upstream: sshsig tweaks and improvements from and suggested by

Markus

ok markus/me

OpenBSD-Commit-ID: ea4f46ad5a16b27af96e08c4877423918c4253e9

5 files changed, 122 insertions, 104 deletions

diff --git a/PROTOCOL.sshsig b/PROTOCOL.sshsig
index 806c35da6..720e1f18a 100644
--- a/PROTOCOL.sshsig
+++ b/PROTOCOL.sshsig
@@ -8,9 +8,9 @@ At present, only detached and armored signatures are supported.
 The Armored SSH signatures consist of a header, a base64
 encoded blob, and a footer.
 
-The header is the string “-----BEGIN SSH SIGNATURE-----”
+The header is the string "-----BEGIN SSH SIGNATURE-----"
 followed by a newline. The footer is the string
-“-----END SSH SIGNATURE-----” immediately after a newline.
+"-----END SSH SIGNATURE-----" immediately after a newline.
 
 The header MUST be present at the start of every signature.
 Files containing the signature MUST start with the header.
diff --git a/ssh-keygen.1 b/ssh-keygen.1
index 93c76ef8a..cbaf29809 100644
--- a/ssh-keygen.1
+++ b/ssh-keygen.1
@@ -1,4 +1,4 @@
-.\"     $OpenBSD: ssh-keygen.1,v 1.163 2019/09/03 08:34:19 djm Exp $
+.\"     $OpenBSD: ssh-keygen.1,v 1.164 2019/09/03 08:35:27 djm Exp $
 .\"
 .\" Author: Tatu Ylonen <ylo@cs.hut.fi>
 .\" Copyright (c) 1995 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -986,7 +986,7 @@ Indicates that this key is accepted as a certificate authority (CA) and
 that certificates signed by this CA may be accepted for verification.
 .It Cm namespaces="namespace-list"
 Specifies a pattern-list of namespaces that are accepted for this key.
-If this option is present, the the signature namespace embedded in the
+If this option is present, the signature namespace embedded in the
 signature object and presented on the verification command-line must
 match the specified list before the key will be considered acceptable.
 .El
diff --git a/ssh-keygen.c b/ssh-keygen.c
index 76bc41b2f..527cfcf63 100644
--- a/ssh-keygen.c
+++ b/ssh-keygen.c
@@ -1,4 +1,4 @@
-/* $OpenBSD: ssh-keygen.c,v 1.344 2019/09/03 08:34:19 djm Exp $ */
+/* $OpenBSD: ssh-keygen.c,v 1.345 2019/09/03 08:35:27 djm Exp $ */
 /*
  * Author: Tatu Ylonen <ylo@cs.hut.fi>
  * Copyright (c) 1994 Tatu Ylonen <ylo@cs.hut.fi>, Espoo, Finland
@@ -2659,10 +2659,10 @@ verify(const char *signature, const char *sig_namespace, const char *principal,
         fp = NULL;
 
         if (revoked_keys != NULL) {
-            if ((r = sshkey_check_revoked(sign_key, revoked_keys)) != 0) {
-                    debug3("sshkey_check_revoked failed: %s", ssh_err(r));
-                    goto done;
-            }
+                if ((r = sshkey_check_revoked(sign_key, revoked_keys)) != 0) {
+                        debug3("sshkey_check_revoked failed: %s", ssh_err(r));
+                        goto done;
+                }
         }
 
         if ((r = sshsig_check_allowed_keys(allowed_keys, sign_key,
diff --git a/sshsig.c b/sshsig.c
index 0a1e14627..c1f2d803f 100644
--- a/sshsig.c
+++ b/sshsig.c
@@ -230,7 +230,7 @@ sshsig_parse_preamble(struct sshbuf *buf)
                 return r;
         }
 
-        if (sversion < SIG_VERSION) {
+        if (sversion > SIG_VERSION) {
                 error("Signature version %lu is larger than supported "
                     "version %u", (unsigned long)sversion, SIG_VERSION);
                 return SSH_ERR_INVALID_FORMAT;
@@ -241,7 +241,8 @@ sshsig_parse_preamble(struct sshbuf *buf)
 static int
 sshsig_check_hashalg(const char *hashalg)
 {
-        if (match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
+        if (hashalg == NULL ||
+            match_pattern_list(hashalg, HASHALG_ALLOWED, 0) == 1)
                 return 0;
         error("%s: unsupported hash algorithm \"%.100s\"", __func__, hashalg);
         return SSH_ERR_SIGN_ALG_UNSUPPORTED;
@@ -268,8 +269,6 @@ sshsig_peek_hashalg(struct sshbuf *signature, char **hashalgp)
                 error("Couldn't parse signature blob: %s", ssh_err(r));
                 goto done;
         }
-        if ((r = sshsig_check_hashalg(hashalg)) != 0)
-                goto done;
 
         /* success */
         r = 0;
@@ -293,6 +292,7 @@ sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
         char *got_namespace = NULL, *sigtype = NULL, *sig_hashalg = NULL;
         size_t siglen;
 
+        debug("%s: verify message length %zu", __func__, sshbuf_len(h_message));
         if (sign_keyp != NULL)
                 *sign_keyp = NULL;
 
@@ -301,9 +301,6 @@ sshsig_wrap_verify(struct sshbuf *signature, const char *hashalg,
                 r = SSH_ERR_ALLOC_FAIL;
                 goto done;
         }
-        if ((r = sshsig_check_hashalg(hashalg)) != 0)
-                goto done;
-
         if ((r = sshbuf_put(toverify, MAGIC_PREAMBLE,
             MAGIC_PREAMBLE_LEN)) != 0 ||
             (r = sshbuf_put_cstring(toverify, expect_namespace)) != 0 ||
@@ -382,36 +379,65 @@ done:
         return r;
 }
 
-int
-sshsig_sign_message(struct sshkey *key, const char *hashalg,
-    const struct sshbuf *message, const char *sig_namespace,
-    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
+static int
+hash_buffer(const struct sshbuf *m, const char *hashalg, struct sshbuf **bp)
 {
-        u_char hash[SSH_DIGEST_MAX_LENGTH];
-        struct sshbuf *b = NULL;
+        char *hex, hash[SSH_DIGEST_MAX_LENGTH];
         int alg, r = SSH_ERR_INTERNAL_ERROR;
+        struct sshbuf *b = NULL;
 
-        if (out != NULL)
-                *out = NULL;
-        if (hashalg == NULL)
-            hashalg = HASHALG_DEFAULT;
+        *bp = NULL;
+        memset(hash, 0, sizeof(hash));
 
         if ((r = sshsig_check_hashalg(hashalg)) != 0)
                 return r;
         if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
                 error("%s: can't look up hash algorithm %s",
-                    __func__, HASHALG_DEFAULT);
+                    __func__, hashalg);
                 return SSH_ERR_INTERNAL_ERROR;
         }
-        if ((r = ssh_digest_buffer(alg, message, hash, sizeof(hash))) != 0) {
+        if ((r = ssh_digest_buffer(alg, m, hash, sizeof(hash))) != 0) {
                 error("%s: ssh_digest_buffer failed: %s", __func__, ssh_err(r));
                 return r;
         }
-        if ((b = sshbuf_from(hash, ssh_digest_bytes(alg))) == NULL) {
-                error("%s: sshbuf_from failed", __func__);
+        if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
+                debug3("%s: final hash: %s", __func__, hex);
+                freezero(hex, strlen(hex));
+        }
+        if ((b = sshbuf_new()) == NULL) {
                 r = SSH_ERR_ALLOC_FAIL;
                 goto out;
         }
+        if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
+                error("%s: sshbuf_put: %s", __func__, ssh_err(r));
+                goto out;
+        }
+        *bp = b;
+        b = NULL; /* transferred */
+        /* success */
+        r = 0;
+ out:
+        sshbuf_free(b);
+        explicit_bzero(hash, sizeof(hash));
+        return 0;
+}
+
+int
+sshsig_signb(struct sshkey *key, const char *hashalg,
+    const struct sshbuf *message, const char *sig_namespace,
+    struct sshbuf **out, sshsig_signer *signer, void *signer_ctx)
+{
+        struct sshbuf *b = NULL;
+        int r = SSH_ERR_INTERNAL_ERROR;
+
+        if (hashalg == NULL)
+                hashalg = HASHALG_DEFAULT;
+        if (out != NULL)
+                *out = NULL;
+        if ((r = hash_buffer(message, hashalg, &b)) != 0) {
+                error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
+                goto out;
+        }
         if ((r = sshsig_wrap_sign(key, hashalg, b, sig_namespace, out,
             signer, signer_ctx)) != 0)
                 goto out;
@@ -419,17 +445,15 @@ sshsig_sign_message(struct sshkey *key, const char *hashalg,
         r = 0;
  out:
         sshbuf_free(b);
-        explicit_bzero(hash, sizeof(hash));
         return r;
 }
 
 int
-sshsig_verify_message(struct sshbuf *signature, const struct sshbuf *message,
+sshsig_verifyb(struct sshbuf *signature, const struct sshbuf *message,
     const char *expect_namespace, struct sshkey **sign_keyp)
 {
-        u_char hash[SSH_DIGEST_MAX_LENGTH];
         struct sshbuf *b = NULL;
-        int alg, r = SSH_ERR_INTERNAL_ERROR;
+        int r = SSH_ERR_INTERNAL_ERROR;
         char *hashalg = NULL;
 
         if (sign_keyp != NULL)
@@ -437,18 +461,9 @@ sshsig_verify_message(struct sshbuf *signature, const struct sshbuf *message,
 
         if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
                 return r;
-        if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
-                error("%s: can't look up hash algorithm %s",
-                    __func__, HASHALG_DEFAULT);
-                return SSH_ERR_INTERNAL_ERROR;
-        }
-        if ((r = ssh_digest_buffer(alg, message, hash, sizeof(hash))) != 0) {
-                error("%s: ssh_digest_buffer failed: %s", __func__, ssh_err(r));
-                goto out;
-        }
-        if ((b = sshbuf_from(hash, ssh_digest_bytes(alg))) == NULL) {
-                error("%s: sshbuf_from failed", __func__);
-                r = SSH_ERR_ALLOC_FAIL;
+        debug("%s: signature made with hash \"%s\"", __func__, hashalg);
+        if ((r = hash_buffer(message, hashalg, &b)) != 0) {
+                error("%s: hash_buffer failed: %s", __func__, ssh_err(r));
                 goto out;
         }
         if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
@@ -459,20 +474,29 @@ sshsig_verify_message(struct sshbuf *signature, const struct sshbuf *message,
  out:
         sshbuf_free(b);
         free(hashalg);
-        explicit_bzero(hash, sizeof(hash));
         return r;
 }
 
 static int
-hash_file(int fd, int hashalg, u_char *hash, size_t hashlen)
+hash_file(int fd, const char *hashalg, struct sshbuf **bp)
 {
-        char *hex, rbuf[8192];
+        char *hex, rbuf[8192], hash[SSH_DIGEST_MAX_LENGTH];
         ssize_t n, total = 0;
         struct ssh_digest_ctx *ctx;
-        int r, oerrno;
+        int alg, oerrno, r = SSH_ERR_INTERNAL_ERROR;
+        struct sshbuf *b = NULL;
+
+        *bp = NULL;
+        memset(hash, 0, sizeof(hash));
 
-        memset(hash, 0, hashlen);
-        if ((ctx = ssh_digest_start(hashalg)) == NULL) {
+        if ((r = sshsig_check_hashalg(hashalg)) != 0)
+                return r;
+        if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
+                error("%s: can't look up hash algorithm %s",
+                    __func__, hashalg);
+                return SSH_ERR_INTERNAL_ERROR;
+        }
+        if ((ctx = ssh_digest_start(alg)) == NULL) {
                 error("%s: ssh_digest_start failed", __func__);
                 return SSH_ERR_INTERNAL_ERROR;
         }
@@ -484,7 +508,8 @@ hash_file(int fd, int hashalg, u_char *hash, size_t hashlen)
                         error("%s: read: %s", __func__, strerror(errno));
                         ssh_digest_free(ctx);
                         errno = oerrno;
-                        return SSH_ERR_SYSTEM_ERROR;
+                        r = SSH_ERR_SYSTEM_ERROR;
+                        goto out;
                 } else if (n == 0) {
                         debug2("%s: hashed %zu bytes", __func__, total);
                         break; /* EOF */
@@ -493,20 +518,33 @@ hash_file(int fd, int hashalg, u_char *hash, size_t hashlen)
                 if ((r = ssh_digest_update(ctx, rbuf, (size_t)n)) != 0) {
                         error("%s: ssh_digest_update: %s",
                             __func__, ssh_err(r));
-                        ssh_digest_free(ctx);
-                        return r;
+                        goto out;
                 }
         }
-        if ((r = ssh_digest_final(ctx, hash, hashlen)) != 0) {
+        if ((r = ssh_digest_final(ctx, hash, sizeof(hash))) != 0) {
                 error("%s: ssh_digest_final: %s", __func__, ssh_err(r));
-                ssh_digest_free(ctx);
+                goto out;
         }
-        if ((hex = tohex(hash, hashlen)) != NULL) {
+        if ((hex = tohex(hash, ssh_digest_bytes(alg))) != NULL) {
                 debug3("%s: final hash: %s", __func__, hex);
                 freezero(hex, strlen(hex));
         }
+        if ((b = sshbuf_new()) == NULL) {
+                r = SSH_ERR_ALLOC_FAIL;
+                goto out;
+        }
+        if ((r = sshbuf_put(b, hash, ssh_digest_bytes(alg))) != 0) {
+                error("%s: sshbuf_put: %s", __func__, ssh_err(r));
+                goto out;
+        }
+        *bp = b;
+        b = NULL; /* transferred */
         /* success */
+        r = 0;
+ out:
+        sshbuf_free(b);
         ssh_digest_free(ctx);
+        explicit_bzero(hash, sizeof(hash));
         return 0;
 }
 
@@ -515,31 +553,17 @@ sshsig_sign_fd(struct sshkey *key, const char *hashalg,
     int fd, const char *sig_namespace, struct sshbuf **out,
     sshsig_signer *signer, void *signer_ctx)
 {
-        u_char hash[SSH_DIGEST_MAX_LENGTH];
         struct sshbuf *b = NULL;
-        int alg, r = SSH_ERR_INTERNAL_ERROR;
+        int r = SSH_ERR_INTERNAL_ERROR;
 
+        if (hashalg == NULL)
+                hashalg = HASHALG_DEFAULT;
         if (out != NULL)
                 *out = NULL;
-        if (hashalg == NULL)
-            hashalg = HASHALG_DEFAULT;
-
-        if ((r = sshsig_check_hashalg(hashalg)) != 0)
-                return r;
-        if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
-                error("%s: can't look up hash algorithm %s",
-                    __func__, HASHALG_DEFAULT);
-                return SSH_ERR_INTERNAL_ERROR;
-        }
-        if ((r = hash_file(fd, alg, hash, sizeof(hash))) != 0) {
+        if ((r = hash_file(fd, hashalg, &b)) != 0) {
                 error("%s: hash_file failed: %s", __func__, ssh_err(r));
                 return r;
         }
-        if ((b = sshbuf_from(hash, ssh_digest_bytes(alg))) == NULL) {
-                error("%s: sshbuf_from failed", __func__);
-                r = SSH_ERR_ALLOC_FAIL;
-                goto out;
-        }
         if ((r = sshsig_wrap_sign(key, hashalg, b, sig_namespace, out,
             signer, signer_ctx)) != 0)
                 goto out;
@@ -547,7 +571,6 @@ sshsig_sign_fd(struct sshkey *key, const char *hashalg,
         r = 0;
  out:
         sshbuf_free(b);
-        explicit_bzero(hash, sizeof(hash));
         return r;
 }
 
@@ -555,9 +578,8 @@ int
 sshsig_verify_fd(struct sshbuf *signature, int fd,
     const char *expect_namespace, struct sshkey **sign_keyp)
 {
-        u_char hash[SSH_DIGEST_MAX_LENGTH];
         struct sshbuf *b = NULL;
-        int alg, r = SSH_ERR_INTERNAL_ERROR;
+        int r = SSH_ERR_INTERNAL_ERROR;
         char *hashalg = NULL;
 
         if (sign_keyp != NULL)
@@ -565,18 +587,9 @@ sshsig_verify_fd(struct sshbuf *signature, int fd,
 
         if ((r = sshsig_peek_hashalg(signature, &hashalg)) != 0)
                 return r;
-        if ((alg = ssh_digest_alg_by_name(hashalg)) == -1) {
-                error("%s: can't look up hash algorithm %s",
-                    __func__, HASHALG_DEFAULT);
-                return SSH_ERR_INTERNAL_ERROR;
-        }
-        if ((r = hash_file(fd, alg, hash, sizeof(hash))) != 0) {
+        debug("%s: signature made with hash \"%s\"", __func__, hashalg);
+        if ((r = hash_file(fd, hashalg, &b)) != 0) {
                 error("%s: hash_file failed: %s", __func__, ssh_err(r));
-                return r;
-        }
-        if ((b = sshbuf_from(hash, ssh_digest_bytes(alg))) == NULL) {
-                error("%s: sshbuf_from failed", __func__);
-                r = SSH_ERR_ALLOC_FAIL;
                 goto out;
         }
         if ((r = sshsig_wrap_verify(signature, hashalg, b, expect_namespace,
@@ -587,7 +600,6 @@ sshsig_verify_fd(struct sshbuf *signature, int fd,
  out:
         sshbuf_free(b);
         free(hashalg);
-        explicit_bzero(hash, sizeof(hash));
         return r;
 }
 
@@ -769,14 +781,14 @@ sshsig_check_allowed_keys(const char *path, const struct sshkey *sign_key,
                 linenum++;
                 r = check_allowed_keys_line(path, linenum, line, sign_key,
                     principal, sig_namespace);
+                free(line);
+                line = NULL;
                 if (r == SSH_ERR_KEY_NOT_FOUND)
                         continue;
                 else if (r == 0) {
                         /* success */
                         fclose(f);
-                        free(line);
                         return 0;
-                        /* XXX continue and check revocation? */
                 } else
                         break;
         }
diff --git a/sshsig.h b/sshsig.h
index 92c675e3a..fc1d607b3 100644
--- a/sshsig.h
+++ b/sshsig.h
@@ -23,16 +23,29 @@ struct sshkey;
 typedef int sshsig_signer(struct sshkey *, u_char **, size_t *,
     const u_char *, size_t, const char *, u_int, void *);
 
+/* Buffer-oriented API */
+
 /*
- * Creates a detached SSH signature for a given message.
+ * Creates a detached SSH signature for a given buffer.
  * Returns 0 on success or a negative SSH_ERR_* error code on failure.
  * out is populated with the detached signature, or NULL on failure.
  */
-int sshsig_sign_message(struct sshkey *key, const char *hashalg,
+int sshsig_signb(struct sshkey *key, const char *hashalg,
     const struct sshbuf *message, const char *sig_namespace,
     struct sshbuf **out, sshsig_signer *signer, void *signer_ctx);
 
 /*
+ * Verifies that a detached signature is valid and optionally returns key
+ * used to sign via argument.
+ * Returns 0 on success or a negative SSH_ERR_* error code on failure.
+ */
+int sshsig_verifyb(struct sshbuf *signature,
+    const struct sshbuf *message, const char *sig_namespace,
+    struct sshkey **sign_keyp);
+
+/* File/FD-oriented API */
+
+/*
  * Creates a detached SSH signature for a given file.
  * Returns 0 on success or a negative SSH_ERR_* error code on failure.
  * out is populated with the detached signature, or NULL on failure.
@@ -42,15 +55,6 @@ int sshsig_sign_fd(struct sshkey *key, const char *hashalg,
     sshsig_signer *signer, void *signer_ctx);
 
 /*
- * Verifies that a detached signature is valid and optionally returns key
- * used to sign via argument.
- * Returns 0 on success or a negative SSH_ERR_* error code on failure.
- */
-int sshsig_verify_message(struct sshbuf *signature,
-    const struct sshbuf *message, const char *sig_namespace,
-    struct sshkey **sign_keyp);
-
-/*
  * Verifies that a detached signature over a file is valid and optionally
  * returns key used to sign via argument.
  * Returns 0 on success or a negative SSH_ERR_* error code on failure.
@@ -58,6 +62,8 @@ int sshsig_verify_message(struct sshbuf *signature,
 int sshsig_verify_fd(struct sshbuf *signature, int fd,
     const char *sig_namespace, struct sshkey **sign_keyp);
 
+/* Utility functions */
+
 /*
  * Return a base64 encoded "ASCII armoured" version of a raw signature.
  */