1 files changed, 224 insertions, 0 deletions
diff --git a/src/auth/password-scheme-scram.c b/src/auth/password-scheme-scram.c
new file mode 100644
index 0000000..a395074
--- /dev/null
+++ b/src/auth/password-scheme-scram.c
@@ -0,0 +1,224 @@
+/*
+ * SCRAM-SHA-1 SASL authentication, see RFC-5802
+ *
+ * Copyright (c) 2012 Florian Zeitz <florob@babelmonkeys.de>
+ *
+ * This software is released under the MIT license.
+ */
+
+
+#include "lib.h"
+#include "safe-memset.h"
+#include "base64.h"
+#include "buffer.h"
+#include "hmac.h"
+#include "randgen.h"
+#include "hash-method.h"
+#include "sha1.h"
+#include "sha2.h"
+#include "str.h"
+#include "password-scheme.h"
+
+/* SCRAM allowed iteration count range. RFC says it SHOULD be at least 4096 */
+#define SCRAM_MIN_ITERATE_COUNT 4096
+#define SCRAM_MAX_ITERATE_COUNT INT_MAX
+
+#define SCRAM_DEFAULT_ITERATE_COUNT 4096
+
+static void
+Hi(const struct hash_method *hmethod, const unsigned char *str, size_t str_size,
+   const unsigned char *salt, size_t salt_size, unsigned int i,
+   unsigned char *result)
+{
+	struct hmac_context ctx;
+	unsigned char U[hmethod->digest_size];
+	unsigned int j, k;
+
+	/* Calculate U1 */
+	hmac_init(&ctx, str, str_size, hmethod);
+	hmac_update(&ctx, salt, salt_size);
+	hmac_update(&ctx, "\0\0\0\1", 4);
+	hmac_final(&ctx, U);
+
+	memcpy(result, U, hmethod->digest_size);
+
+	/* Calculate U2 to Ui and Hi */
+	for (j = 2; j <= i; j++) {
+		hmac_init(&ctx, str, str_size, hmethod);
+		hmac_update(&ctx, U, sizeof(U));
+		hmac_final(&ctx, U);
+		for (k = 0; k < hmethod->digest_size; k++)
+			result[k] ^= U[k];
+	}
+}
+
+int scram_scheme_parse(const struct hash_method *hmethod, const char *name,
+		       const unsigned char *credentials, size_t size,
+		       unsigned int *iter_count_r, const char **salt_r,
+		       unsigned char stored_key_r[],
+		       unsigned char server_key_r[], const char **error_r)
+{
+	const char *const *fields;
+	buffer_t *buf;
+
+	/* password string format: iter,salt,stored_key,server_key */
+	fields = t_strsplit(t_strndup(credentials, size), ",");
+
+	if (str_array_length(fields) != 4) {
+		*error_r = t_strdup_printf(
+			"Invalid %s passdb entry format", name);
+		return -1;
+	}
+	if (str_to_uint(fields[0], iter_count_r) < 0 ||
+	    *iter_count_r < SCRAM_MIN_ITERATE_COUNT ||
+	    *iter_count_r > SCRAM_MAX_ITERATE_COUNT) {
+		*error_r = t_strdup_printf(
+			"Invalid %s iteration count in passdb", name);
+		return -1;
+	}
+	*salt_r = fields[1];
+
+	buf = t_buffer_create(hmethod->digest_size);
+	if (base64_decode(fields[2], strlen(fields[2]), NULL, buf) < 0 ||
+	    buf->used != hmethod->digest_size) {
+		*error_r = t_strdup_printf(
+			"Invalid %s StoredKey in passdb", name);
+		return -1;
+	}
+	memcpy(stored_key_r, buf->data, hmethod->digest_size);
+
+	buffer_set_used_size(buf, 0);
+	if (base64_decode(fields[3], strlen(fields[3]), NULL, buf) < 0 ||
+	    buf->used != hmethod->digest_size) {
+		*error_r = t_strdup_printf(
+			"Invalid %s ServerKey in passdb", name);
+		return -1;
+	}
+	memcpy(server_key_r, buf->data, hmethod->digest_size);
+	return 0;
+}
+
+int scram_verify(const struct hash_method *hmethod, const char *scheme_name,
+		 const char *plaintext, const unsigned char *raw_password,
+		 size_t size, const char **error_r)
+{
+	struct hmac_context ctx;
+	const char *salt_base64;
+	unsigned int iter_count;
+	const unsigned char *salt;
+	size_t salt_len;
+	unsigned char salted_password[hmethod->digest_size];
+	unsigned char client_key[hmethod->digest_size];
+	unsigned char stored_key[hmethod->digest_size];
+	unsigned char calculated_stored_key[hmethod->digest_size];
+	unsigned char server_key[hmethod->digest_size];
+	int ret;
+
+	if (scram_scheme_parse(hmethod, scheme_name, raw_password, size,
+			       &iter_count, &salt_base64,
+			       stored_key, server_key, error_r) < 0)
+		return -1;
+
+	salt = buffer_get_data(t_base64_decode_str(salt_base64), &salt_len);
+
+	/* FIXME: credentials should be SASLprepped UTF8 data here */
+	Hi(hmethod, (const unsigned char *)plaintext, strlen(plaintext),
+	   salt, salt_len, iter_count, salted_password);
+
+	/* Calculate ClientKey */
+	hmac_init(&ctx, salted_password, sizeof(salted_password), hmethod);
+	hmac_update(&ctx, "Client Key", 10);
+	hmac_final(&ctx, client_key);
+
+	/* Calculate StoredKey */
+	hash_method_get_digest(hmethod, client_key, sizeof(client_key),
+			       calculated_stored_key);
+	ret = mem_equals_timing_safe(stored_key, calculated_stored_key,
+				     sizeof(stored_key)) ? 1 : 0;
+
+	safe_memset(salted_password, 0, sizeof(salted_password));
+	safe_memset(client_key, 0, sizeof(client_key));
+	safe_memset(stored_key, 0, sizeof(stored_key));
+
+	return ret;
+}
+
+void scram_generate(const struct hash_method *hmethod, const char *plaintext,
+		    const unsigned char **raw_password_r, size_t *size_r)
+{
+	string_t *str;
+	struct hmac_context ctx;
+	unsigned char salt[16];
+	unsigned char salted_password[hmethod->digest_size];
+	unsigned char client_key[hmethod->digest_size];
+	unsigned char server_key[hmethod->digest_size];
+	unsigned char stored_key[hmethod->digest_size];
+
+	random_fill(salt, sizeof(salt));
+
+	str = t_str_new(MAX_BASE64_ENCODED_SIZE(sizeof(salt)));
+	str_printfa(str, "%d,", SCRAM_DEFAULT_ITERATE_COUNT);
+	base64_encode(salt, sizeof(salt), str);
+
+	/* FIXME: credentials should be SASLprepped UTF8 data here */
+	Hi(hmethod, (const unsigned char *)plaintext, strlen(plaintext), salt,
+	   sizeof(salt), SCRAM_DEFAULT_ITERATE_COUNT, salted_password);
+
+	/* Calculate ClientKey */
+	hmac_init(&ctx, salted_password, sizeof(salted_password), hmethod);
+	hmac_update(&ctx, "Client Key", 10);
+	hmac_final(&ctx, client_key);
+
+	/* Calculate StoredKey */
+	hash_method_get_digest(hmethod, client_key, sizeof(client_key),
+			       stored_key);
+	str_append_c(str, ',');
+	base64_encode(stored_key, sizeof(stored_key), str);
+
+	/* Calculate ServerKey */
+	hmac_init(&ctx, salted_password, sizeof(salted_password), hmethod);
+	hmac_update(&ctx, "Server Key", 10);
+	hmac_final(&ctx, server_key);
+	str_append_c(str, ',');
+	base64_encode(server_key, sizeof(server_key), str);
+
+	safe_memset(salted_password, 0, sizeof(salted_password));
+	safe_memset(client_key, 0, sizeof(client_key));
+	safe_memset(server_key, 0, sizeof(server_key));
+	safe_memset(stored_key, 0, sizeof(stored_key));
+
+	*raw_password_r = (const unsigned char *)str_c(str);
+	*size_r = str_len(str);
+}
+
+int scram_sha1_verify(const char *plaintext,
+		      const struct password_generate_params *params ATTR_UNUSED,
+		      const unsigned char *raw_password, size_t size,
+		      const char **error_r)
+{
+	return scram_verify(&hash_method_sha1, "SCRAM-SHA-1", plaintext,
+			    raw_password, size, error_r);
+}
+
+void scram_sha1_generate(const char *plaintext,
+			 const struct password_generate_params *params ATTR_UNUSED,
+                         const unsigned char **raw_password_r, size_t *size_r)
+{
+	scram_generate(&hash_method_sha1, plaintext, raw_password_r, size_r);
+}
+
+int scram_sha256_verify(const char *plaintext,
+			const struct password_generate_params *params ATTR_UNUSED,
+			const unsigned char *raw_password, size_t size,
+			const char **error_r)
+{
+	return scram_verify(&hash_method_sha256, "SCRAM-SHA-256", plaintext,
+			    raw_password, size, error_r);
+}
+
+void scram_sha256_generate(const char *plaintext,
+			   const struct password_generate_params *params ATTR_UNUSED,
+			   const unsigned char **raw_password_r, size_t *size_r)
+{
+	scram_generate(&hash_method_sha256, plaintext, raw_password_r, size_r);
+}