Add function for converting ASN1_TIME to std::chrono::system_clock::time_point

Summary: As it says on tin.

Reviewed By: yfeldblum

Differential Revision: D15409159

fbshipit-source-id: a99b17b54e0c36d79956213655385d234190ff52

folly/portability/Time.cpp

@@ -345,5 +345,13 @@ char* strptime(
   }
   return const_cast<char*>(s + input.tellg());
 }
+
+time_t timelocal(tm* tm) {
+  return mktime(tm);
+}
+
+time_t timegm(tm* tm) {
+  return _mkgmtime(tm);
+}
 }
 #endif

folly/portability/Time.h

@@ -66,5 +66,7 @@ char* strptime(
     const char* __restrict buf,
     const char* __restrict fmt,
     struct tm* __restrict tm);
+time_t timelocal(tm* tm);
+time_t timegm(tm* tm);
 }
 #endif

folly/ssl/OpenSSLCertUtils.cpp

@@ -163,6 +163,27 @@ std::string OpenSSLCertUtils::getNotBeforeTime(X509& x509) {
   return getDateTimeStr(X509_get0_notBefore(&x509));
 }
 
+std::chrono::system_clock::time_point OpenSSLCertUtils::asnTimeToTimepoint(
+    ASN1_TIME* asnTime) {
+  int dSecs = 0;
+  int dDays = 0;
+
+  auto epoch_time_t = std::chrono::system_clock::to_time_t(
+      std::chrono::system_clock::time_point());
+  folly::ssl::ASN1TimeUniquePtr epoch_asn(ASN1_TIME_set(nullptr, epoch_time_t));
+
+  if (!epoch_asn) {
+    throw std::runtime_error("failed to allocate epoch asn.1 time");
+  }
+
+  if (ASN1_TIME_diff(&dDays, &dSecs, epoch_asn.get(), asnTime) != 1) {
+    throw std::runtime_error("invalid asn.1 time");
+  }
+
+  return std::chrono::system_clock::time_point(
+      std::chrono::seconds(dSecs) + std::chrono::hours(24 * dDays));
+}
+
 std::string OpenSSLCertUtils::getDateTimeStr(const ASN1_TIME* time) {
   if (!time) {
     return "";

folly/ssl/OpenSSLCertUtils.h

@@ -15,6 +15,7 @@
  */
 #pragma once
 
+#include <chrono>
 #include <string>
 #include <vector>
 
@@ -109,6 +110,13 @@ class OpenSSLCertUtils {
    */
   static X509StoreUniquePtr readStoreFromBuffer(ByteRange range);
 
+  /**
+   * Converts an ASN1_TIME* into a system clock time point for use with other
+   * std::chrono classes.
+   */
+  static std::chrono::system_clock::time_point asnTimeToTimepoint(
+      ASN1_TIME* asnTime);
+
  private:
   static std::string getDateTimeStr(const ASN1_TIME* time);
 };

folly/ssl/test/OpenSSLCertUtilsTest.cpp

@@ -21,6 +21,7 @@
 #include <folly/container/Enumerate.h>
 #include <folly/portability/GTest.h>
 #include <folly/portability/OpenSSL.h>
+#include <folly/portability/Time.h>
 #include <folly/ssl/Init.h>
 #include <folly/ssl/OpenSSLPtrTypes.h>
 
@@ -220,6 +221,19 @@ TEST_P(OpenSSLCertUtilsTest, TestX509Dates) {
   EXPECT_EQ(notAfter, "Jul  1 23:21:03 2044 GMT");
 }
 
+TEST_P(OpenSSLCertUtilsTest, TestASN1TimeToTimePoint) {
+  auto x509 = readCertFromData(kTestCertWithSan);
+  EXPECT_NE(x509, nullptr);
+  std::tm tm = {};
+  strptime("Feb 13 23:21:03 2017", "%b %d %H:%M:%S %Y", &tm);
+  auto expected = std::chrono::system_clock::from_time_t(timegm(&tm));
+  auto notBefore = X509_get_notBefore(x509.get());
+  auto result = folly::ssl::OpenSSLCertUtils::asnTimeToTimepoint(notBefore);
+  EXPECT_EQ(
+      std::chrono::time_point_cast<std::chrono::seconds>(expected),
+      std::chrono::time_point_cast<std::chrono::seconds>(result));
+}
+
 TEST_P(OpenSSLCertUtilsTest, TestX509Summary) {
   auto x509 = readCertFromData(kTestCertWithSan);
   EXPECT_NE(x509, nullptr);