pkg: add a pkgsign_verify_data callback

This will be used to verify raw payloads, as if signed by pkg-key(8).
It will be used specifically in pkg(7) to verify .pubkeysig as published
by poudriere.

Amend verify_pubsignature() now to use it.  For the RSA signer, we need
to verify using a sha256 of the data instead of the data itself.

Reviewed by:	bapt
Differential Revision:	https://reviews.freebsd.org/D48109

usr.sbin/pkg/pkg.c

@@ -142,6 +142,17 @@ pkgsign_verify_cert(const struct pkgsign_ctx *ctx, int fd, const char *sigfile,
 	    key, keylen, sig, siglen));
 }
 
+static bool
+pkgsign_verify_data(const struct pkgsign_ctx *ctx, const char *data,
+    size_t datasz, const char *sigfile, const unsigned char *key, int keylen,
+    unsigned char *sig, int siglen)
+{
+
+	return ((*ctx->impl->pi_ops->pkgsign_verify_data)(ctx, data, datasz,
+	    sigfile, key, keylen, sig, siglen));
+}
+
+
 static int
 extract_pkg_static(int fd, char *p, int sz)
 {
@@ -574,12 +585,15 @@ verify_pubsignature(int fd_pkg, int fd_sig)
 {
 	struct pubkey *pk;
 	const char *pubkey;
+	char *data;
 	struct pkgsign_ctx *sctx;
+	size_t datasz;
 	bool ret;
 
 	pk = NULL;
 	pubkey = NULL;
 	sctx = NULL;
+	data = NULL;
 	ret = false;
 	if (config_string(PUBKEY, &pubkey) != 0) {
 		warnx("No CONFIG_PUBKEY defined");
@@ -591,6 +605,19 @@ verify_pubsignature(int fd_pkg, int fd_sig)
 		goto cleanup;
 	}
 
+	if (lseek(fd_pkg, 0, SEEK_SET) == -1) {
+		warn("lseek");
+		goto cleanup;
+	}
+
+	/* Future types shouldn't do this. */
+	if ((data = sha256_fd(fd_pkg)) == NULL) {
+		warnx("Error creating SHA256 hash for package");
+		goto cleanup;
+	}
+
+	datasz = strlen(data);
+
 	if (pkgsign_new("rsa", &sctx) != 0) {
 		warnx("Failed to fetch 'rsa' signer");
 		goto cleanup;
@@ -598,7 +625,7 @@ verify_pubsignature(int fd_pkg, int fd_sig)
 
 	/* Verify the signature. */
 	printf("Verifying signature with public key %s... ", pubkey);
-	if (pkgsign_verify_cert(sctx, fd_pkg, pubkey, NULL, 0, pk->sig,
+	if (pkgsign_verify_data(sctx, data, datasz, pubkey, NULL, 0, pk->sig,
 	    pk->siglen) == false) {
 		fprintf(stderr, "Signature is not valid\n");
 		goto cleanup;
@@ -607,6 +634,7 @@ verify_pubsignature(int fd_pkg, int fd_sig)
 	ret = true;
 
 cleanup:
+	free(data);
 	if (pk) {
 		free(pk->sig);
 		free(pk);

usr.sbin/pkg/pkg.h

@@ -40,11 +40,15 @@ struct pkgsign_ctx {
 typedef int pkgsign_new_cb(const char *, struct pkgsign_ctx *);
 typedef bool pkgsign_verify_cert_cb(const struct pkgsign_ctx *, int,
     const char *, const unsigned char *, int, unsigned char *, int);
+typedef bool pkgsign_verify_data_cb(const struct pkgsign_ctx *,
+    const char *, size_t, const char *, const unsigned char *, int,
+    unsigned char *, int);
 
 struct pkgsign_ops {
 	size_t			 pkgsign_ctx_size;
 	pkgsign_new_cb		*pkgsign_new;
 	pkgsign_verify_cert_cb	*pkgsign_verify_cert;
+	pkgsign_verify_data_cb	*pkgsign_verify_data;
 };
 
 extern const struct pkgsign_ops pkgsign_rsa;

usr.sbin/pkg/rsa.c

@@ -78,33 +78,20 @@ load_public_key_buf(const unsigned char *cert, int certlen)
 }
 
 static bool
-rsa_verify_cert(const struct pkgsign_ctx *ctx __unused, int fd,
-    const char *sigfile, const unsigned char *key, int keylen,
-    unsigned char *sig, int siglen)
+rsa_verify_data(const struct pkgsign_ctx *ctx __unused,
+    const char *data, size_t datasz, const char *sigfile,
+    const unsigned char *key, int keylen, unsigned char *sig, int siglen)
 {
 	EVP_MD_CTX *mdctx;
 	EVP_PKEY *pkey;
-	char *sha256;
 	char errbuf[1024];
 	bool ret;
 
-	sha256 = NULL;
 	pkey = NULL;
 	mdctx = NULL;
 	ret = false;
-
 	SSL_load_error_strings();
 
-	/* Compute SHA256 of the package. */
-	if (lseek(fd, 0, 0) == -1) {
-		warn("lseek");
-		goto cleanup;
-	}
-	if ((sha256 = sha256_fd(fd)) == NULL) {
-		warnx("Error creating SHA256 hash for package");
-		goto cleanup;
-	}
-
 	if (sigfile != NULL) {
 		if ((pkey = load_public_key_file(sigfile)) == NULL) {
 			warnx("Error reading public key");
@@ -127,7 +114,7 @@ rsa_verify_cert(const struct pkgsign_ctx *ctx __unused, int fd,
 		warnx("%s", ERR_error_string(ERR_get_error(), errbuf));
 		goto error;
 	}
-	if (EVP_DigestVerifyUpdate(mdctx, sha256, strlen(sha256)) != 1) {
+	if (EVP_DigestVerifyUpdate(mdctx, data, datasz) != 1) {
 		warnx("%s", ERR_error_string(ERR_get_error(), errbuf));
 		goto error;
 	}
@@ -145,7 +132,6 @@ error:
 	printf("failed\n");
 
 cleanup:
-	free(sha256);
 	if (pkey)
 		EVP_PKEY_free(pkey);
 	if (mdctx)
@@ -155,6 +141,34 @@ cleanup:
 	return (ret);
 }
 
+static bool
+rsa_verify_cert(const struct pkgsign_ctx *ctx __unused, int fd,
+    const char *sigfile, const unsigned char *key, int keylen,
+    unsigned char *sig, int siglen)
+{
+	char *sha256;
+	bool ret;
+
+	sha256 = NULL;
+
+	/* Compute SHA256 of the package. */
+	if (lseek(fd, 0, 0) == -1) {
+		warn("lseek");
+		return (false);
+	}
+	if ((sha256 = sha256_fd(fd)) == NULL) {
+		warnx("Error creating SHA256 hash for package");
+		return (false);
+	}
+
+	ret = rsa_verify_data(ctx, sha256, strlen(sha256), sigfile, key, keylen,
+	    sig, siglen);
+	free(sha256);
+
+	return (ret);
+}
+
 const struct pkgsign_ops pkgsign_rsa = {
 	.pkgsign_verify_cert = rsa_verify_cert,
+	.pkgsign_verify_data = rsa_verify_data,
 };