1 files changed, 216 insertions, 0 deletions

diff --git a/src/sp_cookie_encryption.c b/src/sp_cookie_encryption.c
new file mode 100644
index 0000000..5248486
--- /dev/null
+++ b/src/sp_cookie_encryption.c
@@ -0,0 +1,216 @@
+#include "php_snuffleupagus.h"
+
+#include "ext/standard/url.h"
+
+ZEND_DECLARE_MODULE_GLOBALS(snuffleupagus)
+
+static unsigned int nonce_d = 0;
+
+static inline void generate_key(unsigned char *key) {
+  PHP_SHA256_CTX ctx;
+  const char *user_agent = sp_getenv("HTTP_USER_AGENT");
+  const char *remote_addr = sp_getenv("REMOTE_ADDR");
+  const char *encryption_key =
+      SNUFFLEUPAGUS_G(config).config_snuffleupagus->encryption_key;
+
+  /* 32 is the size of a SHA256. */
+  assert(32 == crypto_secretbox_KEYBYTES);
+
+  PHP_SHA256Init(&ctx);
+
+  if (user_agent) {
+    PHP_SHA256Update(&ctx, (unsigned char *)user_agent, strlen(user_agent));
+  }
+
+  if (remote_addr) {
+    char out[128];
+          apply_mask_on_ip(out, remote_addr);
+    PHP_SHA256Update(&ctx, (unsigned char*)out, sizeof(out));
+  }
+
+  if (encryption_key) {
+    PHP_SHA256Update(&ctx, (const unsigned char *)encryption_key,
+                     strlen(encryption_key));
+  }
+
+  PHP_SHA256Final((unsigned char *)key, &ctx);
+}
+
+int decrypt_cookie(zval *pDest, int num_args, va_list args,
+                   zend_hash_key *hash_key) {
+  unsigned char key[crypto_secretbox_KEYBYTES] = {0};
+  size_t value_len;
+  zend_string *debase64;
+  unsigned char *decrypted;
+  int ret = 0;
+
+  /* If the cookie isn't in the conf, it shouldn't be encrypted. */
+  if (0 ==
+      zend_hash_exists(SNUFFLEUPAGUS_G(config).config_cookie_encryption->names,
+                       hash_key->key)) {
+    return ZEND_HASH_APPLY_KEEP;
+  }
+
+  generate_key(key);
+
+  value_len = php_url_decode(Z_STRVAL_P(pDest), Z_STRLEN_P(pDest));
+
+  if (value_len == 0) {
+    return ZEND_HASH_APPLY_KEEP;
+  }
+
+  debase64 = php_base64_decode((unsigned char *)(Z_STRVAL_P(pDest)), value_len);
+
+  if (value_len <
+      crypto_secretbox_NONCEBYTES + crypto_secretbox_ZEROBYTES) {
+    sp_log_msg("cookie_encryption", LOG_DROP,
+        "Buffer underflow tentative detected in cookie encryption handling.");
+    return ZEND_HASH_APPLY_REMOVE;
+  }
+
+  decrypted = pecalloc(value_len, 1, 0);
+
+  ret = crypto_secretbox_open(
+      decrypted,
+      (unsigned char *)(ZSTR_VAL(debase64) + crypto_secretbox_NONCEBYTES),
+      ZSTR_LEN(debase64) - crypto_secretbox_NONCEBYTES,
+      (unsigned char *)ZSTR_VAL(debase64), key);
+
+  if (ret == -1) {
+    sp_log_msg("cookie_encryption", LOG_DROP,
+      "Something went wrong with the decryption of %s.",
+               ZSTR_VAL(hash_key->key));
+    return ZEND_HASH_APPLY_REMOVE;
+  }
+
+  ZVAL_STRINGL(pDest, (char *)(decrypted + crypto_secretbox_ZEROBYTES),
+               ZSTR_LEN(debase64) - crypto_secretbox_NONCEBYTES - 1 -
+                   crypto_secretbox_ZEROBYTES);
+
+  return ZEND_HASH_APPLY_KEEP;
+}
+
+/**
+  This function will return the `data` of length `data_len` encrypted in the
+  form
+  base64(nonce | encrypted_data) (with `|` being the concatenation
+  operation).
+
+  The `nonce` is time-based.
+*/
+static zend_string *encrypt_data(char *data, unsigned long long data_len) {
+  const size_t encrypted_msg_len = crypto_secretbox_ZEROBYTES + data_len + 1;
+  const size_t emsg_and_nonce_len = encrypted_msg_len + crypto_secretbox_NONCEBYTES;
+
+  unsigned char key[crypto_secretbox_KEYBYTES] = {0};
+  unsigned char nonce[crypto_secretbox_NONCEBYTES] = {0};
+  unsigned char *data_to_encrypt = pecalloc(encrypted_msg_len, 1, 0);
+  unsigned char *encrypted_data = pecalloc(emsg_and_nonce_len, 1, 1);
+
+  generate_key(key);
+
+  /* tweetnacl's API requires the message to be padded with
+  crypto_secretbox_ZEROBYTES zeroes. */
+  memcpy(data_to_encrypt + crypto_secretbox_ZEROBYTES, data, data_len);
+
+  assert(sizeof(size_t) <= crypto_secretbox_NONCEBYTES);
+
+  nonce_d++;
+  sscanf((char*)nonce, "%ud", &nonce_d); 
+
+  memcpy(encrypted_data, nonce, crypto_secretbox_NONCEBYTES);
+  crypto_secretbox(encrypted_data + crypto_secretbox_NONCEBYTES,
+                   data_to_encrypt, encrypted_msg_len, nonce, key);
+
+  zend_string *z = php_base64_encode(encrypted_data, emsg_and_nonce_len);
+  sp_log_debug("cookie_encryption", "Cookie value:%s:", z->val);
+  return z;
+}
+
+PHP_FUNCTION(sp_setcookie) {
+  zval params[7] = { 0 };
+  zend_string *name = NULL, *value = NULL, *path = NULL, *domain = NULL;
+  zend_long expires = 0;
+  zend_bool secure = 0, httponly = 0;
+  zval ret_val;
+  zval func_name;
+
+  ZEND_PARSE_PARAMETERS_START(1, 7)
+  Z_PARAM_STR(name)
+  Z_PARAM_OPTIONAL
+  Z_PARAM_STR(value)
+  Z_PARAM_LONG(expires)
+  Z_PARAM_STR(path)
+  Z_PARAM_STR(domain)
+  Z_PARAM_BOOL(secure)
+  Z_PARAM_BOOL(httponly)
+  ZEND_PARSE_PARAMETERS_END();
+
+  /* If the request was issued over HTTPS, the cookie should be "secure" */
+  if (SNUFFLEUPAGUS_G(config).config_auto_cookie_secure) {
+    const zval server_vars = PG(http_globals)[TRACK_VARS_SERVER];
+    if (Z_TYPE(server_vars) == IS_ARRAY) {
+      const zval *is_https =
+          zend_hash_str_find(Z_ARRVAL(server_vars), "HTTPS", strlen("HTTPS"));
+      if (NULL != is_https) {
+        secure = 1;
+      }
+    }
+  }
+
+  /* If the cookie's value is encrypted, it won't be usable by
+   * javascript anyway.
+   */
+  if (zend_hash_exists(SNUFFLEUPAGUS_G(config).config_cookie_encryption->names,
+                       name) > 0) {
+    httponly = 1;
+  }
+
+  /* Shall we encrypt the cookie's value? */
+  if (zend_hash_exists(SNUFFLEUPAGUS_G(config).config_cookie_encryption->names,
+                       name) > 0 && value) {
+    zend_string *encrypted_data = encrypt_data(value->val, value->len);
+    ZVAL_STR_COPY(&params[1], encrypted_data);
+    zend_string_release(encrypted_data);
+  } else if (value) {
+    ZVAL_STR_COPY(&params[1], value);
+  }
+
+  ZVAL_STRING(&func_name, "setcookie");
+  ZVAL_STR_COPY(&params[0], name);
+  ZVAL_LONG(&params[2], expires);
+  if (path) {
+    ZVAL_STR_COPY(&params[3], path);
+  }
+  if (domain) {
+    ZVAL_STR_COPY(&params[4], domain);
+  }
+  if (secure) {
+    ZVAL_LONG(&params[5], secure);
+  }
+  if (httponly) {
+    ZVAL_LONG(&params[6], httponly);
+  }
+
+  /* This is the _fun_ part: because PHP is utterly idiotic and nonsensical,
+  the `call_user_function` macro will __discard__ (yes) its first argument
+  (the hashtable), effectively calling functions from `CG(function_table)`.
+  This is why were replacing our hook with the original function, calling
+  the function, and then re-hooking it. */
+  void (*handler)(INTERNAL_FUNCTION_PARAMETERS);
+  handler = zend_hash_str_find_ptr(SNUFFLEUPAGUS_G(sp_internal_functions_hook), "setcookie",
+                                   strlen("setcookie"));
+  zend_internal_function *func = zend_hash_str_find_ptr(
+      CG(function_table), "setcookie", strlen("setcookie"));
+  func->handler = handler;
+
+  call_user_function(CG(function_table), NULL, &func_name, &ret_val, 7, params);
+
+  func->handler = PHP_FN(sp_setcookie);
+}
+
+int hook_cookies() {
+  HOOK_FUNCTION("setcookie", sp_internal_functions_hook, PHP_FN(sp_setcookie), false);
+
+  return SUCCESS;
+}