KEYS: Provide keyctls to drive the new key type ops for asymmetric keys [ver #2]

Provide five keyctl functions that permit userspace to make use of the new
key type ops for accessing and driving asymmetric keys.

 (*) Query an asymmetric key.

	long keyctl(KEYCTL_PKEY_QUERY,
		    key_serial_t key, unsigned long reserved,
		    struct keyctl_pkey_query *info);

     Get information about an asymmetric key.  The information is returned
     in the keyctl_pkey_query struct:

	__u32	supported_ops;

     A bit mask of flags indicating which ops are supported.  This is
     constructed from a bitwise-OR of:

	KEYCTL_SUPPORTS_{ENCRYPT,DECRYPT,SIGN,VERIFY}

	__u32	key_size;

     The size in bits of the key.

	__u16	max_data_size;
	__u16	max_sig_size;
	__u16	max_enc_size;
	__u16	max_dec_size;

     The maximum sizes in bytes of a blob of data to be signed, a signature
     blob, a blob to be encrypted and a blob to be decrypted.

     reserved must be set to 0.  This is intended for future use to hand
     over one or more passphrases needed unlock a key.

     If successful, 0 is returned.  If the key is not an asymmetric key,
     EOPNOTSUPP is returned.

 (*) Encrypt, decrypt, sign or verify a blob using an asymmetric key.

	long keyctl(KEYCTL_PKEY_ENCRYPT,
		    const struct keyctl_pkey_params *params,
		    const char *info,
		    const void *in,
		    void *out);

	long keyctl(KEYCTL_PKEY_DECRYPT,
		    const struct keyctl_pkey_params *params,
		    const char *info,
		    const void *in,
		    void *out);

	long keyctl(KEYCTL_PKEY_SIGN,
		    const struct keyctl_pkey_params *params,
		    const char *info,
		    const void *in,
		    void *out);

	long keyctl(KEYCTL_PKEY_VERIFY,
		    const struct keyctl_pkey_params *params,
		    const char *info,
		    const void *in,
		    const void *in2);

     Use an asymmetric key to perform a public-key cryptographic operation
     a blob of data.

     The parameter block pointed to by params contains a number of integer
     values:

	__s32		key_id;
	__u32		in_len;
	__u32		out_len;
	__u32		in2_len;

     For a given operation, the in and out buffers are used as follows:

	Operation ID		in,in_len	out,out_len	in2,in2_len
	=======================	===============	===============	===========
	KEYCTL_PKEY_ENCRYPT	Raw data	Encrypted data	-
	KEYCTL_PKEY_DECRYPT	Encrypted data	Raw data	-
	KEYCTL_PKEY_SIGN	Raw data	Signature	-
	KEYCTL_PKEY_VERIFY	Raw data	-		Signature

     info is a string of key=value pairs that supply supplementary
     information.

     The __spare space in the parameter block must be set to 0.  This is
     intended, amongst other things, to allow the passing of passphrases
     required to unlock a key.

     If successful, encrypt, decrypt and sign all return the amount of data
     written into the output buffer.  Verification returns 0 on success.
Signed-off-by: David Howells <dhowells@redhat.com>
Tested-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Marcel Holtmann <marcel@holtmann.org>
Reviewed-by: Denis Kenzior <denkenz@gmail.com>
Tested-by: Denis Kenzior <denkenz@gmail.com>
Signed-off-by: James Morris <james.morris@microsoft.com>

Documentation/security/keys/core.rst

@@ -859,6 +859,7 @@ The keyctl syscall functions are:
      and either the buffer length or the OtherInfo length exceeds the
      allowed length.
 
+
   *  Restrict keyring linkage::
 
 	long keyctl(KEYCTL_RESTRICT_KEYRING, key_serial_t keyring,
@@ -890,6 +891,116 @@ The keyctl syscall functions are:
      applicable to the asymmetric key type.
 
 
+  *  Query an asymmetric key::
+
+	long keyctl(KEYCTL_PKEY_QUERY,
+		    key_serial_t key_id, unsigned long reserved,
+		    struct keyctl_pkey_query *info);
+
+     Get information about an asymmetric key.  The information is returned in
+     the keyctl_pkey_query struct::
+
+	__u32	supported_ops;
+	__u32	key_size;
+	__u16	max_data_size;
+	__u16	max_sig_size;
+	__u16	max_enc_size;
+	__u16	max_dec_size;
+	__u32	__spare[10];
+
+     ``supported_ops`` contains a bit mask of flags indicating which ops are
+     supported.  This is constructed from a bitwise-OR of::
+
+	KEYCTL_SUPPORTS_{ENCRYPT,DECRYPT,SIGN,VERIFY}
+
+     ``key_size`` indicated the size of the key in bits.
+
+     ``max_*_size`` indicate the maximum sizes in bytes of a blob of data to be
+     signed, a signature blob, a blob to be encrypted and a blob to be
+     decrypted.
+
+     ``__spare[]`` must be set to 0.  This is intended for future use to hand
+     over one or more passphrases needed unlock a key.
+
+     If successful, 0 is returned.  If the key is not an asymmetric key,
+     EOPNOTSUPP is returned.
+
+
+  *  Encrypt, decrypt, sign or verify a blob using an asymmetric key::
+
+	long keyctl(KEYCTL_PKEY_ENCRYPT,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    void *out);
+
+	long keyctl(KEYCTL_PKEY_DECRYPT,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    void *out);
+
+	long keyctl(KEYCTL_PKEY_SIGN,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    void *out);
+
+	long keyctl(KEYCTL_PKEY_VERIFY,
+		    const struct keyctl_pkey_params *params,
+		    const char *info,
+		    const void *in,
+		    const void *in2);
+
+     Use an asymmetric key to perform a public-key cryptographic operation a
+     blob of data.  For encryption and verification, the asymmetric key may
+     only need the public parts to be available, but for decryption and signing
+     the private parts are required also.
+
+     The parameter block pointed to by params contains a number of integer
+     values::
+
+	__s32		key_id;
+	__u32		in_len;
+	__u32		out_len;
+	__u32		in2_len;
+
+     ``key_id`` is the ID of the asymmetric key to be used.  ``in_len`` and
+     ``in2_len`` indicate the amount of data in the in and in2 buffers and
+     ``out_len`` indicates the size of the out buffer as appropriate for the
+     above operations.
+
+     For a given operation, the in and out buffers are used as follows::
+
+	Operation ID		in,in_len	out,out_len	in2,in2_len
+	=======================	===============	===============	===============
+	KEYCTL_PKEY_ENCRYPT	Raw data	Encrypted data	-
+	KEYCTL_PKEY_DECRYPT	Encrypted data	Raw data	-
+	KEYCTL_PKEY_SIGN	Raw data	Signature	-
+	KEYCTL_PKEY_VERIFY	Raw data	-		Signature
+
+     ``info`` is a string of key=value pairs that supply supplementary
+     information.  These include:
+
+	``enc=<encoding>`` The encoding of the encrypted/signature blob.  This
+			can be "pkcs1" for RSASSA-PKCS1-v1.5 or
+			RSAES-PKCS1-v1.5; "pss" for "RSASSA-PSS"; "oaep" for
+			"RSAES-OAEP".  If omitted or is "raw", the raw output
+			of the encryption function is specified.
+
+	``hash=<algo>``	If the data buffer contains the output of a hash
+			function and the encoding includes some indication of
+			which hash function was used, the hash function can be
+			specified with this, eg. "hash=sha256".
+
+     The ``__spare[]`` space in the parameter block must be set to 0.  This is
+     intended, amongst other things, to allow the passing of passphrases
+     required to unlock a key.
+
+     If successful, encrypt, decrypt and sign all return the amount of data
+     written into the output buffer.  Verification returns 0 on success.
+
+
 Kernel Services
 ===============
 

include/uapi/linux/keyctl.h

@@ -61,6 +61,11 @@
 #define KEYCTL_INVALIDATE		21	/* invalidate a key */
 #define KEYCTL_GET_PERSISTENT		22	/* get a user's persistent keyring */
 #define KEYCTL_DH_COMPUTE		23	/* Compute Diffie-Hellman values */
+#define KEYCTL_PKEY_QUERY		24	/* Query public key parameters */
+#define KEYCTL_PKEY_ENCRYPT		25	/* Encrypt a blob using a public key */
+#define KEYCTL_PKEY_DECRYPT		26	/* Decrypt a blob using a public key */
+#define KEYCTL_PKEY_SIGN		27	/* Create a public key signature */
+#define KEYCTL_PKEY_VERIFY		28	/* Verify a public key signature */
 #define KEYCTL_RESTRICT_KEYRING		29	/* Restrict keys allowed to link to a keyring */
 
 /* keyctl structures */
@@ -87,4 +92,24 @@ struct keyctl_kdf_params {
 #define KEYCTL_SUPPORTS_SIGN		0x04
 #define KEYCTL_SUPPORTS_VERIFY		0x08
 
+struct keyctl_pkey_query {
+	__u32		supported_ops;	/* Which ops are supported */
+	__u32		key_size;	/* Size of the key in bits */
+	__u16		max_data_size;	/* Maximum size of raw data to sign in bytes */
+	__u16		max_sig_size;	/* Maximum size of signature in bytes */
+	__u16		max_enc_size;	/* Maximum size of encrypted blob in bytes */
+	__u16		max_dec_size;	/* Maximum size of decrypted blob in bytes */
+	__u32		__spare[10];
+};
+
+struct keyctl_pkey_params {
+	__s32		key_id;		/* Serial no. of public key to use */
+	__u32		in_len;		/* Input data size */
+	union {
+		__u32		out_len;	/* Output buffer size (encrypt/decrypt/sign) */
+		__u32		in2_len;	/* 2nd input data size (verify) */
+	};
+	__u32		__spare[7];
+};
+
 #endif /*  _LINUX_KEYCTL_H */

security/keys/Makefile

@@ -22,6 +22,7 @@ obj-$(CONFIG_PROC_FS) += proc.o
 obj-$(CONFIG_SYSCTL) += sysctl.o
 obj-$(CONFIG_PERSISTENT_KEYRINGS) += persistent.o
 obj-$(CONFIG_KEY_DH_OPERATIONS) += dh.o
+obj-$(CONFIG_ASYMMETRIC_KEY_TYPE) += keyctl_pkey.o
 
 #
 # Key types

security/keys/compat.c

@@ -141,6 +141,24 @@ COMPAT_SYSCALL_DEFINE5(keyctl, u32, option,
 		return keyctl_restrict_keyring(arg2, compat_ptr(arg3),
 					       compat_ptr(arg4));
 
+	case KEYCTL_PKEY_QUERY:
+		if (arg3 != 0)
+			return -EINVAL;
+		return keyctl_pkey_query(arg2,
+					 compat_ptr(arg4),
+					 compat_ptr(arg5));
+
+	case KEYCTL_PKEY_ENCRYPT:
+	case KEYCTL_PKEY_DECRYPT:
+	case KEYCTL_PKEY_SIGN:
+		return keyctl_pkey_e_d_s(option,
+					 compat_ptr(arg2), compat_ptr(arg3),
+					 compat_ptr(arg4), compat_ptr(arg5));
+
+	case KEYCTL_PKEY_VERIFY:
+		return keyctl_pkey_verify(compat_ptr(arg2), compat_ptr(arg3),
+					  compat_ptr(arg4), compat_ptr(arg5));
+
 	default:
 		return -EOPNOTSUPP;
 	}

security/keys/internal.h

@@ -298,6 +298,45 @@ static inline long compat_keyctl_dh_compute(
 #endif
 #endif
 
+#ifdef CONFIG_ASYMMETRIC_KEY_TYPE
+extern long keyctl_pkey_query(key_serial_t,
+			      const char __user *,
+			      struct keyctl_pkey_query __user *);
+
+extern long keyctl_pkey_verify(const struct keyctl_pkey_params __user *,
+			       const char __user *,
+			       const void __user *, const void __user *);
+
+extern long keyctl_pkey_e_d_s(int,
+			      const struct keyctl_pkey_params __user *,
+			      const char __user *,
+			      const void __user *, void __user *);
+#else
+static inline long keyctl_pkey_query(key_serial_t id,
+				     const char __user *_info,
+				     struct keyctl_pkey_query __user *_res)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline long keyctl_pkey_verify(const struct keyctl_pkey_params __user *params,
+				      const char __user *_info,
+				      const void __user *_in,
+				      const void __user *_in2)
+{
+	return -EOPNOTSUPP;
+}
+
+static inline long keyctl_pkey_e_d_s(int op,
+				     const struct keyctl_pkey_params __user *params,
+				     const char __user *_info,
+				     const void __user *_in,
+				     void __user *_out)
+{
+	return -EOPNOTSUPP;
+}
+#endif
+
 /*
  * Debugging key validation
  */

security/keys/keyctl.c

@@ -1747,6 +1747,30 @@ SYSCALL_DEFINE5(keyctl, int, option, unsigned long, arg2, unsigned long, arg3,
 					       (const char __user *) arg3,
 					       (const char __user *) arg4);
 
+	case KEYCTL_PKEY_QUERY:
+		if (arg3 != 0)
+			return -EINVAL;
+		return keyctl_pkey_query((key_serial_t)arg2,
+					 (const char __user *)arg4,
+					 (struct keyctl_pkey_query *)arg5);
+
+	case KEYCTL_PKEY_ENCRYPT:
+	case KEYCTL_PKEY_DECRYPT:
+	case KEYCTL_PKEY_SIGN:
+		return keyctl_pkey_e_d_s(
+			option,
+			(const struct keyctl_pkey_params __user *)arg2,
+			(const char __user *)arg3,
+			(const void __user *)arg4,
+			(void __user *)arg5);
+
+	case KEYCTL_PKEY_VERIFY:
+		return keyctl_pkey_verify(
+			(const struct keyctl_pkey_params __user *)arg2,
+			(const char __user *)arg3,
+			(const void __user *)arg4,
+			(const void __user *)arg5);
+
 	default:
 		return -EOPNOTSUPP;
 	}

security/keys/keyctl_pkey.c

+/* Public-key operation keyctls
+ *
+ * Copyright (C) 2016 Red Hat, Inc. All Rights Reserved.
+ * Written by David Howells (dhowells@redhat.com)
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public Licence
+ * as published by the Free Software Foundation; either version
+ * 2 of the Licence, or (at your option) any later version.
+ */
+
+#include <linux/slab.h>
+#include <linux/err.h>
+#include <linux/key.h>
+#include <linux/keyctl.h>
+#include <linux/parser.h>
+#include <linux/uaccess.h>
+#include <keys/user-type.h>
+#include "internal.h"
+
+static void keyctl_pkey_params_free(struct kernel_pkey_params *params)
+{
+	kfree(params->info);
+	key_put(params->key);
+}
+
+enum {
+	Opt_err = -1,
+	Opt_enc,		/* "enc=<encoding>" eg. "enc=oaep" */
+	Opt_hash,		/* "hash=<digest-name>" eg. "hash=sha1" */
+};
+
+static const match_table_t param_keys = {
+	{ Opt_enc,	"enc=%s" },
+	{ Opt_hash,	"hash=%s" },
+	{ Opt_err,	NULL }
+};
+
+/*
+ * Parse the information string which consists of key=val pairs.
+ */
+static int keyctl_pkey_params_parse(struct kernel_pkey_params *params)
+{
+	unsigned long token_mask = 0;
+	substring_t args[MAX_OPT_ARGS];
+	char *c = params->info, *p, *q;
+	int token;
+
+	while ((p = strsep(&c, " \t"))) {
+		if (*p == '\0' || *p == ' ' || *p == '\t')
+			continue;
+		token = match_token(p, param_keys, args);
+		if (__test_and_set_bit(token, &token_mask))
+			return -EINVAL;
+		q = args[0].from;
+		if (!q[0])
+			return -EINVAL;
+
+		switch (token) {
+		case Opt_enc:
+			params->encoding = q;
+			break;
+
+		case Opt_hash:
+			params->hash_algo = q;
+			break;
+
+		default:
+			return -EINVAL;
+		}
+	}
+
+	return 0;
+}
+
+/*
+ * Interpret parameters.  Callers must always call the free function
+ * on params, even if an error is returned.
+ */
+static int keyctl_pkey_params_get(key_serial_t id,
+				  const char __user *_info,
+				  struct kernel_pkey_params *params)
+{
+	key_ref_t key_ref;
+	void *p;
+	int ret;
+
+	memset(params, 0, sizeof(*params));
+	params->encoding = "raw";
+
+	p = strndup_user(_info, PAGE_SIZE);
+	if (IS_ERR(p))
+		return PTR_ERR(p);
+	params->info = p;
+
+	ret = keyctl_pkey_params_parse(params);
+	if (ret < 0)
+		return ret;
+
+	key_ref = lookup_user_key(id, 0, KEY_NEED_SEARCH);
+	if (IS_ERR(key_ref))
+		return PTR_ERR(key_ref);
+	params->key = key_ref_to_ptr(key_ref);
+
+	if (!params->key->type->asym_query)
+		return -EOPNOTSUPP;
+
+	return 0;
+}
+
+/*
+ * Get parameters from userspace.  Callers must always call the free function
+ * on params, even if an error is returned.
+ */
+static int keyctl_pkey_params_get_2(const struct keyctl_pkey_params __user *_params,
+				    const char __user *_info,
+				    int op,
+				    struct kernel_pkey_params *params)
+{
+	struct keyctl_pkey_params uparams;
+	struct kernel_pkey_query info;
+	int ret;
+
+	memset(params, 0, sizeof(*params));
+	params->encoding = "raw";
+
+	if (copy_from_user(&uparams, _params, sizeof(uparams)) != 0)
+		return -EFAULT;
+
+	ret = keyctl_pkey_params_get(uparams.key_id, _info, params);
+	if (ret < 0)
+		return ret;
+
+	ret = params->key->type->asym_query(params, &info);
+	if (ret < 0)
+		return ret;
+
+	switch (op) {
+	case KEYCTL_PKEY_ENCRYPT:
+	case KEYCTL_PKEY_DECRYPT:
+		if (uparams.in_len  > info.max_enc_size ||
+		    uparams.out_len > info.max_dec_size)
+			return -EINVAL;
+		break;
+	case KEYCTL_PKEY_SIGN:
+	case KEYCTL_PKEY_VERIFY:
+		if (uparams.in_len  > info.max_sig_size ||
+		    uparams.out_len > info.max_data_size)
+			return -EINVAL;
+		break;
+	default:
+		BUG();
+	}
+
+	params->in_len  = uparams.in_len;
+	params->out_len = uparams.out_len;
+	return 0;
+}
+
+/*
+ * Query information about an asymmetric key.
+ */
+long keyctl_pkey_query(key_serial_t id,
+		       const char __user *_info,
+		       struct keyctl_pkey_query __user *_res)
+{
+	struct kernel_pkey_params params;
+	struct kernel_pkey_query res;
+	long ret;
+
+	memset(&params, 0, sizeof(params));
+
+	ret = keyctl_pkey_params_get(id, _info, &params);
+	if (ret < 0)
+		goto error;
+
+	ret = params.key->type->asym_query(&params, &res);
+	if (ret < 0)
+		goto error;
+
+	ret = -EFAULT;
+	if (copy_to_user(_res, &res, sizeof(res)) == 0 &&
+	    clear_user(_res->__spare, sizeof(_res->__spare)) == 0)
+		ret = 0;
+
+error:
+	keyctl_pkey_params_free(&params);
+	return ret;
+}
+
+/*
+ * Encrypt/decrypt/sign
+ *
+ * Encrypt data, decrypt data or sign data using a public key.
+ *
+ * _info is a string of supplementary information in key=val format.  For
+ * instance, it might contain:
+ *
+ *	"enc=pkcs1 hash=sha256"
+ *
+ * where enc= specifies the encoding and hash= selects the OID to go in that
+ * particular encoding if required.  If enc= isn't supplied, it's assumed that
+ * the caller is supplying raw values.
+ *
+ * If successful, the amount of data written into the output buffer is
+ * returned.
+ */
+long keyctl_pkey_e_d_s(int op,
+		       const struct keyctl_pkey_params __user *_params,
+		       const char __user *_info,
+		       const void __user *_in,
+		       void __user *_out)
+{
+	struct kernel_pkey_params params;
+	void *in, *out;
+	long ret;
+
+	ret = keyctl_pkey_params_get_2(_params, _info, op, &params);
+	if (ret < 0)
+		goto error_params;
+
+	ret = -EOPNOTSUPP;
+	if (!params.key->type->asym_eds_op)
+		goto error_params;
+
+	switch (op) {
+	case KEYCTL_PKEY_ENCRYPT:
+		params.op = kernel_pkey_encrypt;
+		break;
+	case KEYCTL_PKEY_DECRYPT:
+		params.op = kernel_pkey_decrypt;
+		break;
+	case KEYCTL_PKEY_SIGN:
+		params.op = kernel_pkey_sign;
+		break;
+	default:
+		BUG();
+	}
+
+	in = memdup_user(_in, params.in_len);
+	if (IS_ERR(in)) {
+		ret = PTR_ERR(in);
+		goto error_params;
+	}
+
+	ret = -ENOMEM;
+	out = kmalloc(params.out_len, GFP_KERNEL);
+	if (!out)
+		goto error_in;
+
+	ret = params.key->type->asym_eds_op(&params, in, out);
+	if (ret < 0)
+		goto error_out;
+
+	if (copy_to_user(_out, out, ret) != 0)
+		ret = -EFAULT;
+
+error_out:
+	kfree(out);
+error_in:
+	kfree(in);
+error_params:
+	keyctl_pkey_params_free(&params);
+	return ret;
+}
+
+/*
+ * Verify a signature.
+ *
+ * Verify a public key signature using the given key, or if not given, search
+ * for a matching key.
+ *
+ * _info is a string of supplementary information in key=val format.  For
+ * instance, it might contain:
+ *
+ *	"enc=pkcs1 hash=sha256"
+ *
+ * where enc= specifies the signature blob encoding and hash= selects the OID
+ * to go in that particular encoding.  If enc= isn't supplied, it's assumed
+ * that the caller is supplying raw values.
+ *
+ * If successful, 0 is returned.
+ */
+long keyctl_pkey_verify(const struct keyctl_pkey_params __user *_params,
+			const char __user *_info,
+			const void __user *_in,
+			const void __user *_in2)
+{
+	struct kernel_pkey_params params;
+	void *in, *in2;
+	long ret;
+
+	ret = keyctl_pkey_params_get_2(_params, _info, KEYCTL_PKEY_VERIFY,
+				       &params);
+	if (ret < 0)
+		goto error_params;
+
+	ret = -EOPNOTSUPP;
+	if (!params.key->type->asym_verify_signature)
+		goto error_params;
+
+	in = memdup_user(_in, params.in_len);
+	if (IS_ERR(in)) {
+		ret = PTR_ERR(in);
+		goto error_params;
+	}
+
+	in2 = memdup_user(_in2, params.in2_len);
+	if (IS_ERR(in2)) {
+		ret = PTR_ERR(in2);
+		goto error_in;
+	}
+
+	params.op = kernel_pkey_verify;
+	ret = params.key->type->asym_verify_signature(&params, in, in2);
+
+	kfree(in2);
+error_in:
+	kfree(in);
+error_params:
+	keyctl_pkey_params_free(&params);
+	return ret;
+}