[PATCH v3 12/14] PGP: Provide a key type for testing PGP signatures

Roberto Sassu
2024-09-11T12:31:56Z

From: David Howells <dhowells@redhat.com>

Provide a key type for testing the PGP signature parser. It is given a
non-detached PGP message as payload:

keyctl padd pgp_test a @s <content.txt.gpg

A suitable message can be generated like this:

echo "This is a test attached-signed content" >content.txt
gpg --compress-algo=none -s content.txt

Signed-off-by: David Howells <dhowells@redhat.com>
Co-developed-by: Roberto Sassu <roberto.sassu@huawei.com>
Signed-off-by: Roberto Sassu <roberto.sassu@huawei.com>
---
crypto/asymmetric_keys/Kconfig | 15 +++
crypto/asymmetric_keys/Makefile | 2 +
crypto/asymmetric_keys/pgp_library.c | 64 +++++++++++++
crypto/asymmetric_keys/pgp_test_key.c | 131 ++++++++++++++++++++++++++
crypto/asymmetric_keys/pgplib.h | 16 ++++
5 files changed, 228 insertions(+)
create mode 100644 crypto/asymmetric_keys/pgp_test_key.c

diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index c69bfdc022c0..d28b9593a70d 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -119,4 +119,19 @@ config PGP_KEY_PARSER
for key data and provides the ability to instantiate a crypto key
from a public key packet found inside the blob.

+config PGP_TEST_KEY
+ tristate "PGP testing key type"
+ depends on SYSTEM_DATA_VERIFICATION
+ depends on PGP_KEY_PARSER=y
+ help
+ This option provides a type of key that can be loaded up from a
+ PGP message - provided the message is signed by a loaded key. If
+ it is, the PGP wrapper is discarded and reading the key returns
+ just the payload. If it isn't, adding the key will fail with an
+ error. If the key used for signature verification isn't in the
+ built-in or secondary keyring, adding a key will succeed but this
+ fact will be signaled through a debug message in the kernel log.
+
+ This is intended for testing the PGP parser.
+
endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index e7ff01997eb2..507a78f9a0a1 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -89,3 +89,5 @@ obj-$(CONFIG_PGP_KEY_PARSER) += pgp_key_parser.o
pgp_key_parser-y := \
pgp_public_key.o \
pgp_signature.o
+
+obj-$(CONFIG_PGP_TEST_KEY) += pgp_test_key.o
diff --git a/crypto/asymmetric_keys/pgp_library.c b/crypto/asymmetric_keys/pgp_library.c
index a9708ccbcb81..ff4bb52790dd 100644
--- a/crypto/asymmetric_keys/pgp_library.c
+++ b/crypto/asymmetric_keys/pgp_library.c
@@ -544,3 +544,67 @@ int pgp_parse_sig_params(const u8 **_data, size_t *_datalen,
return 0;
}
EXPORT_SYMBOL_GPL(pgp_parse_sig_params);
+
+#if IS_ENABLED(CONFIG_PGP_TEST_KEY)
+
+/**
+ * pgp_parse_literal_data - Parse basic params from a PGP literal data packet
+ * @data: Content of packet
+ * @datalen: Length of packet remaining
+ * @p: The basic parameters
+ *
+ * Parse the basic parameters from a PGP literal data packet [RFC 9580: 5.9]
+ * that are needed to work out what form the data is in and where it is.
+ *
+ * Returns 0 if successful or a negative error code.
+ */
+int pgp_parse_literal_data(const u8 *data, size_t datalen,
+ struct pgp_literal_data_parameters *p)
+{
+ unsigned int tmp;
+
+ pr_devel("-->%s(,%zu,,)\n", __func__, datalen);
+
+ if (datalen < 6)
+ goto too_short;
+ datalen -= 6;
+
+ p->format = *data++;
+ switch (p->format) {
+ case PGP_LIT_FORMAT_BINARY:
+ case PGP_LIT_FORMAT_TEXT:
+ case PGP_LIT_FORMAT_TEXT_UTF8:
+ break;
+ default:
+ pr_debug("Literal data packet with unhandled format %02x\n",
+ p->format);
+ return -EBADMSG;
+ }
+
+ p->filename_len = *data++;
+ p->filename_offset = 2;
+ if (datalen < p->filename_len)
+ goto too_short;
+ data += p->filename_len;
+ datalen -= p->filename_len;
+
+ tmp = *data++ << 24;
+ tmp |= *data++ << 16;
+ tmp |= *data++ << 8;
+ tmp |= *data++;
+ p->time = tmp;
+
+ p->content_offset = 6 + p->filename_len;
+ p->content_len = datalen;
+
+ pr_devel("%x,%u,%x,%u\n",
+ p->format, p->filename_len, p->time, p->content_len);
+ return 0;
+
+too_short:
+ pr_debug("Literal data packet too short\n");
+ return -EBADMSG;
+}
+EXPORT_SYMBOL_GPL(pgp_parse_literal_data);
+
+#endif /* CONFIG_PGP_TEST_KEY */
diff --git a/crypto/asymmetric_keys/pgp_test_key.c b/crypto/asymmetric_keys/pgp_test_key.c
new file mode 100644
index 000000000000..80ab72ed09b9
--- /dev/null
+++ b/crypto/asymmetric_keys/pgp_test_key.c
@@ -0,0 +1,131 @@
+// SPDX-License-Identifier: GPL-2.0
+/* Testing module to load key from trusted PGP message
+ *
+ * Copyright (C) 2014 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) "PGPtest: "fmt
+#include <linux/key.h>
+#include <linux/key-type.h>
+#include <linux/cred.h>
+#include <linux/err.h>
+#include <linux/module.h>
+#include <linux/verification.h>
+#include <keys/user-type.h>
+#include <keys/system_keyring.h>
+#include <crypto/pgp.h>
+
+#include "pgp_parser.h"
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("PGP testing key type");
+
+struct pgp_test_parse_context {
+ struct pgp_parse_context pgp;
+ struct pgp_literal_data_parameters params;
+ const void *content;
+};
+
+static int pgp_test_parse_data(struct pgp_parse_context *context,
+ enum pgp_packet_tag type,
+ u8 headerlen,
+ const u8 *data,
+ size_t datalen)
+{
+ struct pgp_test_parse_context *ctx =
+ container_of(context, struct pgp_test_parse_context, pgp);
+ int ret;
+
+ kenter("");
+
+ ret = pgp_parse_literal_data(data, datalen, &ctx->params);
+ if (ret == 0)
+ ctx->content = data + ctx->params.content_offset;
+ return ret;
+}
+
+/*
+ * Instantiate a PGP wrapped and validated key.
+ */
+static int pgp_test_instantiate(struct key *key,
+ struct key_preparsed_payload *prep)
+{
+ struct pgp_test_parse_context p;
+ const void *saved_prep_data;
+ size_t saved_prep_datalen;
+ const struct cred *cred = current_cred();
+ int ret;
+
+ kenter("");
+
+ memset(&p, 0, sizeof(p));
+ p.pgp.types_of_interest = (1 << PGP_PKT_LITERAL_DATA);
+ p.pgp.process_packet = pgp_test_parse_data;
+ ret = pgp_parse_packets(prep->data, prep->datalen, &p.pgp);
+ if (ret < 0) {
+ kleave(" = %d [parse]", ret);
+ return ret;
+ }
+
+ if (!p.params.content_len) {
+ kleave(" = -ENODATA [no literal data");
+ return -ENODATA;
+ }
+
+ ret = verify_pgp_signature(p.content, p.params.content_len,
+ prep->data, prep->datalen,
+ VERIFY_USE_SECONDARY_KEYRING,
+ VERIFYING_UNSPECIFIED_SIGNATURE, NULL, NULL);
+ if (ret < 0 && cred->session_keyring) {
+ ret = verify_pgp_signature(p.content, p.params.content_len,
+ prep->data, prep->datalen,
+ cred->session_keyring,
+ VERIFYING_UNSPECIFIED_SIGNATURE,
+ NULL, NULL);
+ if (ret < 0)
+ goto error;
+
+ pr_warn("PGP message doesn't chain back to a trusted key\n");
+ }
+
+ saved_prep_data = prep->data;
+ saved_prep_datalen = prep->datalen;
+ prep->data = p.content;
+ prep->datalen = p.params.content_len;
+ ret = generic_key_instantiate(key, prep);
+ prep->data = saved_prep_data;
+ prep->datalen = saved_prep_datalen;
+error:
+ kleave(" = %d", ret);
+ return ret;
+}
+
+/*
+ * user defined keys take an arbitrary string as the description and an
+ * arbitrary blob of data as the payload
+ */
+static struct key_type key_type_pgp_test = {
+ .name = "pgp_test",
+ .instantiate = pgp_test_instantiate,
+ .revoke = user_revoke,
+ .destroy = user_destroy,
+ .describe = user_describe,
+ .read = user_read,
+};
+
+/*
+ * Module stuff
+ */
+static int __init pgp_key_init(void)
+{
+ return register_key_type(&key_type_pgp_test);
+}
+
+static void __exit pgp_key_cleanup(void)
+{
+ unregister_key_type(&key_type_pgp_test);
+}
+
+module_init(pgp_key_init);
+module_exit(pgp_key_cleanup);
diff --git a/crypto/asymmetric_keys/pgplib.h b/crypto/asymmetric_keys/pgplib.h
index 25191cea33a4..9c852256d1c9 100644
--- a/crypto/asymmetric_keys/pgplib.h
+++ b/crypto/asymmetric_keys/pgplib.h
@@ -56,3 +56,19 @@ struct pgp_sig_parameters {

extern int pgp_parse_sig_params(const u8 **_data, size_t *_datalen,
struct pgp_sig_parameters *p);
+
+#if IS_ENABLED(CONFIG_PGP_TEST_KEY)
+
+struct pgp_literal_data_parameters {
+ enum pgp_literal_data_format format : 8;
+ u8 filename_len;
+ u8 filename_offset;
+ u8 content_offset;
+ u32 content_len;
+ u32 time;
+};
+
+extern int pgp_parse_literal_data(const u8 *data, size_t datalen,
+ struct pgp_literal_data_parameters *p);
+
+#endif /* CONFIG_PGP_TEST_KEY */
--
2.34.1