From 21cd1994c280c705e99d48ae09f2d94e348875a3 Mon Sep 17 00:00:00 2001
From: Doug Hogan <hogand@users.noreply.github.com>
Date: Thu, 20 Dec 2018 02:00:57 -0800
Subject: Move BN and RSA utility functions to new files

---
 lib/crypto/c_src/bn.c | 101 ++++++++++++++++++++++++++++++++++++++++++++++++++
 1 file changed, 101 insertions(+)
 create mode 100644 lib/crypto/c_src/bn.c

(limited to 'lib/crypto/c_src/bn.c')

diff --git a/lib/crypto/c_src/bn.c b/lib/crypto/c_src/bn.c
new file mode 100644
index 0000000000..4079870abe
--- /dev/null
+++ b/lib/crypto/c_src/bn.c
@@ -0,0 +1,101 @@
+#include "bn.h"
+
+
+int get_bn_from_mpint(ErlNifEnv* env, ERL_NIF_TERM term, BIGNUM** bnp)
+{
+    ErlNifBinary bin;
+    int sz;
+    if (!enif_inspect_binary(env,term,&bin)) {
+	return 0;
+    }
+    ERL_VALGRIND_ASSERT_MEM_DEFINED(bin.data, bin.size);
+    sz = bin.size - 4;
+    if (sz < 0 || get_int32(bin.data) != sz) {
+	return 0;
+    }
+    *bnp = BN_bin2bn(bin.data+4, sz, NULL);
+    return 1;
+}
+
+int get_bn_from_bin(ErlNifEnv* env, ERL_NIF_TERM term, BIGNUM** bnp)
+{
+    ErlNifBinary bin;
+    if (!enif_inspect_binary(env,term,&bin)) {
+	return 0;
+    }
+    ERL_VALGRIND_ASSERT_MEM_DEFINED(bin.data, bin.size);
+    *bnp = BN_bin2bn(bin.data, bin.size, NULL);
+    return 1;
+}
+
+ERL_NIF_TERM bin_from_bn(ErlNifEnv* env, const BIGNUM *bn)
+{
+    int bn_len;
+    unsigned char *bin_ptr;
+    ERL_NIF_TERM term;
+
+    /* Copy the bignum into an erlang binary. */
+    bn_len = BN_num_bytes(bn);
+    bin_ptr = enif_make_new_binary(env, bn_len, &term);
+    BN_bn2bin(bn, bin_ptr);
+
+    return term;
+}
+
+ERL_NIF_TERM mod_exp_nif(ErlNifEnv* env, int argc, const ERL_NIF_TERM argv[])
+{/* (Base,Exponent,Modulo,bin_hdr) */
+    BIGNUM *bn_base=NULL, *bn_exponent=NULL, *bn_modulo=NULL, *bn_result;
+    BN_CTX *bn_ctx;
+    unsigned char* ptr;
+    unsigned dlen;
+    unsigned bin_hdr; /* return type: 0=plain binary, 4: mpint */
+    unsigned extra_byte;
+    ERL_NIF_TERM ret;
+
+    if (!get_bn_from_bin(env, argv[0], &bn_base)
+	|| !get_bn_from_bin(env, argv[1], &bn_exponent)
+	|| !get_bn_from_bin(env, argv[2], &bn_modulo)
+	|| !enif_get_uint(env,argv[3],&bin_hdr) || (bin_hdr & ~4)) {
+
+	if (bn_base) BN_free(bn_base);
+	if (bn_exponent) BN_free(bn_exponent);
+	if (bn_modulo) BN_free(bn_modulo);
+	return enif_make_badarg(env);
+    }
+    bn_result = BN_new();
+    bn_ctx = BN_CTX_new();
+    BN_mod_exp(bn_result, bn_base, bn_exponent, bn_modulo, bn_ctx);
+    dlen = BN_num_bytes(bn_result);
+    extra_byte = bin_hdr && BN_is_bit_set(bn_result, dlen*8-1);
+    ptr = enif_make_new_binary(env, bin_hdr+extra_byte+dlen, &ret);
+    if (bin_hdr) {
+	put_int32(ptr, extra_byte+dlen);
+	ptr[4] = 0; /* extra zeroed byte to ensure a positive mpint */
+	ptr += bin_hdr + extra_byte;
+    }
+    BN_bn2bin(bn_result, ptr);
+    BN_free(bn_result);
+    BN_CTX_free(bn_ctx);
+    BN_free(bn_modulo);
+    BN_free(bn_exponent);
+    BN_free(bn_base);
+    return ret;
+}
+
+#ifdef HAVE_EC
+ERL_NIF_TERM bn2term(ErlNifEnv* env, const BIGNUM *bn)
+{
+    unsigned dlen;
+    unsigned char* ptr;
+    ERL_NIF_TERM ret;
+
+    if (!bn)
+	    return atom_undefined;
+
+    dlen = BN_num_bytes(bn);
+    ptr = enif_make_new_binary(env, dlen, &ret);
+    BN_bn2bin(bn, ptr);
+    ERL_VALGRIND_MAKE_MEM_DEFINED(ptr, dlen);
+    return ret;
+}
+#endif
-- 
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