diff options
author | Damien Miller <djm@mindrot.org> | 2023-07-07 13:30:15 +1000 |
---|---|---|
committer | Damien Miller <djm@mindrot.org> | 2023-07-19 16:24:00 +1000 |
commit | d7790cdce72a1b6982795baa2b4d6f0bdbb0100d (patch) | |
tree | e3b254ade35126dadc911047c0670c2f51c43fdf | |
parent | b23fe83f06ee7e721033769cfa03ae840476d280 (diff) |
disallow remote addition of FIDO/PKCS11 keys
Depends on the local client performing the session-bind@openssh.com
operation, so non-OpenSSH local client may circumvent this.
-rw-r--r-- | ssh-agent.1 | 22 | ||||
-rw-r--r-- | ssh-agent.c | 21 |
2 files changed, 40 insertions, 3 deletions
diff --git a/ssh-agent.1 b/ssh-agent.1 index b0bf65da..97f4cab0 100644 --- a/ssh-agent.1 +++ b/ssh-agent.1 @@ -107,9 +107,27 @@ environment variable). .It Fl O Ar option Specify an option when starting .Nm . -Currently only one option is supported: +Currently two options are supported: +.Cm allow-remote-pkcs11 +and .Cm no-restrict-websafe . -This instructs +.Pp +The +.Cm allow-remote-pkcs11 +option allows clients of a forwarded +.Nm +to load PKCS#11 or FIDO provider libraries. +By default only local clients may perform this operation. +Note that signalling that a +.Nm +client remote is performed by +.Xr ssh 1 , +and use of other tools to forward access to the agent socket may circumvent +this restriction. +.Pp +The +.Cm no-restrict-websafe , +instructs .Nm to permit signatures using FIDO keys that might be web authentication requests. diff --git a/ssh-agent.c b/ssh-agent.c index 618bb198..8ea831f4 100644 --- a/ssh-agent.c +++ b/ssh-agent.c @@ -169,6 +169,12 @@ char socket_dir[PATH_MAX]; /* Pattern-list of allowed PKCS#11/Security key paths */ static char *allowed_providers; +/* + * Allows PKCS11 providers or SK keys that use non-internal providers to + * be added over a remote connection (identified by session-bind@openssh.com). + */ +static int remote_add_provider; + /* locking */ #define LOCK_SIZE 32 #define LOCK_SALT_SIZE 16 @@ -1228,6 +1234,12 @@ process_add_identity(SocketEntry *e) if (strcasecmp(sk_provider, "internal") == 0) { debug_f("internal provider"); } else { + if (e->nsession_ids != 0 && !remote_add_provider) { + verbose("failed add of SK provider \"%.100s\": " + "remote addition of providers is disabled", + sk_provider); + goto out; + } if (realpath(sk_provider, canonical_provider) == NULL) { verbose("failed provider \"%.100s\": " "realpath: %s", sk_provider, @@ -1391,6 +1403,11 @@ process_add_smartcard_key(SocketEntry *e) error_f("failed to parse constraints"); goto send; } + if (e->nsession_ids != 0 && !remote_add_provider) { + verbose("failed PKCS#11 add of \"%.100s\": remote addition of " + "providers is disabled", provider); + goto send; + } if (realpath(provider, canonical_provider) == NULL) { verbose("failed PKCS#11 add of \"%.100s\": realpath: %s", provider, strerror(errno)); @@ -2050,7 +2067,9 @@ main(int ac, char **av) break; case 'O': if (strcmp(optarg, "no-restrict-websafe") == 0) - restrict_websafe = 0; + restrict_websafe = 0; + else if (strcmp(optarg, "allow-remote-pkcs11") == 0) + remote_add_provider = 1; else fatal("Unknown -O option"); break; |