upstream: Add ssh-keygen -Y match-principals operation to perform

matching of principals names against an allowed signers file.

Requested by and mostly written by Fabian Stelzer, towards a TOFU
model for SSH signatures in git. Some tweaks by me.

"doesn't bother me" deraadt@

OpenBSD-Commit-ID: 8d1b71f5a4127bc5e10a880c8ea6053394465247
This commit is contained in:
djm@openbsd.org 2021-11-27 07:14:46 +00:00 committed by Damien Miller
parent 15db86611b
commit 78230b3ec8
4 changed files with 132 additions and 5 deletions

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@ -1,4 +1,4 @@
.\" $OpenBSD: ssh-keygen.1,v 1.216 2021/08/11 08:54:17 djm Exp $
.\" $OpenBSD: ssh-keygen.1,v 1.217 2021/11/27 07:14:46 djm Exp $
.\"
.\" Author: Tatu Ylonen <ylo@cs.hut.fi>
.\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, 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: August 11 2021 $
.Dd $Mdocdate: November 27 2021 $
.Dt SSH-KEYGEN 1
.Os
.Sh NAME
@ -151,6 +151,11 @@
.Fl s Ar signature_file
.Fl f Ar allowed_signers_file
.Nm ssh-keygen
.Fl Y Cm match-principals
.Op Fl O Ar option
.Fl I Ar signer_identity
.Fl f Ar allowed_signers_file
.Nm ssh-keygen
.Fl Y Cm check-novalidate
.Op Fl O Ar option
.Fl n Ar namespace
@ -683,6 +688,14 @@ The format of the allowed signers file is documented in the
section below.
If one or more matching principals are found, they are returned on
standard output.
.It Fl Y Cm match-principals
Find principal matching the principal name provided using the
.Fl I
flag in the authorized signers file specified using the
.Fl f
flag.
If one or more matching principals are found, they are returned on
standard output.
.It Fl Y Cm check-novalidate
Checks that a signature generated using
.Nm

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@ -1,4 +1,4 @@
/* $OpenBSD: ssh-keygen.c,v 1.440 2021/10/29 03:20:46 djm Exp $ */
/* $OpenBSD: ssh-keygen.c,v 1.441 2021/11/27 07:14:46 djm Exp $ */
/*
* Author: Tatu Ylonen <ylo@cs.hut.fi>
* Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@ -2849,6 +2849,32 @@ done:
return ret;
}
static int
sig_match_principals(const char *allowed_keys, char *principal,
char * const *opts, size_t nopts)
{
int r;
char **principals = NULL;
size_t i, nprincipals = 0;
if ((r = sig_process_opts(opts, nopts, NULL, NULL)) != 0)
return r; /* error already logged */
if ((r = sshsig_match_principals(allowed_keys, principal,
&principals, &nprincipals)) != 0) {
debug_f("match: %s", ssh_err(r));
fprintf(stderr, "No principal matched.\n");
return r;
}
for (i = 0; i < nprincipals; i++) {
printf("%s\n", principals[i]);
free(principals[i]);
}
free(principals);
return 0;
}
static void
do_moduli_gen(const char *out_file, char **opts, size_t nopts)
{
@ -3187,6 +3213,7 @@ usage(void)
" file ...\n"
" ssh-keygen -Q [-l] -f krl_file [file ...]\n"
" ssh-keygen -Y find-principals -s signature_file -f allowed_signers_file\n"
" ssh-keygen -Y match-principals -I signer_identity -f allowed_signers_file\n"
" ssh-keygen -Y check-novalidate -n namespace -s signature_file\n"
" ssh-keygen -Y sign -f key_file -n namespace file ...\n"
" ssh-keygen -Y verify -f allowed_signers_file -I signer_identity\n"
@ -3468,6 +3495,19 @@ main(int argc, char **argv)
}
return sig_find_principals(ca_key_path, identity_file,
opts, nopts);
} else if (strncmp(sign_op, "match-principals", 16) == 0) {
if (!have_identity) {
error("Too few arguments for match-principals:"
"missing allowed keys file");
exit(1);
}
if (cert_key_id == NULL) {
error("Too few arguments for match-principals: "
"missing principal ID");
exit(1);
}
return sig_match_principals(identity_file, cert_key_id,
opts, nopts);
} else if (strncmp(sign_op, "sign", 4) == 0) {
if (cert_principals == NULL ||
*cert_principals == '\0') {

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@ -1,4 +1,4 @@
/* $OpenBSD: sshsig.c,v 1.23 2021/11/18 03:50:41 djm Exp $ */
/* $OpenBSD: sshsig.c,v 1.24 2021/11/27 07:14:46 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
@ -1050,6 +1050,76 @@ sshsig_find_principals(const char *path, const struct sshkey *sign_key,
return r == 0 ? SSH_ERR_KEY_NOT_FOUND : r;
}
int
sshsig_match_principals(const char *path, const char *principal,
char ***principalsp, size_t *nprincipalsp)
{
FILE *f = NULL;
char *found, *line = NULL, **principals = NULL, **tmp;
size_t i, nprincipals = 0, linesize = 0;
u_long linenum = 0;
int oerrno, r, ret = 0;
if (principalsp != NULL)
*principalsp = NULL;
if (nprincipalsp != NULL)
*nprincipalsp = 0;
/* Check key and principal against file */
if ((f = fopen(path, "r")) == NULL) {
oerrno = errno;
error("Unable to open allowed keys file \"%s\": %s",
path, strerror(errno));
errno = oerrno;
return SSH_ERR_SYSTEM_ERROR;
}
while (getline(&line, &linesize, f) != -1) {
linenum++;
/* Parse the line */
if ((r = parse_principals_key_and_options(path, linenum, line,
principal, &found, NULL, NULL)) != 0) {
if (r == SSH_ERR_KEY_NOT_FOUND)
continue;
ret = r;
oerrno = errno;
break; /* unexpected error */
}
if ((tmp = recallocarray(principals, nprincipals,
nprincipals + 1, sizeof(*principals))) == NULL) {
ret = SSH_ERR_ALLOC_FAIL;
free(found);
break;
}
principals = tmp;
principals[nprincipals++] = found; /* transferred */
free(line);
line = NULL;
linesize = 0;
}
fclose(f);
if (ret == 0) {
if (nprincipals == 0)
ret = SSH_ERR_KEY_NOT_FOUND;
if (principalsp != NULL) {
*principalsp = principals;
principals = NULL; /* transferred */
}
if (nprincipalsp != 0) {
*nprincipalsp = nprincipals;
nprincipals = 0;
}
}
for (i = 0; i < nprincipals; i++)
free(principals[i]);
free(principals);
errno = oerrno;
return ret;
}
int
sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey)
{

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@ -1,4 +1,4 @@
/* $OpenBSD: sshsig.h,v 1.10 2021/07/23 03:37:52 djm Exp $ */
/* $OpenBSD: sshsig.h,v 1.11 2021/11/27 07:14:46 djm Exp $ */
/*
* Copyright (c) 2019 Google LLC
*
@ -104,4 +104,8 @@ int sshsig_get_pubkey(struct sshbuf *signature, struct sshkey **pubkey);
int sshsig_find_principals(const char *path, const struct sshkey *sign_key,
uint64_t verify_time, char **principal);
/* Find all principals in allowed_keys file matching *principal */
int sshsig_match_principals(const char *path,
const char *principal, char ***principalsp, size_t *nprincipalsp);
#endif /* SSHSIG_H */