7 @@ crypto_digest_free(crypto_digest_t *digest)
{
if (!digest)
return;
- memset(digest, 0, sizeof(crypto_digest_t));
+ memwipe(digest, 0, sizeof(crypto_digest_t));
tor_free(digest);
}
@@ -1571,7 +1571,7 @@ crypto_digest_get_digest(crypto_digest_t *digest,
break;
}
memcpy(out, r, out_len);
- memset(r, 0, sizeof(r));
+ memwipe(r, 0, sizeof(r));
}
/** Allocate and return a new digest object with the same state as
@@ -1673,10 +1673,10 @@ crypto_hmac_sha256(char *hmac_out,
SHA256_Final((uint8_t*)hmac_out, &st);
/* Now clear everything. */
- memset(k, 0, sizeof(k));
- memset(pad, 0, sizeof(pad));
- memset(d, 0, sizeof(d));
- memset(&st, 0, sizeof(st));
+ memwipe(k, 0, sizeof(k));
+ memwipe(pad, 0, sizeof(pad));
+ memwipe(d, 0, sizeof(d));
+ memwipe(&st, 0, sizeof(st));
#undef BLOCKSIZE
#undef DIGESTSIZE
#endif
@@ -2208,7 +2208,7 @@ crypto_dh_compute_secret(int severity, crypto_dh_t *dh,
if (pubkey_bn)
BN_free(pubkey_bn);
if (secret_tmp) {
- memset(secret_tmp, 0, secret_tmp_len);
+ memwipe(secret_tmp, 0, secret_tmp_len);
tor_free(secret_tmp);
}
if (result < 0)
@@ -2243,15 +2243,15 @@ crypto_expand_key_material(const char *key_in, size_t key_in_len,
goto err;
memcpy(cp, digest, MIN(DIGEST_LEN, key_out_len-(cp-key_out)));
}
- memset(tmp, 0, key_in_len+1);
+ memwipe(tmp, 0, key_in_len+1);
tor_free(tmp);
- memset(digest, 0, sizeof(digest));
+ memwipe(digest, 0, sizeof(digest));
return 0;
err:
- memset(tmp, 0, key_in_len+1);
+ memwipe(tmp, 0, key_in_len+1);
tor_free(tmp);
- memset(digest, 0, sizeof(digest));
+ memwipe(digest, 0, sizeof(digest));
return -1;
}
@@ -2343,7 +2343,7 @@ crypto_seed_rng(int startup)
return rand_poll_status ? 0 : -1;
}
RAND_seed(buf, sizeof(buf));
- memset(buf, 0, sizeof(buf));
+ memwipe(buf, 0, sizeof(buf));
seed_weak_rng();
return 0;
#else
@@ -2360,7 +2360,7 @@ crypto_seed_rng(int startup)
return -1;
}
RAND_seed(buf, (int)sizeof(buf));
- memset(buf, 0, sizeof(buf));
+ memwipe(buf, 0, sizeof(buf));
seed_weak_rng();
return 0;
}
@@ -2843,7 +2843,7 @@ base32_decode(char *dest, size_t destlen, const char *src, size_t srclen)
}
}
- memset(tmp, 0, srclen);
+ memwipe(tmp, 0, srclen);
tor_free(tmp);
tmp = NULL;
return 0;
@@ -2888,11 +2888,54 @@ secret_to_key(char *key_out, size_t key_out_len, const char *secret,
}
}
crypto_digest_get_digest(d, key_out, key_out_len);
- memset(tmp, 0, tmplen);
+ memwipe(tmp, 0, tmplen);
tor_free(tmp);
crypto_digest_free(d);
}
+/**
+ * Destroy the <b>sz</b> bytes of data stored at <b>mem</b>, setting them to
+ * the value <b>byte</b>.
+ *
+ * This function is preferable to memset, since many compilers will happily
+ * optimize out memset() when they can convince themselves that the data being
+ * cleared will never be read.
+ *
+ * Right now, our convention is to use this function when we are wiping data
+ * that's about to become inaccessible, such as stack buffers that are about
+ * to go out of scope or structures that are about to get freed. (In
+ * practice, it appears that the compilers we're currently using will optimize
+ * out the memset()s for stack-allocated buffers, but not those for
+ * about-to-be-freed structures. That could change, though, so we're being
+ * wary.) If there are live reads for the data, then you can just use
+ * memset().
+ */
+void
+memwipe(void *mem, uint8_t byte, size_t sz)
+{
+ /* Because whole-program-optimization exists, we may not be able to just
+ * have this function call "memset". A smart compiler could inline it, then
+ * eliminate dead memsets, and declare itself to be clever. */
+
+ /* This is a slow and ugly function from OpenSSL that fills 'mem' with junk
+ * based on the pointer value, then uses that junk to update a global
+ * variable. It's an elaborate ruse to trick the compiler into not
+ * optimizing out the "wipe this memory" code. Read it if you like zany
+ * programming tricks! In later versions of Tor, we should look for better
+ * not-optimized-out memory wiping stuff. */
+ OPENSSL_cleanse(mem, sz);
+ /* Just in case some caller of memwipe() is relying on getting a buffer
+ * filled with a particular value, fill the buffer.
+ *
+ * If this function gets inlined, this memset might get eliminated, but
+ * that's okay: We only care about this particular memset in the case where
+ * the caller should have been using memset(), and the memset() wouldn't get
+ * eliminated. In other words, this is here so that we won't break anything
+ * if somebody accidentally calls memwipe() instead of memset().
+ **/
+ memset(mem, byte, sz);
+}
+
#ifdef TOR_IS_MULTITHREADED
/** Helper: OpenSSL uses this callback to manipulate mutexes. */
static void
diff --git a/src/common/crypto.h b/src/common/crypto.h
index 76bcbf7d43..7d56271785 100644
--- a/src/common/crypto.h
+++ b/src/common/crypto.h
@@ -271,6 +271,9 @@ int digest256_from_base64(char *digest, const char *d64);
void secret_to_key(char *key_out, size_t key_out_len, const char *secret,
size_t secret_len, const char *s2k_specifier);
+/** OpenSSL-based utility functions. */
+void memwipe(void *mem, uint8_t byte, size_t sz);
+
#ifdef CRYPTO_PRIVATE
/* Prototypes for private functions only used by tortls.c, crypto.c, and the
* unit tests. */
diff --git a/src/common/mempool.c b/src/common/mempool.c
index 2416bce473..637f081c88 100644
--- a/src/common/mempool.c
+++ b/src/common/mempool.c
@@ -8,6 +8,7 @@
#include <stdlib.h>
#include <string.h>
#include "torint.h"
+#include "crypto.h"
#define MEMPOOL_PRIVATE
#include "mempool.h"
@@ -519,7 +520,7 @@ mp_pool_destroy(mp_pool_t *pool)
destroy_chunks(pool->empty_chunks);
destroy_chunks(pool->used_chunks);
destroy_chunks(pool->full_chunks);
- memset(pool, 0xe0, sizeof(mp_pool_t));
+ memwipe(pool, 0xe0, sizeof(mp_pool_t));
FREE(pool);
}
diff --git a/src/common/tortls.c b/src/common/tortls.c
index bec2c71232..60aac64929 100644
--- a/src/common/tortls.c
+++ b/src/common/tortls.c
@@ -713,7 +713,7 @@ tor_cert_free(tor_cert_t *cert)
if (cert->cert)
X509_free(cert->cert);
tor_free(cert->encoded);
- memset(cert, 0x03, sizeof(*cert));
+ memwipe(cert, 0x03, sizeof(*cert));
tor_free(cert);
}
@@ -2448,7 +2448,7 @@ tor_tls_get_tlssecrets(tor_tls_t *tls, uint8_t *secrets_out)
(char*)tls->ssl->session->master_key,
tls->ssl->session->master_key_length,
buf, len);
- memset(buf, 0, sizeof(buf));
+ memwipe(buf, 0, sizeof(buf));
return 0;
}
diff --git a/src/common/util.c b/src/common/util.c
index 6fb597a3a5..005c2b52c3 100644
--- a/src/common/util.c
+++ b/src/common/util.c
@@ -3808,7 +3808,7 @@ tor_process_handle_destroy(process_handle_t *process_handle,
fclose(process_handle->stderr_handle);
#endif
- memset(process_handle, 0x0f, sizeof(process_handle_t));
+ memwipe(process_handle, 0x0f, sizeof(process_handle_t));
tor_free(process_handle);
}
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