- djm@cvs.openbsd.org 2010/05/20 23:46:02

     [PROTOCOL.certkeys auth-options.c ssh-keygen.c]
     Move the permit-* options to the non-critical "extensions" field for v01
     certificates. The logic is that if another implementation fails to
     implement them then the connection just loses features rather than fails
     outright.

     ok markus@

4 files changed, 267 insertions, 152 deletions

diff --git a/ChangeLog b/ChangeLog
index 2cc1369fd..86c66d1a7 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -33,6 +33,14 @@
      [auth2-pubkey.c]
      fix logspam when key options (from="..." especially) deny non-matching
      keys; reported by henning@ also bz#1765; ok markus@ dtucker@
+   - djm@cvs.openbsd.org 2010/05/20 23:46:02
+     [PROTOCOL.certkeys auth-options.c ssh-keygen.c]
+     Move the permit-* options to the non-critical "extensions" field for v01
+     certificates. The logic is that if another implementation fails to
+     implement them then the connection just loses features rather than fails
+     outright.
+     
+     ok markus@
 
 20100511
  - (dtucker) [Makefile.in] Bug #1770: Link libopenbsd-compat twice to solve
diff --git a/PROTOCOL.certkeys b/PROTOCOL.certkeys
index 0fa5748f3..81b02a078 100644
--- a/PROTOCOL.certkeys
+++ b/PROTOCOL.certkeys
@@ -131,7 +131,7 @@ must refuse to authorise a key that has an unrecognised option.
 
 extensions is a set of zero or more optional extensions. These extensions
 are not critical, and an implementation that encounters one that it does
-not recognise may safely ignore it. No extensions are defined at present.
+not recognise may safely ignore it.
 
 The reserved field is currently unused and is ignored in this version of
 the protocol.
@@ -172,6 +172,28 @@ force-command           string        Specifies a command that is executed
                                       ssh command-line) whenever this key is
                                       used for authentication.
 
+source-address          string        Comma-separated list of source addresses
+                                      from which this certificate is accepted
+                                      for authentication. Addresses are
+                                      specified in CIDR format (nn.nn.nn.nn/nn
+                                      or hhhh::hhhh/nn).
+                                      If this option is not present then
+                                      certificates may be presented from any
+                                      source address.
+
+Extensions
+----------
+
+The extensions section of the certificate specifies zero or more
+non-critical certificate extensions. The encoding of extensions in this
+field is identical to that of the critical options. If an implementation
+does not recognise an extension, then it should ignore it.
+
+The supported extensions and the contents and structure of their data
+fields are:
+
+Name                    Format        Description
+-----------------------------------------------------------------------------
 permit-X11-forwarding   empty         Flag indicating that X11 forwarding
                                       should be permitted. X11 forwarding will
                                       be refused if this option is absent.
@@ -196,13 +218,4 @@ permit-user-rc          empty         Flag indicating that execution of
                                       of this script will not be permitted if
                                       this option is not present.
 
-source-address          string        Comma-separated list of source addresses
-                                      from which this certificate is accepted
-                                      for authentication. Addresses are
-                                      specified in CIDR format (nn.nn.nn.nn/nn
-                                      or hhhh::hhhh/nn).
-                                      If this option is not present then
-                                      certificates may be presented from any
-                                      source address.
-
-$OpenBSD: PROTOCOL.certkeys,v 1.5 2010/05/01 02:50:50 djm Exp $
+$OpenBSD: PROTOCOL.certkeys,v 1.6 2010/05/20 23:46:02 djm Exp $
diff --git a/auth-options.c b/auth-options.c
index 57a67ec79..a7040247f 100644
--- a/auth-options.c
+++ b/auth-options.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: auth-options.c,v 1.51 2010/05/07 11:30:29 djm Exp $ */
+/* $OpenBSD: auth-options.c,v 1.52 2010/05/20 23:46:02 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -417,32 +417,31 @@ bad_option:
         return 0;
 }
 
-/*
- * Set options from critical certificate options. These supersede user key
- * options so this must be called after auth_parse_options().
- */
-int
-auth_cert_options(Key *k, struct passwd *pw)
+#define OPTIONS_CRITICAL        1
+#define OPTIONS_EXTENSIONS      2
+static int
+parse_option_list(u_char *optblob, size_t optblob_len, struct passwd *pw,
+    u_int which, int crit,
+    int *cert_no_port_forwarding_flag,
+    int *cert_no_agent_forwarding_flag,
+    int *cert_no_x11_forwarding_flag,
+    int *cert_no_pty_flag,
+    int *cert_no_user_rc,
+    char **cert_forced_command,
+    int *cert_source_address_done)
 {
+        char *command, *allowed;
+        const char *remote_ip;
         u_char *name = NULL, *data_blob = NULL;
         u_int nlen, dlen, clen;
         Buffer c, data;
-        int ret = -1;
-
-        int cert_no_port_forwarding_flag = 1;
-        int cert_no_agent_forwarding_flag = 1;
-        int cert_no_x11_forwarding_flag = 1;
-        int cert_no_pty_flag = 1;
-        int cert_no_user_rc = 1;
-        char *cert_forced_command = NULL;
-        int cert_source_address_done = 0;
+        int ret = -1, found;
 
         buffer_init(&data);
 
         /* Make copy to avoid altering original */
         buffer_init(&c);
-        buffer_append(&c,
-            buffer_ptr(&k->cert->critical), buffer_len(&k->cert->critical));
+        buffer_append(&c, optblob, optblob_len);
 
         while (buffer_len(&c) > 0) {
                 if ((name = buffer_get_string_ret(&c, &nlen)) == NULL ||
@@ -451,90 +450,114 @@ auth_cert_options(Key *k, struct passwd *pw)
                         goto out;
                 }
                 buffer_append(&data, data_blob, dlen);
-                debug3("found certificate constraint \"%.100s\" len %u",
+                debug3("found certificate option \"%.100s\" len %u",
                     name, dlen);
                 if (strlen(name) != nlen) {
                         error("Certificate constraint name contains \\0");
                         goto out;
                 }
-                if (strcmp(name, "permit-X11-forwarding") == 0)
-                        cert_no_x11_forwarding_flag = 0;
-                else if (strcmp(name, "permit-agent-forwarding") == 0)
-                        cert_no_agent_forwarding_flag = 0;
-                else if (strcmp(name, "permit-port-forwarding") == 0)
-                        cert_no_port_forwarding_flag = 0;
-                else if (strcmp(name, "permit-pty") == 0)
-                        cert_no_pty_flag = 0;
-                else if (strcmp(name, "permit-user-rc") == 0)
-                        cert_no_user_rc = 0;
-                else if (strcmp(name, "force-command") == 0) {
-                        char *command = buffer_get_string_ret(&data, &clen);
-
-                        if (command == NULL) {
-                                error("Certificate constraint \"%s\" corrupt",
-                                    name);
-                                goto out;
-                        }
-                        if (strlen(command) != clen) {
-                                error("force-command constraint contains \\0");
-                                goto out;
-                        }
-                        if (cert_forced_command != NULL) {
-                                error("Certificate has multiple "
-                                    "force-command options");
-                                xfree(command);
-                                goto out;
-                        }
-                        cert_forced_command = command;
-                } else if (strcmp(name, "source-address") == 0) {
-                        char *allowed = buffer_get_string_ret(&data, &clen);
-                        const char *remote_ip = get_remote_ipaddr();
-                        
-                        if (allowed == NULL) {
-                                error("Certificate constraint \"%s\" corrupt",
-                                    name);
-                                goto out;
-                        }
-                        if (strlen(allowed) != clen) {
-                                error("source-address constraint contains \\0");
-                                goto out;
+                found = 0;
+                if ((which & OPTIONS_EXTENSIONS) != 0) {
+                        if (strcmp(name, "permit-X11-forwarding") == 0) {
+                                *cert_no_x11_forwarding_flag = 0;
+                                found = 1;
+                        } else if (strcmp(name,
+                            "permit-agent-forwarding") == 0) {
+                                *cert_no_agent_forwarding_flag = 0;
+                                found = 1;
+                        } else if (strcmp(name,
+                            "permit-port-forwarding") == 0) {
+                                *cert_no_port_forwarding_flag = 0;
+                                found = 1;
+                        } else if (strcmp(name, "permit-pty") == 0) {
+                                *cert_no_pty_flag = 0;
+                                found = 1;
+                        } else if (strcmp(name, "permit-user-rc") == 0) {
+                                *cert_no_user_rc = 0;
+                                found = 1;
                         }
-                        if (cert_source_address_done++) {
-                                error("Certificate has multiple "
-                                    "source-address options");
-                                xfree(allowed);
-                                goto out;
+                }
+                if (!found && (which & OPTIONS_CRITICAL) != 0) {
+                        if (strcmp(name, "force-command") == 0) {
+                                if ((command = buffer_get_string_ret(&data,
+                                    &clen)) == NULL) {
+                                        error("Certificate constraint \"%s\" "
+                                            "corrupt", name);
+                                        goto out;
+                                }
+                                if (strlen(command) != clen) {
+                                        error("force-command constraint "
+                                            "contains \\0");
+                                        goto out;
+                                }
+                                if (*cert_forced_command != NULL) {
+                                        error("Certificate has multiple "
+                                            "force-command options");
+                                        xfree(command);
+                                        goto out;
+                                }
+                                *cert_forced_command = command;
+                                found = 1;
                         }
-                        switch (addr_match_cidr_list(remote_ip, allowed)) {
-                        case 1:
-                                /* accepted */
-                                xfree(allowed);
-                                break;
-                        case 0:
-                                /* no match */
-                                logit("Authentication tried for %.100s with "
-                                    "valid certificate but not from a "
-                                    "permitted host (ip=%.200s).",
-                                    pw->pw_name, remote_ip);
-                                auth_debug_add("Your address '%.200s' is not "
-                                    "permitted to use this certificate for "
-                                    "login.", remote_ip);
-                                xfree(allowed);
-                                goto out;
-                        case -1:
-                                error("Certificate source-address contents "
-                                    "invalid");
-                                xfree(allowed);
-                                goto out;
+                        if (strcmp(name, "source-address") == 0) {
+                                if ((allowed = buffer_get_string_ret(&data,
+                                    &clen)) == NULL) {
+                                        error("Certificate constraint "
+                                            "\"%s\" corrupt", name);
+                                        goto out;
+                                }
+                                if (strlen(allowed) != clen) {
+                                        error("source-address constraint "
+                                            "contains \\0");
+                                        goto out;
+                                }
+                                if ((*cert_source_address_done)++) {
+                                        error("Certificate has multiple "
+                                            "source-address options");
+                                        xfree(allowed);
+                                        goto out;
+                                }
+                                remote_ip = get_remote_ipaddr();
+                                switch (addr_match_cidr_list(remote_ip,
+                                    allowed)) {
+                                case 1:
+                                        /* accepted */
+                                        xfree(allowed);
+                                        break;
+                                case 0:
+                                        /* no match */
+                                        logit("Authentication tried for %.100s "
+                                            "with valid certificate but not "
+                                            "from a permitted host "
+                                            "(ip=%.200s).", pw->pw_name,
+                                            remote_ip);
+                                        auth_debug_add("Your address '%.200s' "
+                                            "is not permitted to use this "
+                                            "certificate for login.",
+                                            remote_ip);
+                                        xfree(allowed);
+                                        goto out;
+                                case -1:
+                                        error("Certificate source-address "
+                                            "contents invalid");
+                                        xfree(allowed);
+                                        goto out;
+                                }
+                                found = 1;
                         }
-                } else {
-                        error("Certificate constraint \"%s\" is not supported",
-                            name);
-                        goto out;
                 }
 
-                if (buffer_len(&data) != 0) {
-                        error("Certificate constraint \"%s\" corrupt "
+                if (!found) {
+                        if (crit) {
+                                error("Certificate critical option \"%s\" "
+                                    "is not supported", name);
+                                goto out;
+                        } else {
+                                logit("Certificate extension \"%s\" "
+                                    "is not supported", name);
+                        }
+                } else if (buffer_len(&data) != 0) {
+                        error("Certificate option \"%s\" corrupt "
                             "(extra data)", name);
                         goto out;
                 }
@@ -543,10 +566,73 @@ auth_cert_options(Key *k, struct passwd *pw)
                 xfree(data_blob);
                 name = data_blob = NULL;
         }
-
         /* successfully parsed all options */
         ret = 0;
 
+ out:
+        if (ret != 0 &&
+            cert_forced_command != NULL &&
+            *cert_forced_command != NULL) {
+                xfree(*cert_forced_command);
+                *cert_forced_command = NULL;
+        }
+        if (name != NULL)
+                xfree(name);
+        if (data_blob != NULL)
+                xfree(data_blob);
+        buffer_free(&data);
+        buffer_free(&c);
+        return ret;
+}
+
+/*
+ * Set options from critical certificate options. These supersede user key
+ * options so this must be called after auth_parse_options().
+ */
+int
+auth_cert_options(Key *k, struct passwd *pw)
+{
+        int cert_no_port_forwarding_flag = 1;
+        int cert_no_agent_forwarding_flag = 1;
+        int cert_no_x11_forwarding_flag = 1;
+        int cert_no_pty_flag = 1;
+        int cert_no_user_rc = 1;
+        char *cert_forced_command = NULL;
+        int cert_source_address_done = 0;
+
+        if (key_cert_is_legacy(k)) {
+                /* All options are in the one field for v00 certs */
+                if (parse_option_list(buffer_ptr(&k->cert->critical),
+                    buffer_len(&k->cert->critical), pw,
+                    OPTIONS_CRITICAL|OPTIONS_EXTENSIONS, 1,
+                    &cert_no_port_forwarding_flag,
+                    &cert_no_agent_forwarding_flag,
+                    &cert_no_x11_forwarding_flag,
+                    &cert_no_pty_flag,
+                    &cert_no_user_rc,
+                    &cert_forced_command,
+                    &cert_source_address_done) == -1)
+                        return -1;
+        } else {
+                /* Separate options and extensions for v01 certs */
+                if (parse_option_list(buffer_ptr(&k->cert->critical),
+                    buffer_len(&k->cert->critical), pw,
+                    OPTIONS_CRITICAL, 1, NULL, NULL, NULL, NULL, NULL,
+                    &cert_forced_command,
+                    &cert_source_address_done) == -1)
+                        return -1;
+                if (parse_option_list(buffer_ptr(&k->cert->extensions),
+                    buffer_len(&k->cert->extensions), pw,
+                    OPTIONS_EXTENSIONS, 1,
+                    &cert_no_port_forwarding_flag,
+                    &cert_no_agent_forwarding_flag,
+                    &cert_no_x11_forwarding_flag,
+                    &cert_no_pty_flag,
+                    &cert_no_user_rc,
+                    NULL, NULL) == -1)
+                        return -1;
+        }
+
         no_port_forwarding_flag |= cert_no_port_forwarding_flag;
         no_agent_forwarding_flag |= cert_no_agent_forwarding_flag;
         no_x11_forwarding_flag |= cert_no_x11_forwarding_flag;
@@ -558,14 +644,6 @@ auth_cert_options(Key *k, struct passwd *pw)
                         xfree(forced_command);
                 forced_command = cert_forced_command;
         }
-        
- out:
-        if (name != NULL)
-                xfree(name);
-        if (data_blob != NULL)
-                xfree(data_blob);
-        buffer_free(&data);
-        buffer_free(&c);
-        return ret;
+        return 0;
 }
 
diff --git a/ssh-keygen.c b/ssh-keygen.c
index 1eb25bd94..14eee6f87 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.189 2010/04/23 22:48:31 djm Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.190 2010/05/20 23:46:02 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -122,17 +122,16 @@ u_int64_t cert_valid_from = 0;
 u_int64_t cert_valid_to = ~0ULL;
 
 /* Certificate options */
-#define CRITOPT_X_FWD   (1)
-#define CRITOPT_AGENT_FWD       (1<<1)
-#define CRITOPT_PORT_FWD        (1<<2)
-#define CRITOPT_PTY             (1<<3)
-#define CRITOPT_USER_RC (1<<4)
-#define CRITOPT_DEFAULT (CRITOPT_X_FWD|CRITOPT_AGENT_FWD| \
-                                CRITOPT_PORT_FWD|CRITOPT_PTY| \
-                                CRITOPT_USER_RC)
-u_int32_t critical_flags = CRITOPT_DEFAULT;
-char *critical_command = NULL;
-char *critical_src_addr = NULL;
+#define CERTOPT_X_FWD   (1)
+#define CERTOPT_AGENT_FWD       (1<<1)
+#define CERTOPT_PORT_FWD        (1<<2)
+#define CERTOPT_PTY             (1<<3)
+#define CERTOPT_USER_RC (1<<4)
+#define CERTOPT_DEFAULT (CERTOPT_X_FWD|CERTOPT_AGENT_FWD| \
+                         CERTOPT_PORT_FWD|CERTOPT_PTY|CERTOPT_USER_RC)
+u_int32_t certflags_flags = CERTOPT_DEFAULT;
+char *certflags_command = NULL;
+char *certflags_src_addr = NULL;
 
 /* Dump public key file in format used by real and the original SSH 2 */
 int convert_to_ssh2 = 0;
@@ -1133,24 +1132,33 @@ add_string_option(Buffer *c, const char *name, const char *value)
         buffer_free(&b);
 }
 
+#define OPTIONS_CRITICAL        1
+#define OPTIONS_EXTENSIONS      2
 static void
-prepare_options_buf(Buffer *c)
+prepare_options_buf(Buffer *c, int which)
 {
         buffer_clear(c);
-        if ((critical_flags & CRITOPT_X_FWD) != 0)
+        if ((which & OPTIONS_EXTENSIONS) != 0 &&
+            (certflags_flags & CERTOPT_X_FWD) != 0)
                 add_flag_option(c, "permit-X11-forwarding");
-        if ((critical_flags & CRITOPT_AGENT_FWD) != 0)
+        if ((which & OPTIONS_EXTENSIONS) != 0 &&
+            (certflags_flags & CERTOPT_AGENT_FWD) != 0)
                 add_flag_option(c, "permit-agent-forwarding");
-        if ((critical_flags & CRITOPT_PORT_FWD) != 0)
+        if ((which & OPTIONS_EXTENSIONS) != 0 &&
+            (certflags_flags & CERTOPT_PORT_FWD) != 0)
                 add_flag_option(c, "permit-port-forwarding");
-        if ((critical_flags & CRITOPT_PTY) != 0)
+        if ((which & OPTIONS_EXTENSIONS) != 0 &&
+            (certflags_flags & CERTOPT_PTY) != 0)
                 add_flag_option(c, "permit-pty");
-        if ((critical_flags & CRITOPT_USER_RC) != 0)
+        if ((which & OPTIONS_EXTENSIONS) != 0 &&
+            (certflags_flags & CERTOPT_USER_RC) != 0)
                 add_flag_option(c, "permit-user-rc");
-        if (critical_command != NULL)
-                add_string_option(c, "force-command", critical_command);
-        if (critical_src_addr != NULL)
-                add_string_option(c, "source-address", critical_src_addr);
+        if ((which & OPTIONS_CRITICAL) != 0 &&
+            certflags_command != NULL)
+                add_string_option(c, "force-command", certflags_command);
+        if ((which & OPTIONS_CRITICAL) != 0 &&
+            certflags_src_addr != NULL)
+                add_string_option(c, "source-address", certflags_src_addr);
 }
 
 static void
@@ -1218,7 +1226,15 @@ do_ca_sign(struct passwd *pw, int argc, char **argv)
                 public->cert->principals = plist;
                 public->cert->valid_after = cert_valid_from;
                 public->cert->valid_before = cert_valid_to;
-                prepare_options_buf(&public->cert->critical);
+                if (v00) {
+                        prepare_options_buf(&public->cert->critical,
+                            OPTIONS_CRITICAL|OPTIONS_EXTENSIONS);
+                } else {
+                        prepare_options_buf(&public->cert->critical,
+                            OPTIONS_CRITICAL);
+                        prepare_options_buf(&public->cert->extensions,
+                            OPTIONS_EXTENSIONS);
+                }
                 public->cert->signature_key = key_from_private(ca);
 
                 if (key_certify(public, ca) != 0)
@@ -1354,43 +1370,43 @@ add_cert_option(char *opt)
         char *val;
 
         if (strcmp(opt, "clear") == 0)
-                critical_flags = 0;
+                certflags_flags = 0;
         else if (strcasecmp(opt, "no-x11-forwarding") == 0)
-                critical_flags &= ~CRITOPT_X_FWD;
+                certflags_flags &= ~CERTOPT_X_FWD;
         else if (strcasecmp(opt, "permit-x11-forwarding") == 0)
-                critical_flags |= CRITOPT_X_FWD;
+                certflags_flags |= CERTOPT_X_FWD;
         else if (strcasecmp(opt, "no-agent-forwarding") == 0)
-                critical_flags &= ~CRITOPT_AGENT_FWD;
+                certflags_flags &= ~CERTOPT_AGENT_FWD;
         else if (strcasecmp(opt, "permit-agent-forwarding") == 0)
-                critical_flags |= CRITOPT_AGENT_FWD;
+                certflags_flags |= CERTOPT_AGENT_FWD;
         else if (strcasecmp(opt, "no-port-forwarding") == 0)
-                critical_flags &= ~CRITOPT_PORT_FWD;
+                certflags_flags &= ~CERTOPT_PORT_FWD;
         else if (strcasecmp(opt, "permit-port-forwarding") == 0)
-                critical_flags |= CRITOPT_PORT_FWD;
+                certflags_flags |= CERTOPT_PORT_FWD;
         else if (strcasecmp(opt, "no-pty") == 0)
-                critical_flags &= ~CRITOPT_PTY;
+                certflags_flags &= ~CERTOPT_PTY;
         else if (strcasecmp(opt, "permit-pty") == 0)
-                critical_flags |= CRITOPT_PTY;
+                certflags_flags |= CERTOPT_PTY;
         else if (strcasecmp(opt, "no-user-rc") == 0)
-                critical_flags &= ~CRITOPT_USER_RC;
+                certflags_flags &= ~CERTOPT_USER_RC;
         else if (strcasecmp(opt, "permit-user-rc") == 0)
-                critical_flags |= CRITOPT_USER_RC;
+                certflags_flags |= CERTOPT_USER_RC;
         else if (strncasecmp(opt, "force-command=", 14) == 0) {
                 val = opt + 14;
                 if (*val == '\0')
                         fatal("Empty force-command option");
-                if (critical_command != NULL)
+                if (certflags_command != NULL)
                         fatal("force-command already specified");
-                critical_command = xstrdup(val);
+                certflags_command = xstrdup(val);
         } else if (strncasecmp(opt, "source-address=", 15) == 0) {
                 val = opt + 15;
                 if (*val == '\0')
                         fatal("Empty source-address option");
-                if (critical_src_addr != NULL)
+                if (certflags_src_addr != NULL)
                         fatal("source-address already specified");
                 if (addr_match_cidr_list(NULL, val) != 0)
                         fatal("Invalid source-address list");
-                critical_src_addr = xstrdup(val);
+                certflags_src_addr = xstrdup(val);
         } else
                 fatal("Unsupported certificate option \"%s\"", opt);
 }
@@ -1667,7 +1683,7 @@ main(int argc, char **argv)
                         break;
                 case 'h':
                         cert_key_type = SSH2_CERT_TYPE_HOST;
-                        critical_flags = 0;
+                        certflags_flags = 0;
                         break;
                 case 'i':
                 case 'X':