+/* $OpenBSD: auth-rsa.c,v 1.73 2008/07/02 12:03:51 dtucker Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
*/
#include "includes.h"
-RCSID("$OpenBSD: auth-rsa.c,v 1.49 2001/12/28 12:14:27 markus Exp $");
+
+#include <sys/types.h>
+#include <sys/stat.h>
#include <openssl/rsa.h>
#include <openssl/md5.h>
+#include <pwd.h>
+#include <stdio.h>
+#include <stdarg.h>
+#include <string.h>
+
+#include "xmalloc.h"
#include "rsa.h"
#include "packet.h"
-#include "xmalloc.h"
#include "ssh1.h"
-#include "mpaux.h"
#include "uidswap.h"
#include "match.h"
+#include "buffer.h"
#include "auth-options.h"
#include "pathnames.h"
#include "log.h"
#include "servconf.h"
-#include "auth.h"
+#include "key.h"
#include "hostfile.h"
+#include "auth.h"
+#ifdef GSSAPI
+#include "ssh-gss.h"
+#endif
+#include "monitor_wrap.h"
+#include "ssh.h"
+#include "misc.h"
/* import */
extern ServerOptions options;
* options bits e n comment
* where bits, e and n are decimal numbers,
* and comment is any string of characters up to newline. The maximum
- * length of a line is 8000 characters. See the documentation for a
+ * length of a line is SSH_MAX_PUBKEY_BYTES characters. See sshd(8) for a
* description of the options.
*/
+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. */
+ if (BN_rand(challenge, 256, 0, 0) == 0)
+ fatal("auth_rsa_generate_challenge: BN_rand failed");
+ if ((ctx = BN_CTX_new()) == NULL)
+ fatal("auth_rsa_generate_challenge: BN_CTX_new failed");
+ if (BN_mod(challenge, challenge, key->rsa->n, ctx) == 0)
+ fatal("auth_rsa_generate_challenge: BN_mod failed");
+ BN_CTX_free(ctx);
+
+ return challenge;
+}
+
+int
+auth_rsa_verify_response(Key *key, BIGNUM *challenge, u_char response[16])
+{
+ u_char buf[32], mdbuf[16];
+ MD5_CTX md;
+ int len;
+
+ /* don't allow short keys */
+ if (BN_num_bits(key->rsa->n) < SSH_RSA_MINIMUM_MODULUS_SIZE) {
+ error("auth_rsa_verify_response: RSA modulus too small: %d < minimum %d bits",
+ BN_num_bits(key->rsa->n), SSH_RSA_MINIMUM_MODULUS_SIZE);
+ return (0);
+ }
+
+ /* 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
*/
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 plen, 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 = PRIVSEP(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);
packet_write_wait();
/* Wait for a response. */
- packet_read_expect(&plen, SSH_CMSG_AUTH_RSA_RESPONSE);
+ packet_read_expect(SSH_CMSG_AUTH_RSA_RESPONSE);
for (i = 0; i < 16; i++)
- response[i] = packet_get_char();
+ response[i] = (u_char)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 = PRIVSEP(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)
+auth_rsa_key_allowed(struct passwd *pw, BIGNUM *client_n, Key **rkey)
{
- char line[8192], *file;
- int authenticated;
+ char line[SSH_MAX_PUBKEY_BYTES], *file;
+ int allowed = 0;
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);
/* The authorized keys. */
file = authorized_keys_file(pw);
debug("trying public RSA key file %s", file);
-
- /* Fail quietly if file does not exist */
- if (stat(file, &st) < 0) {
- /* Restore the privileged uid. */
- restore_uid();
- xfree(file);
- return 0;
- }
- /* Open the file containing the authorized keys. */
- f = fopen(file, "r");
+ f = auth_openkeyfile(file, pw, options.strict_modes);
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;
- }
- 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 (0);
}
- /* Flag indicating whether authentication has succeeded. */
- authenticated = 0;
+
+ /* Flag indicating whether the key is allowed. */
+ allowed = 0;
key = key_new(KEY_RSA1);
* found, perform a challenge-response dialog to verify that the
* user really has the corresponding private key.
*/
- while (fgets(line, sizeof(line), f)) {
+ while (read_keyfile_line(f, file, line, sizeof(line), &linenum) != -1) {
char *cp;
- char *options;
-
- linenum++;
+ char *key_options;
+ int keybits;
/* Skip leading whitespace, empty and comment lines. */
for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
*/
if (*cp < '0' || *cp > '9') {
int quoted = 0;
- options = cp;
+ key_options = cp;
for (; *cp && (quoted || (*cp != ' ' && *cp != '\t')); cp++) {
if (*cp == '\\' && cp[1] == '"')
cp++; /* Skip both */
quoted = !quoted;
}
} else
- options = NULL;
+ key_options = NULL;
/* Parse the key from the line. */
if (hostfile_read_key(&cp, &bits, key) == 0) {
continue;
/* check the real bits */
- if (bits != BN_num_bits(key->rsa->n))
- log("Warning: %s, line %lu: keysize mismatch: "
+ keybits = BN_num_bits(key->rsa->n);
+ if (keybits < 0 || bits != (u_int)keybits)
+ logit("Warning: %s, line %lu: keysize mismatch: "
"actual %d vs. announced %d.",
file, linenum, BN_num_bits(key->rsa->n), bits);
* If our options do not allow this key to be used,
* do not send challenge.
*/
- if (!auth_parse_options(pw, options, file, linenum))
+ if (!auth_parse_options(pw, key_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;
}
xfree(file);
fclose(f);
- key_free(key);
-
- if (authenticated)
- packet_send_debug("RSA authentication accepted.");
+ /* 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(Authctxt *authctxt, BIGNUM *client_n)
+{
+ Key *key;
+ char *fp;
+ struct passwd *pw = authctxt->pw;
+
+ /* no user given */
+ if (!authctxt->valid)
+ return 0;
+
+ if (!PRIVSEP(auth_rsa_key_allowed(pw, client_n, &key))) {
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);
- /* Return authentication result. */
- return authenticated;
+ packet_send_debug("RSA authentication accepted.");
+ return (1);
}
andersk / openssh.git / blobdiff