[PATCH v3 04/14] PGPLIB: Basic packet parser

Roberto Sassu
2024-09-11T12:30:06Z

From: David Howells <dhowells@redhat.com>

Provide a simple parser that extracts the packets from a PGP packet blob
and passes the desirous ones to the given processor function:

struct pgp_parse_context {
u64 types_of_interest;
int (*process_packet)(struct pgp_parse_context *context,
enum pgp_packet_tag type,
u8 headerlen,
const u8 *data,
size_t datalen);
};

int pgp_parse_packets(const u8 *data, size_t datalen,
struct pgp_parse_context *ctx);

This is configured on with CONFIG_PGP_LIBRARY.

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 | 6 +
crypto/asymmetric_keys/Makefile | 5 +
crypto/asymmetric_keys/pgp_library.c | 262 +++++++++++++++++++++++++++
crypto/asymmetric_keys/pgplib.h | 33 ++++
4 files changed, 306 insertions(+)
create mode 100644 crypto/asymmetric_keys/pgp_library.c
create mode 100644 crypto/asymmetric_keys/pgplib.h

diff --git a/crypto/asymmetric_keys/Kconfig b/crypto/asymmetric_keys/Kconfig
index e1345b8f39f1..8215e3fcd8db 100644
--- a/crypto/asymmetric_keys/Kconfig
+++ b/crypto/asymmetric_keys/Kconfig
@@ -103,4 +103,10 @@ config FIPS_SIGNATURE_SELFTEST_ECDSA
depends on CRYPTO_SHA256=y || CRYPTO_SHA256=FIPS_SIGNATURE_SELFTEST
depends on CRYPTO_ECDSA=y || CRYPTO_ECDSA=FIPS_SIGNATURE_SELFTEST

+config PGP_LIBRARY
+ tristate "PGP parsing library"
+ help
+ This option enables a library that provides a number of simple
+ utility functions for parsing PGP (RFC 9580) packet-based messages.
+
endif # ASYMMETRIC_KEY_TYPE
diff --git a/crypto/asymmetric_keys/Makefile b/crypto/asymmetric_keys/Makefile
index bc65d3b98dcb..055b28207111 100644
--- a/crypto/asymmetric_keys/Makefile
+++ b/crypto/asymmetric_keys/Makefile
@@ -79,3 +79,8 @@ verify_signed_pefile-y := \

$(obj)/mscode_parser.o: $(obj)/mscode.asn1.h $(obj)/mscode.asn1.h
$(obj)/mscode.asn1.o: $(obj)/mscode.asn1.c $(obj)/mscode.asn1.h
+
+#
+# PGP handling
+#
+obj-$(CONFIG_PGP_LIBRARY) += pgp_library.o
diff --git a/crypto/asymmetric_keys/pgp_library.c b/crypto/asymmetric_keys/pgp_library.c
new file mode 100644
index 000000000000..1b87f8af411b
--- /dev/null
+++ b/crypto/asymmetric_keys/pgp_library.c
@@ -0,0 +1,262 @@
+// SPDX-License-Identifier: GPL-2.0
+/* PGP packet parser (RFC 9580)
+ *
+ * Copyright (C) 2011 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#define pr_fmt(fmt) "PGPL: "fmt
+#include <linux/errno.h>
+#include <linux/kernel.h>
+#include <linux/module.h>
+
+#include "pgplib.h"
+
+MODULE_LICENSE("GPL");
+MODULE_DESCRIPTION("PGP library");
+
+const char *const pgp_hash_algorithms[PGP_HASH__LAST] = {
+ [PGP_HASH_MD5] = "md5",
+ [PGP_HASH_SHA1] = "sha1",
+ [PGP_HASH_RIPE_MD_160] = "rmd160",
+ [PGP_HASH_SHA256] = "sha256",
+ [PGP_HASH_SHA384] = "sha384",
+ [PGP_HASH_SHA512] = "sha512",
+ [PGP_HASH_SHA224] = "sha224",
+ [PGP_HASH_SHA3_256] = "sha3-256",
+ [PGP_HASH_SHA3_512] = "sha3-512",
+};
+EXPORT_SYMBOL_GPL(pgp_hash_algorithms);
+
+/**
+ * pgp_parse_packet_header - Parse a PGP packet header
+ * @_data: Start of the PGP packet (updated to PGP packet data)
+ * @_datalen: Amount of data remaining in buffer (decreased)
+ * @_type: Where the packet type will be returned
+ * @_headerlen: Where the header length will be returned
+ *
+ * Parse a set of PGP packet header [RFC 9580: 4.2].
+ *
+ * Return: Packet data size on success; non-zero on error. If successful,
+ * *_data and *_datalen will have been updated and *_headerlen will be set to
+ * hold the length of the packet header.
+ */
+static ssize_t pgp_parse_packet_header(const u8 **_data, size_t *_datalen,
+ enum pgp_packet_tag *_type,
+ u8 *_headerlen)
+{
+ enum pgp_packet_tag type;
+ const u8 *data = *_data;
+ size_t size, datalen = *_datalen;
+
+ pr_devel("-->%s(,%zu,,)\n", __func__, datalen);
+
+ if (datalen < 2)
+ goto short_packet;
+
+ pr_devel("pkthdr %02x, %02x\n", data[0], data[1]);
+
+ type = *data++;
+ datalen--;
+ if (!(type & 0x80)) {
+ pr_debug("Packet type does not have MSB set\n");
+ return -EBADMSG;
+ }
+ type &= ~0x80;
+
+ if (type & 0x40) {
+ /* New packet length format */
+ type &= ~0x40;
+ pr_devel("new format: t=%u\n", type);
+ switch (data[0]) {
+ case 0x00 ... 0xbf:
+ /* One-byte length */
+ size = data[0];
+ data++;
+ datalen--;
+ *_headerlen = 2;
+ break;
+ case 0xc0 ... 0xdf:
+ /* Two-byte length */
+ if (datalen < 2)
+ goto short_packet;
+ size = (data[0] - 192) * 256;
+ size += data[1] + 192;
+ data += 2;
+ datalen -= 2;
+ *_headerlen = 3;
+ break;
+ case 0xff:
+ /* Five-byte length */
+ if (datalen < 5)
+ goto short_packet;
+ size = data[1] << 24;
+ size |= data[2] << 16;
+ size |= data[3] << 8;
+ size |= data[4];
+ data += 5;
+ datalen -= 5;
+ *_headerlen = 6;
+ break;
+ default:
+ pr_debug("Partial body length packet not supported\n");
+ return -EBADMSG;
+ }
+ } else {
+ /* Old packet length format */
+ u8 length_type = type & 0x03;
+
+ type >>= 2;
+ pr_devel("old format: t=%u lt=%u\n", type, length_type);
+
+ switch (length_type) {
+ case 0:
+ /* One-byte length */
+ size = data[0];
+ data++;
+ datalen--;
+ *_headerlen = 2;
+ break;
+ case 1:
+ /* Two-byte length */
+ if (datalen < 2)
+ goto short_packet;
+ size = data[0] << 8;
+ size |= data[1];
+ data += 2;
+ datalen -= 2;
+ *_headerlen = 3;
+ break;
+ case 2:
+ /* Four-byte length */
+ if (datalen < 4)
+ goto short_packet;
+ size = data[0] << 24;
+ size |= data[1] << 16;
+ size |= data[2] << 8;
+ size |= data[3];
+ data += 4;
+ datalen -= 4;
+ *_headerlen = 5;
+ break;
+ default:
+ pr_debug("Indefinite length packet not supported\n");
+ return -EBADMSG;
+ }
+ }
+
+ pr_devel("datalen=%zu size=%zu\n", datalen, size);
+ if (datalen < size)
+ goto short_packet;
+ if (size > INT_MAX)
+ goto too_big;
+
+ *_data = data;
+ *_datalen = datalen;
+ *_type = type;
+ pr_devel("Found packet type=%u size=%zd\n", type, size);
+ return size;
+
+short_packet:
+ pr_debug("Attempt to parse short packet\n");
+ return -EBADMSG;
+too_big:
+ pr_debug("Signature subpacket size >2G\n");
+ return -EMSGSIZE;
+}
+
+/**
+ * pgp_parse_packets - Parse a set of PGP packets
+ * @data: Data to be parsed (updated)
+ * @datalen: Amount of data (updated)
+ * @ctx: Parsing context
+ *
+ * Parse a set of PGP packets [RFC 9580: 4].
+ *
+ * Return: 0 on successful parsing, a negative value otherwise.
+ */
+int pgp_parse_packets(const u8 *data, size_t datalen,
+ struct pgp_parse_context *ctx)
+{
+ enum pgp_packet_tag type;
+ ssize_t pktlen;
+ u8 headerlen;
+ int ret;
+
+ while (datalen > 2) {
+ pktlen = pgp_parse_packet_header(&data, &datalen, &type,
+ &headerlen);
+ if (pktlen < 0)
+ return pktlen;
+
+ if ((ctx->types_of_interest >> type) & 1) {
+ ret = ctx->process_packet(ctx, type, headerlen,
+ data, pktlen);
+ if (ret < 0)
+ return ret;
+ }
+ data += pktlen;
+ datalen -= pktlen;
+ }
+
+ if (datalen != 0) {
+ pr_debug("Excess octets in packet stream\n");
+ return -EBADMSG;
+ }
+
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pgp_parse_packets);
+
+/**
+ * pgp_parse_public_key - Parse the common part of a PGP pubkey packet
+ * @_data: Content of packet (updated)
+ * @_datalen: Length of packet remaining (updated)
+ * @pk: Public key data
+ *
+ * Parse the common data struct for a PGP pubkey packet [RFC 9580: 5.5.2].
+ *
+ * Return: 0 on successful parsing, a negative value otherwise.
+ */
+int pgp_parse_public_key(const u8 **_data, size_t *_datalen,
+ struct pgp_parse_pubkey *pk)
+{
+ const u8 *data = *_data;
+ size_t datalen = *_datalen;
+ unsigned int tmp;
+
+ if (datalen < 12) {
+ pr_debug("Public key packet too short\n");
+ return -EBADMSG;
+ }
+
+ pk->version = *data++;
+ switch (pk->version) {
+ case PGP_KEY_VERSION_4:
+ break;
+ default:
+ pr_debug("Public key packet with unhandled version %d\n",
+ pk->version);
+ return -EBADMSG;
+ }
+
+ tmp = *data++ << 24;
+ tmp |= *data++ << 16;
+ tmp |= *data++ << 8;
+ tmp |= *data++;
+ pk->creation_time = tmp;
+ if (pk->version == PGP_KEY_VERSION_4)
+ pk->expires_at = 0; /* Have to get it from the selfsignature */
+
+ pk->pubkey_algo = *data++;
+ datalen -= 6;
+
+ pr_devel("%x,%x,%lx,%lx\n",
+ pk->version, pk->pubkey_algo, pk->creation_time,
+ pk->expires_at);
+
+ *_data = data;
+ *_datalen = datalen;
+ return 0;
+}
+EXPORT_SYMBOL_GPL(pgp_parse_public_key);
diff --git a/crypto/asymmetric_keys/pgplib.h b/crypto/asymmetric_keys/pgplib.h
new file mode 100644
index 000000000000..3ec4b408a11e
--- /dev/null
+++ b/crypto/asymmetric_keys/pgplib.h
@@ -0,0 +1,33 @@
+/* SPDX-License-Identifier: GPL-2.0 */
+/* PGP library definitions (RFC 9580)
+ *
+ * Copyright (C) 2012 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ */
+
+#include "pgp.h"
+
+/*
+ * PGP library packet parser
+ */
+struct pgp_parse_context {
+ u64 types_of_interest;
+ int (*process_packet)(struct pgp_parse_context *context,
+ enum pgp_packet_tag type,
+ u8 headerlen,
+ const u8 *data,
+ size_t datalen);
+};
+
+extern int pgp_parse_packets(const u8 *data, size_t datalen,
+ struct pgp_parse_context *ctx);
+
+struct pgp_parse_pubkey {
+ enum pgp_key_version version : 8;
+ enum pgp_pubkey_algo pubkey_algo : 8;
+ __kernel_old_time_t creation_time;
+ __kernel_old_time_t expires_at;
+};
+
+extern int pgp_parse_public_key(const u8 **_data, size_t *_datalen,
+ struct pgp_parse_pubkey *pk);
--
2.34.1