X-Git-Url: http://git.tuebingen.mpg.de/?a=blobdiff_plain;f=gcrypt.c;h=052546dd60733d143e6c12bdcfcc92ce36ac5e50;hb=23dd2200dd4fc74025ae87f5c2127f3b0ff71e9b;hp=0de619595f362788111eb24654a2c5749b74b782;hpb=56e2e6b938e7e3d318964f095ffcabc151411446;p=paraslash.git

diff --git a/gcrypt.c b/gcrypt.c
index 0de61959..052546dd 100644
--- a/gcrypt.c
+++ b/gcrypt.c
@@ -1,96 +1,653 @@
-/*
- * Copyright (C) 2011 Andre Noll <maan@systemlinux.org>
- *
- * Licensed under the GPL v2. For licencing details see COPYING.
- */
+/* Copyright (C) 2011 Andre Noll <maan@tuebingen.mpg.de>, see file COPYING. */
 
 /** \file gcrypt.c Libgrcypt-based encryption/decryption routines. */
 
 #include <regex.h>
-#include <sys/types.h>
-#include <sys/socket.h>
+#include <gcrypt.h>
 
 #include "para.h"
 #include "error.h"
 #include "string.h"
 #include "crypt.h"
+#include "crypt_backend.h"
 #include "fd.h"
+#include "base64.h"
 
-struct asymmetric_key {
-	int x;
-};
+//#define GCRYPT_DEBUG 1
+
+#ifdef GCRYPT_DEBUG
+static void dump_buffer(const char *msg, unsigned char *buf, int len)
+{
+	int i;
+
+	fprintf(stderr, "%s (%d bytes): ", msg, len);
+	for (i = 0; i < len; i++)
+		fprintf(stderr, "%02x ", buf[i]);
+	fprintf(stderr, "\n");
+}
+#else
+/** Empty. Define GCRYPT_DEBUG to dump buffers. */
+#define dump_buffer(a, b, c)
+#endif
+
+void hash_function(const char *data, unsigned long len, unsigned char *hash)
+{
+	gcry_error_t gret;
+	gcry_md_hd_t handle;
+	unsigned char *md;
+
+	gret = gcry_md_open(&handle, GCRY_MD_SHA1, 0);
+	assert(gret == 0);
+	gcry_md_write(handle, data, (size_t)len);
+	gcry_md_final(handle);
+	md = gcry_md_read(handle, GCRY_MD_SHA1);
+	assert(md);
+	memcpy(hash, md, HASH_SIZE);
+	gcry_md_close(handle);
+}
 
 void get_random_bytes_or_die(unsigned char *buf, int num)
 {
+	gcry_randomize(buf, (size_t)num, GCRY_STRONG_RANDOM);
 }
 
+/*
+ * This is called at the beginning of every program that uses libgcrypt. The
+ * call to gcry_check_version() initializes the gcrypt library and checks that
+ * we have at least the minimal required version.
+ */
 void init_random_seed_or_die(void)
 {
+	const char *req_ver = "1.5.0";
+	int seed;
+
+	if (!gcry_check_version(req_ver)) {
+		PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
+			req_ver, gcry_check_version(NULL));
+		exit(EXIT_FAILURE);
+	}
+	get_random_bytes_or_die((unsigned char *)&seed, sizeof(seed));
+	srandom(seed);
 }
 
-int get_asymmetric_key(const char *key_file, int private,
-		struct asymmetric_key **result)
+/** S-expression for the public part of an RSA key. */
+#define RSA_PUBKEY_SEXP "(public-key (rsa (n %m) (e %m)))"
+/** S-expression for a private RSA key. */
+#define RSA_PRIVKEY_SEXP "(private-key (rsa (n %m) (e %m) (d %m) (p %m) (q %m) (u %m)))"
+/** S-expression for decryption. */
+#define RSA_DECRYPT_SEXP "(enc-val(flags oaep)(rsa(a %m)))"
+
+struct asymmetric_key {
+	gcry_sexp_t sexp;
+	int num_bytes;
+};
+
+static const char *gcrypt_strerror(gcry_error_t gret)
 {
-	return 0;
+	return gcry_strerror(gcry_err_code(gret));
 }
 
-void free_asymmetric_key(struct asymmetric_key *key)
+static int decode_key(const char *key_file, const char *header_str,
+		const char *footer_str, unsigned char **result)
 {
+	int ret, ret2, i, j;
+	void *map;
+	size_t map_size, key_size, blob_size;
+	unsigned char *blob = NULL;
+	char *begin, *footer, *key;
+
+	ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
+	if (ret < 0)
+		goto out;
+	ret = -E_KEY_MARKER;
+	if (strncmp(map, header_str, strlen(header_str)))
+		goto unmap;
+	footer = strstr(map, footer_str);
+	ret = -E_KEY_MARKER;
+	if (!footer)
+		goto unmap;
+	begin = map + strlen(header_str);
+	/* skip whitespace at the beginning */
+	for (; begin < footer; begin++) {
+		if (para_isspace(*begin))
+			continue;
+		break;
+	}
+	ret = -E_KEY_MARKER;
+	if (begin >= footer)
+		goto unmap;
+
+	key_size = footer - begin;
+	key = para_malloc(key_size + 1);
+	for (i = 0, j = 0; begin + i < footer; i++) {
+		if (para_isspace(begin[i]))
+			continue;
+		key[j++] = begin[i];
+	}
+	key[j] = '\0';
+	ret = base64_decode(key, j, (char **)&blob, &blob_size);
+	free(key);
+	if (ret < 0)
+		goto free_unmap;
+	ret = blob_size;
+	goto unmap;
+free_unmap:
+	free(blob);
+	blob = NULL;
+unmap:
+	ret2 = para_munmap(map, map_size);
+	if (ret >= 0 && ret2 < 0)
+		ret = ret2;
+	if (ret < 0) {
+		free(blob);
+		blob = NULL;
+	}
+out:
+	*result = blob;
+	return ret;
 }
 
-int priv_decrypt(const char *key_file, unsigned char *outbuf,
-		unsigned char *inbuf, int inlen)
+/** ASN Types and their code. */
+enum asn1_types {
+	/** The next object is an integer. */
+	ASN1_TYPE_INTEGER = 0x2,
+	/** Bit string object. */
+	ASN1_TYPE_BIT_STRING = 0x03,
+	/** Keys start with one big type sequence. */
+	ASN1_TYPE_SEQUENCE = 0x30,
+};
+
+/* bit 6 has value 0 */
+static inline bool is_primitive(unsigned char c)
 {
-	return 0;
+	return (c & (1<<6)) == 0;
 }
 
-int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
-		unsigned len, unsigned char *outbuf)
+static inline bool is_primitive_integer(unsigned char c)
 {
-	return 0;
+	if (!is_primitive(c))
+		return false;
+	return (c & 0x1f) == ASN1_TYPE_INTEGER;
 }
 
-struct stream_cipher {
-	int x;
-};
+/* Bit 8 is zero (and bits 7-1 give the length) */
+static inline bool is_short_form(unsigned char c)
+{
+	return (c & 0x80) == 0;
+}
 
-struct stream_cipher *sc_new(const unsigned char *data, int len)
+static inline int get_short_form_length(unsigned char c)
 {
-	return NULL;
+	return c & 0x7f;
 }
 
-void sc_free(struct stream_cipher *sc)
+static inline int get_long_form_num_length_bytes(unsigned char c)
 {
+	return c & 0x7f;
 }
 
-int sc_send_bin_buffer(struct stream_cipher_context *scc, const char *buf,
-		size_t len)
+/*
+ * Returns: Number of bytes scanned. This may differ from the value returned via
+ * bn_bytes because the latter does not include the ASN.1 prefix and a leading
+ * zero is not considered as an additional byte for bn_bytes.
+ */
+static int read_bignum(unsigned char *start, unsigned char *end, gcry_mpi_t *bn,
+		int *bn_bytes)
 {
-	return 0;
+	int i, bn_size;
+	gcry_error_t gret;
+	unsigned char *cp = start;
+
+	if (!is_primitive_integer(*cp))
+		return -E_BAD_PRIVATE_KEY;
+	cp++;
+	if (is_short_form(*cp)) {
+		bn_size = get_short_form_length(*cp);
+		cp++;
+	} else {
+		int num_bytes = get_long_form_num_length_bytes(*cp);
+		if (cp + num_bytes > end)
+			return -E_BAD_PRIVATE_KEY;
+		if (num_bytes > 4) /* nobody has such a large modulus */
+			return -E_BAD_PRIVATE_KEY;
+		cp++;
+		bn_size = 0;
+		for (i = 0; i < num_bytes; i++, cp++)
+			bn_size = (bn_size << 8) + *cp;
+	}
+	PARA_DEBUG_LOG("bn_size %d (0x%x)\n", bn_size, (unsigned)bn_size);
+	gret = gcry_mpi_scan(bn, GCRYMPI_FMT_STD, cp, bn_size, NULL);
+	if (gret) {
+		PARA_ERROR_LOG("%s while scanning n\n",
+			gcry_strerror(gcry_err_code(gret)));
+		return-E_MPI_SCAN;
+	}
+	/*
+	 * Don't take the first leading zero into account for the size of the
+	 * bignum.
+	 */
+	if (*cp == '\0') {
+		cp++;
+		bn_size--;
+	}
+	if (bn_bytes)
+		*bn_bytes = bn_size;
+	cp += bn_size;
+//	unsigned char *buf;
+//	gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, *bn);
+//	PARA_CRIT_LOG("bn: %s\n", buf);
+	return cp - start;
 }
 
-int sc_send_buffer(struct stream_cipher_context *scc, const char *buf)
+static int find_privkey_bignum_offset(const unsigned char *data, int len)
 {
-	return 0;
+	const unsigned char *p = data, *end = data + len;
+
+	/* like the public key, the whole thing is contained in a sequence */
+	if (*p != ASN1_TYPE_SEQUENCE)
+		return -E_ASN1_PARSE;
+	p++;
+	if (p >= end)
+		return -E_ASN1_PARSE;
+	if (is_short_form(*p))
+		p++;
+	else
+		p += 1 + get_long_form_num_length_bytes(*p);
+	if (p >= end)
+		return -E_ASN1_PARSE;
+
+	/* skip next integer */
+	if (*p != ASN1_TYPE_INTEGER)
+		return -E_ASN1_PARSE;
+	p++;
+	if (p >= end)
+		return -E_ASN1_PARSE;
+	if (is_short_form(*p))
+		p += 1 + get_short_form_length(*p);
+	else
+		p += 1 + get_long_form_num_length_bytes(*p);
+	if (p >= end)
+		return -E_ASN1_PARSE;
+	return p - data;
 }
 
-__printf_2_3 int sc_send_va_buffer(struct stream_cipher_context *scc,
-		const char *fmt, ...)
+/** Private keys start with this header. */
+#define PRIVATE_KEY_HEADER "-----BEGIN RSA PRIVATE KEY-----"
+/** Private keys end with this footer. */
+#define PRIVATE_KEY_FOOTER "-----END RSA PRIVATE KEY-----"
+
+static int get_private_key(const char *key_file, struct asymmetric_key **result)
 {
-	return 0;
+	gcry_mpi_t n = NULL, e = NULL, d = NULL, p = NULL, q = NULL,
+		u = NULL;
+	unsigned char *blob, *cp, *end;
+	int blob_size, ret, n_size;
+	gcry_error_t gret;
+	size_t erroff;
+	gcry_sexp_t sexp;
+	struct asymmetric_key *key;
+
+	*result = NULL;
+	ret = decode_key(key_file, PRIVATE_KEY_HEADER, PRIVATE_KEY_FOOTER,
+		&blob);
+	if (ret < 0)
+		return ret;
+	blob_size = ret;
+	end = blob + blob_size;
+	ret = find_privkey_bignum_offset(blob, blob_size);
+	if (ret < 0)
+		goto free_blob;
+	PARA_INFO_LOG("reading RSA params at offset %d\n", ret);
+	cp = blob + ret;
+
+	ret = read_bignum(cp, end, &n, &n_size);
+	if (ret < 0)
+		goto free_blob;
+	cp += ret;
+
+	ret = read_bignum(cp, end, &e, NULL);
+	if (ret < 0)
+		goto release_n;
+	cp += ret;
+
+	ret = read_bignum(cp, end, &d, NULL);
+	if (ret < 0)
+		goto release_e;
+	cp += ret;
+
+	ret = read_bignum(cp, end, &p, NULL);
+	if (ret < 0)
+		goto release_d;
+	cp += ret;
+
+	ret = read_bignum(cp, end, &q, NULL);
+	if (ret < 0)
+		goto release_p;
+	cp += ret;
+	ret = read_bignum(cp, end, &u, NULL);
+	if (ret < 0)
+		goto release_q;
+	/*
+	 * OpenSSL uses slightly different parameters than gcrypt. To use these
+	 * parameters we need to swap the values of p and q and recompute u.
+	 */
+	if (gcry_mpi_cmp(p, q) > 0) {
+		gcry_mpi_swap(p, q);
+		gcry_mpi_invm(u, p, q);
+	}
+	gret = gcry_sexp_build(&sexp, &erroff, RSA_PRIVKEY_SEXP,
+		n, e, d, p, q, u);
+
+	if (gret) {
+		PARA_ERROR_LOG("offset %zu: %s\n", erroff,
+			gcry_strerror(gcry_err_code(gret)));
+		ret = -E_SEXP_BUILD;
+		goto release_u;
+	}
+	key = para_malloc(sizeof(*key));
+	key->sexp = sexp;
+	*result = key;
+	ret = n_size * 8;
+	PARA_INFO_LOG("succesfully read %d bit private key\n", ret);
+release_u:
+	gcry_mpi_release(u);
+release_q:
+	gcry_mpi_release(q);
+release_p:
+	gcry_mpi_release(p);
+release_d:
+	gcry_mpi_release(d);
+release_e:
+	gcry_mpi_release(e);
+release_n:
+	gcry_mpi_release(n);
+free_blob:
+	free(blob);
+	return ret;
 }
 
-int sc_recv_bin_buffer(struct stream_cipher_context *scc, char *buf,
-		size_t size)
+static int get_ssh_public_key(unsigned char *data, int size, gcry_sexp_t *result)
 {
-	return 0;
+	int ret;
+	gcry_error_t gret;
+	unsigned char *blob = NULL, *p, *end;
+	size_t nr_scanned, erroff, decoded_size;
+	gcry_mpi_t e = NULL, n = NULL;
+
+	PARA_DEBUG_LOG("decoding %d byte public rsa-ssh key\n", size);
+	ret = uudecode((char *)data, size, (char **)&blob, &decoded_size);
+	if (ret < 0)
+		goto free_blob;
+	end = blob + decoded_size;
+	dump_buffer("decoded key", blob, decoded_size);
+	ret = check_ssh_key_header(blob, decoded_size);
+	if (ret < 0)
+		goto free_blob;
+	p = blob + ret;
+	ret = -E_SSH_PARSE;
+	if (p >= end)
+		goto free_blob;
+	PARA_DEBUG_LOG("scanning modulus and public exponent\n");
+	gret = gcry_mpi_scan(&e, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
+	if (gret) {
+		ret = -E_MPI_SCAN;
+		PARA_CRIT_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
+		goto free_blob;
+	}
+	PARA_DEBUG_LOG("scanned e (%zu bytes)\n", nr_scanned);
+//	gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_e);
+//	PARA_CRIT_LOG("e: %s\n", buf);
+	p += nr_scanned;
+	if (p >= end)
+		goto release_e;
+	gret = gcry_mpi_scan(&n, GCRYMPI_FMT_SSH, p, end - p, &nr_scanned);
+	if (gret) {
+		ret = -E_MPI_SCAN;
+		PARA_ERROR_LOG("%s\n", gcry_strerror(gcry_err_code(gret)));
+		goto release_e;
+	}
+	PARA_DEBUG_LOG("scanned n (%zu bytes)\n", nr_scanned);
+//	gcry_mpi_aprint(GCRYMPI_FMT_HEX, &buf, NULL, rsa_n);
+//	PARA_CRIT_LOG("n: %s\n", buf);
+	gret = gcry_sexp_build(result, &erroff, RSA_PUBKEY_SEXP, n, e);
+	if (gret) {
+		PARA_ERROR_LOG("offset %zu: %s\n", erroff,
+			gcry_strerror(gcry_err_code(gret)));
+		ret = -E_SEXP_BUILD;
+		goto release_n;
+	}
+	ret = nr_scanned / 32 * 32;
+	PARA_INFO_LOG("successfully read %d bit ssh public key\n", ret * 8);
+release_n:
+	gcry_mpi_release(n);
+release_e:
+	gcry_mpi_release(e);
+free_blob:
+	free(blob);
+	return ret;
 }
 
-int sc_recv_buffer(struct stream_cipher_context *scc, char *buf, size_t size)
+int get_public_key(const char *key_file, struct asymmetric_key **result)
 {
-	return 0;
+	int ret, ret2;
+	void *map;
+	size_t map_size;
+	unsigned char *start, *end;
+	gcry_sexp_t sexp;
+	struct asymmetric_key *key;
+
+	ret = mmap_full_file(key_file, O_RDONLY, &map, &map_size, NULL);
+	if (ret < 0)
+		return ret;
+	ret = is_ssh_rsa_key(map, map_size);
+	if (!ret) {
+		para_munmap(map, map_size);
+		return -E_SSH_PARSE;
+	}
+	start = map + ret;
+	end = map + map_size;
+	ret = -E_SSH_PARSE;
+	if (start >= end)
+		goto unmap;
+	ret = get_ssh_public_key(start, end - start, &sexp);
+	if (ret < 0)
+		goto unmap;
+	key = para_malloc(sizeof(*key));
+	key->num_bytes = ret;
+	key->sexp = sexp;
+	*result = key;
+unmap:
+	ret2 = para_munmap(map, map_size);
+	if (ret >= 0 && ret2 < 0)
+		ret = ret2;
+	return ret;
 }
 
-void hash_function(const char *data, unsigned long len, unsigned char *hash)
+void free_public_key(struct asymmetric_key *key)
+{
+	if (!key)
+		return;
+	gcry_sexp_release(key->sexp);
+	free(key);
+}
+
+static int decode_rsa(gcry_sexp_t sexp, unsigned char *outbuf, size_t *nbytes)
+{
+	const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
+
+	if (!p)
+		return -E_RSA_DECODE;
+	memcpy(outbuf, p, *nbytes);
+	return 1;
+}
+
+int priv_decrypt(const char *key_file, unsigned char *outbuf,
+		unsigned char *inbuf, int inlen)
 {
+	gcry_error_t gret;
+	int ret;
+	struct asymmetric_key *priv;
+	gcry_mpi_t in_mpi = NULL;
+	gcry_sexp_t in, out, priv_key;
+	size_t nbytes;
+
+	ret = check_private_key_file(key_file);
+	if (ret < 0)
+		return ret;
+	PARA_INFO_LOG("decrypting %d byte input\n", inlen);
+	/* key_file -> asymmetric key priv */
+	ret = get_private_key(key_file, &priv);
+	if (ret < 0)
+		return ret;
+
+	/* asymmetric key priv -> sexp priv_key */
+	ret = -E_SEXP_FIND;
+	priv_key = gcry_sexp_find_token(priv->sexp, "private-key", 0);
+	if (!priv_key)
+		goto free_key;
+
+	/* inbuf -> in_mpi */
+	gret = gcry_mpi_scan(&in_mpi, GCRYMPI_FMT_USG, inbuf,
+		inlen, NULL);
+	if (gret) {
+		PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
+		ret = -E_MPI_SCAN;
+		goto key_release;
+	}
+	/* in_mpi -> in sexp */
+	gret = gcry_sexp_build(&in, NULL, RSA_DECRYPT_SEXP, in_mpi);
+	if (gret) {
+		PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
+		ret = -E_SEXP_BUILD;
+		goto in_mpi_release;
+	}
+
+	/* rsa decryption: in sexp -> out sexp */
+	gret = gcry_pk_decrypt(&out, in, priv_key);
+	if (gret) {
+		PARA_ERROR_LOG("decrypt: %s\n", gcrypt_strerror(gret));
+		ret = -E_SEXP_DECRYPT;
+		goto in_release;
+	}
+	ret = decode_rsa(out, outbuf, &nbytes);
+	if (ret < 0)
+		goto out_release;
+	PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
+	ret = nbytes;
+out_release:
+	gcry_sexp_release(out);
+in_release:
+	gcry_sexp_release(in);
+in_mpi_release:
+	gcry_mpi_release(in_mpi);
+key_release:
+	gcry_sexp_release(priv_key);
+free_key:
+	gcry_sexp_release(priv->sexp);
+	free(priv);
+	return ret;
+}
+
+int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
+		unsigned len, unsigned char *outbuf)
+{
+	gcry_error_t gret;
+	gcry_sexp_t pub_key, in, out, out_a;
+	gcry_mpi_t out_mpi = NULL;
+	size_t nbytes;
+	int ret;
+
+	PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
+
+	/* get pub key */
+	pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
+	if (!pub_key)
+		return -E_SEXP_FIND;
+	gret = gcry_sexp_build(&in, NULL, "(data(flags oaep)(value %b))", len, inbuf);
+	if (gret) {
+		PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
+		ret = -E_SEXP_BUILD;
+		goto key_release;
+	}
+	/* rsa sexp encryption: in -> out */
+	gret = gcry_pk_encrypt(&out, in, pub_key);
+	if (gret) {
+		PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
+		ret = -E_SEXP_ENCRYPT;
+		goto in_release;
+	}
+	/* extract a, an MPI with the result of the RSA operation */
+	ret = -E_SEXP_FIND;
+	out_a = gcry_sexp_find_token(out, "a", 0);
+	if (!out_a)
+		goto out_release;
+	/* convert sexp out_a -> out_mpi */
+	out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
+	if (!out_mpi) {
+		ret = -E_SEXP_FIND;
+		goto out_a_release;
+	}
+	gret = gcry_mpi_print(GCRYMPI_FMT_USG, outbuf, 512 /* FIXME */, &nbytes, out_mpi);
+	if (gret) {
+		PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
+		ret = -E_SEXP_ENCRYPT;
+		goto out_mpi_release;
+	}
+	PARA_INFO_LOG("encrypted buffer is %zu bytes\n", nbytes);
+	dump_buffer("enc buf", outbuf, nbytes);
+	ret = nbytes;
+
+out_mpi_release:
+	gcry_mpi_release(out_mpi);
+out_a_release:
+	gcry_sexp_release(out_a);
+out_release:
+	gcry_sexp_release(out);
+in_release:
+	gcry_sexp_release(in);
+key_release:
+	gcry_sexp_release(pub_key);
+	return ret;
+}
+
+struct stream_cipher {
+	gcry_cipher_hd_t handle;
+};
+
+struct stream_cipher *sc_new(const unsigned char *data, int len)
+{
+	gcry_error_t gret;
+	struct stream_cipher *sc = para_malloc(sizeof(*sc));
+
+	assert(len >= 2 * AES_CRT128_BLOCK_SIZE);
+	gret = gcry_cipher_open(&sc->handle, GCRY_CIPHER_AES128,
+		GCRY_CIPHER_MODE_CTR, 0);
+	assert(gret == 0);
+	gret = gcry_cipher_setkey(sc->handle, data,
+		AES_CRT128_BLOCK_SIZE);
+	assert(gret == 0);
+	gret = gcry_cipher_setctr(sc->handle,
+		data + AES_CRT128_BLOCK_SIZE, AES_CRT128_BLOCK_SIZE);
+	assert(gret == 0);
+	return sc;
+}
+
+void sc_free(struct stream_cipher *sc)
+{
+	if (!sc)
+		return;
+	gcry_cipher_close(sc->handle);
+	free(sc);
+}
+
+void sc_crypt(struct stream_cipher *sc, struct iovec *src, struct iovec *dst)
+{
+	gcry_cipher_hd_t handle = sc->handle;
+	gcry_error_t gret;
+
+	/* perform in-place encryption */
+	*dst = *src;
+	gret = gcry_cipher_encrypt(handle, src->iov_base, src->iov_len,
+		NULL, 0);
+	assert(gret == 0);
 }