diff options
Diffstat (limited to 'ssh-rsa.c')
| -rw-r--r-- | ssh-rsa.c | 60 |
1 files changed, 45 insertions, 15 deletions
@@ -1,4 +1,4 @@ -/* $OpenBSD: ssh-rsa.c,v 1.66 2018/02/14 16:27:24 jsing Exp $ */ +/* $OpenBSD: ssh-rsa.c,v 1.67 2018/07/03 11:39:54 djm Exp $ */ /* * Copyright (c) 2000, 2003 Markus Friedl <markus@openbsd.org> * @@ -51,11 +51,14 @@ rsa_hash_alg_ident(int hash_alg) return NULL; } +/* + * Returns the hash algorithm ID for a given algorithm identifier as used + * inside the signature blob, + */ static int -rsa_hash_alg_from_ident(const char *ident) +rsa_hash_id_from_ident(const char *ident) { - if (strcmp(ident, "ssh-rsa") == 0 || - strcmp(ident, "ssh-rsa-cert-v01@openssh.com") == 0) + if (strcmp(ident, "ssh-rsa") == 0) return SSH_DIGEST_SHA1; if (strcmp(ident, "rsa-sha2-256") == 0) return SSH_DIGEST_SHA256; @@ -64,6 +67,27 @@ rsa_hash_alg_from_ident(const char *ident) return -1; } +/* + * Return the hash algorithm ID for the specified key name. This includes + * all the cases of rsa_hash_id_from_ident() but also the certificate key + * types. + */ +static int +rsa_hash_id_from_keyname(const char *alg) +{ + int r; + + if ((r = rsa_hash_id_from_ident(alg)) != -1) + return r; + if (strcmp(alg, "ssh-rsa-cert-v01@openssh.com") == 0) + return SSH_DIGEST_SHA1; + if (strcmp(alg, "rsa-sha2-256-cert-v01@openssh.com") == 0) + return SSH_DIGEST_SHA256; + if (strcmp(alg, "rsa-sha2-512-cert-v01@openssh.com") == 0) + return SSH_DIGEST_SHA512; + return -1; +} + static int rsa_hash_alg_nid(int type) { @@ -135,7 +159,7 @@ ssh_rsa_sign(const struct sshkey *key, u_char **sigp, size_t *lenp, if (alg_ident == NULL || strlen(alg_ident) == 0) hash_alg = SSH_DIGEST_SHA1; else - hash_alg = rsa_hash_alg_from_ident(alg_ident); + hash_alg = rsa_hash_id_from_keyname(alg_ident); if (key == NULL || key->rsa == NULL || hash_alg == -1 || sshkey_type_plain(key->type) != KEY_RSA) return SSH_ERR_INVALID_ARGUMENT; @@ -202,7 +226,7 @@ ssh_rsa_verify(const struct sshkey *key, const char *alg) { char *sigtype = NULL; - int hash_alg, ret = SSH_ERR_INTERNAL_ERROR; + int hash_alg, want_alg, ret = SSH_ERR_INTERNAL_ERROR; size_t len = 0, diff, modlen, dlen; struct sshbuf *b = NULL; u_char digest[SSH_DIGEST_MAX_LENGTH], *osigblob, *sigblob = NULL; @@ -220,18 +244,24 @@ ssh_rsa_verify(const struct sshkey *key, ret = SSH_ERR_INVALID_FORMAT; goto out; } - /* XXX djm: need cert types that reliably yield SHA-2 signatures */ - if (alg != NULL && strcmp(alg, sigtype) != 0 && - strcmp(alg, "ssh-rsa-cert-v01@openssh.com") != 0) { - error("%s: RSA signature type mismatch: " - "expected %s received %s", __func__, alg, sigtype); - ret = SSH_ERR_SIGNATURE_INVALID; - goto out; - } - if ((hash_alg = rsa_hash_alg_from_ident(sigtype)) == -1) { + if ((hash_alg = rsa_hash_id_from_ident(sigtype)) == -1) { ret = SSH_ERR_KEY_TYPE_MISMATCH; goto out; } + /* + * Allow ssh-rsa-cert-v01 certs to generate SHA2 signatures for + * legacy reasons, but otherwise the signature type should match. + */ + if (alg != NULL && strcmp(alg, "ssh-rsa-cert-v01@openssh.com") != 0) { + if ((want_alg = rsa_hash_id_from_keyname(alg)) == -1) { + ret = SSH_ERR_INVALID_ARGUMENT; + goto out; + } + if (hash_alg != want_alg) { + ret = SSH_ERR_SIGNATURE_INVALID; + goto out; + } + } if (sshbuf_get_string(b, &sigblob, &len) != 0) { ret = SSH_ERR_INVALID_FORMAT; goto out; |