Add additional checks for size_t overflows

This change mainly affects 32-bit platforms. Similar to
4618865caf8596742a9fd7c28a70a46b5e277794, check for size_t overflow
in all places where string result sizes are precomputed before allocation.

PiperOrigin-RevId: 615792028
Change-Id: I71c774c5ef2c2978bd812c70e9bab36d266b7c90

1 files changed, 5 insertions, 2 deletions

diff --git a/absl/strings/internal/escaping.cc b/absl/strings/internal/escaping.cc
index 56a4cbed..d2abe669 100644
--- a/absl/strings/internal/escaping.cc
+++ b/absl/strings/internal/escaping.cc
@@ -14,6 +14,8 @@
 
 #include "absl/strings/internal/escaping.h"
 
+#include <limits>
+
 #include "absl/base/internal/endian.h"
 #include "absl/base/internal/raw_logging.h"
 
@@ -31,12 +33,14 @@ ABSL_CONST_INIT const char kBase64Chars[] =
 ABSL_CONST_INIT const char kWebSafeBase64Chars[] =
     "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789-_";
 
-
 size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding) {
   // Base64 encodes three bytes of input at a time. If the input is not
   // divisible by three, we pad as appropriate.
   //
   // Base64 encodes each three bytes of input into four bytes of output.
+  constexpr size_t kMaxSize = (std::numeric_limits<size_t>::max() - 1) / 4 * 3;
+  ABSL_INTERNAL_CHECK(input_len <= kMaxSize,
+                      "CalculateBase64EscapedLenInternal() overflow");
   size_t len = (input_len / 3) * 4;
 
   // Since all base 64 input is an integral number of octets, only the following
@@ -66,7 +70,6 @@ size_t CalculateBase64EscapedLenInternal(size_t input_len, bool do_padding) {
     }
   }
 
-  assert(len >= input_len);  // make sure we didn't overflow
   return len;
 }