Add BN_bn2lebinpad and BN_lebin2bn

These are OpenSSL names for BN_bn2le_padded and BN_le2bn. We can just
replace BN_le2bn with BN_lebin2bn. BN_bn2lebinpad is not size_t-clean,
so handle it as a separate function like we did BN_bn2binpad.

Change-Id: I6999ca06140a0c8c25942362dc79d1821971d679
Reviewed-on: https://boringssl-review.googlesource.com/c/boringssl/+/62665
Commit-Queue: Adam Langley <agl@google.com>
Auto-Submit: David Benjamin <davidben@google.com>
Reviewed-by: Adam Langley <agl@google.com>
Commit-Queue: David Benjamin <davidben@google.com>

crypto/bn_extra/convert.c

@@ -455,3 +455,11 @@ int BN_bn2binpad(const BIGNUM *in, uint8_t *out, int len) {
   }
   return len;
 }
+
+int BN_bn2lebinpad(const BIGNUM *in, uint8_t *out, int len) {
+  if (len < 0 ||
+      !BN_bn2le_padded(out, (size_t)len, in)) {
+    return -1;
+  }
+  return len;
+}

crypto/fipsmodule/bn/bn_test.cc

@@ -1158,8 +1158,8 @@ TEST_F(BNTest, LittleEndian) {
   ASSERT_TRUE(BN_bn2le_padded(out, sizeof(out), x.get()));
   EXPECT_EQ(Bytes(zeros), Bytes(out));
 
-  ASSERT_TRUE(BN_le2bn(out, sizeof(out), y.get()));
-  EXPECT_BIGNUMS_EQUAL("BN_le2bn round-trip", x.get(), y.get());
+  ASSERT_TRUE(BN_lebin2bn(out, sizeof(out), y.get()));
+  EXPECT_BIGNUMS_EQUAL("BN_lebin2bn round-trip", x.get(), y.get());
 
   // Test random numbers at various byte lengths.
   for (size_t bytes = 128 - 7; bytes <= 128; bytes++) {
@@ -1182,8 +1182,8 @@ TEST_F(BNTest, LittleEndian) {
     EXPECT_EQ(Bytes(out), Bytes(expected));
 
     // Make sure the decoding produces the same BIGNUM.
-    ASSERT_TRUE(BN_le2bn(out, bytes, y.get()));
-    EXPECT_BIGNUMS_EQUAL("BN_le2bn round-trip", x.get(), y.get());
+    ASSERT_TRUE(BN_lebin2bn(out, bytes, y.get()));
+    EXPECT_BIGNUMS_EQUAL("BN_lebin2bn round-trip", x.get(), y.get());
   }
 }
 

crypto/fipsmodule/bn/bytes.c

@@ -116,7 +116,7 @@ BIGNUM *BN_bin2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
   return ret;
 }
 
-BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
+BIGNUM *BN_lebin2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
   BIGNUM *bn = NULL;
   if (ret == NULL) {
     bn = BN_new();
@@ -149,6 +149,10 @@ BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
   return ret;
 }
 
+BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret) {
+  return BN_lebin2bn(in, len, ret);
+}
+
 // fits_in_bytes returns one if the |num_words| words in |words| can be
 // represented in |num_bytes| bytes.
 static int fits_in_bytes(const BN_ULONG *words, size_t num_words,

include/openssl/bn.h

@@ -254,11 +254,11 @@ OPENSSL_EXPORT BIGNUM *BN_bin2bn(const uint8_t *in, size_t len, BIGNUM *ret);
 // |in| is secret, use |BN_bn2bin_padded| instead.
 OPENSSL_EXPORT size_t BN_bn2bin(const BIGNUM *in, uint8_t *out);
 
-// BN_le2bn sets |*ret| to the value of |len| bytes from |in|, interpreted as
+// BN_lebin2bn sets |*ret| to the value of |len| bytes from |in|, interpreted as
 // a little-endian number, and returns |ret|. If |ret| is NULL then a fresh
 // |BIGNUM| is allocated and returned. It returns NULL on allocation
 // failure.
-OPENSSL_EXPORT BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret);
+OPENSSL_EXPORT BIGNUM *BN_lebin2bn(const uint8_t *in, size_t len, BIGNUM *ret);
 
 // BN_bn2le_padded serialises the absolute value of |in| to |out| as a
 // little-endian integer, which must have |len| of space available, padding
@@ -972,6 +972,12 @@ OPENSSL_EXPORT int BN_MONT_CTX_set(BN_MONT_CTX *mont, const BIGNUM *mod,
 // Use |BN_bn2bin_padded| instead. It is |size_t|-clean.
 OPENSSL_EXPORT int BN_bn2binpad(const BIGNUM *in, uint8_t *out, int len);
 
+// BN_bn2lebinpad behaves like |BN_bn2le_padded|, but it returns |len| on
+// success and -1 on error.
+//
+// Use |BN_bn2le_padded| instead. It is |size_t|-clean.
+OPENSSL_EXPORT int BN_bn2lebinpad(const BIGNUM *in, uint8_t *out, int len);
+
 // BN_prime_checks is a deprecated alias for |BN_prime_checks_for_validation|.
 // Use |BN_prime_checks_for_generation| or |BN_prime_checks_for_validation|
 // instead. (This defaults to the |_for_validation| value in order to be
@@ -981,6 +987,9 @@ OPENSSL_EXPORT int BN_bn2binpad(const BIGNUM *in, uint8_t *out, int len);
 // BN_secure_new calls |BN_new|.
 OPENSSL_EXPORT BIGNUM *BN_secure_new(void);
 
+// BN_le2bn calls |BN_lebin2bn|.
+OPENSSL_EXPORT BIGNUM *BN_le2bn(const uint8_t *in, size_t len, BIGNUM *ret);
+
 
 // Private functions