Check for IO stream failures in various format's truncate/seek operations

For the formats that support seek and/or truncate operations, many of
the C library calls used to determine or set the current position indicator
in the file stream were not being checked.  In some situations, if an error 
occurred, a negative value would be returned from the library call.  This
could then be interpreted inappropriately as positional data.

This patch checks the return values from these library calls before
using them in subsequent operations.

(issue ASTERISK-19655)
Reported by: Matt Jordan

Review: https://reviewboard.asterisk.org/r/1863/
........

Merged revisions 362151 from http://svn.asterisk.org/svn/asterisk/branches/1.8
........

Merged revisions 362152 from http://svn.asterisk.org/svn/asterisk/branches/10


git-svn-id: https://origsvn.digium.com/svn/asterisk/trunk@362153 65c4cc65-6c06-0410-ace0-fbb531ad65f3

1 files changed, 31 insertions, 6 deletions

diff --git a/formats/format_wav_gsm.c b/formats/format_wav_gsm.c
index 35d4339f9..bbf3339bc 100644
--- a/formats/format_wav_gsm.c
+++ b/formats/format_wav_gsm.c
@@ -475,13 +475,25 @@ static int wav_write(struct ast_filestream *s, struct ast_frame *f)
 
 static int wav_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 {
-	off_t offset=0, distance, max;
+	off_t offset = 0, min = MSGSM_DATA_OFFSET, distance, max, cur;
 	struct wavg_desc *s = (struct wavg_desc *)fs->_private;
 
-	off_t min = MSGSM_DATA_OFFSET;
-	off_t cur = ftello(fs->f);
-	fseek(fs->f, 0, SEEK_END);
-	max = ftello(fs->f);	/* XXX ideally, should round correctly */
+	if ((cur = ftello(fs->f)) < 0) {
+		ast_log(AST_LOG_WARNING, "Unable to determine current position in WAV filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+
+	if (fseeko(fs->f, 0, SEEK_END) < 0) {
+		ast_log(AST_LOG_WARNING, "Unable to seek to end of WAV filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+
+	/* XXX ideally, should round correctly */
+	if ((max = ftello(fs->f) < 0)) {
+		ast_log(AST_LOG_WARNING, "Unable to determine max position in WAV filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+
 	/* Compute the distance in bytes, rounded to the block size */
 	distance = (sample_offset/MSGSM_SAMPLES) * MSGSM_FRAME_SIZE;
 	if (whence == SEEK_SET)
@@ -511,8 +523,21 @@ static int wav_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 
 static int wav_trunc(struct ast_filestream *fs)
 {
-	if (ftruncate(fileno(fs->f), ftello(fs->f)))
+	int fd;
+	off_t cur;
+
+	if ((fd = fileno(fs->f)) < 0) {
+		ast_log(AST_LOG_WARNING, "Unable to determine file descriptor for WAV filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+	if ((cur = ftello(fs->f) < 0)) {
+		ast_log(AST_LOG_WARNING, "Unable to determine current position in WAV filestream %p: %s\n", fs, strerror(errno));
 		return -1;
+	}
+	/* Truncate file to current length */
+	if (ftruncate(fd, cur)) {
+		return -1;
+	}
 	return update_header(fs->f);
 }