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Prevent logfile corruption by control codes

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Do not corrupt logfiles when kernel messages contain control codes,
notably \n. Instead, preserve the kernel's protective C-style hex
encoding. For example, \n embedded in a message by a kernel-level
facility is received as "\x0a". Kernel-level facilities cannot be
trusted to use only syslog-safe codes in kernel messages. See:
<https://kernel.org/doc/Documentation/ABI/testing/dev-kmsg>
This commit is contained in:
Edward K. McGuire 2022-06-16 15:52:04 -05:00
parent 8f83328850
commit bcc3c7c1fb
2 changed files with 7 additions and 12 deletions
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7
ChangeLog.md
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@ -4,7 +4,7 @@ Change Log
All relevant changes to the project are documented in this file. All relevant changes to the project are documented in this file.
[v2.4.0][] - 2022-05-29 [v2.4.0][] - 2022-06-16
----------------------- -----------------------
### Changes ### Changes
@ -31,6 +31,11 @@ All relevant changes to the project are documented in this file.
data to be logged -- this is a temporary fix until we have support data to be logged -- this is a temporary fix until we have support
for parsing the Unicode BOM, as defined in RFC5424 for parsing the Unicode BOM, as defined in RFC5424
- Issue #50: fix issue with wall message, by Edward K. McGuire - Issue #50: fix issue with wall message, by Edward K. McGuire
- Do not corrupt logfiles when kernel messages contain control codes,
notably `\n`. Instead, preserve the kernel's protective C-style hex
encoding. For example, `\n` embedded in a message by a kernel-level
facility is received as `\x0a`. See:
<https://kernel.org/doc/Documentation/ABI/testing/dev-kmsg>
[v2.3.0][] - 2021-11-27 [v2.3.0][] - 2021-11-27

12
src/syslogd.c
View File

@ -1428,18 +1428,8 @@ void printsys(char *msg)
} }
q = lp; q = lp;
while (*p != '\0' && (c = *p++) != '\n' && q < &line[MAXLINE]) { while (*p != '\0' && (c = *p++) != '\n' && q < &line[MAXLINE])
/* Linux /dev/kmsg C-style hex encoding. */
if (c == '\\' && *p == 'x') {
char code[5] = "0x\0\0\0";
p++;
code[2] = *p++;
code[3] = *p++;
c = (int)strtol(code, NULL, 16);
}
*q++ = c; *q++ = c;
}
*q = '\0'; *q = '\0';
logmsg(&buffer); logmsg(&buffer);