Add additional checks for size_t overflows

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

PiperOrigin-RevId: 615792028
Change-Id: I71c774c5ef2c2978bd812c70e9bab36d266b7c90

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;
 }
 

absl/strings/internal/str_join_internal.h

@@ -31,13 +31,16 @@
 #ifndef ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
 #define ABSL_STRINGS_INTERNAL_STR_JOIN_INTERNAL_H_
 
+#include <cstdint>
 #include <cstring>
 #include <iterator>
+#include <limits>
 #include <memory>
 #include <string>
 #include <type_traits>
 #include <utility>
 
+#include "absl/base/internal/raw_logging.h"
 #include "absl/strings/internal/ostringstream.h"
 #include "absl/strings/internal/resize_uninitialized.h"
 #include "absl/strings/str_cat.h"
@@ -230,14 +233,19 @@ std::string JoinAlgorithm(Iterator start, Iterator end, absl::string_view s,
   if (start != end) {
     // Sums size
     auto&& start_value = *start;
-    size_t result_size = start_value.size();
+    // Use uint64_t to prevent size_t overflow. We assume it is not possible for
+    // in memory strings to overflow a uint64_t.
+    uint64_t result_size = start_value.size();
     for (Iterator it = start; ++it != end;) {
       result_size += s.size();
       result_size += (*it).size();
     }
 
     if (result_size > 0) {
-      STLStringResizeUninitialized(&result, result_size);
+      constexpr uint64_t kMaxSize =
+          uint64_t{(std::numeric_limits<size_t>::max)()};
+      ABSL_INTERNAL_CHECK(result_size <= kMaxSize, "size_t overflow");
+      STLStringResizeUninitialized(&result, static_cast<size_t>(result_size));
 
       // Joins strings
       char* result_buf = &*result.begin();

absl/strings/str_cat.cc

@@ -20,10 +20,12 @@
 #include <cstdint>
 #include <cstring>
 #include <initializer_list>
+#include <limits>
 #include <string>
 #include <type_traits>
 
 #include "absl/base/config.h"
+#include "absl/base/internal/raw_logging.h"
 #include "absl/base/nullability.h"
 #include "absl/strings/internal/resize_uninitialized.h"
 #include "absl/strings/numbers.h"
@@ -32,7 +34,6 @@
 namespace absl {
 ABSL_NAMESPACE_BEGIN
 
-
 // ----------------------------------------------------------------------
 // StrCat()
 //    This merges the given strings or integers, with no delimiter. This
@@ -57,8 +58,14 @@ absl::Nonnull<char*> Append(absl::Nonnull<char*> out, const AlphaNum& x) {
 
 std::string StrCat(const AlphaNum& a, const AlphaNum& b) {
   std::string result;
-  absl::strings_internal::STLStringResizeUninitialized(&result,
-                                                       a.size() + b.size());
+  // Use uint64_t to prevent size_t overflow. We assume it is not possible for
+  // in memory strings to overflow a uint64_t.
+  constexpr uint64_t kMaxSize = uint64_t{std::numeric_limits<size_t>::max()};
+  const uint64_t result_size =
+      static_cast<uint64_t>(a.size()) + static_cast<uint64_t>(b.size());
+  ABSL_INTERNAL_CHECK(result_size <= kMaxSize, "size_t overflow");
+  absl::strings_internal::STLStringResizeUninitialized(
+      &result, static_cast<size_t>(result_size));
   char* const begin = &result[0];
   char* out = begin;
   out = Append(out, a);
@@ -69,8 +76,15 @@ std::string StrCat(const AlphaNum& a, const AlphaNum& b) {
 
 std::string StrCat(const AlphaNum& a, const AlphaNum& b, const AlphaNum& c) {
   std::string result;
+  // Use uint64_t to prevent size_t overflow. We assume it is not possible for
+  // in memory strings to overflow a uint64_t.
+  constexpr uint64_t kMaxSize = uint64_t{std::numeric_limits<size_t>::max()};
+  const uint64_t result_size = static_cast<uint64_t>(a.size()) +
+                               static_cast<uint64_t>(b.size()) +
+                               static_cast<uint64_t>(c.size());
+  ABSL_INTERNAL_CHECK(result_size <= kMaxSize, "size_t overflow");
   strings_internal::STLStringResizeUninitialized(
-      &result, a.size() + b.size() + c.size());
+      &result, static_cast<size_t>(result_size));
   char* const begin = &result[0];
   char* out = begin;
   out = Append(out, a);
@@ -83,8 +97,16 @@ std::string StrCat(const AlphaNum& a, const AlphaNum& b, const AlphaNum& c) {
 std::string StrCat(const AlphaNum& a, const AlphaNum& b, const AlphaNum& c,
                    const AlphaNum& d) {
   std::string result;
+  // Use uint64_t to prevent size_t overflow. We assume it is not possible for
+  // in memory strings to overflow a uint64_t.
+  constexpr uint64_t kMaxSize = uint64_t{std::numeric_limits<size_t>::max()};
+  const uint64_t result_size = static_cast<uint64_t>(a.size()) +
+                               static_cast<uint64_t>(b.size()) +
+                               static_cast<uint64_t>(c.size()) +
+                               static_cast<uint64_t>(d.size());
+  ABSL_INTERNAL_CHECK(result_size <= kMaxSize, "size_t overflow");
   strings_internal::STLStringResizeUninitialized(
-      &result, a.size() + b.size() + c.size() + d.size());
+      &result, static_cast<size_t>(result_size));
   char* const begin = &result[0];
   char* out = begin;
   out = Append(out, a);
@@ -224,9 +246,16 @@ void SingleArgStrAppend(std::string& str, unsigned long long x) {
 
 std::string CatPieces(std::initializer_list<absl::string_view> pieces) {
   std::string result;
-  size_t total_size = 0;
-  for (absl::string_view piece : pieces) total_size += piece.size();
-  strings_internal::STLStringResizeUninitialized(&result, total_size);
+  // Use uint64_t to prevent size_t overflow. We assume it is not possible for
+  // in memory strings to overflow a uint64_t.
+  constexpr uint64_t kMaxSize = uint64_t{std::numeric_limits<size_t>::max()};
+  uint64_t total_size = 0;
+  for (absl::string_view piece : pieces) {
+    total_size += piece.size();
+  }
+  ABSL_INTERNAL_CHECK(total_size <= kMaxSize, "size_t overflow");
+  strings_internal::STLStringResizeUninitialized(
+      &result, static_cast<size_t>(total_size));
 
   char* const begin = &result[0];
   char* out = begin;

absl/strings/substitute.cc

@@ -18,6 +18,7 @@
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
+#include <limits>
 #include <string>
 
 #include "absl/base/config.h"
@@ -84,6 +85,9 @@ void SubstituteAndAppendArray(
 
   // Build the string.
   size_t original_size = output->size();
+  ABSL_INTERNAL_CHECK(
+      size <= std::numeric_limits<size_t>::max() - original_size,
+      "size_t overflow");
   strings_internal::STLStringResizeUninitializedAmortized(output,
                                                           original_size + size);
   char* target = &(*output)[original_size];