From a98339edbc1fc21342a390f345179a9c3031bef7 Mon Sep 17 00:00:00 2001 From: "djm@openbsd.org" Date: Wed, 28 Jun 2017 01:09:22 +0000 Subject: [PATCH] upstream commit Allow ssh-keygen to use a key held in ssh-agent as a CA when signing certificates. bz#2377 ok markus Upstream-ID: fb42e920b592edcbb5b50465739a867c09329c8f --- authfd.c | 6 ++--- authfd.h | 4 +-- ssh-keygen.1 | 22 +++++++++++++-- ssh-keygen.c | 76 +++++++++++++++++++++++++++++++++++++++++++++------- sshkey.c | 25 ++++++++++++++--- sshkey.h | 10 +++++-- 6 files changed, 121 insertions(+), 22 deletions(-) diff --git a/authfd.c b/authfd.c index 8486e28b3..6c9843c87 100644 --- a/authfd.c +++ b/authfd.c @@ -1,4 +1,4 @@ -/* $OpenBSD: authfd.c,v 1.103 2017/05/05 10:42:49 naddy Exp $ */ +/* $OpenBSD: authfd.c,v 1.104 2017/06/28 01:09:22 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -326,7 +326,7 @@ ssh_free_identitylist(struct ssh_identitylist *idl) /* encode signature algoritm in flag bits, so we can keep the msg format */ static u_int -agent_encode_alg(struct sshkey *key, const char *alg) +agent_encode_alg(const struct sshkey *key, const char *alg) { if (alg != NULL && key->type == KEY_RSA) { if (strcmp(alg, "rsa-sha2-256") == 0) @@ -339,7 +339,7 @@ agent_encode_alg(struct sshkey *key, const char *alg) /* ask agent to sign data, returns err.h code on error, 0 on success */ int -ssh_agent_sign(int sock, struct sshkey *key, +ssh_agent_sign(int sock, const struct sshkey *key, u_char **sigp, size_t *lenp, const u_char *data, size_t datalen, const char *alg, u_int compat) { diff --git a/authfd.h b/authfd.h index 0e98331d7..43abf85da 100644 --- a/authfd.h +++ b/authfd.h @@ -1,4 +1,4 @@ -/* $OpenBSD: authfd.h,v 1.40 2017/05/05 10:42:49 naddy Exp $ */ +/* $OpenBSD: authfd.h,v 1.41 2017/06/28 01:09:22 djm Exp $ */ /* * Author: Tatu Ylonen @@ -38,7 +38,7 @@ int ssh_remove_all_identities(int sock, int version); int ssh_decrypt_challenge(int sock, struct sshkey* key, BIGNUM *challenge, u_char session_id[16], u_char response[16]); -int ssh_agent_sign(int sock, struct sshkey *key, +int ssh_agent_sign(int sock, const struct sshkey *key, u_char **sigp, size_t *lenp, const u_char *data, size_t datalen, const char *alg, u_int compat); diff --git a/ssh-keygen.1 b/ssh-keygen.1 index 786d37d51..66f8321c5 100644 --- a/ssh-keygen.1 +++ b/ssh-keygen.1 @@ -1,4 +1,4 @@ -.\" $OpenBSD: ssh-keygen.1,v 1.141 2017/05/05 10:41:58 naddy Exp $ +.\" $OpenBSD: ssh-keygen.1,v 1.142 2017/06/28 01:09:22 djm Exp $ .\" .\" Author: Tatu Ylonen .\" Copyright (c) 1995 Tatu Ylonen , Espoo, Finland @@ -35,7 +35,7 @@ .\" (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF .\" THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. .\" -.Dd $Mdocdate: May 5 2017 $ +.Dd $Mdocdate: June 28 2017 $ .Dt SSH-KEYGEN 1 .Os .Sh NAME @@ -114,6 +114,8 @@ .Fl s Ar ca_key .Fl I Ar certificate_identity .Op Fl h +.Op Fl U +.Op Fl D Ar pkcs11_provider .Op Fl n Ar principals .Op Fl O Ar option .Op Fl V Ar validity_interval @@ -558,6 +560,14 @@ The possible values are .Dq ed25519 , or .Dq rsa . +.It Fl U +When used in combination with +.Fl s , +this option indicates that a CA key resides in a +.Xr ssh-agent 1 . +See the +.Sx CERTIFICATES +section for more information. .It Fl u Update a KRL. When specified with @@ -705,6 +715,14 @@ to .Pp .Dl $ ssh-keygen -s ca_key.pub -D libpkcs11.so -I key_id user_key.pub .Pp +Similarly, it is possible for the CA key to be hosted in a +.Xr ssh-agent 1 . +This is indicated by the +.Fl U +flag and, again, the CA key must be identified by its public half. +.Pp +.Dl $ ssh-keygen -Us ca_key.pub -I key_id user_key.pub +.Pp In all cases, .Ar key_id is a "key identifier" that is logged by the server when the certificate diff --git a/ssh-keygen.c b/ssh-keygen.c index cc3a7df18..b6b690051 100644 --- a/ssh-keygen.c +++ b/ssh-keygen.c @@ -1,4 +1,4 @@ -/* $OpenBSD: ssh-keygen.c,v 1.304 2017/05/30 14:16:41 markus Exp $ */ +/* $OpenBSD: ssh-keygen.c,v 1.305 2017/06/28 01:09:22 djm Exp $ */ /* * Author: Tatu Ylonen * Copyright (c) 1994 Tatu Ylonen , Espoo, Finland @@ -59,6 +59,7 @@ #include "krl.h" #include "digest.h" #include "utf8.h" +#include "authfd.h" #ifdef WITH_OPENSSL # define DEFAULT_KEY_TYPE_NAME "rsa" @@ -121,6 +122,9 @@ char *identity_comment = NULL; /* Path to CA key when certifying keys. */ char *ca_key_path = NULL; +/* Prefer to use agent keys for CA signing */ +int prefer_agent = 0; + /* Certificate serial number */ unsigned long long cert_serial = 0; @@ -1597,24 +1601,66 @@ load_pkcs11_key(char *path) #endif /* ENABLE_PKCS11 */ } +/* Signer for sshkey_certify_custom that uses the agent */ +static int +agent_signer(const struct sshkey *key, u_char **sigp, size_t *lenp, + const u_char *data, size_t datalen, + const char *alg, u_int compat, void *ctx) +{ + int *agent_fdp = (int *)ctx; + + return ssh_agent_sign(*agent_fdp, key, sigp, lenp, + data, datalen, alg, compat); +} + static void do_ca_sign(struct passwd *pw, int argc, char **argv) { - int r, i, fd; + int r, i, fd, found, agent_fd = -1; u_int n; struct sshkey *ca, *public; char valid[64], *otmp, *tmp, *cp, *out, *comment, **plist = NULL; FILE *f; + struct ssh_identitylist *agent_ids; + size_t j; #ifdef ENABLE_PKCS11 pkcs11_init(1); #endif tmp = tilde_expand_filename(ca_key_path, pw->pw_uid); if (pkcs11provider != NULL) { + /* If a PKCS#11 token was specified then try to use it */ if ((ca = load_pkcs11_key(tmp)) == NULL) fatal("No PKCS#11 key matching %s found", ca_key_path); - } else + } else if (prefer_agent) { + /* + * Agent signature requested. Try to use agent after making + * sure the public key specified is actually present in the + * agent. + */ + if ((r = sshkey_load_public(tmp, &ca, NULL)) != 0) + fatal("Cannot load CA public key %s: %s", + tmp, ssh_err(r)); + if ((r = ssh_get_authentication_socket(&agent_fd)) != 0) + fatal("Cannot use public key for CA signature: %s", + ssh_err(r)); + if ((r = ssh_fetch_identitylist(agent_fd, &agent_ids)) != 0) + fatal("Retrieve agent key list: %s", ssh_err(r)); + found = 0; + for (j = 0; j < agent_ids->nkeys; j++) { + if (sshkey_equal(ca, agent_ids->keys[j])) { + found = 1; + break; + } + } + if (!found) + fatal("CA key %s not found in agent", tmp); + ssh_free_identitylist(agent_ids); + ca->flags |= SSHKEY_FLAG_EXT; + } else { + /* CA key is assumed to be a private key on the filesystem */ ca = load_identity(tmp); + } free(tmp); if (key_type_name != NULL && @@ -1664,8 +1710,16 @@ do_ca_sign(struct passwd *pw, int argc, char **argv) &public->cert->signature_key)) != 0) fatal("sshkey_from_private (ca key): %s", ssh_err(r)); - if ((r = sshkey_certify(public, ca, key_type_name)) != 0) - fatal("Couldn't certify key %s: %s", tmp, ssh_err(r)); + if (agent_fd != -1 && (ca->flags & SSHKEY_FLAG_EXT) != 0) { + if ((r = sshkey_certify_custom(public, ca, + key_type_name, agent_signer, &agent_fd)) != 0) + fatal("Couldn't certify key %s via agent: %s", + tmp, ssh_err(r)); + } else { + if ((sshkey_certify(public, ca, key_type_name)) != 0) + fatal("Couldn't certify key %s: %s", + tmp, ssh_err(r)); + } if ((cp = strrchr(tmp, '.')) != NULL && strcmp(cp, ".pub") == 0) *cp = '\0'; @@ -2261,8 +2315,9 @@ usage(void) " ssh-keygen -T output_file -f input_file [-v] [-a rounds] [-J num_lines]\n" " [-j start_line] [-K checkpt] [-W generator]\n" #endif - " ssh-keygen -s ca_key -I certificate_identity [-h] [-n principals]\n" - " [-O option] [-V validity_interval] [-z serial_number] file ...\n" + " ssh-keygen -s ca_key -I certificate_identity [-h] [-U]\n" + " [-D pkcs11_provider] [-n principals] [-O option]\n" + " [-V validity_interval] [-z serial_number] file ...\n" " ssh-keygen -L [-f input_keyfile]\n" " ssh-keygen -A\n" " ssh-keygen -k -f krl_file [-u] [-s ca_public] [-z version_number]\n" @@ -2320,8 +2375,8 @@ main(int argc, char **argv) if (gethostname(hostname, sizeof(hostname)) < 0) fatal("gethostname: %s", strerror(errno)); - /* Remaining characters: UYdw */ - while ((opt = getopt(argc, argv, "ABHLQXceghiklopquvxy" + /* Remaining characters: Ydw */ + while ((opt = getopt(argc, argv, "ABHLQUXceghiklopquvxy" "C:D:E:F:G:I:J:K:M:N:O:P:R:S:T:V:W:Z:" "a:b:f:g:j:m:n:r:s:t:z:")) != -1) { switch (opt) { @@ -2448,6 +2503,9 @@ main(int argc, char **argv) case 'D': pkcs11provider = optarg; break; + case 'U': + prefer_agent = 1; + break; case 'u': update_krl = 1; break; diff --git a/sshkey.c b/sshkey.c index a138a6f66..acc6e3f2d 100644 --- a/sshkey.c +++ b/sshkey.c @@ -1,4 +1,4 @@ -/* $OpenBSD: sshkey.c,v 1.52 2017/06/09 06:40:24 djm Exp $ */ +/* $OpenBSD: sshkey.c,v 1.53 2017/06/28 01:09:22 djm Exp $ */ /* * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. * Copyright (c) 2008 Alexander von Gernler. All rights reserved. @@ -2253,7 +2253,8 @@ sshkey_drop_cert(struct sshkey *k) /* Sign a certified key, (re-)generating the signed certblob. */ int -sshkey_certify(struct sshkey *k, struct sshkey *ca, const char *alg) +sshkey_certify_custom(struct sshkey *k, struct sshkey *ca, const char *alg, + sshkey_certify_signer *signer, void *signer_ctx) { struct sshbuf *principals = NULL; u_char *ca_blob = NULL, *sig_blob = NULL, nonce[32]; @@ -2342,8 +2343,8 @@ sshkey_certify(struct sshkey *k, struct sshkey *ca, const char *alg) goto out; /* Sign the whole mess */ - if ((ret = sshkey_sign(ca, &sig_blob, &sig_len, sshbuf_ptr(cert), - sshbuf_len(cert), alg, 0)) != 0) + if ((ret = signer(ca, &sig_blob, &sig_len, sshbuf_ptr(cert), + sshbuf_len(cert), alg, 0, signer_ctx)) != 0) goto out; /* Append signature and we are done */ @@ -2359,6 +2360,22 @@ sshkey_certify(struct sshkey *k, struct sshkey *ca, const char *alg) return ret; } +static int +default_key_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, + const u_char *data, size_t datalen, + const char *alg, u_int compat, void *ctx) +{ + if (ctx != NULL) + return SSH_ERR_INVALID_ARGUMENT; + return sshkey_sign(key, sigp, lenp, data, datalen, alg, compat); +} + +int +sshkey_certify(struct sshkey *k, struct sshkey *ca, const char *alg) +{ + return sshkey_certify_custom(k, ca, alg, default_key_sign, NULL); +} + int sshkey_cert_check_authority(const struct sshkey *k, int want_host, int require_principal, diff --git a/sshkey.h b/sshkey.h index 8aaa31532..d8346a57b 100644 --- a/sshkey.h +++ b/sshkey.h @@ -1,4 +1,4 @@ -/* $OpenBSD: sshkey.h,v 1.19 2017/06/13 11:22:15 djm Exp $ */ +/* $OpenBSD: sshkey.h,v 1.20 2017/06/28 01:09:22 djm Exp $ */ /* * Copyright (c) 2000, 2001 Markus Friedl. All rights reserved. @@ -137,13 +137,19 @@ int sshkey_type_is_cert(int); int sshkey_type_plain(int); int sshkey_to_certified(struct sshkey *); int sshkey_drop_cert(struct sshkey *); -int sshkey_certify(struct sshkey *, struct sshkey *, const char *); int sshkey_cert_copy(const struct sshkey *, struct sshkey *); int sshkey_cert_check_authority(const struct sshkey *, int, int, const char *, const char **); size_t sshkey_format_cert_validity(const struct sshkey_cert *, char *, size_t) __attribute__((__bounded__(__string__, 2, 3))); +int sshkey_certify(struct sshkey *, struct sshkey *, const char *); +/* Variant allowing use of a custom signature function (e.g. for ssh-agent) */ +typedef int sshkey_certify_signer(const struct sshkey *, u_char **, size_t *, + const u_char *, size_t, const char *, u_int, void *); +int sshkey_certify_custom(struct sshkey *, struct sshkey *, const char *, + sshkey_certify_signer *, void *); + int sshkey_ecdsa_nid_from_name(const char *); int sshkey_curve_name_to_nid(const char *); const char * sshkey_curve_nid_to_name(int);