/*
- *
- * auth-rsa.c
- *
* Author: Tatu Ylonen <ylo@cs.hut.fi>
- *
* Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
* All rights reserved
- *
- * Created: Mon Mar 27 01:46:52 1995 ylo
- *
* RSA-based authentication. This code determines whether to admit a login
* based on RSA authentication. This file also contains functions to check
* validity of the host key.
- *
+ *
+ * As far as I am concerned, the code I have written for this software
+ * can be used freely for any purpose. Any derived versions of this
+ * software must be clearly marked as such, and if the derived work is
+ * incompatible with the protocol description in the RFC file, it must be
+ * called by a name other than "ssh" or "Secure Shell".
*/
#include "includes.h"
-RCSID("$Id$");
+RCSID("$OpenBSD: auth-rsa.c,v 1.44 2001/07/23 18:14:58 stevesk Exp $");
+
+#include <openssl/rsa.h>
+#include <openssl/md5.h>
#include "rsa.h"
#include "packet.h"
#include "xmalloc.h"
-#include "ssh.h"
+#include "ssh1.h"
#include "mpaux.h"
#include "uidswap.h"
+#include "match.h"
+#include "auth-options.h"
+#include "pathnames.h"
+#include "log.h"
#include "servconf.h"
+#include "auth.h"
-#ifdef HAVE_OPENSSL
-#include <openssl/rsa.h>
-#include <openssl/md5.h>
-#endif
-#ifdef HAVE_SSL
-#include <ssl/rsa.h>
-#include <ssl/md5.h>
-#endif
-
-/* Flags that may be set in authorized_keys options. */
-extern int no_port_forwarding_flag;
-extern int no_agent_forwarding_flag;
-extern int no_x11_forwarding_flag;
-extern int no_pty_flag;
-extern char *forced_command;
-extern struct envstring *custom_environment;
-
-/* Session identifier that is used to bind key exchange and authentication
- responses to a particular session. */
-extern unsigned char session_id[16];
-
-/* The .ssh/authorized_keys file contains public keys, one per line, in the
- following format:
- 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
- description of the options.
-*/
-
-/* Performs the RSA authentication challenge-response dialog with the client,
- and returns true (non-zero) if the client gave the correct answer to
- our challenge; returns zero if the client gives a wrong answer. */
+/* import */
+extern ServerOptions options;
+
+/*
+ * Session identifier that is used to bind key exchange and authentication
+ * responses to a particular session.
+ */
+extern u_char session_id[16];
+
+/*
+ * The .ssh/authorized_keys file contains public keys, one per line, in the
+ * following format:
+ * 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
+ * description of the options.
+ */
+
+/*
+ * Performs the RSA authentication challenge-response dialog with the client,
+ * and returns true (non-zero) if the client gave the correct answer to
+ * our challenge; returns zero if the client gives a wrong answer.
+ */
int
-auth_rsa_challenge_dialog(BIGNUM *e, BIGNUM *n)
+auth_rsa_challenge_dialog(RSA *pk)
{
- BIGNUM *challenge, *encrypted_challenge, *aux;
- RSA *pk;
- BN_CTX *ctx = BN_CTX_new();
- unsigned char buf[32], mdbuf[16], response[16];
+ BIGNUM *challenge, *encrypted_challenge;
+ BN_CTX *ctx;
+ u_char buf[32], mdbuf[16], response[16];
MD5_CTX md;
- unsigned int i;
+ u_int i;
int plen, len;
encrypted_challenge = BN_new();
challenge = BN_new();
- aux = BN_new();
/* Generate a random challenge. */
BN_rand(challenge, 256, 0, 0);
- BN_mod(challenge, challenge, n, ctx);
-
- /* Create the public key data structure. */
- pk = RSA_new();
- pk->e = BN_new();
- BN_copy(pk->e, e);
- pk->n = BN_new();
- BN_copy(pk->n, n);
+ ctx = BN_CTX_new();
+ BN_mod(challenge, challenge, pk->n, ctx);
+ BN_CTX_free(ctx);
/* Encrypt the challenge with the public key. */
rsa_public_encrypt(encrypted_challenge, challenge, pk);
- RSA_free(pk);
/* Send the encrypted challenge to the client. */
packet_start(SSH_SMSG_AUTH_RSA_CHALLENGE);
packet_put_bignum(encrypted_challenge);
packet_send();
+ BN_clear_free(encrypted_challenge);
packet_write_wait();
+ /* Wait for a response. */
+ packet_read_expect(&plen, SSH_CMSG_AUTH_RSA_RESPONSE);
+ packet_integrity_check(plen, 16, SSH_CMSG_AUTH_RSA_RESPONSE);
+ for (i = 0; i < 16; i++)
+ response[i] = packet_get_char();
+
/* The response is MD5 of decrypted challenge plus session id. */
len = BN_num_bytes(challenge);
if (len <= 0 || len > 32)
MD5_Update(&md, buf, 32);
MD5_Update(&md, session_id, 16);
MD5_Final(mdbuf, &md);
-
- /* We will no longer need these. */
- BN_clear_free(encrypted_challenge);
BN_clear_free(challenge);
- BN_clear_free(aux);
- BN_CTX_free(ctx);
-
- /* Wait for a response. */
- packet_read_expect(&plen, SSH_CMSG_AUTH_RSA_RESPONSE);
- packet_integrity_check(plen, 16, SSH_CMSG_AUTH_RSA_RESPONSE);
- for (i = 0; i < 16; i++)
- response[i] = packet_get_char();
/* Verify that the response is the original challenge. */
if (memcmp(response, mdbuf, 16) != 0) {
return 1;
}
-/* 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. */
+/*
+ * 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)
{
- extern ServerOptions options;
- char line[8192], file[1024];
+ char line[8192], *file;
int authenticated;
- unsigned int bits;
+ u_int bits;
FILE *f;
- unsigned long linenum = 0;
+ u_long linenum = 0;
struct stat st;
- BIGNUM *e, *n;
+ RSA *pk;
+
+ /* no user given */
+ if (pw == NULL)
+ return 0;
/* Temporarily use the user's uid. */
- temporarily_use_uid(pw->pw_uid);
+ temporarily_use_uid(pw);
/* The authorized keys. */
- snprintf(file, sizeof file, "%.500s/%.100s", pw->pw_dir,
- SSH_USER_PERMITTED_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. */
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) {
- int fail = 0;
- char buf[1024];
- /* Check open file in order to avoid open/stat races */
- if (fstat(fileno(f), &st) < 0 ||
- (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
- (st.st_mode & 022) != 0) {
- snprintf(buf, sizeof buf, "RSA authentication refused for %.100s: "
- "bad ownership or modes for '%s'.", pw->pw_name, file);
- fail = 1;
- } else {
- /* Check path to SSH_USER_PERMITTED_KEYS */
- int i;
- static const char *check[] = {
- "", SSH_USER_DIR, NULL
- };
- for (i = 0; check[i]; i++) {
- snprintf(line, sizeof line, "%.500s/%.100s", pw->pw_dir, check[i]);
- if (stat(line, &st) < 0 ||
- (st.st_uid != 0 && st.st_uid != pw->pw_uid) ||
- (st.st_mode & 022) != 0) {
- snprintf(buf, sizeof buf, "RSA authentication refused for %.100s: "
- "bad ownership or modes for '%s'.", pw->pw_name, line);
- fail = 1;
- break;
- }
- }
- }
- if (fail) {
- log(buf);
- packet_send_debug(buf);
- restore_uid();
- 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;
}
/* Flag indicating whether authentication has succeeded. */
authenticated = 0;
- /* Initialize mp-int variables. */
- e = BN_new();
- n = BN_new();
+ pk = RSA_new();
+ pk->e = BN_new();
+ pk->n = BN_new();
- /* Go though the accepted keys, looking for the current key. If
- found, perform a challenge-response dialog to verify that the
- user really has the corresponding private key. */
+ /*
+ * Go though the accepted keys, looking for the current key. If
+ * found, perform a challenge-response dialog to verify that the
+ * user really has the corresponding private key.
+ */
while (fgets(line, sizeof(line), f)) {
char *cp;
char *options;
linenum++;
- /* Skip leading whitespace. */
- for (cp = line; *cp == ' ' || *cp == '\t'; cp++);
-
- /* Skip empty and comment lines. */
+ /* Skip leading whitespace, empty and comment lines. */
+ for (cp = line; *cp == ' ' || *cp == '\t'; cp++)
+ ;
if (!*cp || *cp == '\n' || *cp == '#')
continue;
- /* Check if there are options for this key, and if so,
- save their starting address and skip the option part
- for now. If there are no options, set the starting
- address to NULL. */
+ /*
+ * Check if there are options for this key, and if so,
+ * save their starting address and skip the option part
+ * for now. If there are no options, set the starting
+ * address to NULL.
+ */
if (*cp < '0' || *cp > '9') {
int quoted = 0;
options = cp;
options = NULL;
/* Parse the key from the line. */
- if (!auth_rsa_read_key(&cp, &bits, e, n)) {
- debug("%.100s, line %lu: bad key syntax",
- SSH_USER_PERMITTED_KEYS, linenum);
- packet_send_debug("%.100s, line %lu: bad key syntax",
- SSH_USER_PERMITTED_KEYS, linenum);
+ if (!auth_rsa_read_key(&cp, &bits, pk->e, pk->n)) {
+ debug("%.100s, line %lu: non ssh1 key syntax",
+ file, linenum);
continue;
}
/* cp now points to the comment part. */
- /* check the real bits */
- if (bits != BN_num_bits(n))
- error("Warning: error in %s, line %ld: keysize mismatch: "
- "actual size %d vs. announced %d.",
- file, linenum, BN_num_bits(n), bits);
-
/* Check if the we have found the desired key (identified by its modulus). */
- if (BN_cmp(n, client_n) != 0)
- continue; /* Wrong key. */
+ if (BN_cmp(pk->n, client_n) != 0)
+ continue;
+
+ /* check the real bits */
+ if (bits != BN_num_bits(pk->n))
+ log("Warning: %s, line %lu: keysize mismatch: "
+ "actual %d vs. announced %d.",
+ file, linenum, BN_num_bits(pk->n), bits);
/* We have found the desired key. */
+ /*
+ * If our options do not allow this key to be used,
+ * do not send challenge.
+ */
+ if (!auth_parse_options(pw, options, file, linenum))
+ continue;
/* Perform the challenge-response dialog for this key. */
- if (!auth_rsa_challenge_dialog(e, n)) {
+ if (!auth_rsa_challenge_dialog(pk)) {
/* Wrong response. */
verbose("Wrong response to RSA authentication challenge.");
packet_send_debug("Wrong response to RSA authentication challenge.");
continue;
}
- /* 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. */
+ /*
+ * 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;
-
- /* RSA part of authentication was accepted. Now process the options. */
- if (options) {
- while (*options && *options != ' ' && *options != '\t') {
- cp = "no-port-forwarding";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- packet_send_debug("Port forwarding disabled.");
- no_port_forwarding_flag = 1;
- options += strlen(cp);
- goto next_option;
- }
- cp = "no-agent-forwarding";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- packet_send_debug("Agent forwarding disabled.");
- no_agent_forwarding_flag = 1;
- options += strlen(cp);
- goto next_option;
- }
- cp = "no-X11-forwarding";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- packet_send_debug("X11 forwarding disabled.");
- no_x11_forwarding_flag = 1;
- options += strlen(cp);
- goto next_option;
- }
- cp = "no-pty";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- packet_send_debug("Pty allocation disabled.");
- no_pty_flag = 1;
- options += strlen(cp);
- goto next_option;
- }
- cp = "command=\"";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- int i;
- options += strlen(cp);
- forced_command = xmalloc(strlen(options) + 1);
- i = 0;
- while (*options) {
- if (*options == '"')
- break;
- if (*options == '\\' && options[1] == '"') {
- options += 2;
- forced_command[i++] = '"';
- continue;
- }
- forced_command[i++] = *options++;
- }
- if (!*options) {
- debug("%.100s, line %lu: missing end quote",
- SSH_USER_PERMITTED_KEYS, linenum);
- packet_send_debug("%.100s, line %lu: missing end quote",
- SSH_USER_PERMITTED_KEYS, linenum);
- continue;
- }
- forced_command[i] = 0;
- packet_send_debug("Forced command: %.900s", forced_command);
- options++;
- goto next_option;
- }
- cp = "environment=\"";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- int i;
- char *s;
- struct envstring *new_envstring;
- options += strlen(cp);
- s = xmalloc(strlen(options) + 1);
- i = 0;
- while (*options) {
- if (*options == '"')
- break;
- if (*options == '\\' && options[1] == '"') {
- options += 2;
- s[i++] = '"';
- continue;
- }
- s[i++] = *options++;
- }
- if (!*options) {
- debug("%.100s, line %lu: missing end quote",
- SSH_USER_PERMITTED_KEYS, linenum);
- packet_send_debug("%.100s, line %lu: missing end quote",
- SSH_USER_PERMITTED_KEYS, linenum);
- continue;
- }
- s[i] = 0;
- packet_send_debug("Adding to environment: %.900s", s);
- debug("Adding to environment: %.900s", s);
- options++;
- new_envstring = xmalloc(sizeof(struct envstring));
- new_envstring->s = s;
- new_envstring->next = custom_environment;
- custom_environment = new_envstring;
- goto next_option;
- }
- cp = "from=\"";
- if (strncmp(options, cp, strlen(cp)) == 0) {
- char *patterns = xmalloc(strlen(options) + 1);
- int i;
- options += strlen(cp);
- i = 0;
- while (*options) {
- if (*options == '"')
- break;
- if (*options == '\\' && options[1] == '"') {
- options += 2;
- patterns[i++] = '"';
- continue;
- }
- patterns[i++] = *options++;
- }
- if (!*options) {
- debug("%.100s, line %lu: missing end quote",
- SSH_USER_PERMITTED_KEYS, linenum);
- packet_send_debug("%.100s, line %lu: missing end quote",
- SSH_USER_PERMITTED_KEYS, linenum);
- continue;
- }
- patterns[i] = 0;
- options++;
- if (!match_hostname(get_canonical_hostname(), patterns,
- strlen(patterns)) &&
- !match_hostname(get_remote_ipaddr(), patterns,
- strlen(patterns))) {
- log("RSA authentication tried for %.100s with correct key but not from a permitted host (host=%.200s, ip=%.200s).",
- pw->pw_name, get_canonical_hostname(),
- get_remote_ipaddr());
- packet_send_debug("Your host '%.200s' is not permitted to use this key for login.",
- get_canonical_hostname());
- xfree(patterns);
- authenticated = 0;
- break;
- }
- xfree(patterns);
- /* Host name matches. */
- goto next_option;
- }
- bad_option:
- /* Unknown option. */
- log("Bad options in %.100s file, line %lu: %.50s",
- SSH_USER_PERMITTED_KEYS, linenum, options);
- packet_send_debug("Bad options in %.100s file, line %lu: %.50s",
- SSH_USER_PERMITTED_KEYS, linenum, options);
- authenticated = 0;
- break;
-
- next_option:
- /* Skip the comma, and move to the next option
- (or break out if there are no more). */
- if (!*options)
- fatal("Bugs in auth-rsa.c option processing.");
- if (*options == ' ' || *options == '\t')
- break; /* End of options. */
- if (*options != ',')
- goto bad_option;
- options++;
- /* Process the next option. */
- continue;
- }
- }
- /* Break out of the loop if authentication was successful;
- otherwise continue searching. */
- if (authenticated)
- break;
+ break;
}
/* Restore the privileged uid. */
restore_uid();
/* Close the file. */
+ xfree(file);
fclose(f);
- /* Clear any mp-int variables. */
- BN_clear_free(n);
- BN_clear_free(e);
+ RSA_free(pk);
if (authenticated)
packet_send_debug("RSA authentication accepted.");
+ else
+ auth_clear_options();
/* Return authentication result. */
return authenticated;
andersk / openssh.git / blobdiff