Differential D16335 Diff 52904 lib/libsecureboot/vectx.c

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lib/libsecureboot/vectx.c

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				/*-
				* Copyright (c) 2018, Juniper Networks, Inc.
				*
				* Redistribution and use in source and binary forms, with or without
				* modification, are permitted provided that the following conditions
				* are met:
				* 1. Redistributions of source code must retain the above copyright
				* notice, this list of conditions and the following disclaimer.
				* 2. Redistributions in binary form must reproduce the above copyright
				* notice, this list of conditions and the following disclaimer in the
				* documentation and/or other materials provided with the distribution.
				*
				* THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
				* "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
				* LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
				* A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT
				* OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL,
				* SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT
				* LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
				* DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
				* THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
				* (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE
				* OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
				*/
				#include <sys/cdefs.h>
				__FBSDID("$FreeBSD$");

				#ifndef _STANDALONE
				/* Avoid unwanted userlandish components */
				#define _KERNEL
				#include <sys/errno.h>
				#undef _KERNEL
				#endif

				#include "libsecureboot-priv.h"

				/**
				* @file vectx.c
				* @brief api to verify file while reading
				*
				* This API allows the hash of a file to be computed as it is read.
				* Key to this is seeking by reading.
				*
				* On close an indication of the verification result is returned.
				*/

				struct vectx {
				br_hash_compat_context vec_ctx; /* hash ctx */
				const br_hash_class vec_md; / hash method */
				const char vec_path; / path we are verifying */
				const char vec_want; / hash value we want */
				off_t vec_off; /* current offset */
				size_t vec_size; /* size of path */
				size_t vec_hashsz; /* size of hash */
				int vec_fd; /* file descriptor */
				int vec_status; /* verification status */
				};

				/**
				* @brief
				* verify an open file as we read it
				*
				* If the file has no fingerprint to match, we will still return a
				* verification context containing little more than the file
				* descriptor, and an error code in @c error.
				*
				* @param[in] fd
				* open descriptor
				*
				* @param[in] path
				* pathname to open
				*
				* @param[in] off
				* current offset
				*
				* @param[in] stp
				* pointer to struct stat
				*
				* @param[out] error
				* @li 0 all is good
				* @li ENOMEM out of memory
				* @li VE_FINGERPRINT_NONE no entry found
				* @li VE_FINGERPRINT_UNKNOWN no fingerprint in entry
				*
				* @return ctx or NULL on error.
				* NULL is only returned for non-files or out-of-memory.
				*/
				struct vectx *
				vectx_open(int fd, const char path, off_t off, struct stat stp, int *error)
				{
				struct vectx *ctx;
				struct stat st;
				size_t hashsz;
				char *cp;

				if (!stp) {
				if (fstat(fd, &st) == 0)
				stp = &st;
				}

				/* we should only get called for files */
				if (stp && !S_ISREG(stp->st_mode)) {
				*error = 0;
				return (NULL);
				}

				ctx = malloc(sizeof(struct vectx));
				if (!ctx)
				goto enomem;
				ctx->vec_fd = fd;
				ctx->vec_path = path;
				ctx->vec_size = stp->st_size;
				ctx->vec_off = 0;
				ctx->vec_want = NULL;
				ctx->vec_status = 0;
				hashsz = 0;

				cp = fingerprint_info_lookup(fd, path);
				if (!cp) {
				ctx->vec_status = VE_FINGERPRINT_NONE;
				ve_error_set("%s: no entry", path);
				} else {
				if (strncmp(cp, "sha256=", 7) == 0) {
				ctx->vec_md = &br_sha256_vtable;
				hashsz = br_sha256_SIZE;
				cp += 7;
				#ifdef VE_SHA1_SUPPORT
				} else if (strncmp(cp, "sha1=", 5) == 0) {
				ctx->vec_md = &br_sha1_vtable;
				hashsz = br_sha1_SIZE;
				cp += 5;
				#endif
				#ifdef VE_SHA384_SUPPORT
				} else if (strncmp(cp, "sha384=", 7) == 0) {
				ctx->vec_md = &br_sha384_vtable;
				hashsz = br_sha384_SIZE;
				cp += 7;
				#endif
				#ifdef VE_SHA512_SUPPORT
				} else if (strncmp(cp, "sha512=", 7) == 0) {
				ctx->vec_md = &br_sha512_vtable;
				hashsz = br_sha512_SIZE;
				cp += 7;
				#endif
				} else {
				ctx->vec_status = VE_FINGERPRINT_UNKNOWN;
				ve_error_set("%s: no supported fingerprint", path);
				}
				}
				*error = ctx->vec_status;
				ctx->vec_hashsz = hashsz;
				ctx->vec_want = cp;
				ctx->vec_md->init(&ctx->vec_ctx.vtable);

				if (hashsz > 0 && off > 0) {
				lseek(fd, 0, SEEK_SET);
				vectx_lseek(ctx, off, SEEK_SET);
				}
				return (ctx);

				enomem: /* unlikely */
				*error = ENOMEM;
				free(ctx);
				return (NULL);
				}

				/**
				* @brief
				* read bytes from file and update hash
				*
				* It is critical that all file I/O comes through here.
				* We keep track of current offset.
				*
				* @param[in] pctx
				* pointer to ctx
				*
				* @param[in] buf
				*
				* @param[in] nbytes
				*
				* @return bytes read or error.
				*/
				ssize_t
				vectx_read(struct vectx ctx, void buf, size_t nbytes)
				{
				unsigned char *bp = buf;
				int n;
				size_t off;

				if (ctx->vec_hashsz == 0) /* nothing to do */
				return (read(ctx->vec_fd, buf, nbytes));

				off = 0;
				do {
				n = read(ctx->vec_fd, &bp[off], nbytes - off);
				if (n < 0)
				return (n);
				if (n > 0) {
				ctx->vec_md->update(&ctx->vec_ctx.vtable, &bp[off], n);
				off += n;
				ctx->vec_off += n;
				}
				} while (n > 0 && off < nbytes);
				return (off);
				}

				/**
				* @brief
				* vectx equivalent of lseek
				*
				* We do not actually, seek, but call vectx_read
				* to reach the desired offset.
				*
				* We do not support seeking backwards.
				*
				* @param[in] pctx
				* pointer to ctx
				*
				* @param[in] off
				* desired offset
				*
				* @param[in] whence
				*
				* @return offset or error.
				*/
				off_t
				vectx_lseek(struct vectx *ctx, off_t off, int whence)
				{
				unsigned char buf[PAGE_SIZE];
				size_t delta;
				ssize_t n;

				if (ctx->vec_hashsz == 0) /* nothing to do */
				return (lseek(ctx->vec_fd, off, whence));

				/*
				* Try to convert whence to SEEK_SET
				* but we cannot support seeking backwards!
				* Nor beyond end of file.
				*/
				if (whence == SEEK_END && off <= 0) {
				whence = SEEK_SET;
				off += ctx->vec_size;
				} else if (whence == SEEK_CUR && off >= 0) {
				whence = SEEK_SET;
				off += ctx->vec_off;
				}
				if (whence != SEEK_SET \|\| off < ctx->vec_off \|\|
				(size_t)off > ctx->vec_size) {
				printf("ERROR: %s: unsupported operation\n", __func__);
				return (-1);
				}
				n = 0;
				do {
				delta = off - ctx->vec_off;
				if (delta > 0) {
				delta = MIN(PAGE_SIZE, delta);
				n = vectx_read(ctx, buf, delta);
				if (n < 0)
				return (n);
				}
				} while (ctx->vec_off < off && n > 0);
				return (ctx->vec_off);
				}

				/**
				* @brief
				* check that hashes match and cleanup
				*
				* We have finished reading file, compare the hash with what
				* we wanted.
				*
				* @param[in] pctx
				* pointer to ctx
				*
				* @return 0 or an error.
				*/
				int
				vectx_close(struct vectx *ctx)
				{
				int rc;

				if (ctx->vec_hashsz == 0) {
				rc = ctx->vec_status;
				} else {
				rc = ve_check_hash(&ctx->vec_ctx, ctx->vec_md,
				ctx->vec_path, ctx->vec_want, ctx->vec_hashsz);
				}
				free(ctx);
				return ((rc < 0) ? rc : 0);
				}