Size the new strsafe buffers away from sizeof(char*)

char[8] equals a pointer on LP64, so MSVC's array-vs-pointer heuristic
read the unterminated source as a pointer, skipped the bound and never
aborted; the x64 build failed while Win32 passed. Same trap the existing
comment in that function already warns about.

Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Signed-off-by: Xavier Roche <roche@httrack.com>

src/htsparse.c

@@ -4583,7 +4583,7 @@ int hts_wait_delayed(htsmoduleStruct * str, lien_adrfilsave *afs,
             /* seen as in error */
             in_error = back[b].r.statuscode;
             in_error_msg[0] = 0;
-            strncat(in_error_msg, back[b].r.msg, sizeof(in_error_msg) - 1);
+            strncatbuff(in_error_msg, back[b].r.msg, sizeof(in_error_msg) - 1);
             in_error_size = back[b].r.totalsize;
             /* don't break, even with "don't take error pages" switch, because we need to process the slot anyway (and cache the error) */
           }

src/htssafe.h

@@ -116,6 +116,15 @@ static HTS_UNUSED void abortf_(const char *exp, const char *file, int line) {
 #endif
 #define HTS_IS_NOT_CHAR_BUFFER(VAR) (!HTS_IS_CHAR_BUFFER(VAR))
 
+/* Source capacity for the buff() family, (size_t)-1 when unknown; sizeof of the
+   TYPE keeps a decayed operand ("buf + 1") off -Wsizeof-array-decay. */
+#if (defined(__GNUC__) && !defined(__cplusplus))
+#define HTS_SIZEOF_SRC_(B)                                                     \
+  (HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(__typeof__(B)))
+#else
+#define HTS_SIZEOF_SRC_(B) (HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B))
+#endif
+
 /* Compile-time checks. */
 static HTS_UNUSED void htssafe_compile_time_check_(void) {
   char array[32];
@@ -205,19 +214,17 @@ static char *strncatbuff_ptr_(char *dest, const char *src, size_t n) {
 #if (defined(__GNUC__) && !defined(__cplusplus))
 
 #define strncatbuff(A, B, N)                                                   \
-  __builtin_choose_expr(                                                       \
-      HTS_IS_CHAR_BUFFER(A),                                                   \
-      strncat_safe_(A, sizeof(A), B,                                           \
-                    HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B), N,    \
-                    "overflow while appending '" #B "' to '" #A "'", __FILE__, \
-                    __LINE__),                                                 \
-      strncatbuff_ptr_((A), (B), (N)))
+  __builtin_choose_expr(HTS_IS_CHAR_BUFFER(A),                                 \
+                        strncat_safe_(A, sizeof(A), B, HTS_SIZEOF_SRC_(B), N,  \
+                                      "overflow while appending '" #B          \
+                                      "' to '" #A "'",                         \
+                                      __FILE__, __LINE__),                     \
+                        strncatbuff_ptr_((A), (B), (N)))
 #else
 #define strncatbuff(A, B, N)                                                   \
   (HTS_IS_NOT_CHAR_BUFFER(A)                                                   \
        ? strncat(A, B, N)                                                      \
-       : strncat_safe_(A, sizeof(A), B,                                        \
-                       HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B), N, \
+       : strncat_safe_(A, sizeof(A), B, HTS_SIZEOF_SRC_(B), N,                 \
                        "overflow while appending '" #B "' to '" #A "'",        \
                        __FILE__, __LINE__))
 #endif
@@ -232,9 +239,7 @@ static char *strncatbuff_ptr_(char *dest, const char *src, size_t n) {
 #define strcatbuff(A, B)                                                       \
   __builtin_choose_expr(                                                       \
       HTS_IS_CHAR_BUFFER(A),                                                   \
-      strncat_safe_(A, sizeof(A), B,                                           \
-                    HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),       \
-                    (size_t) -1,                                               \
+      strncat_safe_(A, sizeof(A), B, HTS_SIZEOF_SRC_(B), (size_t) -1,          \
                     "overflow while appending '" #B "' to '" #A "'", __FILE__, \
                     __LINE__),                                                 \
       strcatbuff_ptr_((A), (B)))
@@ -242,9 +247,7 @@ static char *strncatbuff_ptr_(char *dest, const char *src, size_t n) {
 #define strcatbuff(A, B)                                                       \
   (HTS_IS_NOT_CHAR_BUFFER(A)                                                   \
        ? strcat(A, B)                                                          \
-       : strncat_safe_(A, sizeof(A), B,                                        \
-                       HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),    \
-                       (size_t) -1,                                            \
+       : strncat_safe_(A, sizeof(A), B, HTS_SIZEOF_SRC_(B), (size_t) -1,       \
                        "overflow while appending '" #B "' to '" #A "'",        \
                        __FILE__, __LINE__))
 #endif
@@ -257,19 +260,17 @@ static char *strncatbuff_ptr_(char *dest, const char *src, size_t n) {
 #if (defined(__GNUC__) && !defined(__cplusplus))
 
 #define strcpybuff(A, B)                                                       \
-  __builtin_choose_expr(                                                       \
-      HTS_IS_CHAR_BUFFER(A),                                                   \
-      strcpy_safe_(A, sizeof(A), B,                                            \
-                   HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),        \
-                   "overflow while copying '" #B "' to '" #A "'", __FILE__,    \
-                   __LINE__),                                                  \
-      strcpybuff_ptr_((A), (B)))
+  __builtin_choose_expr(HTS_IS_CHAR_BUFFER(A),                                 \
+                        strcpy_safe_(A, sizeof(A), B, HTS_SIZEOF_SRC_(B),      \
+                                     "overflow while copying '" #B "' to '" #A \
+                                     "'",                                      \
+                                     __FILE__, __LINE__),                      \
+                        strcpybuff_ptr_((A), (B)))
 #else
 #define strcpybuff(A, B)                                                       \
   (HTS_IS_NOT_CHAR_BUFFER(A)                                                   \
        ? strcpy(A, B)                                                          \
-       : strcpy_safe_(A, sizeof(A), B,                                         \
-                      HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),     \
+       : strcpy_safe_(A, sizeof(A), B, HTS_SIZEOF_SRC_(B),                     \
                       "overflow while copying '" #B "' to '" #A "'", __FILE__, \
                       __LINE__))
 #endif
@@ -286,24 +287,24 @@ static char *strncatbuff_ptr_(char *dest, const char *src, size_t n) {
  * Append characters of "B" to "A", "A" having a maximum capacity of "S".
  */
 #define strlcatbuff(A, B, S)                                                   \
-  strncat_safe_(A, S, B, HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),  \
-                (size_t) -1, "overflow while appending '" #B "' to '" #A "'",  \
-                __FILE__, __LINE__)
+  strncat_safe_(A, S, B, HTS_SIZEOF_SRC_(B), (size_t) -1,                      \
+                "overflow while appending '" #B "' to '" #A "'", __FILE__,     \
+                __LINE__)
 
 /**
  * Append at most "N" characters of "B" to "A", "A" having a maximum capacity
  * of "S".
  */
 #define strlncatbuff(A, B, S, N)                                               \
-  strncat_safe_(A, S, B, HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),  \
-                N, "overflow while appending '" #B "' to '" #A "'", __FILE__,  \
+  strncat_safe_(A, S, B, HTS_SIZEOF_SRC_(B), N,                                \
+                "overflow while appending '" #B "' to '" #A "'", __FILE__,     \
                 __LINE__)
 
 /**
  * Copy characters of "B" to "A", "A" having a maximum capacity of "S".
  */
 #define strlcpybuff(A, B, S)                                                   \
-  strcpy_safe_(A, S, B, HTS_IS_NOT_CHAR_BUFFER(B) ? (size_t) -1 : sizeof(B),   \
+  strcpy_safe_(A, S, B, HTS_SIZEOF_SRC_(B),                                    \
                "overflow while copying '" #B "' to '" #A "'", __FILE__,        \
                __LINE__)
 
@@ -422,7 +423,9 @@ static HTS_INLINE HTS_UNUSED htsbuff htsbuff_ptr_(char *buf, size_t cap) {
  */
 static HTS_INLINE HTS_UNUSED void htsbuff_catn(htsbuff *b, const char *s,
                                                size_t n) {
-  const size_t add = strnlen(s, n);
+  /* the (size_t)-1 "no limit" sentinel would reach strnlen as a bound past
+     PTRDIFF_MAX */
+  const size_t add = n != (size_t) -1 ? strnlen(s, n) : strlen(s);
   /* Overflow-safe: keep the (potentially huge) 'add' alone on one side. The
      maintained invariant len < cap makes 'cap - len' >= 1 (no underflow), so
      'add < cap - len' cannot wrap the way 'len + add < cap' could. */

src/htsselftest.c

@@ -481,6 +481,28 @@ static int string_safety_selftests(void) {
   if (strcmp(buf, "abcd") != 0)
     return 1;
 
+  /* A decayed source has no known capacity, so the whole tail must land; a
+     sizeof(char*) capacity would abort here instead. */
+  {
+    char src[32] = "0123456789abcdefghij";
+    char dst[32];
+
+    strcpybuff(dst, src + 1);
+    if (strcmp(dst, "123456789abcdefghij") != 0)
+      return 1;
+  }
+
+  /* Truncating append: stops at N without aborting, what the status-message
+     call sites rely on. */
+  {
+    char dst[10]; /* never sizeof(char*), or MSVC reads it as a pointer */
+
+    dst[0] = '\0';
+    strncatbuff(dst, "abcdefghijkl", sizeof(dst) - 1);
+    if (strcmp(dst, "abcdefghi") != 0)
+      return 1;
+  }
+
   /* strlcpybuff: explicit-capacity copy into a pointer destination, the form
      the migration moves toward */
   {
@@ -1299,6 +1321,14 @@ static int st_strsafe(httrackp *opt, int argc, char **argv) {
       htsbuff b = htsbuff_array(small);
 
       htsbuff_cat(&b, src);
+    } else if (strcmp(argv[0], "overflow-src") == 0) {
+      /* Array source with no NUL: its capacity still comes from sizeof(), so
+         the bounded strlen aborts rather than running off the array. */
+      char nonul[6]; /* never sizeof(char*), per the note above */
+      char big[64];
+
+      memset(nonul, src[0], sizeof(nonul));
+      strcpybuff(big, nonul);
     } else {
       strcpybuff(small, src);
     }
@@ -4807,8 +4837,8 @@ static const struct selftest_entry {
     {"unescape-bounds", "", "unescapers reserve the NUL byte (no 1-byte OOB)",
      st_unescape_bounds},
     {"hashtable", "<count|file>", "coucal hashtable stress test", st_hashtable},
-    {"strsafe", "[overflow|overflow-buff [str]]", "bounded string-op self-test",
-     st_strsafe},
+    {"strsafe", "[overflow|overflow-buff|overflow-src [str]]",
+     "bounded string-op self-test", st_strsafe},
     {"copyopt", "", "copy_htsopt option-copy self-test", st_copyopt},
     {"pause", "", "randomized inter-file pause target self-test", st_pause},
     {"relative", "<link> <curr-file>", "relative link between two paths",

src/htsweb.c

@@ -671,10 +671,10 @@ int __cdecl htsshow_loop(t_hts_callbackarg * carg, httrackp * opt, lien_back * b
                     char *eps = strchr(back[i].url_adr, '/');
                     int count;
 
-                    if (ep != NULL && ep < eps
-                        && (count = (int) (ep - back[i].url_adr)) < 4) {
+                    if (ep != NULL && eps != NULL && ep < eps &&
+                        (count = (int) (ep - back[i].url_adr)) < 4) {
                       proto[0] = '\0';
-                      strncat(proto, back[i].url_adr, count);
+                      strncatbuff(proto, back[i].url_adr, count);
                     }
                   }
                   snprintf(StatsBuffer[index].state, sizeof(StatsBuffer[index].state),

src/proxy/store.c

@@ -2191,7 +2191,7 @@ static PT_Element PT_ReadCache__Arc_u(PT_Index index_, const char *url,
           }
           if ((pos = getArcField(index->line, 2)) != NULL) {
             r->msg[0] = '\0';
-            strncat(r->msg, pos, sizeof(pos) - 1);
+            strncatbuff(r->msg, pos, sizeof(r->msg) - 1);
           }
           while(linput(index->file, index->line, sizeof(index->line) - 1)
                 && index->line[0] != '\0') {

tests/01_engine-strsafe.test

@@ -47,3 +47,18 @@ case "$err" in
     exit 1
     ;;
 esac
+
+# An array source with no NUL must abort on the source bound rather than run
+# off the array: the array half of the source-capacity selection.
+err=$(httrack -#test=strsafe overflow-src "x" 2>&1) || true
+case "$err" in
+*"strsafe: NOT aborted"*)
+    echo "unterminated source array was NOT caught" >&2
+    exit 1
+    ;;
+*"size < sizeof_source"*) ;;
+*)
+    echo "expected htssafe source-bound abort, got: $err" >&2
+    exit 1
+    ;;
+esac

tests/53_local-proxytrack-arc-reason.test

@@ -0,0 +1,32 @@
+#!/bin/bash
+# An ARC entry's HTTP reason phrase must survive a proxytrack --convert
+# round-trip; it used to be clipped to sizeof(char*) - 1 bytes.
+
+set -euo pipefail
+
+dir=$(mktemp -d)
+trap 'rm -rf "$dir"' EXIT
+
+printf 'HTTP/1.1 404 Not Found Here At All\r\nContent-Type: text/html\r\nLast-Modified: Wed, 01 Jan 2025 00:00:00 GMT\r\nContent-Length: 5\r\n\r\n' >"$dir/hdr"
+printf 'hello' >"$dir/body"
+alen=$(($(wc -c <"$dir/hdr") + $(wc -c <"$dir/body")))
+
+# ARC 1.0: filedesc record and version block, then per entry
+# <nl> <URL-record> <nl> <headers> <body>; the record's last field is that length.
+{
+    printf 'filedesc://t.arc 0.0.0.0 20250101000000 text/plain 200 - - 0 t.arc 9\n'
+    printf '2 0 test\n'
+    printf '\n\n'
+    printf 'http://example.com/page.html 0.0.0.0 20250101000000 text/html 404 - - 0 t.arc %d\n' "$alen"
+    cat "$dir/hdr" "$dir/body"
+} >"$dir/in.arc"
+
+proxytrack --convert "$dir/out.arc" "$dir/in.arc" >/dev/null 2>&1
+
+# HTTP/1.0 is the writer's own prefix (the input says 1.1), so a verbatim copy
+# of the input cannot satisfy this match.
+grep -aqF 'HTTP/1.0 404 Not Found Here At All' "$dir/out.arc" || {
+    echo "reason phrase lost in the ARC round-trip:" >&2
+    grep -a '^HTTP/' "$dir/out.arc" >&2 || echo "(no status line at all)" >&2
+    exit 1
+}

tests/Makefile.am

@@ -147,6 +147,7 @@ TESTS = \
 	50_local-contentcodings.test \
 	51_local-update-codec.test \
 	52_local-socks5.test \
+	53_local-proxytrack-arc-reason.test \
 	53_local-proxytrack-cache-corrupt.test \
 	54_local-update-truncate-purge.test \
 	55_local-chunked.test \