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, 43 insertions, 12 deletions

diff --git a/formats/format_gsm.c b/formats/format_gsm.c
index 03419c2f6..4cf6579a6 100644
--- a/formats/format_gsm.c
+++ b/formats/format_gsm.c
@@ -108,20 +108,33 @@ static int gsm_write(struct ast_filestream *fs, struct ast_frame *f)
 
 static int gsm_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 {
-	off_t offset=0,min,cur,max,distance;
-	
-	min = 0;
-	cur = ftello(fs->f);
-	fseeko(fs->f, 0, SEEK_END);
-	max = ftello(fs->f);
+	off_t offset = 0, min = 0, cur, max, distance;
+
+	if ((cur = ftello(fs->f)) < 0) {
+		ast_log(AST_LOG_WARNING, "Unable to determine current position in g719 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 g719 filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+
+	if ((max = ftello(fs->f) < 0)) {
+		ast_log(AST_LOG_WARNING, "Unable to determine max position in g719 filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+
 	/* have to fudge to frame here, so not fully to sample */
-	distance = (sample_offset/GSM_SAMPLES) * GSM_FRAME_SIZE;
-	if(whence == SEEK_SET)
+	distance = (sample_offset / GSM_SAMPLES) * GSM_FRAME_SIZE;
+	if (whence == SEEK_SET) {
 		offset = distance;
-	else if(whence == SEEK_CUR || whence == SEEK_FORCECUR)
+	} else if (whence == SEEK_CUR || whence == SEEK_FORCECUR) {
 		offset = distance + cur;
-	else if(whence == SEEK_END)
+	} else if (whence == SEEK_END) {
 		offset = max - distance;
+	}
+
 	/* Always protect against seeking past the begining. */
 	offset = (offset < min)?min:offset;
 	if (whence != SEEK_FORCECUR) {
@@ -140,13 +153,31 @@ static int gsm_seek(struct ast_filestream *fs, off_t sample_offset, int whence)
 
 static int gsm_trunc(struct ast_filestream *fs)
 {
-	return 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 gsm 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 gsm filestream %p: %s\n", fs, strerror(errno));
+		return -1;
+	}
+	/* Truncate file to current length */
+	return ftruncate(fd, cur);
 }
 
 static off_t gsm_tell(struct ast_filestream *fs)
 {
 	off_t offset = ftello(fs->f);
-	return (offset/GSM_FRAME_SIZE)*GSM_SAMPLES;
+
+	if (offset < 0) {
+		ast_log(AST_LOG_WARNING, "Unable to determine offset for gsm filestream %p: %s\n", fs, strerror(errno));
+		return 0;
+	}
+
+	return (offset / GSM_FRAME_SIZE) * GSM_SAMPLES;
 }
 
 static struct ast_format_def gsm_f = {