[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]

[libvirt] [PATCH 03/11] Refactor virStorageFileGetMetadataFromFD to separate functionality



The virStorageFileGetMetadataFromFD did two jobs in one. First
it probed for storage type, then it extracted metadata for the
type. It is desirable to be able to separate these jobs, allowing
probing without querying metadata, and querying metadata without
probing.

To prepare for this, split out probing code into a new pair of
methods

  virStorageFileProbeFormatFromFD
  virStorageFileProbeFormat

* src/util/storage_file.c, src/util/storage_file.h,
  src/libvirt_private.syms: Introduce virStorageFileProbeFormat
  and virStorageFileProbeFormatFromFD
---
 src/libvirt_private.syms |    2 +
 src/util/storage_file.c  |  460 +++++++++++++++++++++++++++++++++-------------
 src/util/storage_file.h  |    4 +
 3 files changed, 335 insertions(+), 131 deletions(-)

diff --git a/src/libvirt_private.syms b/src/libvirt_private.syms
index 778ceb1..4607f49 100644
--- a/src/libvirt_private.syms
+++ b/src/libvirt_private.syms
@@ -628,6 +628,8 @@ virStorageGenerateQcowPassphrase;
 # storage_file.h
 virStorageFileFormatTypeToString;
 virStorageFileFormatTypeFromString;
+virStorageFileProbeFormat;
+virStorageFileProbeFormatFromFD;
 virStorageFileGetMetadata;
 virStorageFileGetMetadataFromFD;
 virStorageFileIsSharedFS;
diff --git a/src/util/storage_file.c b/src/util/storage_file.c
index df0e3a1..221268b 100644
--- a/src/util/storage_file.c
+++ b/src/util/storage_file.c
@@ -104,6 +104,9 @@ static int vmdk4GetBackingStore(char **, int *,
 #define QCOW2_HDR_EXTENSION_END 0
 #define QCOW2_HDR_EXTENSION_BACKING_FORMAT 0xE2792ACA
 
+/* VMDK needs at least this to find backing store,
+ * other formats are less */
+#define STORAGE_MAX_HEAD (20*512)
 
 
 static struct FileTypeInfo const fileTypeInfo[] = {
@@ -349,9 +352,14 @@ vmdk4GetBackingStore(char **res,
                      size_t buf_size)
 {
     static const char prefix[] = "parentFileNameHint=\"";
-
-    char desc[20*512 + 1], *start, *end;
+    char *desc, *start, *end;
     size_t len;
+    int ret = BACKING_STORE_ERROR;
+
+    if (VIR_ALLOC_N(desc, STORAGE_MAX_HEAD + 1) < 0) {
+        virReportOOMError();
+        goto cleanup;
+    }
 
     *res = NULL;
     /*
@@ -363,29 +371,42 @@ vmdk4GetBackingStore(char **res,
      */
     *format = VIR_STORAGE_FILE_AUTO;
 
-    if (buf_size <= 0x200)
-        return BACKING_STORE_INVALID;
+    if (buf_size <= 0x200) {
+        ret = BACKING_STORE_INVALID;
+        goto cleanup;
+    }
     len = buf_size - 0x200;
-    if (len > sizeof(desc) - 1)
-        len = sizeof(desc) - 1;
+    if (len > STORAGE_MAX_HEAD)
+        len = STORAGE_MAX_HEAD;
     memcpy(desc, buf + 0x200, len);
     desc[len] = '\0';
     start = strstr(desc, prefix);
-    if (start == NULL)
-        return BACKING_STORE_OK;
+    if (start == NULL) {
+        ret = BACKING_STORE_OK;
+        goto cleanup;
+    }
     start += strlen(prefix);
     end = strchr(start, '"');
-    if (end == NULL)
-        return BACKING_STORE_INVALID;
-    if (end == start)
-        return BACKING_STORE_OK;
+    if (end == NULL) {
+        ret = BACKING_STORE_INVALID;
+        goto cleanup;
+    }
+    if (end == start) {
+        ret = BACKING_STORE_OK;
+        goto cleanup;
+    }
     *end = '\0';
     *res = strdup(start);
     if (*res == NULL) {
         virReportOOMError();
-        return BACKING_STORE_ERROR;
+        goto cleanup;
     }
-    return BACKING_STORE_OK;
+
+    ret = BACKING_STORE_OK;
+
+cleanup:
+    VIR_FREE(desc);
+    return ret;
 }
 
 /**
@@ -411,148 +432,325 @@ absolutePathFromBaseFile(const char *base_file, const char *path)
     return res;
 }
 
-/**
- * Probe the header of a file to determine what type of disk image
- * it is, and info about its capacity if available.
- */
-int
-virStorageFileGetMetadataFromFD(const char *path,
-                                int fd,
-                                virStorageFileMetadata *meta)
+
+static bool
+virStorageFileMatchesMagic(int format,
+                           unsigned char *buf,
+                           size_t buflen)
 {
-    unsigned char head[20*512]; /* vmdk4GetBackingStore needs this much. */
-    int len, i;
+    int mlen;
 
-    memset(meta, 0, sizeof (*meta));
+    if (fileTypeInfo[format].magic == NULL)
+        return false;
 
-    /* If all else fails, call it a raw file */
-    meta->format = VIR_STORAGE_FILE_RAW;
+    /* Validate magic data */
+    mlen = strlen(fileTypeInfo[format].magic);
+    if (mlen > buflen)
+        return false;
 
-    if ((len = read(fd, head, sizeof(head))) < 0) {
-        virReportSystemError(errno, _("cannot read header '%s'"), path);
-        return -1;
+    if (memcmp(buf, fileTypeInfo[format].magic, mlen) != 0)
+        return false;
+
+    return true;
+}
+
+
+static bool
+virStorageFileMatchesExtension(int format,
+                               const char *path)
+{
+    if (fileTypeInfo[format].extension == NULL)
+        return false;
+
+    if (virFileHasSuffix(path, fileTypeInfo[format].extension))
+        return true;
+
+    return false;
+}
+
+
+static bool
+virStorageFileMatchesVersion(int format,
+                             unsigned char *buf,
+                             size_t buflen)
+{
+    int version;
+
+    /* Validate version number info */
+    if (fileTypeInfo[format].versionOffset == -1)
+        return false;
+
+    if ((fileTypeInfo[format].versionOffset + 4) > buflen)
+        return false;
+
+    if (fileTypeInfo[format].endian == LV_LITTLE_ENDIAN) {
+        version =
+            (buf[fileTypeInfo[format].versionOffset+3] << 24) |
+            (buf[fileTypeInfo[format].versionOffset+2] << 16) |
+            (buf[fileTypeInfo[format].versionOffset+1] << 8) |
+            (buf[fileTypeInfo[format].versionOffset]);
+    } else {
+        version =
+            (buf[fileTypeInfo[format].versionOffset] << 24) |
+            (buf[fileTypeInfo[format].versionOffset+1] << 16) |
+            (buf[fileTypeInfo[format].versionOffset+2] << 8) |
+            (buf[fileTypeInfo[format].versionOffset+3]);
     }
+    if (version != fileTypeInfo[format].versionNumber)
+        return false;
 
-    /* First check file magic */
-    for (i = 0 ; i < ARRAY_CARDINALITY(fileTypeInfo) ; i++) {
-        int mlen;
-
-        if (fileTypeInfo[i].magic == NULL)
-            continue;
-
-        /* Validate magic data */
-        mlen = strlen(fileTypeInfo[i].magic);
-        if (mlen > len)
-            continue;
-        if (memcmp(head, fileTypeInfo[i].magic, mlen) != 0)
-            continue;
-
-        /* Validate version number info */
-        if (fileTypeInfo[i].versionNumber != -1) {
-            int version;
-
-            if (fileTypeInfo[i].endian == LV_LITTLE_ENDIAN) {
-                version = (head[fileTypeInfo[i].versionOffset+3] << 24) |
-                    (head[fileTypeInfo[i].versionOffset+2] << 16) |
-                    (head[fileTypeInfo[i].versionOffset+1] << 8) |
-                    head[fileTypeInfo[i].versionOffset];
-            } else {
-                version = (head[fileTypeInfo[i].versionOffset] << 24) |
-                    (head[fileTypeInfo[i].versionOffset+1] << 16) |
-                    (head[fileTypeInfo[i].versionOffset+2] << 8) |
-                    head[fileTypeInfo[i].versionOffset+3];
-            }
-            if (version != fileTypeInfo[i].versionNumber)
-                continue;
-        }
+    return true;
+}
 
-        /* Optionally extract capacity from file */
-        if (fileTypeInfo[i].sizeOffset != -1) {
-            if (fileTypeInfo[i].endian == LV_LITTLE_ENDIAN) {
-                meta->capacity =
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+7] << 56) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+6] << 48) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+5] << 40) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+4] << 32) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+3] << 24) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+2] << 16) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+1] << 8) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset]);
-            } else {
-                meta->capacity =
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset] << 56) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+1] << 48) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+2] << 40) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+3] << 32) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+4] << 24) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+5] << 16) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+6] << 8) |
-                    ((unsigned long long)head[fileTypeInfo[i].sizeOffset+7]);
-            }
-            /* Avoid unlikely, but theoretically possible overflow */
-            if (meta->capacity > (ULLONG_MAX / fileTypeInfo[i].sizeMultiplier))
-                continue;
-            meta->capacity *= fileTypeInfo[i].sizeMultiplier;
-        }
 
-        if (fileTypeInfo[i].qcowCryptOffset != -1) {
-            int crypt_format;
+static int
+virStorageFileGetMetadataFromBuf(int format,
+                                 const char *path,
+                                 unsigned char *buf,
+                                 size_t buflen,
+                                 virStorageFileMetadata *meta)
+{
+    /* XXX we should consider moving virStorageBackendUpdateVolInfo
+     * code into this method, for non-magic files
+     */
+    if (!fileTypeInfo[format].magic) {
+        return 0;
+    }
 
-            crypt_format = (head[fileTypeInfo[i].qcowCryptOffset] << 24) |
-                (head[fileTypeInfo[i].qcowCryptOffset+1] << 16) |
-                (head[fileTypeInfo[i].qcowCryptOffset+2] << 8) |
-                head[fileTypeInfo[i].qcowCryptOffset+3];
-            meta->encrypted = crypt_format != 0;
+    /* Optionally extract capacity from file */
+    if (fileTypeInfo[format].sizeOffset != -1) {
+        if ((fileTypeInfo[format].sizeOffset + 8) > buflen)
+            return 1;
+
+        if (fileTypeInfo[format].endian == LV_LITTLE_ENDIAN) {
+            meta->capacity =
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+7] << 56) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+6] << 48) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+5] << 40) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+4] << 32) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+3] << 24) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+2] << 16) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+1] << 8) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset]);
+        } else {
+            meta->capacity =
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset] << 56) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+1] << 48) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+2] << 40) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+3] << 32) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+4] << 24) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+5] << 16) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+6] << 8) |
+                ((unsigned long long)buf[fileTypeInfo[format].sizeOffset+7]);
         }
+        /* Avoid unlikely, but theoretically possible overflow */
+        if (meta->capacity > (ULLONG_MAX / fileTypeInfo[format].sizeMultiplier))
+            return 1;
+        meta->capacity *= fileTypeInfo[format].sizeMultiplier;
+    }
 
-        /* Validation passed, we know the file format now */
-        meta->format = i;
-        if (fileTypeInfo[i].getBackingStore != NULL) {
-            char *backing;
-            int backingFormat;
+    if (fileTypeInfo[format].qcowCryptOffset != -1) {
+        int crypt_format;
 
-            switch (fileTypeInfo[i].getBackingStore(&backing,
-                                                    &backingFormat,
-                                                    head, len)) {
-            case BACKING_STORE_OK:
-                break;
+        crypt_format =
+            (buf[fileTypeInfo[format].qcowCryptOffset] << 24) |
+            (buf[fileTypeInfo[format].qcowCryptOffset+1] << 16) |
+            (buf[fileTypeInfo[format].qcowCryptOffset+2] << 8) |
+            (buf[fileTypeInfo[format].qcowCryptOffset+3]);
+        meta->encrypted = crypt_format != 0;
+    }
 
-            case BACKING_STORE_INVALID:
-                continue;
+    if (fileTypeInfo[format].getBackingStore != NULL) {
+        char *backing;
+        int backingFormat;
+        int ret = fileTypeInfo[format].getBackingStore(&backing,
+                                                       &backingFormat,
+                                                       buf, buflen);
+        if (ret == BACKING_STORE_INVALID)
+            return 1;
+
+        if (ret == BACKING_STORE_ERROR)
+            return -1;
 
-            case BACKING_STORE_ERROR:
+        if (backing != NULL) {
+            meta->backingStore = absolutePathFromBaseFile(path, backing);
+            VIR_FREE(backing);
+            if (meta->backingStore == NULL) {
+                virReportOOMError();
                 return -1;
             }
-            if (backing != NULL) {
-                meta->backingStore = absolutePathFromBaseFile(path, backing);
-                VIR_FREE(backing);
-                if (meta->backingStore == NULL) {
-                    virReportOOMError();
-                    return -1;
-                }
-                meta->backingStoreFormat = backingFormat;
-            } else {
-                meta->backingStoreFormat = VIR_STORAGE_FILE_AUTO;
-            }
+            meta->backingStoreFormat = backingFormat;
+        } else {
+            meta->backingStore = NULL;
+            meta->backingStoreFormat = VIR_STORAGE_FILE_AUTO;
+        }
+    }
+
+    return 0;
+}
+
+
+static int
+virStorageFileProbeFormatFromBuf(const char *path,
+                                 unsigned char *buf,
+                                 size_t buflen)
+{
+    int format = VIR_STORAGE_FILE_RAW;
+    int i;
+
+    /* First check file magic */
+    for (i = 0 ; i < VIR_STORAGE_FILE_LAST ; i++) {
+        if (virStorageFileMatchesMagic(i, buf, buflen) &&
+            virStorageFileMatchesVersion(i, buf, buflen)) {
+            format = i;
+            goto cleanup;
         }
-        return 0;
     }
 
     /* No magic, so check file extension */
-    for (i = 0 ; i < ARRAY_CARDINALITY(fileTypeInfo) ; i++) {
-        if (fileTypeInfo[i].extension == NULL)
-            continue;
+    for (i = 0 ; i < VIR_STORAGE_FILE_LAST ; i++) {
+        if (virStorageFileMatchesExtension(i, path)) {
+            format = i;
+            goto cleanup;
+        }
+    }
 
-        if (!virFileHasSuffix(path, fileTypeInfo[i].extension))
-            continue;
+cleanup:
+    return format;
+}
 
-        meta->format = i;
-        return 0;
+
+/**
+ * virStorageFileProbeFormatFromFD:
+ *
+ * Probe for the format of 'fd' (which is an open file descriptor
+ * pointing to 'path'), returning the detected disk format.
+ *
+ * Callers are advised never to trust the returned 'format'
+ * unless it is listed as VIR_STORAGE_FILE_RAW, since a
+ * malicious guest can turn a file into any other non-raw
+ * format at will.
+ *
+ * Best option: Don't use this function
+ */
+int
+virStorageFileProbeFormatFromFD(const char *path, int fd)
+{
+    unsigned char *head;
+    ssize_t len = STORAGE_MAX_HEAD;
+    int ret = -1;
+
+    if (VIR_ALLOC_N(head, len) < 0) {
+        virReportOOMError();
+        return -1;
     }
 
-    return 0;
+    if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
+        virReportSystemError(errno, _("cannot set to start of '%s'"), path);
+        goto cleanup;
+    }
+
+    if ((len = read(fd, head, len)) < 0) {
+        virReportSystemError(errno, _("cannot read header '%s'"), path);
+        goto cleanup;
+    }
+
+    ret = virStorageFileProbeFormatFromBuf(path, head, len);
+
+cleanup:
+    VIR_FREE(head);
+    return ret;
+}
+
+
+/**
+ * virStorageFileProbeFormat:
+ *
+ * Probe for the format of 'path', returning the detected
+ * disk format.
+ *
+ * Callers are advised never to trust the returned 'format'
+ * unless it is listed as VIR_STORAGE_FILE_RAW, since a
+ * malicious guest can turn a raw file into any other non-raw
+ * format at will.
+ *
+ * Best option: Don't use this function
+ */
+int
+virStorageFileProbeFormat(const char *path)
+{
+    int fd, ret;
+
+    if ((fd = open(path, O_RDONLY)) < 0) {
+        virReportSystemError(errno, _("cannot open file '%s'"), path);
+        return -1;
+    }
+
+    ret = virStorageFileProbeFormatFromFD(path, fd);
+
+    close(fd);
+
+    return ret;
 }
 
+/**
+ * virStorageFileGetMetadataFromFD:
+ *
+ * Probe for the format of 'fd' (which is an open file descriptor
+ * for the file 'path'), filling 'meta' with the detected
+ * format and other associated metadata.
+ *
+ * Callers are advised never to trust the returned 'meta->format'
+ * unless it is listed as VIR_STORAGE_FILE_RAW, since a
+ * malicious guest can turn a raw file into any other non-raw
+ * format at will.
+ */
+int
+virStorageFileGetMetadataFromFD(const char *path,
+                                int fd,
+                                virStorageFileMetadata *meta)
+{
+    unsigned char *head;
+    ssize_t len = STORAGE_MAX_HEAD;
+    int ret = -1;
+
+    if (VIR_ALLOC_N(head, len) < 0) {
+        virReportOOMError();
+        return -1;
+    }
+
+    memset(meta, 0, sizeof (*meta));
+
+    if (lseek(fd, 0, SEEK_SET) == (off_t)-1) {
+        virReportSystemError(errno, _("cannot set to start of '%s'"), path);
+        goto cleanup;
+    }
+
+    if ((len = read(fd, head, len)) < 0) {
+        virReportSystemError(errno, _("cannot read header '%s'"), path);
+        goto cleanup;
+    }
+
+    meta->format = virStorageFileProbeFormatFromBuf(path, head, len);
+
+    ret = virStorageFileGetMetadataFromBuf(meta->format, path, head, len, meta);
+
+cleanup:
+    VIR_FREE(head);
+    return ret;
+}
+
+/**
+ * virStorageFileGetMetadata:
+ *
+ * Probe for the format of 'path', filling 'meta' with the detected
+ * format and other associated metadata.
+ *
+ * Callers are advised never to trust the returned 'meta->format'
+ * unless it is listed as VIR_STORAGE_FILE_RAW, since a
+ * malicious guest can turn a raw file into any other non-raw
+ * format at will.
+ */
 int
 virStorageFileGetMetadata(const char *path,
                           virStorageFileMetadata *meta)
diff --git a/src/util/storage_file.h b/src/util/storage_file.h
index 6328ba7..3420d44 100644
--- a/src/util/storage_file.h
+++ b/src/util/storage_file.h
@@ -57,6 +57,10 @@ typedef struct _virStorageFileMetadata {
 #  define DEV_BSIZE 512
 # endif
 
+int virStorageFileProbeFormat(const char *path);
+int virStorageFileProbeFormatFromFD(const char *path,
+                                    int fd);
+
 int virStorageFileGetMetadata(const char *path,
                               virStorageFileMetadata *meta);
 int virStorageFileGetMetadataFromFD(const char *path,
-- 
1.7.1.1


[Date Prev][Date Next]   [Thread Prev][Thread Next]   [Thread Index] [Date Index] [Author Index]