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authordjm@openbsd.org <djm@openbsd.org>2019-12-30 09:21:16 +0000
committerDamien Miller <djm@mindrot.org>2019-12-30 20:58:19 +1100
commit14cea36df397677b8f8568204300ef654114fd76 (patch)
tree4c9b0bf5108df396f8d9eaff576537e7c9cc50e9
parent2fe05fcb4a2695f190b4fcf27770b655586ab349 (diff)
upstream: resident keys support in SK API
Adds a sk_load_resident_keys() function to the security key API that accepts a security key provider and a PIN and returns a list of keys. Implement support for this in the usbhid middleware. feedback and ok markus@ OpenBSD-Commit-ID: 67e984e4e87f4999ce447a6178c4249a9174eff0
-rw-r--r--sk-api.h13
-rw-r--r--sk-usbhid.c238
-rw-r--r--ssh-sk.c116
-rw-r--r--ssh-sk.h11
4 files changed, 366 insertions, 12 deletions
diff --git a/sk-api.h b/sk-api.h
index 5947e0ed..10f1fdb1 100644
--- a/sk-api.h
+++ b/sk-api.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: sk-api.h,v 1.3 2019/12/30 09:19:52 djm Exp $ */
+/* $OpenBSD: sk-api.h,v 1.4 2019/12/30 09:21:16 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
@@ -52,6 +52,13 @@ struct sk_sign_response {
size_t sig_s_len;
};
+struct sk_resident_key {
+ uint8_t alg;
+ size_t slot;
+ char *application;
+ struct sk_enroll_response key;
+};
+
#define SSH_SK_VERSION_MAJOR 0x00020000 /* current API version */
#define SSH_SK_VERSION_MAJOR_MASK 0xffff0000
@@ -68,4 +75,8 @@ int sk_sign(int alg, const uint8_t *message, size_t message_len,
const char *application, const uint8_t *key_handle, size_t key_handle_len,
uint8_t flags, struct sk_sign_response **sign_response);
+/* Enumerate all resident keys */
+int sk_load_resident_keys(const char *pin,
+ struct sk_resident_key ***rks, size_t *nrks);
+
#endif /* _SK_API_H */
diff --git a/sk-usbhid.c b/sk-usbhid.c
index 61b52bbb..fa442448 100644
--- a/sk-usbhid.c
+++ b/sk-usbhid.c
@@ -34,6 +34,7 @@
#endif /* WITH_OPENSSL */
#include <fido.h>
+#include <fido/credman.h>
#ifndef SK_STANDALONE
#include "log.h"
@@ -84,11 +85,19 @@ struct sk_sign_response {
size_t sig_s_len;
};
+struct sk_resident_key {
+ uint8_t alg;
+ size_t slot;
+ char *application;
+ struct sk_enroll_response key;
+};
+
/* If building as part of OpenSSH, then rename exported functions */
#if !defined(SK_STANDALONE)
-#define sk_api_version ssh_sk_api_version
-#define sk_enroll ssh_sk_enroll
-#define sk_sign ssh_sk_sign
+#define sk_api_version ssh_sk_api_version
+#define sk_enroll ssh_sk_enroll
+#define sk_sign ssh_sk_sign
+#define sk_load_resident_keys ssh_sk_load_resident_keys
#endif
/* Return the version of the middleware API */
@@ -104,6 +113,10 @@ int sk_sign(int alg, const uint8_t *message, size_t message_len,
const char *application, const uint8_t *key_handle, size_t key_handle_len,
uint8_t flags, struct sk_sign_response **sign_response);
+/* Load resident keys */
+int sk_load_resident_keys(const char *pin,
+ struct sk_resident_key ***rks, size_t *nrks);
+
static void skdebug(const char *func, const char *fmt, ...)
__attribute__((__format__ (printf, 2, 3)));
@@ -281,7 +294,8 @@ find_device(const uint8_t *message, size_t message_len, const char *application,
* but the API expects a SEC1 octet string.
*/
static int
-pack_public_key_ecdsa(fido_cred_t *cred, struct sk_enroll_response *response)
+pack_public_key_ecdsa(const fido_cred_t *cred,
+ struct sk_enroll_response *response)
{
const uint8_t *ptr;
BIGNUM *x = NULL, *y = NULL;
@@ -351,7 +365,8 @@ pack_public_key_ecdsa(fido_cred_t *cred, struct sk_enroll_response *response)
#endif /* WITH_OPENSSL */
static int
-pack_public_key_ed25519(fido_cred_t *cred, struct sk_enroll_response *response)
+pack_public_key_ed25519(const fido_cred_t *cred,
+ struct sk_enroll_response *response)
{
const uint8_t *ptr;
size_t len;
@@ -382,7 +397,8 @@ pack_public_key_ed25519(fido_cred_t *cred, struct sk_enroll_response *response)
}
static int
-pack_public_key(int alg, fido_cred_t *cred, struct sk_enroll_response *response)
+pack_public_key(int alg, const fido_cred_t *cred,
+ struct sk_enroll_response *response)
{
switch(alg) {
#ifdef WITH_OPENSSL
@@ -715,4 +731,214 @@ sk_sign(int alg, const uint8_t *message, size_t message_len,
}
return ret;
}
+
+static int
+read_rks(const char *devpath, const char *pin,
+ struct sk_resident_key ***rksp, size_t *nrksp)
+{
+ int r = -1;
+ fido_dev_t *dev = NULL;
+ fido_credman_metadata_t *metadata = NULL;
+ fido_credman_rp_t *rp = NULL;
+ fido_credman_rk_t *rk = NULL;
+ size_t i, j, nrp, nrk;
+ const fido_cred_t *cred;
+ struct sk_resident_key *srk = NULL, **tmp;
+
+ if ((dev = fido_dev_new()) == NULL) {
+ skdebug(__func__, "fido_dev_new failed");
+ return -1;
+ }
+ if ((r = fido_dev_open(dev, devpath)) != FIDO_OK) {
+ skdebug(__func__, "fido_dev_open %s failed: %s",
+ devpath, fido_strerr(r));
+ fido_dev_free(&dev);
+ return -1;
+ }
+ if ((metadata = fido_credman_metadata_new()) == NULL) {
+ r = -1;
+ skdebug(__func__, "alloc failed");
+ goto out;
+ }
+
+ if ((r = fido_credman_get_dev_metadata(dev, metadata, pin)) != 0) {
+ if (r == FIDO_ERR_INVALID_COMMAND) {
+ skdebug(__func__, "device %s does not support "
+ "resident keys", devpath);
+ r = 0;
+ goto out;
+ }
+ skdebug(__func__, "get metadata for %s failed: %s",
+ devpath, fido_strerr(r));
+ goto out;
+ }
+ skdebug(__func__, "existing %llu, remaining %llu",
+ (unsigned long long)fido_credman_rk_existing(metadata),
+ (unsigned long long)fido_credman_rk_remaining(metadata));
+ if ((rp = fido_credman_rp_new()) == NULL) {
+ r = -1;
+ skdebug(__func__, "alloc rp failed");
+ goto out;
+ }
+ if ((r = fido_credman_get_dev_rp(dev, rp, pin)) != 0) {
+ skdebug(__func__, "get RPs for %s failed: %s",
+ devpath, fido_strerr(r));
+ goto out;
+ }
+ nrp = fido_credman_rp_count(rp);
+ skdebug(__func__, "Device %s has resident keys for %zu RPs",
+ devpath, nrp);
+
+ /* Iterate over RP IDs that have resident keys */
+ for (i = 0; i < nrp; i++) {
+ skdebug(__func__, "rp %zu: name=\"%s\" id=\"%s\" hashlen=%zu",
+ i, fido_credman_rp_name(rp, i), fido_credman_rp_id(rp, i),
+ fido_credman_rp_id_hash_len(rp, i));
+
+ /* Skip non-SSH RP IDs */
+ if (strncasecmp(fido_credman_rp_id(rp, i), "ssh:", 4) != 0)
+ continue;
+
+ fido_credman_rk_free(&rk);
+ if ((rk = fido_credman_rk_new()) == NULL) {
+ r = -1;
+ skdebug(__func__, "alloc rk failed");
+ goto out;
+ }
+ if ((r = fido_credman_get_dev_rk(dev, fido_credman_rp_id(rp, i),
+ rk, pin)) != 0) {
+ skdebug(__func__, "get RKs for %s slot %zu failed: %s",
+ devpath, i, fido_strerr(r));
+ goto out;
+ }
+ nrk = fido_credman_rk_count(rk);
+ skdebug(__func__, "RP \"%s\" has %zu resident keys",
+ fido_credman_rp_id(rp, i), nrk);
+
+ /* Iterate over resident keys for this RP ID */
+ for (j = 0; j < nrk; j++) {
+ if ((cred = fido_credman_rk(rk, j)) == NULL) {
+ skdebug(__func__, "no RK in slot %zu", j);
+ continue;
+ }
+ skdebug(__func__, "Device %s RP \"%s\" slot %zu: "
+ "type %d", devpath, fido_credman_rp_id(rp, i), j,
+ fido_cred_type(cred));
+
+ /* build response entry */
+ if ((srk = calloc(1, sizeof(*srk))) == NULL ||
+ (srk->key.key_handle = calloc(1,
+ fido_cred_id_len(cred))) == NULL ||
+ (srk->application = strdup(fido_credman_rp_id(rp,
+ i))) == NULL) {
+ r = -1;
+ skdebug(__func__, "alloc sk_resident_key");
+ goto out;
+ }
+
+ srk->key.key_handle_len = fido_cred_id_len(cred);
+ memcpy(srk->key.key_handle,
+ fido_cred_id_ptr(cred),
+ srk->key.key_handle_len);
+
+ switch (fido_cred_type(cred)) {
+ case COSE_ES256:
+ srk->alg = SK_ECDSA;
+ break;
+ case COSE_EDDSA:
+ srk->alg = SK_ED25519;
+ break;
+ default:
+ skdebug(__func__, "unsupported key type %d",
+ fido_cred_type(cred));
+ goto out;
+ }
+
+ if ((r = pack_public_key(srk->alg, cred,
+ &srk->key)) != 0) {
+ skdebug(__func__, "pack public key failed");
+ goto out;
+ }
+ /* append */
+ if ((tmp = recallocarray(*rksp, *nrksp, (*nrksp) + 1,
+ sizeof(**rksp))) == NULL) {
+ r = -1;
+ skdebug(__func__, "alloc rksp");
+ goto out;
+ }
+ *rksp = tmp;
+ (*rksp)[(*nrksp)++] = srk;
+ srk = NULL;
+ }
+ }
+ /* Success */
+ r = 0;
+ out:
+ if (srk != NULL) {
+ free(srk->application);
+ freezero(srk->key.public_key, srk->key.public_key_len);
+ freezero(srk->key.key_handle, srk->key.key_handle_len);
+ freezero(srk, sizeof(*srk));
+ }
+ fido_credman_rp_free(&rp);
+ fido_credman_rk_free(&rk);
+ fido_dev_close(dev);
+ fido_dev_free(&dev);
+ fido_credman_metadata_free(&metadata);
+ return r;
+}
+
+int
+sk_load_resident_keys(const char *pin,
+ struct sk_resident_key ***rksp, size_t *nrksp)
+{
+ int r = -1;
+ fido_dev_info_t *devlist = NULL;
+ size_t i, ndev = 0, nrks = 0;
+ const fido_dev_info_t *di;
+ struct sk_resident_key **rks = NULL;
+ *rksp = NULL;
+ *nrksp = 0;
+
+ if ((devlist = fido_dev_info_new(MAX_FIDO_DEVICES)) == NULL) {
+ skdebug(__func__, "fido_dev_info_new failed");
+ goto out;
+ }
+ if ((r = fido_dev_info_manifest(devlist,
+ MAX_FIDO_DEVICES, &ndev)) != FIDO_OK) {
+ skdebug(__func__, "fido_dev_info_manifest failed: %s",
+ fido_strerr(r));
+ goto out;
+ }
+ for (i = 0; i < ndev; i++) {
+ if ((di = fido_dev_info_ptr(devlist, i)) == NULL) {
+ skdebug(__func__, "no dev info at %zu", i);
+ continue;
+ }
+ skdebug(__func__, "trying %s", fido_dev_info_path(di));
+ if ((r = read_rks(fido_dev_info_path(di), pin,
+ &rks, &nrks)) != 0) {
+ skdebug(__func__, "read_rks failed for %s",
+ fido_dev_info_path(di));
+ continue;
+ }
+ }
+ /* success */
+ r = 0;
+ *rksp = rks;
+ *nrksp = nrks;
+ rks = NULL;
+ nrks = 0;
+ out:
+ for (i = 0; i < nrks; i++) {
+ free(rks[i]->application);
+ freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
+ freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
+ freezero(rks[i], sizeof(*rks[i]));
+ }
+ free(rks);
+ fido_dev_info_free(&devlist, MAX_FIDO_DEVICES);
+ return r;
+}
+
#endif /* ENABLE_SK_INTERNAL */
diff --git a/ssh-sk.c b/ssh-sk.c
index 01927669..d48f34e3 100644
--- a/ssh-sk.c
+++ b/ssh-sk.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-sk.c,v 1.19 2019/12/30 09:20:36 djm Exp $ */
+/* $OpenBSD: ssh-sk.c,v 1.20 2019/12/30 09:21:16 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
@@ -60,6 +60,10 @@ struct sshsk_provider {
const char *application,
const uint8_t *key_handle, size_t key_handle_len,
uint8_t flags, struct sk_sign_response **sign_response);
+
+ /* Enumerate resident keys */
+ int (*sk_load_resident_keys)(const char *pin,
+ struct sk_resident_key ***rks, size_t *nrks);
};
/* Built-in version */
@@ -70,6 +74,8 @@ int ssh_sk_sign(int alg, const uint8_t *message, size_t message_len,
const char *application,
const uint8_t *key_handle, size_t key_handle_len,
uint8_t flags, struct sk_sign_response **sign_response);
+int ssh_sk_load_resident_keys(const char *pin,
+ struct sk_resident_key ***rks, size_t *nrks);
static void
sshsk_free(struct sshsk_provider *p)
@@ -101,6 +107,7 @@ sshsk_open(const char *path)
#ifdef ENABLE_SK_INTERNAL
ret->sk_enroll = ssh_sk_enroll;
ret->sk_sign = ssh_sk_sign;
+ ret->sk_load_resident_keys = ssh_sk_load_resident_keys;
#else
error("internal security key support not enabled");
#endif
@@ -136,6 +143,12 @@ sshsk_open(const char *path)
path, dlerror());
goto fail;
}
+ if ((ret->sk_load_resident_keys = dlsym(ret->dlhandle,
+ "sk_load_resident_keys")) == NULL) {
+ error("Security key provider %s dlsym(sk_load_resident_keys) "
+ "failed: %s", path, dlerror());
+ goto fail;
+ }
/* success */
return ret;
fail:
@@ -264,9 +277,7 @@ sshsk_key_from_response(int alg, const char *application, uint8_t flags,
*keyp = NULL;
/* Check response validity */
- if (resp->public_key == NULL || resp->key_handle == NULL ||
- resp->signature == NULL ||
- (resp->attestation_cert == NULL && resp->attestation_cert_len != 0)) {
+ if (resp->public_key == NULL || resp->key_handle == NULL) {
error("%s: sk_enroll response invalid", __func__);
r = SSH_ERR_INVALID_FORMAT;
goto out;
@@ -595,4 +606,101 @@ sshsk_sign(const char *provider_path, struct sshkey *key,
sshbuf_free(inner_sig);
return r;
}
+
+static void
+sshsk_free_sk_resident_keys(struct sk_resident_key **rks, size_t nrks)
+{
+ size_t i;
+
+ if (nrks == 0 || rks == NULL)
+ return;
+ for (i = 0; i < nrks; i++) {
+ free(rks[i]->application);
+ freezero(rks[i]->key.key_handle, rks[i]->key.key_handle_len);
+ freezero(rks[i]->key.public_key, rks[i]->key.public_key_len);
+ freezero(rks[i]->key.signature, rks[i]->key.signature_len);
+ freezero(rks[i]->key.attestation_cert,
+ rks[i]->key.attestation_cert_len);
+ freezero(rks[i], sizeof(**rks));
+ }
+ free(rks);
+}
+
+int
+sshsk_load_resident(const char *provider_path, const char *pin,
+ struct sshkey ***keysp, size_t *nkeysp)
+{
+ struct sshsk_provider *skp = NULL;
+ int r = SSH_ERR_INTERNAL_ERROR;
+ struct sk_resident_key **rks = NULL;
+ size_t i, nrks = 0, nkeys = 0;
+ struct sshkey *key = NULL, **keys = NULL, **tmp;
+ uint8_t flags;
+
+ debug("%s: provider \"%s\"%s", __func__, provider_path,
+ (pin != NULL && *pin != '\0') ? ", have-pin": "");
+
+ if (keysp == NULL || nkeysp == NULL)
+ return SSH_ERR_INVALID_ARGUMENT;
+ *keysp = NULL;
+ *nkeysp = 0;
+
+ if ((skp = sshsk_open(provider_path)) == NULL) {
+ r = SSH_ERR_INVALID_FORMAT; /* XXX sshsk_open return code? */
+ goto out;
+ }
+ if ((r = skp->sk_load_resident_keys(pin, &rks, &nrks)) != 0) {
+ error("Security key provider %s returned failure %d",
+ provider_path, r);
+ r = SSH_ERR_INVALID_FORMAT; /* XXX error codes in API? */
+ goto out;
+ }
+ for (i = 0; i < nrks; i++) {
+ debug3("%s: rk %zu: slot = %zu, alg = %d, application = \"%s\"",
+ __func__, i, rks[i]->slot, rks[i]->alg,
+ rks[i]->application);
+ /* XXX need better filter here */
+ if (strncmp(rks[i]->application, "ssh:", 4) != 0)
+ continue;
+ switch (rks[i]->alg) {
+ case SSH_SK_ECDSA:
+ case SSH_SK_ED25519:
+ break;
+ default:
+ continue;
+ }
+ /* XXX where to get flags? */
+ flags = SSH_SK_USER_PRESENCE_REQD|SSH_SK_RESIDENT_KEY;
+ if ((r = sshsk_key_from_response(rks[i]->alg,
+ rks[i]->application, flags, &rks[i]->key, &key)) != 0)
+ goto out;
+ if ((tmp = recallocarray(keys, nkeys, nkeys + 1,
+ sizeof(*tmp))) == NULL) {
+ error("%s: recallocarray failed", __func__);
+ r = SSH_ERR_ALLOC_FAIL;
+ goto out;
+ }
+ keys = tmp;
+ keys[nkeys++] = key;
+ key = NULL;
+ /* XXX synthesise comment */
+ }
+ /* success */
+ *keysp = keys;
+ *nkeysp = nkeys;
+ keys = NULL;
+ nkeys = 0;
+ r = 0;
+ out:
+ sshsk_free(skp);
+ sshsk_free_sk_resident_keys(rks, nrks);
+ sshkey_free(key);
+ if (nkeys != 0) {
+ for (i = 0; i < nkeys; i++)
+ sshkey_free(keys[i]);
+ free(keys);
+ }
+ return r;
+}
+
#endif /* ENABLE_SK */
diff --git a/ssh-sk.h b/ssh-sk.h
index 4d667884..1afe839d 100644
--- a/ssh-sk.h
+++ b/ssh-sk.h
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-sk.h,v 1.6 2019/12/13 19:09:10 djm Exp $ */
+/* $OpenBSD: ssh-sk.h,v 1.7 2019/12/30 09:21:16 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
@@ -45,5 +45,14 @@ int sshsk_sign(const char *provider_path, struct sshkey *key,
u_char **sigp, size_t *lenp, const u_char *data, size_t datalen,
u_int compat);
+/*
+ * Enumerates and loads all SSH-compatible resident keys from a security
+ * key.
+ *
+ * Returns 0 on success or a ssherr.h error code on failure.
+ */
+int sshsk_load_resident(const char *provider_path, const char *pin,
+ struct sshkey ***keysp, size_t *nkeysp);
+
#endif /* _SSH_SK_H */