[Qemu-devel] [PATCH 1/4] added qga hash file command (win/linux)

[itamar . tal4]

From: Itamar Tal <address@hidden>

Added support for retrieving file hash from the guest machine.
This is command is useful for ensuring that no changes were made for a given
file between consecutive read operations and reduce read/write operations.

---
 qga/Makefile.objs      |   2 +-
 qga/commands.c         |  43 +++++++++++++
 qga/guest-agent-core.h |   6 ++
 qga/qapi-schema.json   |  13 ++++
 qga/sha256.c           | 171 +++++++++++++++++++++++++++++++++++++++++++++++++
 qga/sha256.h           |  40 ++++++++++++
 6 files changed, 274 insertions(+), 1 deletion(-)
 create mode 100644 qga/sha256.c
 create mode 100644 qga/sha256.h

diff --git a/qga/Makefile.objs b/qga/Makefile.objs
index 1c5986c..a68d78d 100644
--- a/qga/Makefile.objs
+++ b/qga/Makefile.objs
@@ -1,4 +1,4 @@
-qga-obj-y = commands.o guest-agent-command-state.o main.o
+qga-obj-y = commands.o guest-agent-command-state.o main.o sha256.o
 qga-obj-$(CONFIG_POSIX) += commands-posix.o channel-posix.o
 qga-obj-$(CONFIG_WIN32) += commands-win32.o channel-win32.o service-win32.o
 qga-obj-$(CONFIG_WIN32) += vss-win32.o
diff --git a/qga/commands.c b/qga/commands.c
index 7834967..f9378f4 100644
--- a/qga/commands.c
+++ b/qga/commands.c
@@ -11,6 +11,7 @@
  */
 
 #include <glib.h>
+#include "qga/sha256.h"
 #include "qga/guest-agent-core.h"
 #include "qga-qmp-commands.h"
 #include "qapi/qmp/qerror.h"
@@ -70,3 +71,45 @@ struct GuestAgentInfo *qmp_guest_info(Error **errp)
     qmp_for_each_command(qmp_command_info, info);
     return info;
 }
+
+char *qmp_guest_file_hash(const char *path, Error **errp)
+{
+    const char *hex = "0123456789abcdef";
+    BYTE sha256_block[SHA256_BLOCK_SIZE];
+    char sha256_hexdigest[SHA256_BLOCK_SIZE * 2 + 1];
+    BYTE buffer[1024];
+    size_t len = 0;
+    SHA256_CTX ctx;
+    FILE *file = NULL;
+    int i = 0;
+
+    sha256_init(&ctx);
+
+    file = fopen(path, "rb");
+    if (NULL == file) {
+        error_setg(errp, "Error opening file '%s'", path);
+        return NULL;
+    }
+
+    for (;;) {
+        len = fread(buffer, 1, 1024, file);
+        if (0 == len) {
+            break;
+        }
+
+        sha256_update(&ctx, buffer, len);
+    }
+
+    fclose(file);
+
+    sha256_final(&ctx, sha256_block);
+
+    /* transform the digest to hex string */
+    for (i = 0; i < SHA256_BLOCK_SIZE; ++i) {
+        sha256_hexdigest[i * 2] = hex[(sha256_block[i] >> 4) & 0xF];
+        sha256_hexdigest[i * 2 + 1] = hex[sha256_block[i] & 0xF];
+    }
+    sha256_hexdigest[SHA256_BLOCK_SIZE * 2] = '\0';
+
+    return g_strdup((char *)sha256_hexdigest);
+}
diff --git a/qga/guest-agent-core.h b/qga/guest-agent-core.h
index e92c6ab..b496c47 100644
--- a/qga/guest-agent-core.h
+++ b/qga/guest-agent-core.h
@@ -10,6 +10,10 @@
  * This work is licensed under the terms of the GNU GPL, version 2 or later.
  * See the COPYING file in the top-level directory.
  */
+
+#ifndef _GUEST_AGENT_CORE_H_
+#define _GUEST_AGENT_CORE_H_
+
 #include "qapi/qmp/dispatch.h"
 #include "qemu-common.h"
 
@@ -41,3 +45,5 @@ int64_t ga_get_fd_handle(GAState *s, Error **errp);
 #ifndef _WIN32
 void reopen_fd_to_null(int fd);
 #endif
+
+#endif /* _GUEST_AGENT_CORE_H_ */
diff --git a/qga/qapi-schema.json b/qga/qapi-schema.json
index 95f49e3..68b420d 100644
--- a/qga/qapi-schema.json
+++ b/qga/qapi-schema.json
@@ -891,3 +891,16 @@
 ##
 { 'command': 'guest-get-memory-block-info',
   'returns': 'GuestMemoryBlockInfo' }
+
+##
+# @guest-file-hash:
+#
+# Get the a SHA256 hash for a file in the guest's operating system
+#
+# Returns: file SHA256 hash string
+#
+# Since 2.4
+##
+{ 'command': 'guest-file-hash',
+  'data': { 'path': 'str' },
+  'returns': 'str' }
diff --git a/qga/sha256.c b/qga/sha256.c
new file mode 100644
index 0000000..40abb42
--- /dev/null
+++ b/qga/sha256.c
@@ -0,0 +1,171 @@
+/*********************************************************************
+* Filename:   sha256.c
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Implementation of the SHA-256 hashing algorithm.
+              SHA-256 is one of the three algorithms in the SHA2
+              specification. The others, SHA-384 and SHA-512, are not
+              offered in this implementation.
+              Algorithm specification can be found here:
+               * http://csrc.nist.gov/publications/fips/fips180-2/
+                 fips180-2withchangenotice.pdf
+              This implementation uses little endian byte order.
+*********************************************************************/
+
+/*************************** HEADER FILES ***************************/
+
+#include <memory.h>
+#include "sha256.h"
+
+/****************************** MACROS ******************************/
+#define ROTLEFT(a, b) (((a) << (b)) | ((a) >> (32-(b))))
+#define ROTRIGHT(a, b) (((a) >> (b)) | ((a) << (32-(b))))
+
+#define CH(x, y, z) (((x) & (y)) ^ (~(x) & (z)))
+#define MAJ(x, y, z) (((x) & (y)) ^ ((x) & (z)) ^ ((y) & (z)))
+#define EP0(x) (ROTRIGHT(x, 2) ^ ROTRIGHT(x, 13) ^ ROTRIGHT(x, 22))
+#define EP1(x) (ROTRIGHT(x, 6) ^ ROTRIGHT(x, 11) ^ ROTRIGHT(x, 25))
+#define SIG0(x) (ROTRIGHT(x, 7) ^ ROTRIGHT(x, 18) ^ ((x) >> 3))
+#define SIG1(x) (ROTRIGHT(x, 17) ^ ROTRIGHT(x, 19) ^ ((x) >> 10))
+
+/**************************** VARIABLES *****************************/
+static const uint32_t k[64] = {
+    0x428a2f98, 0x71374491, 0xb5c0fbcf, 0xe9b5dba5, 0x3956c25b, 0x59f111f1,
+    0x923f82a4, 0xab1c5ed5, 0xd807aa98, 0x12835b01, 0x243185be, 0x550c7dc3,
+    0x72be5d74, 0x80deb1fe, 0x9bdc06a7, 0xc19bf174, 0xe49b69c1, 0xefbe4786,
+    0x0fc19dc6, 0x240ca1cc, 0x2de92c6f, 0x4a7484aa, 0x5cb0a9dc, 0x76f988da,
+    0x983e5152, 0xa831c66d, 0xb00327c8, 0xbf597fc7, 0xc6e00bf3, 0xd5a79147,
+    0x06ca6351, 0x14292967, 0x27b70a85, 0x2e1b2138, 0x4d2c6dfc, 0x53380d13,
+    0x650a7354, 0x766a0abb, 0x81c2c92e, 0x92722c85, 0xa2bfe8a1, 0xa81a664b,
+    0xc24b8b70, 0xc76c51a3, 0xd192e819, 0xd6990624, 0xf40e3585, 0x106aa070,
+    0x19a4c116, 0x1e376c08, 0x2748774c, 0x34b0bcb5, 0x391c0cb3, 0x4ed8aa4a,
+    0x5b9cca4f, 0x682e6ff3, 0x748f82ee, 0x78a5636f, 0x84c87814, 0x8cc70208,
+    0x90befffa, 0xa4506ceb, 0xbef9a3f7, 0xc67178f2
+};
+
+/*********************** FUNCTION DEFINITIONS ***********************/
+
+void sha256_transform(SHA256_CTX *ctx, const BYTE data[])
+{
+    uint32_t a, b, c, d, e, f, g, h, i, j, t1, t2, m[64];
+
+    for (i = 0, j = 0; i < 16; ++i, j += 4) {
+        m[i] = (data[j] << 24) |
+               (data[j + 1] << 16) |
+               (data[j + 2] << 8) |
+               (data[j + 3]);
+    }
+    for ( ; i < 64; ++i) {
+        m[i] = SIG1(m[i - 2]) + m[i - 7] + SIG0(m[i - 15]) + m[i - 16];
+    }
+
+    a = ctx->state[0];
+    b = ctx->state[1];
+    c = ctx->state[2];
+    d = ctx->state[3];
+    e = ctx->state[4];
+    f = ctx->state[5];
+    g = ctx->state[6];
+    h = ctx->state[7];
+
+    for (i = 0; i < 64; ++i) {
+        t1 = h + EP1(e) + CH(e, f, g) + k[i] + m[i];
+        t2 = EP0(a) + MAJ(a, b, c);
+        h = g;
+        g = f;
+        f = e;
+        e = d + t1;
+        d = c;
+        c = b;
+        b = a;
+        a = t1 + t2;
+    }
+
+    ctx->state[0] += a;
+    ctx->state[1] += b;
+    ctx->state[2] += c;
+    ctx->state[3] += d;
+    ctx->state[4] += e;
+    ctx->state[5] += f;
+    ctx->state[6] += g;
+    ctx->state[7] += h;
+}
+
+void sha256_init(SHA256_CTX *ctx)
+{
+    ctx->datalen = 0;
+    ctx->bitlen = 0;
+    ctx->state[0] = 0x6a09e667;
+    ctx->state[1] = 0xbb67ae85;
+    ctx->state[2] = 0x3c6ef372;
+    ctx->state[3] = 0xa54ff53a;
+    ctx->state[4] = 0x510e527f;
+    ctx->state[5] = 0x9b05688c;
+    ctx->state[6] = 0x1f83d9ab;
+    ctx->state[7] = 0x5be0cd19;
+}
+
+void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len)
+{
+    uint32_t i;
+
+    for (i = 0; i < len; ++i) {
+        ctx->data[ctx->datalen] = data[i];
+        ctx->datalen++;
+        if (ctx->datalen == 64) {
+            sha256_transform(ctx, ctx->data);
+            ctx->bitlen += 512;
+            ctx->datalen = 0;
+        }
+    }
+}
+
+void sha256_final(SHA256_CTX *ctx, BYTE hash[])
+{
+    uint32_t i;
+
+    i = ctx->datalen;
+
+    /* Pad whatever data is left in the buffer */
+    if (ctx->datalen < 56) {
+        ctx->data[i++] = 0x80;
+        while (i < 56) {
+            ctx->data[i++] = 0x00;
+        }
+    } else {
+        ctx->data[i++] = 0x80;
+        while (i < 64) {
+            ctx->data[i++] = 0x00;
+        }
+        sha256_transform(ctx, ctx->data);
+        memset(ctx->data, 0, 56);
+    }
+
+    /* Append to the padding the total message's length in bits and
+    transform */
+    ctx->bitlen += ctx->datalen * 8;
+    ctx->data[63] = ctx->bitlen;
+    ctx->data[62] = ctx->bitlen >> 8;
+    ctx->data[61] = ctx->bitlen >> 16;
+    ctx->data[60] = ctx->bitlen >> 24;
+    ctx->data[59] = ctx->bitlen >> 32;
+    ctx->data[58] = ctx->bitlen >> 40;
+    ctx->data[57] = ctx->bitlen >> 48;
+    ctx->data[56] = ctx->bitlen >> 56;
+    sha256_transform(ctx, ctx->data);
+
+    /* Since this implementation uses little endian byte ordering and SHA uses
+    big endian, reverse all the bytes when copying the final state to the
+    output hash. */
+    for (i = 0; i < 4; ++i) {
+        hash[i]      = (ctx->state[0] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 4]  = (ctx->state[1] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 8]  = (ctx->state[2] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 12] = (ctx->state[3] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 16] = (ctx->state[4] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 20] = (ctx->state[5] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 24] = (ctx->state[6] >> (24 - i * 8)) & 0x000000ff;
+        hash[i + 28] = (ctx->state[7] >> (24 - i * 8)) & 0x000000ff;
+    }
+}
diff --git a/qga/sha256.h b/qga/sha256.h
new file mode 100644
index 0000000..e62f99b
--- /dev/null
+++ b/qga/sha256.h
@@ -0,0 +1,40 @@
+/*********************************************************************
+* Filename:   sha256.h
+* Author:     Brad Conte (brad AT bradconte.com)
+* Copyright:
+* Disclaimer: This code is presented "as is" without any guarantees.
+* Details:    Defines the API for the corresponding SHA1 implementation.
+*********************************************************************/
+
+#ifndef _SHA256_H_INCLUDE
+#define _SHA256_H_INCLUDE
+
+/*************************** HEADER FILES ***************************/
+
+#include <stddef.h>
+#include <stdlib.h>
+#include <stdio.h>
+#include "qga/guest-agent-core.h"
+
+/****************************** MACROS ******************************/
+#define SHA256_BLOCK_SIZE 32            /* SHA256 outputs a 32 byte digest */
+
+/**************************** DATA TYPES ****************************/
+
+typedef unsigned char BYTE;             /* 8-bit byte */
+
+typedef struct {
+    BYTE data[64];
+    unsigned int datalen;
+    unsigned long long bitlen;
+    unsigned int state[8];
+} SHA256_CTX;
+
+/*********************** FUNCTION DECLARATIONS **********************/
+
+void sha256_init(SHA256_CTX *ctx);
+void sha256_update(SHA256_CTX *ctx, const BYTE data[], size_t len);
+void sha256_final(SHA256_CTX *ctx, BYTE hash[]);
+void sha256_transform(SHA256_CTX *ctx, const BYTE data[]);
+
+#endif /* _SHA256_H_INCLUDE */
-- 
2.3.4