InvalidAuthenticationInfo - Invalid Authentication Info: Header Format Error

#Common Causes

• →Missing Bearer Prefix: Your Authorization header contains the token but lacks the "Bearer " prefix. ARM requires exactly "Authorization: Bearer <token>" with a single space between "Bearer" and the token. Common mistakes include "Authorization: <token>" (no Bearer), "Authorization: bearer <token>" (lowercase), or "Authorization: Bearer<token>" (no space).
• →Header Name Case Mismatch: ARM's validation is case-sensitive for the Authorization header, even though HTTP headers are case-insensitive per RFC 7230. The header name must be exactly "Authorization" (capital A). "authorization" or "AUTHORIZATION" will fail.
• →JWT Structure Violation: Your token doesn't have exactly 3 dot-separated segments (header.payload.signature). Tokens with more or fewer segments can't be parsed by ARM. This happens when tokens are truncated, concatenated incorrectly, or corrupted during transmission.
• →Token Encoding Corruption: The token may contain invalid base64url characters, incorrect padding, or encoding issues. This can occur when tokens are modified, stored incorrectly, or transmitted through systems that alter encoding.
• →Extra Spaces or Characters: The format must be exactly "Bearer <token>" with no leading/trailing spaces or special characters.

✓Solutions

1. 1Step 1: Diagnose - Inspect the exact Authorization header value by logging or printing it. It should be exactly "Bearer <token>" with a single space.
2. 2Step 2: Diagnose - Check for missing "Bearer " prefix, lowercase "bearer", or missing space between "Bearer" and token.
3. 3Step 3: Diagnose - Verify header name is exactly "Authorization" (capital A). Use network inspection tools to confirm the case.
4. 4Step 4: Diagnose - Decode and validate JWT structure using jwt.io. Verify your token has exactly 3 dot-separated segments.
5. 5Step 5: Fix - Ensure Authorization header format is exactly "Authorization: Bearer <token>" with proper spacing.
6. 6Step 6: Fix - Use Azure SDK credential libraries instead of manually constructing headers. @azure/identity credential classes handle header formatting correctly.
7. 7Step 7: Fix - Verify your credential source isn't producing malformed tokens: az ad app credential list --id <app-id> --query "[].{keyId:keyId, endDate:endDate}" --output table
8. 8Step 8: Verify - Retry your operation. It should succeed instead of returning InvalidAuthenticationInfo.

</>Code Examples

1# This script helps diagnose InvalidAuthenticationInfo errors by checking credential validity
2
3# Step 1: Check service principal credentials (replace APP_ID)
4APP_ID="your-service-principal-id"
5echo "Checking service principal credentials for APP_ID: $APP_ID"
6az ad app credential list --id $APP_ID --query "[].{keyId:keyId, endDate:endDate}" --output table
7
8# Step 2: Check if credentials are expired
9echo "Checking for expired credentials..."
10CURRENT_DATE=$(date +%s)
11az ad app credential list --id $APP_ID --query "[?endDate < '$CURRENT_DATE'].{keyId:keyId, endDate:endDate}" --output table
12
13# Step 3: Test authentication
14echo "Testing authentication..."
15if az account show --output table 2>&1; then
16  echo "Authentication successful"
17else
18  echo "Authentication failed - check the error message above"
19  echo "Common issues:"
20  echo "  1. Missing 'Bearer ' prefix in Authorization header"
21  echo "  2. Header name case mismatch (must be 'Authorization', not 'authorization')"
22  echo "  3. JWT token structure violation (must have 3 dot-separated segments)"
23  echo "  4. Token encoding corruption"
24fi
25
26# Step 4: Get a fresh token using Azure CLI
27echo "Getting fresh access token..."
28TOKEN=$(az account get-access-token --query accessToken -o tsv)
29if [ ! -z "$TOKEN" ]; then
30  echo "Token obtained successfully"
31  echo "Token preview (first 50 chars): ${TOKEN:0:50}..."
32  
33  # Step 5: Validate JWT structure (check for 3 segments)
34  SEGMENT_COUNT=$(echo $TOKEN | tr -cd '.' | wc -c)
35  if [ $SEGMENT_COUNT -eq 2 ]; then
36    echo "JWT structure valid (3 segments found)"
37  else
38    echo "ERROR: JWT structure invalid (expected 3 segments, found $((SEGMENT_COUNT + 1)))"
39  fi
40else
41  echo "ERROR: Failed to obtain token"
42fi
43
44# Step 6: Instructions for manual header construction
45echo ""
46echo "If manually constructing headers, ensure:"
47echo "  1. Header name is exactly 'Authorization' (capital A)"
48echo "  2. Header value is exactly 'Bearer <token>' (with space)"
49echo "  3. Token has 3 dot-separated segments"
50echo "  4. No extra spaces or special characters"

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