From e705e0a24ea26c6e8f92583d1d885c186f1cfded Mon Sep 17 00:00:00 2001
From: Stephen Lombardo <sjlombardo@zetetic.net>
Date: Mon, 15 Nov 2021 17:12:44 -0500
Subject: [PATCH] add facility for testing random codec failures

---
 src/crypto.c      | 19 +++++++++++++++++--
 src/crypto.h      |  3 +++
 src/crypto_impl.c | 17 +++++++++++++++++
 3 files changed, 37 insertions(+), 2 deletions(-)

diff --git a/src/crypto.c b/src/crypto.c
index a0bc3d2a..fef032b4 100644
--- a/src/crypto.c
+++ b/src/crypto.c
@@ -145,6 +145,15 @@ int sqlcipher_codec_pragma(sqlite3* db, int iDb, Parse *pParse, const char *zLef
     char *flags = sqlite3_mprintf("%i", sqlcipher_get_test_flags());
     codec_vdbe_return_string(pParse, "cipher_test", flags, P4_DYNAMIC);
   }else
+  if( sqlite3StrICmp(zLeft,"cipher_test_rand")==0 ){
+    if( zRight ) {
+      int rand = atoi(zRight);
+      sqlcipher_set_test_rand(rand);
+    } else {
+      char *rand = sqlite3_mprintf("%d", sqlcipher_get_test_rand());
+      codec_vdbe_return_string(pParse, "cipher_test_rand", rand, P4_DYNAMIC);
+    }
+  } else
 #endif
   if( sqlite3StrICmp(zLeft, "cipher_fips_status")== 0 && !zRight ){
     if(ctx) {
@@ -734,7 +743,10 @@ static void* sqlite3Codec(void *iCtx, void *data, Pgno pgno, int mode) {
 
       rc = sqlcipher_page_cipher(ctx, cctx, pgno, CIPHER_DECRYPT, page_sz - offset, pData + offset, (unsigned char*)buffer + offset);
 #ifdef SQLCIPHER_TEST
-      if((sqlcipher_get_test_flags() & TEST_FAIL_ENCRYPT) > 0) rc = SQLITE_ERROR;
+      if((sqlcipher_get_test_flags() & TEST_FAIL_ENCRYPT) > 0 && sqlcipher_get_test_fail()) {
+        rc = SQLITE_ERROR;
+        fprintf(stderr, "simulating encryption failure\n");
+      }
 #endif
       if(rc != SQLITE_OK) { /* clear results of failed cipher operation */
         /* this will be considered a temporary error condition. the pager is still usable */
@@ -759,7 +771,10 @@ static void* sqlite3Codec(void *iCtx, void *data, Pgno pgno, int mode) {
       }
       rc = sqlcipher_page_cipher(ctx, cctx, pgno, CIPHER_ENCRYPT, page_sz - offset, pData + offset, (unsigned char*)buffer + offset);
 #ifdef SQLCIPHER_TEST
-      if((sqlcipher_get_test_flags() & TEST_FAIL_DECRYPT) > 0) rc = SQLITE_ERROR;
+      if((sqlcipher_get_test_flags() & TEST_FAIL_DECRYPT) > 0 && sqlcipher_get_test_fail()) {
+        fprintf(stderr, "simulating decryption failure\n");
+        rc = SQLITE_ERROR;
+      }
 #endif
       if(rc != SQLITE_OK) { /* clear results of failed cipher operation and set error */
         /* failure to encrypt a page is considered a permanent error and will render the pager unusable
diff --git a/src/crypto.h b/src/crypto.h
index 3aaf2387..e4626a41 100644
--- a/src/crypto.h
+++ b/src/crypto.h
@@ -198,6 +198,9 @@ static int cipher_isHex(const unsigned char *hex, int sz){
 #define TEST_FAIL_MIGRATE 0x04
 unsigned int sqlcipher_get_test_flags(void);
 void sqlcipher_set_test_flags(unsigned int);
+int sqlcipher_get_test_rand(void);
+void sqlcipher_set_test_rand(int);
+int sqlcipher_get_test_fail(void);
 #endif
 
 /* extensions defined in crypto_impl.c */
diff --git a/src/crypto_impl.c b/src/crypto_impl.c
index ee7e0f5d..57b2b846 100644
--- a/src/crypto_impl.c
+++ b/src/crypto_impl.c
@@ -52,6 +52,23 @@ unsigned int sqlcipher_get_test_flags() {
 void sqlcipher_set_test_flags(unsigned int flags) {
   cipher_test_flags = flags;
 }
+
+static volatile int cipher_test_rand = 0;
+int sqlcipher_get_test_rand() {
+  return cipher_test_rand;
+}
+void sqlcipher_set_test_rand(int rand) {
+  cipher_test_rand = rand;
+}
+int sqlcipher_get_test_fail() {
+  int x;
+
+  /* if cipher_test_rand is not set to a non-zero value always fail (return true) */
+  if (cipher_test_rand == 0) return 1;
+
+  sqlite3_randomness(sizeof(x), &x);
+  return ((x % cipher_test_rand) == 0);
+}
 #endif
 
 /* Generate code to return a string value */
-- 
2.11.4.GIT