X-Git-Url: http://git.tuebingen.mpg.de/?p=paraslash.git;a=blobdiff_plain;f=gcrypt.c;h=f825f6c6a3de6388959d7b900f31ef9d48e6397b;hp=1312aaedc275206ba88ce4cd44cd89c01d2ba9ba;hb=4a4d8f266a79275d7b2c902dc69b5ec8d46406b2;hpb=1ecb886f1aa76e72bd11d45782210b5ca19bce42

diff --git a/gcrypt.c b/gcrypt.c
index 1312aaed..f825f6c6 100644
--- a/gcrypt.c
+++ b/gcrypt.c
@@ -19,6 +19,9 @@
 
 //#define GCRYPT_DEBUG 1
 
+static bool libgcrypt_has_oaep;
+static const char *rsa_decrypt_sexp;
+
 #ifdef GCRYPT_DEBUG
 static void dump_buffer(const char *msg, unsigned char *buf, int len)
 {
@@ -56,14 +59,32 @@ void get_random_bytes_or_die(unsigned char *buf, int num)
 }
 
 /*
- * This is called at the beginning of every program that uses libgcrypt.  We
- * don't have to initialize any random seed here, but the call to gcry_control
- * is necessary to avoid warnings of the form "missing initialization - please
- * fix the application".
+ * This is called at the beginning of every program that uses libgcrypt. We
+ * don't have to initialize any random seed here, but we must initialize the
+ * gcrypt library. This task is performed by gcry_check_version() which can
+ * also check that the gcrypt library version is at least the minimal required
+ * version. This function also tells us whether we have to use our own OAEP
+ * padding code.
  */
 void init_random_seed_or_die(void)
 {
-	gcry_control(GCRYCTL_INITIALIZATION_FINISHED, 0);
+	const char *ver, *req_ver;
+
+	ver = gcry_check_version(NULL);
+	req_ver = "1.4.0";
+	if (!gcry_check_version(req_ver)) {
+		PARA_EMERG_LOG("fatal: need at least libgcrypt-%s, have: %s\n",
+			req_ver, ver);
+		exit(EXIT_FAILURE);
+	}
+	req_ver = "1.5.0";
+	if (gcry_check_version(req_ver)) {
+		libgcrypt_has_oaep = true;
+		rsa_decrypt_sexp = "(enc-val(flags oaep)(rsa(a %m)))";
+	} else {
+		libgcrypt_has_oaep = false;
+		rsa_decrypt_sexp = "(enc-val(rsa(a %m)))";
+	}
 }
 
 /** S-expression for the public part of an RSA key. */
@@ -143,7 +164,7 @@ static void pad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
 /* rfc 3447, section 7.1.2 */
 static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
 		size_t *out_len)
-{	int ret;
+{
 	unsigned char *masked_seed = in + 1;
 	unsigned char *db = in + 1 + HASH_SIZE;
 	unsigned char seed[HASH_SIZE], seed_mask[HASH_SIZE];
@@ -168,7 +189,7 @@ static int unpad_oaep(unsigned char *in, size_t in_len, unsigned char *out,
 	p++;
 	*out_len = in + in_len - p;
 	memcpy(out, p, *out_len);
-	return ret;
+	return 1;
 }
 
 struct asymmetric_key {
@@ -566,7 +587,7 @@ static int get_asn_public_key(const char *key_file, struct asymmetric_key **resu
 	key = para_malloc(sizeof(*key));
 	key->sexp = sexp;
 	*result = key;
-	ret = n_size * 8;
+	ret = n_size;
 	PARA_INFO_LOG("successfully read %u bit asn public key\n", n_size * 8);
 
 release_e:
@@ -693,16 +714,76 @@ void free_asymmetric_key(struct asymmetric_key *key)
 	free(key);
 }
 
+static int decode_rsa(gcry_sexp_t sexp, int key_size, unsigned char *outbuf,
+		size_t *nbytes)
+{
+	int ret;
+	gcry_error_t gret;
+	unsigned char oaep_buf[512];
+	gcry_mpi_t out_mpi;
+
+	if (libgcrypt_has_oaep) {
+		const char *p = gcry_sexp_nth_data(sexp, 1, nbytes);
+
+		if (!p) {
+			PARA_ERROR_LOG("could not get data from list\n");
+			return -E_OEAP;
+		}
+		memcpy(outbuf, p, *nbytes);
+		return 1;
+	}
+	out_mpi = gcry_sexp_nth_mpi(sexp, 0, GCRYMPI_FMT_USG);
+	if (!out_mpi)
+		return -E_SEXP_FIND;
+	gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
+		nbytes, out_mpi);
+	if (gret) {
+		PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
+		ret = -E_MPI_PRINT;
+		goto out_mpi_release;
+	}
+	/*
+	 * An oaep-encoded buffer always starts with at least one zero byte.
+	 * However, leading zeroes in an mpi are omitted in the output of
+	 * gcry_mpi_print() when using the GCRYMPI_FMT_USG format. The
+	 * alternative, GCRYMPI_FMT_STD, does not work either because here the
+	 * leading zero(es) might also be omitted, depending on the value of
+	 * the second byte.
+	 *
+	 * To circumvent this, we shift the oaep buffer to the right. But first
+	 * we check that the buffer actually started with a zero byte, i.e. that
+	 * nbytes < key_size. Otherwise a decoding error occurred.
+	 */
+	ret = -E_SEXP_DECRYPT;
+	if (*nbytes >= key_size)
+		goto out_mpi_release;
+	memmove(oaep_buf + key_size - *nbytes, oaep_buf, *nbytes);
+	memset(oaep_buf, 0, key_size - *nbytes);
+
+	PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
+		key_size);
+	dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);;
+	ret = unpad_oaep(oaep_buf, key_size, outbuf, nbytes);
+	if (ret < 0)
+		goto out_mpi_release;
+	PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
+		*nbytes);
+	dump_buffer("unpadded decrypted buffer", outbuf, *nbytes);;
+	ret = 1;
+out_mpi_release:
+	gcry_mpi_release(out_mpi);
+	return ret;
+}
+
 int priv_decrypt(const char *key_file, unsigned char *outbuf,
 		unsigned char *inbuf, int inlen)
 {
 	gcry_error_t gret;
 	int ret, key_size;
 	struct asymmetric_key *priv;
-	gcry_mpi_t in_mpi = NULL, out_mpi = NULL;
+	gcry_mpi_t in_mpi = NULL;
 	gcry_sexp_t in, out, priv_key;
 	size_t nbytes;
-	unsigned char oaep_buf[512];
 
 	PARA_INFO_LOG("decrypting %d byte input\n", inlen);
 	/* key_file -> asymmetric key priv */
@@ -725,9 +806,8 @@ int priv_decrypt(const char *key_file, unsigned char *outbuf,
 		ret = -E_MPI_SCAN;
 		goto key_release;
 	}
-
 	/* in_mpi -> in sexp */
-	gret = gcry_sexp_build(&in, NULL, "(enc-val(rsa(a %m)))", in_mpi);
+	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;
@@ -741,47 +821,11 @@ int priv_decrypt(const char *key_file, unsigned char *outbuf,
 		ret = -E_SEXP_DECRYPT;
 		goto in_release;
 	}
-	out_mpi = gcry_sexp_nth_mpi(out, 0, GCRYMPI_FMT_USG);
-	if (!out_mpi) {
-		ret = -E_SEXP_FIND;
+	ret = decode_rsa(out, key_size, outbuf, &nbytes);
+	if (ret < 0)
 		goto out_release;
-	}
-	gret = gcry_mpi_print(GCRYMPI_FMT_USG, oaep_buf, sizeof(oaep_buf),
-		&nbytes, out_mpi);
-	if (gret) {
-		PARA_ERROR_LOG("mpi_print: %s\n", gcrypt_strerror(gret));
-		ret = -E_MPI_PRINT;
-		goto out_mpi_release;
-	}
-	/*
-	 * An oaep-encoded buffer always starts with at least one zero byte.
-	 * However, leading zeroes in an mpi are omitted in the output of
-	 * gcry_mpi_print() when using the GCRYMPI_FMT_USG format. The
-	 * alternative, GCRYMPI_FMT_STD, does not work either because here the
-	 * leading zero(es) might also be omitted, depending on the value of
-	 * the second byte.
-	 *
-	 * To circumvent this, we shift the oaep buffer to the right. But first
-	 * we check that the buffer actually started with a zero byte, i.e. that
-	 * nbytes < key_size. Otherwise a decoding error occurred.
-	 */
-	ret = -E_SEXP_DECRYPT;
-	if (nbytes >= key_size)
-		goto out_mpi_release;
-	memmove(oaep_buf + key_size - nbytes, oaep_buf, nbytes);
-	memset(oaep_buf, 0, key_size - nbytes);
-
-	PARA_DEBUG_LOG("decrypted buffer before unpad (%d bytes):\n",
-		key_size);
-	dump_buffer("non-unpadded decrypted buffer", oaep_buf, key_size);;
-	unpad_oaep(oaep_buf, key_size, outbuf, &nbytes);
-	PARA_DEBUG_LOG("decrypted buffer after unpad (%zu bytes):\n",
-		nbytes);
-	dump_buffer("unpadded decrypted buffer", outbuf, nbytes);;
+	PARA_INFO_LOG("successfully decrypted %zu byte message\n", nbytes);
 	ret = nbytes;
-	PARA_INFO_LOG("successfully decrypted %u byte message\n", ret);
-out_mpi_release:
-	gcry_mpi_release(out_mpi);
 out_release:
 	gcry_sexp_release(out);
 in_release:
@@ -799,12 +843,10 @@ int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 		unsigned len, unsigned char *outbuf)
 {
 	gcry_error_t gret;
-	const size_t pad_size = 256;
 	gcry_sexp_t pub_key, in, out, out_a;
 	gcry_mpi_t out_mpi = NULL;
 	size_t nbytes;
 	int ret;
-	unsigned char padded_input[256];
 
 	PARA_INFO_LOG("encrypting %u byte input with %d-byte key\n", len, pub->num_bytes);
 
@@ -812,13 +854,18 @@ int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 	pub_key = gcry_sexp_find_token(pub->sexp, "public-key", 0);
 	if (!pub_key)
 		return -E_SEXP_FIND;
-
-	/* inbuf -> padded inbuf */
-	pad_oaep(inbuf, len, padded_input, pad_size);
-
-	/* padded inbuf -> in sexp */
-	gret = gcry_sexp_build(&in, NULL, "(data(flags raw)(value %b))",
-		pad_size, padded_input);
+	if (libgcrypt_has_oaep) {
+		gret = gcry_sexp_build(&in, NULL,
+			"(data(flags oaep)(value %b))", len, inbuf);
+	} else {
+		unsigned char padded_input[256];
+		const size_t pad_size = 256;
+		/* inbuf -> padded inbuf */
+		pad_oaep(inbuf, len, padded_input, pad_size);
+		/* padded inbuf -> in sexp */
+		gret = gcry_sexp_build(&in, NULL,
+			"(data(flags raw)(value %b))", pad_size, padded_input);
+	}
 	if (gret) {
 		PARA_ERROR_LOG("%s\n", gcrypt_strerror(gret));
 		ret = -E_SEXP_BUILD;
@@ -837,7 +884,7 @@ int pub_encrypt(struct asymmetric_key *pub, unsigned char *inbuf,
 	if (!out_a)
 		goto out_release;
 	/* convert sexp out_a -> out_mpi */
-	out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_STD);
+	out_mpi = gcry_sexp_nth_mpi(out_a, 1, GCRYMPI_FMT_USG);
 	if (!out_mpi) {
 		ret = -E_SEXP_FIND;
 		goto out_a_release;