[SECURITY PATCH 01/73] misc: Implement grub_strlcpy()

* [SECURITY PATCH 01/73] misc: Implement grub_strlcpy()
  2025-02-18 18:00 [SECURITY PATCH 00/73] GRUB2 vulnerabilities - 2025/02/18 Daniel Kiper via Grub-devel
@ 2025-02-18 18:00 ` Daniel Kiper via Grub-devel
  2025-02-18 18:00 ` [SECURITY PATCH 02/73] fs/ufs: Fix a heap OOB write Daniel Kiper via Grub-devel
                   ` (74 subsequent siblings)
  75 siblings, 0 replies; 102+ messages in thread
From: Daniel Kiper via Grub-devel @ 2025-02-18 18:00 UTC (permalink / raw)
  To: grub-devel; +Cc: Daniel Kiper

From: B Horn <b@horn.uk>

grub_strlcpy() acts the same way as strlcpy() does on most *NIX,
returning the length of src and ensuring dest is always NUL
terminated except when size is 0.

Signed-off-by: B Horn <b@horn.uk>
Reviewed-by: Daniel Kiper <daniel.kiper@oracle.com>
---
 include/grub/misc.h | 39 +++++++++++++++++++++++++++++++++++++++
 1 file changed, 39 insertions(+)

diff --git a/include/grub/misc.h b/include/grub/misc.h
index 1578f36c3..14d8f37ac 100644
--- a/include/grub/misc.h
+++ b/include/grub/misc.h
@@ -64,6 +64,45 @@ grub_stpcpy (char *dest, const char *src)
   return d - 1;
 }
 
+static inline grub_size_t
+grub_strlcpy (char *dest, const char *src, grub_size_t size)
+{
+  char *d = dest;
+  grub_size_t res = 0;
+  /*
+   * We do not subtract one from size here to avoid dealing with underflowing
+   * the value, which is why to_copy is always checked to be greater than one
+   * throughout this function.
+   */
+  grub_size_t to_copy = size;
+
+  /* Copy size - 1 bytes to dest. */
+  if (to_copy > 1)
+    while ((*d++ = *src++) != '\0' && ++res && --to_copy > 1)
+      ;
+
+  /*
+   * NUL terminate if size != 0. The previous step may have copied a NUL byte
+   * if it reached the end of the string, but we know dest[size - 1] must always
+   * be a NUL byte.
+   */
+  if (size != 0)
+    dest[size - 1] = '\0';
+
+  /* If there is still space in dest, but are here, we reached the end of src. */
+  if (to_copy > 1)
+    return res;
+
+  /*
+   * If we haven't reached the end of the string, iterate through to determine
+   * the strings total length.
+   */
+  while (*src++ != '\0' && ++res)
+   ;
+
+  return res;
+}
+
 /* XXX: If grub_memmove is too slow, we must implement grub_memcpy.  */
 static inline void *
 grub_memcpy (void *dest, const void *src, grub_size_t n)
-- 
2.11.0


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