On 07/27/2015 09:21 AM, Yuli Khodorkovskiy wrote:
> This patch allows the tokenizer previously introduced for libselinux to
> use any delimiter for tokenization. Delimiters may be squashed by
> setting the squash_delim flag to 1. When any whitespace delimiter is used,
> isspace() allows any whitespace character to be used as the delimiter.
>
> Previously, read_spec_entries() trimmed whitespace and ignored comments and
> empty lines. This functionality has been removed as is now the
> responsiblity of the caller to implement.
Doesn't yield the same output from sefcontext_compile before and after
this change if file_contexts has any lines trailing in whitespace (old:
trailing whitespace ignored; new: trailing whitespace included in
context field).
>
> Signed-off-by: Yuli Khodorkovskiy <ykhodorkovskiy@xxxxxxxxxx>
> ---
> libselinux/src/label_android_property.c | 11 ++-
> libselinux/src/label_file.h | 10 ++-
> libselinux/src/label_internal.h | 7 +-
> libselinux/src/label_support.c | 129 +++++++++++++++++++-------------
> 4 files changed, 97 insertions(+), 60 deletions(-)
>
> diff --git a/libselinux/src/label_android_property.c b/libselinux/src/label_android_property.c
> index 4af9896..5c06ed3 100644
> --- a/libselinux/src/label_android_property.c
> +++ b/libselinux/src/label_android_property.c
> @@ -90,9 +90,14 @@ static int process_line(struct selabel_handle *rec,
> spec_t *spec_arr = data->spec_arr;
> unsigned int nspec = data->nspec;
>
> - items = read_spec_entries(line_buf, 2, &prop, &context);
> - if (items <= 0)
> - return items;
> + trim_buf(&line_buf);
> +
> + /* Skip comment lines and empty lines. */
> + if (*line_buf == '#' || *line_buf == '\0') {
> + return 0;
> + }
> +
> + items = tokenize(line_buf, 1, ' ', 2, &prop, &context);
> if (items != 2) {
> selinux_log(SELINUX_WARNING,
> "%s: line %u is missing fields, skipping\n", path,
> diff --git a/libselinux/src/label_file.h b/libselinux/src/label_file.h
> index db961ba..3499da1 100644
> --- a/libselinux/src/label_file.h
> +++ b/libselinux/src/label_file.h
> @@ -387,10 +387,14 @@ static inline int process_line(struct selabel_handle *rec,
> unsigned int nspec = data->nspec;
> const char *errbuf = NULL;
>
> - items = read_spec_entries(line_buf, 3, ®ex, &type, &context);
> - if (items <= 0)
> - return items;
> + trim_buf(&line_buf);
>
> + /* Skip comment lines and empty lines. */
> + if (*line_buf == '#' || *line_buf == '\0') {
> + return 0;
> + }
> +
> + items = tokenize(line_buf, 1, ' ', 3, ®ex, &type, &context);
> if (items < 2) {
> COMPAT_LOG(SELINUX_WARNING,
> "%s: line %u is missing fields, skipping\n", path,
> diff --git a/libselinux/src/label_internal.h b/libselinux/src/label_internal.h
> index 861eca1..81a4f37 100644
> --- a/libselinux/src/label_internal.h
> +++ b/libselinux/src/label_internal.h
> @@ -108,9 +108,10 @@ compat_validate(struct selabel_handle *rec,
> const char *path, unsigned lineno) hidden;
>
> /*
> - * The read_spec_entries function may be used to
> - * replace sscanf to read entries from spec files.
> + * The tokenize function may be used to
> + * replace sscanf.
> */
> -extern int read_spec_entries(char *line_buf, int num_args, ...);
> +extern int tokenize(char *line_buf, int squash_delim, char delim, int num_args, ...);
> +extern void trim_buf(char **buf);
>
> #endif /* _SELABEL_INTERNAL_H_ */
> diff --git a/libselinux/src/label_support.c b/libselinux/src/label_support.c
> index b3ab8ab..08ef303 100644
> --- a/libselinux/src/label_support.c
> +++ b/libselinux/src/label_support.c
> @@ -11,88 +11,115 @@
> #include "label_internal.h"
>
> /*
> - * The read_spec_entries and read_spec_entry functions may be used to
> - * replace sscanf to read entries from spec files. The file and
> - * property services now use these.
> + * The tokenize and tokenize_str functions may be used to
> + * replace sscanf to read tokens from buffers.
> */
>
> -/* Read an entry from a spec file (e.g. file_contexts) */
> -static inline int read_spec_entry(char **entry, char **ptr, int *len)
> +/* Read a token from a buffer */
> +static inline int tokenize_str(int squash_delim, char delim, char **str, char **ptr, int *len)
Not introduced by this change, but should likely use size_t *len here.
> {
> - *entry = NULL;
> - char *tmp_buf = NULL;
> + char *tmp_buf = *ptr;
> + *str = NULL;
> +
> + while (**ptr != '\0') {
> + if (isspace(delim) && isspace(**ptr)) {
> + (*ptr)++;
> + break;
> + } else if (!isspace(delim) && **ptr == delim) {
> + (*ptr)++;
> + break;
> + }
This seems unnecessarily complicated. First, all users within
libselinux want squash_delim=1, delim=' ', so we might as well just make
that the only supported case in libselinux until such a time as we have
a need for another. Also, can't quite see why
squash_delim=1,delim=<non-space> would ever be desired, or
squash_delim=0,delim=<space>, so it seems like we would simplify the
interface even when supporting both cases.
>
> - while (isspace(**ptr) && **ptr != '\0')
> (*ptr)++;
> + }
>
> - tmp_buf = *ptr;
> - *len = 0;
> + *len = *ptr - tmp_buf;
> + /* If the end of the string has not been reached, this will ensure the
> + * delimiter is not included when returning the token.
> + */
> + if (**ptr != '\0') {
> + (*len)--;
Can *len underflow here?
> + }
>
> - while (!isspace(**ptr) && **ptr != '\0') {
> - (*ptr)++;
> - (*len)++;
> + *str = strndup(tmp_buf, *len);
Can *len be 0 here?
> + if (!*str) {
> + return -1;
> }
>
> - if (*len) {
> - *entry = strndup(tmp_buf, *len);
> - if (!*entry)
> - return -1;
> + while (**ptr != '\0' && squash_delim == 1) {
> + if (isspace(delim) && isspace(**ptr)) {
> + (*ptr)++;
> + } else if (!isspace(delim) && **ptr == delim) {
> + (*ptr)++;
> + } else {
> + break;
> + }
> }
>
> return 0;
> }
>
> /*
> - * line_buf - Buffer containing the spec entries .
> - * num_args - The number of spec parameter entries to process.
> - * ... - A 'char **spec_entry' for each parameter.
> + * line_buf - Buffer containing string to tokenize.
> + * squash_delim - Whether or not to squash repeating delimiters in input data.
> + * Set to 1 to squash_delimiter or 0 to disable squashing delimiter.
> + * delim - The delimiter used to tokenize line_buf. A whitespace delimiter will
> + * be tokenized using isspace().
> + * num_args - The number of parameter entries to process.
> + * ... - A 'char **' for each parameter.
> * returns - The number of items processed.
> *
> - * This function calls read_spec_entry() to do the actual string processing.
> + * This function calls tokenize_str() to do the actual string processing. The
> + * caller is responsible for calling free() on each additional argument. The
> + * function will not tokenize more than num_args and the last argument will
> + * contain the remaining content of line_buf.
> */
> -int hidden read_spec_entries(char *line_buf, int num_args, ...)
> +int tokenize(char *line_buf, int squash_delim, char delim, int num_args, ...)
Must be hidden or it becomes part of the libselinux.so ABI.
> {
> - char **spec_entry, *buf_p;
> - int len, rc, items, entry_len = 0;
> + char **arg, *buf_p;
> + int rc, items, arg_len = 0;
> va_list ap;
>
> - len = strlen(line_buf);
> - if (line_buf[len - 1] == '\n')
> - line_buf[len - 1] = '\0';
> - else
> - /* Handle case if line not \n terminated by bumping
> - * the len for the check below (as the line is NUL
> - * terminated by getline(3)) */
> - len++;
> -
> buf_p = line_buf;
> - while (isspace(*buf_p))
> - buf_p++;
>
> - /* Skip comment lines and empty lines. */
> - if (*buf_p == '#' || *buf_p == '\0')
> - return 0;
> -
> - /* Process the spec file entries */
> + /* Process the arguments */
> va_start(ap, num_args);
>
> - items = 0;
> - while (items < num_args) {
> - spec_entry = va_arg(ap, char **);
> + for (items = 0; items < num_args && *buf_p != '\0'; items++) {
> + arg = va_arg(ap, char **);
> +
> + /* Save the remainder of the string in arg */
> + if (items == num_args - 1) {
> + *arg = strdup(buf_p);
> + if (*arg == NULL) {
> + goto exit;
> + }
Needs to prune last argument at delimiter.
>
> - if (len - 1 == buf_p - line_buf) {
> - va_end(ap);
> - return items;
> + continue;
> }
>
> - rc = read_spec_entry(spec_entry, &buf_p, &entry_len);
> + rc = tokenize_str(squash_delim, delim, arg, &buf_p, &arg_len);
> if (rc < 0) {
> - va_end(ap);
> - return rc;
> + goto exit;
> }
> - if (entry_len)
> - items++;
> }
> +
> +exit:
> va_end(ap);
> return items;
> }
> +
> +/* This function removes leading whitespace. If the buffer ends in a newline,
> + * the newline is removed.
> + */
> +void trim_buf(char **buf)
Must be hidden or it becomes part of the libselinux.so ABI.
> +{
> + int len = strlen(*buf);
size_t len
> + if ((*buf)[len - 1] == '\n') {
Can len == 0 here?
> + (*buf)[len - 1] = '\0';
> + }
> +
> + while (isspace(**buf)) {
> + (*buf)++;
> + }
> +}
>
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