From: Robert Pengelly <robertapengelly@hotmail.com>
Date: Fri, 3 Oct 2025 06:41:40 +0000 (+0100)
Subject: Calculate and compare CRC-32
X-Git-Url: https://git.candlhat.org/?a=commitdiff_plain;h=6a7441ba23762ccc5c6bf6922f75e6958b280ef4;p=unzip.git

Calculate and compare CRC-32
---

diff --git a/tables.c b/tables.c
index b065708..a74aaf9 100644
--- a/tables.c
+++ b/tables.c
@@ -662,3 +662,264 @@ struct dist_tbl_t dist_tbl[30] = {
   /* 29 */ { 24577, 13 },
 
 };
+
+const uint32_t crc32_tbl[256] = {
+
+  0x00000000,
+  0x77073096,
+  0xee0e612c,
+  0x990951ba,
+  0x076dc419,
+  0x706af48f,
+  0xe963a535,
+  0x9e6495a3,
+  0x0edb8832,
+  0x79dcb8a4,
+  0xe0d5e91e,
+  0x97d2d988,
+  0x09b64c2b,
+  0x7eb17cbd,
+  0xe7b82d07,
+  0x90bf1d91,
+  0x1db71064,
+  0x6ab020f2,
+  0xf3b97148,
+  0x84be41de,
+  0x1adad47d,
+  0x6ddde4eb,
+  0xf4d4b551,
+  0x83d385c7,
+  0x136c9856,
+  0x646ba8c0,
+  0xfd62f97a,
+  0x8a65c9ec,
+  0x14015c4f,
+  0x63066cd9,
+  0xfa0f3d63,
+  0x8d080df5,
+  0x3b6e20c8,
+  0x4c69105e,
+  0xd56041e4,
+  0xa2677172,
+  0x3c03e4d1,
+  0x4b04d447,
+  0xd20d85fd,
+  0xa50ab56b,
+  0x35b5a8fa,
+  0x42b2986c,
+  0xdbbbc9d6,
+  0xacbcf940,
+  0x32d86ce3,
+  0x45df5c75,
+  0xdcd60dcf,
+  0xabd13d59,
+  0x26d930ac,
+  0x51de003a,
+  0xc8d75180,
+  0xbfd06116,
+  0x21b4f4b5,
+  0x56b3c423,
+  0xcfba9599,
+  0xb8bda50f,
+  0x2802b89e,
+  0x5f058808,
+  0xc60cd9b2,
+  0xb10be924,
+  0x2f6f7c87,
+  0x58684c11,
+  0xc1611dab,
+  0xb6662d3d,
+  0x76dc4190,
+  0x01db7106,
+  0x98d220bc,
+  0xefd5102a,
+  0x71b18589,
+  0x06b6b51f,
+  0x9fbfe4a5,
+  0xe8b8d433,
+  0x7807c9a2,
+  0x0f00f934,
+  0x9609a88e,
+  0xe10e9818,
+  0x7f6a0dbb,
+  0x086d3d2d,
+  0x91646c97,
+  0xe6635c01,
+  0x6b6b51f4,
+  0x1c6c6162,
+  0x856530d8,
+  0xf262004e,
+  0x6c0695ed,
+  0x1b01a57b,
+  0x8208f4c1,
+  0xf50fc457,
+  0x65b0d9c6,
+  0x12b7e950,
+  0x8bbeb8ea,
+  0xfcb9887c,
+  0x62dd1ddf,
+  0x15da2d49,
+  0x8cd37cf3,
+  0xfbd44c65,
+  0x4db26158,
+  0x3ab551ce,
+  0xa3bc0074,
+  0xd4bb30e2,
+  0x4adfa541,
+  0x3dd895d7,
+  0xa4d1c46d,
+  0xd3d6f4fb,
+  0x4369e96a,
+  0x346ed9fc,
+  0xad678846,
+  0xda60b8d0,
+  0x44042d73,
+  0x33031de5,
+  0xaa0a4c5f,
+  0xdd0d7cc9,
+  0x5005713c,
+  0x270241aa,
+  0xbe0b1010,
+  0xc90c2086,
+  0x5768b525,
+  0x206f85b3,
+  0xb966d409,
+  0xce61e49f,
+  0x5edef90e,
+  0x29d9c998,
+  0xb0d09822,
+  0xc7d7a8b4,
+  0x59b33d17,
+  0x2eb40d81,
+  0xb7bd5c3b,
+  0xc0ba6cad,
+  0xedb88320,
+  0x9abfb3b6,
+  0x03b6e20c,
+  0x74b1d29a,
+  0xead54739,
+  0x9dd277af,
+  0x04db2615,
+  0x73dc1683,
+  0xe3630b12,
+  0x94643b84,
+  0x0d6d6a3e,
+  0x7a6a5aa8,
+  0xe40ecf0b,
+  0x9309ff9d,
+  0x0a00ae27,
+  0x7d079eb1,
+  0xf00f9344,
+  0x8708a3d2,
+  0x1e01f268,
+  0x6906c2fe,
+  0xf762575d,
+  0x806567cb,
+  0x196c3671,
+  0x6e6b06e7,
+  0xfed41b76,
+  0x89d32be0,
+  0x10da7a5a,
+  0x67dd4acc,
+  0xf9b9df6f,
+  0x8ebeeff9,
+  0x17b7be43,
+  0x60b08ed5,
+  0xd6d6a3e8,
+  0xa1d1937e,
+  0x38d8c2c4,
+  0x4fdff252,
+  0xd1bb67f1,
+  0xa6bc5767,
+  0x3fb506dd,
+  0x48b2364b,
+  0xd80d2bda,
+  0xaf0a1b4c,
+  0x36034af6,
+  0x41047a60,
+  0xdf60efc3,
+  0xa867df55,
+  0x316e8eef,
+  0x4669be79,
+  0xcb61b38c,
+  0xbc66831a,
+  0x256fd2a0,
+  0x5268e236,
+  0xcc0c7795,
+  0xbb0b4703,
+  0x220216b9,
+  0x5505262f,
+  0xc5ba3bbe,
+  0xb2bd0b28,
+  0x2bb45a92,
+  0x5cb36a04,
+  0xc2d7ffa7,
+  0xb5d0cf31,
+  0x2cd99e8b,
+  0x5bdeae1d,
+  0x9b64c2b0,
+  0xec63f226,
+  0x756aa39c,
+  0x026d930a,
+  0x9c0906a9,
+  0xeb0e363f,
+  0x72076785,
+  0x05005713,
+  0x95bf4a82,
+  0xe2b87a14,
+  0x7bb12bae,
+  0x0cb61b38,
+  0x92d28e9b,
+  0xe5d5be0d,
+  0x7cdcefb7,
+  0x0bdbdf21,
+  0x86d3d2d4,
+  0xf1d4e242,
+  0x68ddb3f8,
+  0x1fda836e,
+  0x81be16cd,
+  0xf6b9265b,
+  0x6fb077e1,
+  0x18b74777,
+  0x88085ae6,
+  0xff0f6a70,
+  0x66063bca,
+  0x11010b5c,
+  0x8f659eff,
+  0xf862ae69,
+  0x616bffd3,
+  0x166ccf45,
+  0xa00ae278,
+  0xd70dd2ee,
+  0x4e048354,
+  0x3903b3c2,
+  0xa7672661,
+  0xd06016f7,
+  0x4969474d,
+  0x3e6e77db,
+  0xaed16a4a,
+  0xd9d65adc,
+  0x40df0b66,
+  0x37d83bf0,
+  0xa9bcae53,
+  0xdebb9ec5,
+  0x47b2cf7f,
+  0x30b5ffe9,
+  0xbdbdf21c,
+  0xcabac28a,
+  0x53b39330,
+  0x24b4a3a6,
+  0xbad03605,
+  0xcdd70693,
+  0x54de5729,
+  0x23d967bf,
+  0xb3667a2e,
+  0xc4614ab8,
+  0x5d681b02,
+  0x2a6f2b94,
+  0xb40bbe37,
+  0xc30c8ea1,
+  0x5a05df1b,
+  0x2d02ef8d,
+
+};
diff --git a/tables.h b/tables.h
index 6fb6f9c..d751a74 100644
--- a/tables.h
+++ b/tables.h
@@ -27,4 +27,7 @@ extern struct litlen_tbl_t litlen_tbl[29];
 struct dist_tbl_t { uint16_t base_dist, ebits; };
 extern struct dist_tbl_t dist_tbl[30];
 
+/* Table for computing CRC-32. */
+extern const uint32_t crc32_tbl[256];
+
 #endif      /* _TABLES_H */
diff --git a/unzip.c b/unzip.c
index 060a609..8d69f04 100755
--- a/unzip.c
+++ b/unzip.c
@@ -10,6 +10,7 @@
 #include    "lib.h"
 #include    "report.h"
 #include    "stdint.h"
+#include    "tables.h"
 #include    "unzip.h"
 #include    "vector.h"
 
@@ -575,6 +576,31 @@ static int read_lfh (struct lfh *lfh) {
 
 }
 
+/**
+ * See Figure 14-7 in Hacker's Delight (2nd ed.), or
+ * crc_reflected() in https://www.zlib.net/crc_v3.txt
+ * or Garry S. Brown's implementation e.g. in
+ * https://opensource.apple.com/source/xnu/xnu-792.13.8/bsd/libkern/crc32.c
+ */
+uint32_t crc32 (FILE *fp) {
+
+    uint32_t crc = 0xffffffff;
+    
+    unsigned char buf[32];
+    uint64_t i, n;
+    
+    while ((n = fread (buf, 1, sizeof (buf), fp))) {
+    
+        for (i = 0; i < n; i++) {
+            crc = (crc >> 8) ^ crc32_tbl[(crc ^ buf[i]) & UCHAR_MAX];
+        }
+    
+    }
+    
+    return crc ^ 0xffffffff;
+
+}
+
 static void extract_zip (const char *path) {
 
     struct eocdr eocdr = { 0 };
@@ -964,6 +990,20 @@ static void extract_zip (const char *path) {
             
             }
             
+            rewind (outfile);
+            
+            if (crc32 (outfile) != cfh.crc32) {
+            
+                report_at (program_name, 0, REPORT_ERROR, "%s: CRC-32 mismatch!", temp);
+                fclose (outfile);
+                
+                free (data);
+                remove (temp);
+                
+                break;
+            
+            }
+            
             free (data);
             fclose (outfile);