- markus@cvs.openbsd.org 2002/03/14 16:56:33
[auth-rh-rsa.c auth-rsa.c auth.h]
split auth_rsa() for better readability and privsep; ok provos@
diff --git a/auth-rsa.c b/auth-rsa.c
index f7ae03c..ff9bf3b 100644
--- a/auth-rsa.c
+++ b/auth-rsa.c
@@ -14,7 +14,7 @@
*/
#include "includes.h"
-RCSID("$OpenBSD: auth-rsa.c,v 1.50 2001/12/28 14:50:54 markus Exp $");
+RCSID("$OpenBSD: auth-rsa.c,v 1.51 2002/03/14 16:56:33 markus Exp $");
#include <openssl/rsa.h>
#include <openssl/md5.h>
@@ -52,6 +52,51 @@
* description of the options.
*/
+static BIGNUM *
+auth_rsa_generate_challenge(Key *key)
+{
+ BIGNUM *challenge;
+ BN_CTX *ctx;
+
+ if ((challenge = BN_new()) == NULL)
+ fatal("auth_rsa_generate_challenge: BN_new() failed");
+ /* Generate a random challenge. */
+ BN_rand(challenge, 256, 0, 0);
+ if ((ctx = BN_CTX_new()) == NULL)
+ fatal("auth_rsa_generate_challenge: BN_CTX_new() failed");
+ BN_mod(challenge, challenge, key->rsa->n, ctx);
+ BN_CTX_free(ctx);
+
+ return challenge;
+}
+
+static int
+auth_rsa_verify_response(Key *key, BIGNUM *challenge, u_char response[16])
+{
+ u_char buf[32], mdbuf[16];
+ MD5_CTX md;
+ int len;
+
+ /* The response is MD5 of decrypted challenge plus session id. */
+ len = BN_num_bytes(challenge);
+ if (len <= 0 || len > 32)
+ fatal("auth_rsa_verify_response: bad challenge length %d", len);
+ memset(buf, 0, 32);
+ BN_bn2bin(challenge, buf + 32 - len);
+ MD5_Init(&md);
+ MD5_Update(&md, buf, 32);
+ MD5_Update(&md, session_id, 16);
+ MD5_Final(mdbuf, &md);
+
+ /* Verify that the response is the original challenge. */
+ if (memcmp(response, mdbuf, 16) != 0) {
+ /* Wrong answer. */
+ return (0);
+ }
+ /* Correct answer. */
+ return (1);
+}
+
/*
* Performs the RSA authentication challenge-response dialog with the client,
* and returns true (non-zero) if the client gave the correct answer to
@@ -59,29 +104,19 @@
*/
int
-auth_rsa_challenge_dialog(RSA *pk)
+auth_rsa_challenge_dialog(Key *key)
{
BIGNUM *challenge, *encrypted_challenge;
- BN_CTX *ctx;
- u_char buf[32], mdbuf[16], response[16];
- MD5_CTX md;
- u_int i;
- int len;
+ u_char response[16];
+ int i, success;
if ((encrypted_challenge = BN_new()) == NULL)
fatal("auth_rsa_challenge_dialog: BN_new() failed");
- if ((challenge = BN_new()) == NULL)
- fatal("auth_rsa_challenge_dialog: BN_new() failed");
- /* Generate a random challenge. */
- BN_rand(challenge, 256, 0, 0);
- if ((ctx = BN_CTX_new()) == NULL)
- fatal("auth_rsa_challenge_dialog: BN_CTX_new() failed");
- BN_mod(challenge, challenge, pk->n, ctx);
- BN_CTX_free(ctx);
+ challenge = auth_rsa_generate_challenge(key);
/* Encrypt the challenge with the public key. */
- rsa_public_encrypt(encrypted_challenge, challenge, pk);
+ rsa_public_encrypt(encrypted_challenge, challenge, key->rsa);
/* Send the encrypted challenge to the client. */
packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE);
@@ -96,48 +131,26 @@
response[i] = packet_get_char();
packet_check_eom();
- /* The response is MD5 of decrypted challenge plus session id. */
- len = BN_num_bytes(challenge);
- if (len <= 0 || len > 32)
- fatal("auth_rsa_challenge_dialog: bad challenge length %d", len);
- memset(buf, 0, 32);
- BN_bn2bin(challenge, buf + 32 - len);
- MD5_Init(&md);
- MD5_Update(&md, buf, 32);
- MD5_Update(&md, session_id, 16);
- MD5_Final(mdbuf, &md);
+ success = auth_rsa_verify_response(key, challenge, response);
BN_clear_free(challenge);
-
- /* Verify that the response is the original challenge. */
- if (memcmp(response, mdbuf, 16) != 0) {
- /* Wrong answer. */
- return 0;
- }
- /* Correct answer. */
- return 1;
+ return (success);
}
/*
- * Performs the RSA authentication dialog with the client. This returns
- * 0 if the client could not be authenticated, and 1 if authentication was
- * successful. This may exit if there is a serious protocol violation.
+ * check if there's user key matching client_n,
+ * return key if login is allowed, NULL otherwise
*/
-int
-auth_rsa(struct passwd *pw, BIGNUM *client_n)
+static int
+auth_rsa_key_allowed(struct passwd *pw, BIGNUM *client_n, Key **rkey)
{
char line[8192], *file;
- int authenticated;
+ int allowed;
u_int bits;
FILE *f;
u_long linenum = 0;
struct stat st;
Key *key;
- char *fp;
-
- /* no user given */
- if (pw == NULL)
- return 0;
/* Temporarily use the user's uid. */
temporarily_use_uid(pw);
@@ -151,29 +164,27 @@
/* Restore the privileged uid. */
restore_uid();
xfree(file);
- return 0;
+ return (NULL);
}
/* Open the file containing the authorized keys. */
f = fopen(file, "r");
if (!f) {
/* Restore the privileged uid. */
restore_uid();
- packet_send_debug("Could not open %.900s for reading.", file);
- packet_send_debug("If your home is on an NFS volume, it may need to be world-readable.");
xfree(file);
- return 0;
+ return (NULL);
}
if (options.strict_modes &&
secure_filename(f, file, pw, line, sizeof(line)) != 0) {
xfree(file);
fclose(f);
log("Authentication refused: %s", line);
- packet_send_debug("Authentication refused: %s", line);
restore_uid();
- return 0;
+ return (NULL);
}
- /* Flag indicating whether authentication has succeeded. */
- authenticated = 0;
+
+ /* Flag indicating whether the key is allowed. */
+ allowed = 0;
key = key_new(KEY_RSA1);
@@ -238,32 +249,8 @@
if (!auth_parse_options(pw, options, file, linenum))
continue;
- /* Perform the challenge-response dialog for this key. */
- if (!auth_rsa_challenge_dialog(key->rsa)) {
- /* Wrong response. */
- verbose("Wrong response to RSA authentication challenge.");
- packet_send_debug("Wrong response to RSA authentication challenge.");
- /*
- * Break out of the loop. Otherwise we might send
- * another challenge and break the protocol.
- */
- break;
- }
- /*
- * Correct response. The client has been successfully
- * authenticated. Note that we have not yet processed the
- * options; this will be reset if the options cause the
- * authentication to be rejected.
- * Break out of the loop if authentication was successful;
- * otherwise continue searching.
- */
- authenticated = 1;
-
- fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
- verbose("Found matching %s key: %s",
- key_type(key), fp);
- xfree(fp);
-
+ /* break out, this key is allowed */
+ allowed = 1;
break;
}
@@ -274,13 +261,58 @@
xfree(file);
fclose(f);
+ /* return key if allowed */
+ if (allowed && rkey != NULL)
+ *rkey = key;
+ else
+ key_free(key);
+ return (allowed);
+}
+
+/*
+ * Performs the RSA authentication dialog with the client. This returns
+ * 0 if the client could not be authenticated, and 1 if authentication was
+ * successful. This may exit if there is a serious protocol violation.
+ */
+int
+auth_rsa(struct passwd *pw, BIGNUM *client_n)
+{
+ Key *key;
+ char *fp;
+
+ /* no user given */
+ if (pw == NULL)
+ return 0;
+
+ if (auth_rsa_key_allowed(pw, client_n, &key) == 0) {
+ auth_clear_options();
+ return (0);
+ }
+
+ /* Perform the challenge-response dialog for this key. */
+ if (!auth_rsa_challenge_dialog(key)) {
+ /* Wrong response. */
+ verbose("Wrong response to RSA authentication challenge.");
+ packet_send_debug("Wrong response to RSA authentication challenge.");
+ /*
+ * Break out of the loop. Otherwise we might send
+ * another challenge and break the protocol.
+ */
+ key_free(key);
+ return (0);
+ }
+ /*
+ * Correct response. The client has been successfully
+ * authenticated. Note that we have not yet processed the
+ * options; this will be reset if the options cause the
+ * authentication to be rejected.
+ */
+ fp = key_fingerprint(key, SSH_FP_MD5, SSH_FP_HEX);
+ verbose("Found matching %s key: %s",
+ key_type(key), fp);
+ xfree(fp);
key_free(key);
- if (authenticated)
- packet_send_debug("RSA authentication accepted.");
- else
- auth_clear_options();
-
- /* Return authentication result. */
- return authenticated;
+ packet_send_debug("RSA authentication accepted.");
+ return (1);
}