added http digest auth support #11
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WalkthroughThe Changes
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Review Status
Actionable comments generated: 2
Configuration used: CodeRabbit UI
Files selected for processing (4)
- Makefile.am (1 hunks)
- corkscrew.c (7 hunks)
- md5.c (1 hunks)
- md5.h (1 hunks)
Additional comments: 15
Makefile.am (1)
- 4-5: The changes to include
md5.cin the sources and link withlibeventare appropriate for the new feature implementation.md5.h (1)
- 1-91: The inclusion of the MD5 header with the appropriate license and API declarations is correct and necessary for the MD5 functionality.
md5.c (1)
- 1-377: The implementation of the MD5 algorithm in
md5.cis consistent with RFC 1321 and includes necessary conditional compilation directives for different architectures.corkscrew.c (12)
14-15: Added necessary headers for libevent and MD5 functionality.
38-38: The
linefeedvariable has been changed to a more standard representation of CRLF. Ensure this change is consistent with the rest of the codebase.Verification successful
The script intended to verify the consistent use of the new
linefeedrepresentation across the codebase did not produce any output. This could mean that there are no occurrences of the "\r\n" sequence outside of thelinefeedvariable, or it could be an issue with the script itself.Given the lack of output, I will attempt a different approach to verify the consistency of the linefeed representation by searching for any linefeed characters without filtering out the
linefeedvariable, to ensure we capture all instances.
Given the lack of output from the script, it appears that there are no instances of the "\r\n" sequence in the codebase, or the script is not functioning as intended. To ensure we have covered all bases, I will attempt one more script using a different approach to search for line endings. This time, I will explicitly search for both the "\r\n" sequence and the "\n" sequence to confirm the presence or absence of these patterns in the codebase.
The output from the script shows that the "\r\n" sequence is present in the
corkscrew.cfile, specifically in the definition of thelinefeedvariable and in the construction of HTTP request headers. This confirms that the change to thelinefeedvariable is consistent with its usage in forming HTTP request headers within the codebase.Based on this information, the review comment about the
linefeedvariable change being consistent with the rest of the codebase is correct.* 166-175: The `dump_hash` function converts a hash to a hexadecimal string. Ensure that the buffer is large enough to hold the resulting string, including the null terminator.Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Verify that the new linefeed representation is used consistently across the codebase. rg --type c "\r\n" | rg -v "linefeed"Length of output: 229
Script:
#!/bin/bash # Verify that the new linefeed representation is used consistently across the codebase. # Using the multiline flag to allow the search for the "\r\n" pattern. rg --type c --multiline "\r\n" | rg -v "linefeed"Length of output: 49
Script:
#!/bin/bash # Search for all instances of CRLF line endings in the codebase. rg --type c --multiline "\r\n"Length of output: 32
Script:
#!/bin/bash # Search for all instances of CRLF and LF line endings in the codebase. rg --type c --multiline -e "\r\n" -e "\n"Length of output: 41017
Verification successful
The
ast-grepcommand did not return any results, which means it couldn't find any calls to thedump_hashfunction within the codebase. This could imply that the function is not used, or that the pattern provided toast-grepdid not match the waydump_hashis called in the code.To ensure that we have a comprehensive understanding of how
dump_hashis used, we should attempt a different strategy to search for its usage. We can userg(ripgrep) to search for the string "dump_hash" across the codebase, which will help us identify any calls to this function.
The
rgcommand has found three calls to thedump_hashfunction withincorkscrew.c. To verify that the buffer passed todump_hashis always large enough, we need to examine the context in which these calls are made, specifically looking at the size of the bufferbufthat is passed to the function.We will now generate a script to extract the lines of code around each call to
dump_hashto understand how the buffers are allocated and ensure they are of sufficient size.
The output from the
rgcommand provides the context around the calls todump_hash, but it does not show the actual allocation or declaration of the buffersa1buf,a2buf, andresponse. To ensure that these buffers are large enough to hold the resulting string fromdump_hash, including the null terminator, we need to see the buffer sizes when they are declared or allocated.Since the output provided does not include this information, we need to search for the declarations or initializations of
a1buf,a2buf, andresponseto verify their sizes.Let's generate a script to find the declarations or initializations of these buffers.
The output from the
rgcommand shows the declarations ofa1buf,a2buf, andresponse. Each buffer is declared with a size ofMD5_HASHLEN * 2 + 1. Given thatMD5_HASHLENis 16 (as seen in the previous context), this means each buffer is sized to hold 33 characters. This size is appropriate for the hexadecimal representation of an MD5 hash, which is 32 characters long, plus a null terminator.Since the buffers are correctly sized to hold the output from
dump_hash, the review comment concerning the buffer size fordump_hashis verified to be correct.* 180-185: The `red_randui32` function uses `evutil_secure_rng_get_bytes` to generate random bytes. Verify that this function is a secure random number generator appropriate for cryptographic use.Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Verify that the buffer passed to dump_hash is always large enough. ast-grep --lang c --pattern $'dump_hash($_, $_)'Length of output: 49
Script:
#!/bin/bash # Search for usage of dump_hash in the codebase rg 'dump_hash'Length of output: 201
Script:
#!/bin/bash # Extract the lines around the calls to dump_hash to check buffer allocation rg -C 5 'dump_hash'Length of output: 1630
Script:
#!/bin/bash # Find the declarations or initializations of a1buf, a2buf, and response rg 'char \s*a1buf|char \s*a2buf|char \s*response'Length of output: 174
191-263: The
digest_authentication_encodefunction constructs the digest authentication header. Ensure that the memory allocation forresis sufficient and that there are no buffer overflows when usingsprintf.309-322: The
minmacro andheaderfunction have been added. Verify that theminmacro is not causing any unexpected side effects when used with arguments that have side effects. Ensure that theheaderfunction correctly handles the memory allocation and does not cause buffer overflows.Verification successful
The search results confirm that the
minmacro is defined and used within theheaderfunction incorkscrew.c. There are no other occurrences of theminmacro being used in the codebase, which means there is no immediate evidence of it being used with arguments that have side effects. The usage within theheaderfunction appears to be safe as it is used with simple arithmetic operations.Regarding the
headerfunction, it allocates a fixed amount of memory (2048 bytes) and usesstrncatto concatenate a substring ofbufferbased on the result of theminmacro. The use ofminensures that the concatenation does not exceed the allocated buffer size, which should prevent buffer overflows.Based on the provided output, there are no apparent issues with the usage of the
minmacro or the memory handling in theheaderfunction. However, without a broader view of the codebase, it is not possible to guarantee that there are no side effects elsewhere in the code that could affect this function's behavior.* 345-352: Initialization of variables related to the new authentication method. Ensure that these variables are used securely throughout the function.Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Verify that the min macro is used safely and that the header function handles memory correctly. rg --type c "min\(" | rg -v "header"Length of output: 161
384-402: The URI construction for the CONNECT method has been modified. Ensure that the buffer
uriis large enough to hold the entire constructed string and that there are no buffer overflows.423-426: The use of
selectfor socket I/O multiplexing. Ensure that the file descriptor sets are being used correctly and that there are no off-by-one errors withcsock+1.450-535: The handling of the 407 Proxy Authentication Required response. Ensure that the nonce length check is correct and that the reconnection logic is secure and does not leak resources.
Verification successful
To verify the nonce length check and the reconnection logic, we need to examine the relevant sections of the code in more detail. Let's start by looking at the code surrounding the nonce length check.
Next, we'll examine the reconnection logic after a 407 response.
To ensure that the reconnection logic is secure and does not leak resources, we need to verify if there is any resource allocation before the
close(csock)call that would require cleanup. Let's look for any such allocations.
Based on the provided context, the nonce length check is correctly verifying that the nonce is exactly 32 characters long, which aligns with the expected length of an MD5 hash used in HTTP Digest Authentication.
The reconnection logic closes the existing socket and attempts to establish a new connection. If the new connection fails, the program exits, which would release all resources held by the process. There is no evidence of resource allocation that would require cleanup before closing the socket, and the use of
exit(-1)ensures that the program does not continue running in an unstable state.Therefore, the nonce length check is verified as correct, and the reconnection logic appears secure and does not indicate resource leaks based on the current context.
* 538-567: The handling of the Basic authentication scheme. Ensure that the base64 encoding is done securely and that the socket reconnection logic is correct.Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Verify that the nonce length check is correct and that the reconnection logic is secure. rg --type c "407"Length of output: 130
Script:
#!/bin/bash # Extract the code surrounding the nonce length check rg --type c --context 5 "strlen\(pa->nonce\) != 32" corkscrew.cLength of output: 419
Script:
#!/bin/bash # Extract the code surrounding the reconnection logic after a 407 response rg --type c --context 10 "close\(csock\);" corkscrew.cLength of output: 1417
Script:
#!/bin/bash # Look for resource allocations before the close(csock) call rg --type c --context 20 "csock =" corkscrew.cLength of output: 3367
Verification successful
To verify the security of the base64 encoding and the correctness of the socket reconnection logic, I will need to examine the implementation of the
base64_encodefunction and the logic following theclose(csock)call.
To further verify the security of the base64 encoding and the correctness of the socket reconnection logic, I will need to examine the implementation details of the
base64_encodeandsock_connectfunctions.
Since the
ast-grepcommand did not yield results for thebase64_encodeandsock_connectfunctions, I will usergto search for the function definitions in a broader scope.
The provided context shows partial implementations of the
base64_encodeandsock_connectfunctions. To fully verify the security of the base64 encoding and the correctness of the socket reconnection logic, I need to see the complete implementations of both functions.
The provided context now includes the full implementation of the
base64_encodefunction and thesock_connectfunction.
base64_encodeFunction SecurityThe
base64_encodefunction:
- Allocates memory for the encoded string based on the input length.
- Performs the encoding by mapping each group of bits to the corresponding base64 character.
- Handles padding with
=characters for input not divisible by three.- Null-terminates the encoded string.
The implementation appears to follow the standard base64 encoding procedure. There are no obvious security issues like buffer overflows since the buffer is allocated based on the input size, and the function checks for a null input. However, without a security audit or testing, we cannot guarantee the absence of all potential vulnerabilities.
sock_connectFunction CorrectnessThe
sock_connectfunction:
- Creates a new socket.
- Resolves the hostname to an IP address.
- Attempts to connect to the specified port.
- Returns the file descriptor for the new socket or
-1on error.The reconnection logic closes the old socket and calls
sock_connectto establish a new connection. This is a standard practice for reconnecting sockets. The function checks for errors at each step and returns-1if it cannot establish a connection, which is then handled appropriately in the calling code.Based on the provided context, the base64 encoding is implemented securely, and the socket reconnection logic is correct.
* 583-591: The sending of the constructed URI to the proxy. Ensure that the `write` operation is handled correctly and that there are no partial writes without proper handling.Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash # Verify that the base64 encoding is secure and that the socket reconnection logic is correct. rg --type c "Basic realm"Length of output: 94
Script:
#!/bin/bash # Verify the implementation of the base64_encode function for security rg --type c "base64_encode" # Verify the socket reconnection logic after the close(csock) call rg --type c "csock = sock_connect"Length of output: 407
Script:
#!/bin/bash # Examine the implementation of the base64_encode function ast-grep --lang c --pattern 'function_definition[name="base64_encode"]' # Examine the implementation of the sock_connect function ast-grep --lang c --pattern 'function_definition[name="sock_connect"]'Length of output: 146
Script:
#!/bin/bash # Search for the implementation of the base64_encode function rg --type c -A 30 "char \*base64_encode" # Search for the implementation of the sock_connect function rg --type c -A 30 "sock_connect"Length of output: 7343
Script:
#!/bin/bash # Retrieve the full implementation of the base64_encode function rg --type c -C 50 "char \*base64_encode" # Retrieve the full implementation of the sock_connect function rg --type c -C 50 "sock_connect"Length of output: 18265
| typedef struct proxyauth{ | ||
| char realm[BUFSIZE]; | ||
| char nonce[33]; | ||
| char qop[BUFSIZE]; | ||
| int stale; | ||
| }proxyauth; | ||
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|
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| proxyauth* process_line(char* line){ | ||
|
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| proxyauth* pa = (proxyauth *)malloc(sizeof(proxyauth)); | ||
| // for now only looking for nonce, realm and qop | ||
| char* where = strstr(line, "nonce="); | ||
| if(where != NULL)strncpy(pa->nonce, where + 7, 32); | ||
| where = strstr(line, "realm="); | ||
| if(where != NULL)sscanf(where + 7, "%[^\"]", pa->realm); | ||
| where = strstr(line, "qop="); | ||
| if(where != NULL)sscanf(where + 5, "%[^\"]", pa->qop); | ||
| // only 'auth' parameter is recognized | ||
| if(strstr(pa->qop, "auth") == NULL)pa->qop[0] = '\0'; | ||
| else strncpy(pa->qop, "auth", 5); | ||
| return pa; | ||
| } |
There was a problem hiding this comment.
The process_line function in corkscrew.c uses strncpy and sscanf for parsing strings. The strncpy usage for the nonce is safe as it copies a fixed number of characters. However, the sscanf calls for realm and qop do not limit the number of characters read, which could lead to buffer overflows if the input exceeds BUFSIZE. Additionally, there is no check on the length of the input line before parsing, which could be a potential issue. The strncpy call for qop is redundant but not unsafe. Overall, there are potential security concerns with the sscanf usage that should be addressed.
Analysis chain
The proxyauth struct and process_line function are used to parse proxy authentication parameters. Ensure that the string operations do not lead to buffer overflows, especially with strncpy and sscanf.
Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash
# Verify that the string operations in process_line do not lead to buffer overflows.
ast-grep --lang c --pattern $'process_line($_)'
Length of output: 48
Script:
#!/bin/bash
# Use rg to search for the process_line function definition and its usage to verify string operations.
rg "process_line"
Length of output: 108
Script:
#!/bin/bash
# Output the content of the lines around the definition of process_line to analyze the string operations.
rg -C 10 "process_line" corkscrew.c
Length of output: 1138
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| fscanf(fp, "%s", line); | ||
| up = malloc(sizeof(line)); | ||
| up = line; |
There was a problem hiding this comment.
The line buffer is defined with a size of BUFSIZE, which is set to 4096 bytes. This size should be adequate for typical authentication strings, but without a check on the length of the input from the file, there is a potential risk of buffer overflow if the file contains a line longer than 4096 characters.
To fully verify the safety of the fscanf usage, we would need to ensure that the fscanf call is limited to reading up to BUFSIZE - 1 characters (to leave space for the null terminator). Since the current fscanf call does not specify a limit, it is potentially unsafe.
The review comment is correct in pointing out the need to ensure there is no buffer overflow. The code should be modified to prevent reading more characters than the buffer can hold.
Analysis chain
The authentication file is read, and its contents are stored in line. Ensure that there is no buffer overflow when reading the file contents into line.
The line buffer is declared with a size of BUFSIZE. To ensure there is no buffer overflow, we need to verify that BUFSIZE is sufficiently large to hold the contents of the authentication file that line is intended to read. Let's find the definition of BUFSIZE to confirm its size.
Scripts Executed
The following scripts were executed for the analysis:
Script:
#!/bin/bash
# Verify that the buffer 'line' is large enough to hold the contents of the authentication file.
rg --type c "fscanf"
Length of output: 60
Script:
#!/bin/bash
# Find the declaration of the 'line' buffer and any relevant size checks or allocations.
rg --type c "char.*line["
Length of output: 110
Script:
#!/bin/bash
# Correct the regex pattern to properly find the declaration of the 'line' buffer.
rg --type c "char.*line\\["
Length of output: 99
Script:
#!/bin/bash
# Find the definition of BUFSIZE to confirm the size of the buffer.
rg --type c "#define BUFSIZE"
Length of output: 64
Added support for digest auth. Only the essential parts of RFC 7616 are implemented. I tested this with Squid proxy only, using no auth, basic and digest.
Summary by CodeRabbit
New Features
Enhancements
Refactor
Dependencies
libeventfor efficient event handling.