From c30f6fe7fb7e7bb5b4e5015fa8abbb04006ccea3 Mon Sep 17 00:00:00 2001
From: Zorg <zorgiepoo@gmail.com>
Date: Tue, 18 Jan 2022 00:04:40 -0800
Subject: [PATCH] Calculate hash of file for delta updates without using mmap
 (#2067)

---
 Autoupdate/SUBinaryDeltaCommon.m | 57 ++++++++++++++++++++++----------
 1 file changed, 40 insertions(+), 17 deletions(-)

diff --git a/Autoupdate/SUBinaryDeltaCommon.m b/Autoupdate/SUBinaryDeltaCommon.m
index 1975f923..13662464 100644
--- a/Autoupdate/SUBinaryDeltaCommon.m
+++ b/Autoupdate/SUBinaryDeltaCommon.m
@@ -165,7 +165,7 @@ static void _hashOfBuffer(unsigned char *hash, const char *buffer, ssize_t buffe
     CC_SHA1_Final(hash, &hashContext);
 }
 
-static BOOL _hashOfFileContents(unsigned char *hash, FTSENT *ent)
+static BOOL _hashOfFileContents(unsigned char *hash, FTSENT *ent, void *tempBuffer, size_t tempBufferSize)
 {
     if (ent->fts_info == FTS_SL) {
         char linkDestination[MAXPATHLEN + 1];
@@ -177,27 +177,37 @@ static BOOL _hashOfFileContents(unsigned char *hash, FTSENT *ent)
 
         _hashOfBuffer(hash, linkDestination, linkDestinationLength);
     } else if (ent->fts_info == FTS_F) {
-        int fileDescriptor = open(ent->fts_path, O_RDONLY);
-        if (fileDescriptor == -1) {
-            perror("open");
-            return NO;
-        }
-
         ssize_t fileSize = ent->fts_statp->st_size;
-        if (fileSize == 0) {
+        if (fileSize <= 0) {
             _hashOfBuffer(hash, NULL, 0);
         } else {
-            void *buffer = mmap(0, (size_t)fileSize, PROT_READ, MAP_FILE | MAP_PRIVATE, fileDescriptor, 0);
-            if (buffer == (void *)-1) {
-                close(fileDescriptor);
-                perror("mmap");
+            FILE *file = fopen(ent->fts_path, "rb");
+            if (file == NULL) {
+                perror("fopen");
                 return NO;
             }
-
-            _hashOfBuffer(hash, buffer, fileSize);
-            munmap(buffer, (size_t)fileSize);
+            
+            CC_SHA1_CTX hashContext;
+            CC_SHA1_Init(&hashContext);
+            
+            size_t bytesLeft = (size_t)fileSize;
+            while (bytesLeft > 0) {
+                size_t bytesToConsume = (bytesLeft >= tempBufferSize) ? tempBufferSize : bytesLeft;
+                
+                if (fread(tempBuffer, bytesToConsume, 1, file) < 1) {
+                    perror("fread");
+                    fclose(file);
+                    return NO;
+                }
+                
+                CC_SHA1_Update(&hashContext, tempBuffer, (CC_LONG)bytesToConsume);
+                bytesLeft -= bytesToConsume;
+            }
+            
+            CC_SHA1_Final(hash, &hashContext);
+            
+            fclose(file);
         }
-        close(fileDescriptor);
     } else if (ent->fts_info == FTS_D) {
         memset(hash, 0xdd, CC_SHA1_DIGEST_LENGTH);
     } else {
@@ -218,10 +228,18 @@ BOOL getRawHashOfTreeAndFileTablesWithVersion(unsigned char *hashBuffer, NSStrin
         return NO;
     }
 
+    const size_t tempBufferSize = 16384;
+    void *tempBuffer = calloc(1, tempBufferSize);
+    if (tempBuffer == NULL) {
+        perror("calloc");
+        return NO;
+    }
+    
     char *const sourcePaths[] = { pathBuffer, 0 };
     FTS *fts = fts_open(sourcePaths, FTS_PHYSICAL | FTS_NOCHDIR, compareFiles);
     if (!fts) {
         perror("fts_open");
+        free(tempBuffer);
         return NO;
     }
 
@@ -241,7 +259,9 @@ BOOL getRawHashOfTreeAndFileTablesWithVersion(unsigned char *hashBuffer, NSStrin
             continue;
 
         unsigned char fileHash[CC_SHA1_DIGEST_LENGTH];
-        if (!_hashOfFileContents(fileHash, ent)) {
+        if (!_hashOfFileContents(fileHash, ent, tempBuffer, tempBufferSize)) {
+            fts_close(fts);
+            free(tempBuffer);
             return NO;
         }
         CC_SHA1_Update(&hashContext, fileHash, sizeof(fileHash));
@@ -277,6 +297,9 @@ BOOL getRawHashOfTreeAndFileTablesWithVersion(unsigned char *hashBuffer, NSStrin
         CC_SHA1_Update(&hashContext, &type, sizeof(type));
         CC_SHA1_Update(&hashContext, &hashedPermissions, sizeof(hashedPermissions));
     }
+    
+    free(tempBuffer);
+    
     fts_close(fts);
 
     CC_SHA1_Final(hashBuffer, &hashContext);